轉載請標明出處:
http://blog.csdn.net/lmj623565791/article/details/46858663;
本文出自:【張鴻洋的博客】
一、概述
在自定義ViewGroup中,很多效果都包含用戶手指去拖動其內部的某個View(eg:側滑菜單等),針對具體的需要去寫好onInterceptTouchEvent
和onTouchEvent
這兩個方法是一件很不容易的事,需要自己去處理:多手指的處理、加速度檢測等等。
好在官方在v4的支持包中提供了ViewDragHelper
這樣一個類來幫助我們方便的編寫自定義ViewGroup。簡單看一下它的註釋:
ViewDragHelper is a utility class for writing custom ViewGroups. It offers a number
of useful operations and state tracking for allowing a user to drag and reposition
views within their parent ViewGroup.
本篇博客將重點介紹ViewDragHelper
的使用,並且最終去實現一個類似DrawerLayout
的一個自定義的ViewGroup。(ps:官方的DrawerLayout就是用此類實現)
二、入門小示例
首先我們通過一個簡單的例子來看看其快捷的用法,分爲以下幾個步驟:
- 創建實例
- 觸摸相關的方法的調用
- ViewDragHelper.Callback實例的編寫
(一) 自定義ViewGroup
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">package</span> com.zhy.learn.view; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.content.Context; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.support.v4.widget.ViewDragHelper; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.util.AttributeSet; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.view.MotionEvent; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.view.View; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.widget.LinearLayout; <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** * Created by zhy on 15/6/3. */</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">VDHLayout</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">LinearLayout</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> ViewDragHelper mDragger; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">VDHLayout</span>(Context context, AttributeSet attrs) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context, attrs); mDragger = ViewDragHelper.create(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ViewDragHelper.Callback() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">tryCaptureView</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> pointerId) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionHorizontal</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> left, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dx) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> left; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionVertical</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> top, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dy) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> top; } }); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">onInterceptTouchEvent</span>(MotionEvent event) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mDragger.shouldInterceptTouchEvent(event); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">onTouchEvent</span>(MotionEvent event) { mDragger.processTouchEvent(event); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li></ul>
可以看到,上面整個自定義ViewGroup的代碼非常簡潔,遵循上述3個步驟:
1、創建實例
<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">mDragger = ViewDragHelper.create(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0f</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ViewDragHelper.Callback() { });</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>
創建實例需要3個參數,第一個就是當前的ViewGroup,第二個sensitivity,主要用於設置touchSlop:
<code class="language-java hljs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">helper.mTouchSlop = (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>) (helper.mTouchSlop * (<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> / sensitivity));</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
可見傳入越大,mTouchSlop的值就會越小。第三個參數就是Callback,在用戶的觸摸過程中會回調相關方法,後面會細說。
2、觸摸相關方法
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">onInterceptTouchEvent</span>(MotionEvent <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mDragger.shouldInterceptTouchEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>); } @Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">onTouchEvent</span>(MotionEvent <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>) { mDragger.processTouchEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>
onInterceptTouchEvent
中通過使用mDragger.shouldInterceptTouchEvent(event)
來決定我們是否應該攔截當前的事件。onTouchEvent
中通過mDragger.processTouchEvent(event)
處理事件。
3、實現ViewDragHelper.CallCack相關方法
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ViewDragHelper.Callback() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">tryCaptureView</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> pointerId) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionHorizontal</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> left, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dx) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> left; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionVertical</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> top, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dy) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> top; } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li></ul>
ViewDragHelper中攔截和處理事件時,需要會回調CallBack中的很多方法來決定一些事,比如:哪些子View可以移動、對個移動的View的邊界的控制等等。
上面複寫的3個方法:
- tryCaptureView如何返回ture則表示可以捕獲該view,你可以根據傳入的第一個view參數決定哪些可以捕獲
- clampViewPositionHorizontal,clampViewPositionVertical可以在該方法中對child移動的邊界進行控制,left , top 分別爲即將移動到的位置,比如橫向的情況下,我希望只在ViewGroup的內部移動,即:最小>=paddingleft,最大<=ViewGroup.getWidth()-paddingright-child.getWidth。就可以按照如下代碼編寫:
<code class="language-java hljs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionHorizontal</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> left, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dx) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> leftBound = getPaddingLeft(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> rightBound = getWidth() - mDragView.getWidth() - leftBound; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> newLeft = Math.min(Math.max(left, leftBound), rightBound); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> newLeft; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>
經過上述3個步驟,我們就完成了一個簡單的自定義ViewGroup,可以自由的拖動子View。
簡單看一下佈局文件
(二) 佈局文件
<code class="language-xml hljs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">com.zhy.learn.view.VDHLayout</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:tools</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/tools"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:orientation</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"vertical"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"match_parent"</span> ></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView </span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_margin</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"10dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:background</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"#44ff0000"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"I can be dragged !"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"100dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"100dp"</span>/></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView </span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_margin</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"10dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:background</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"#44ff0000"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"I can be dragged !"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"100dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"100dp"</span>/></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">TextView </span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_margin</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"10dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:gravity</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"center"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:background</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"#44ff0000"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:text</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"I can be dragged !"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"100dp"</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:layout_height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"100dp"</span>/></span> <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">com.zhy.learn.view.VDHLayout</span>></span> </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li></ul>
我們的自定義ViewGroup中有三個TextView。
當前效果:
可以看到短短數行代碼就可以玩起來了~~~
有了直觀的認識以後,我們還需要對ViewDragHelper.CallBack裏面的方法做下深入的理解。首先我們需要考慮的是:我們的ViewDragHelper不僅僅說只能夠去讓子View去跟隨我們手指移動,我們繼續往下學習其他的功能。
三、功能展示
ViewDragHelper還能做以下的一些操作:
- 邊界檢測、加速度檢測(eg:DrawerLayout邊界觸發拉出)
- 回調Drag Release(eg:DrawerLayout部分,手指擡起,自動展開/收縮)
- 移動到某個指定的位置(eg:點擊Button,展開/關閉Drawerlayout)
那麼我們接下來對我們最基本的例子進行改造,包含上述的幾個操作。
首先看一下我們修改後的效果:
簡單的爲每個子View添加了不同的操作:
第一個View,就是演示簡單的移動
第二個View,演示除了移動後,鬆手自動返回到原本的位置。(注意你拖動的越快,返回的越快)
第三個View,邊界移動時對View進行捕獲。
好了,看完效果圖,來看下代碼的修改:
修改後的代碼
<code class="language-java hljs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">package</span> com.zhy.learn.view; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.content.Context; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.graphics.Point; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.support.v4.widget.ViewDragHelper; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.util.AttributeSet; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.view.MotionEvent; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.view.View; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.widget.LinearLayout; <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** * Created by zhy on 15/6/3. */</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">VDHLayout</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">LinearLayout</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> ViewDragHelper mDragger; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> View mDragView; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> View mAutoBackView; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> View mEdgeTrackerView; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Point mAutoBackOriginPos = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Point(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">VDHLayout</span>(Context context, AttributeSet attrs) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context, attrs); mDragger = ViewDragHelper.create(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ViewDragHelper.Callback() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">tryCaptureView</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> pointerId) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//mEdgeTrackerView禁止直接移動</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> child == mDragView || child == mAutoBackView; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionHorizontal</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> left, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dx) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> left; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">clampViewPositionVertical</span>(View child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> top, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> dy) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> top; } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//手指釋放的時候回調</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onViewReleased</span>(View releasedChild, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> xvel, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> yvel) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//mAutoBackView手指釋放時可以自動回去</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (releasedChild == mAutoBackView) { mDragger.settleCapturedViewAt(mAutoBackOriginPos.x, mAutoBackOriginPos.y); invalidate(); } } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//在邊界拖動時回調</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onEdgeDragStarted</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> edgeFlags, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> pointerId) { mDragger.captureChildView(mEdgeTrackerView, pointerId); } }); mDragger.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">onInterceptTouchEvent</span>(MotionEvent event) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mDragger.shouldInterceptTouchEvent(event); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">onTouchEvent</span>(MotionEvent event) { mDragger.processTouchEvent(event); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">computeScroll</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(mDragger.continueSettling(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>)) { invalidate(); } } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onLayout</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> changed, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> l, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> t, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> r, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> b) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onLayout(changed, l, t, r, b); mAutoBackOriginPos.x = mAutoBackView.getLeft(); mAutoBackOriginPos.y = mAutoBackView.getTop(); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onFinishInflate</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onFinishInflate(); mDragView = getChildAt(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>); mAutoBackView = getChildAt(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>); mEdgeTrackerView = getChildAt(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>); } } </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li><li style="box-sizing: border-box; padding: 0px 5px;">87</li><li style="box-sizing: border-box; padding: 0px 5px;">88</li><li style="box-sizing: border-box; padding: 0px 5px;">89</li><li style="box-sizing: border-box; padding: 0px 5px;">90</li><li style="box-sizing: border-box; padding: 0px 5px;">91</li><li style="box-sizing: border-box; padding: 0px 5px;">92</li><li style="box-sizing: border-box; padding: 0px 5px;">93</li><li style="box-sizing: border-box; padding: 0px 5px;">94</li><li style="box-sizing: border-box; padding: 0px 5px;">95</li><li style="box-sizing: border-box; padding: 0px 5px;">96</li><li style="box-sizing: border-box; padding: 0px 5px;">97</li><li style="box-sizing: border-box; padding: 0px 5px;">98</li><li style="box-sizing: border-box; padding: 0px 5px;">99</li><li style="box-sizing: border-box; padding: 0px 5px;">100</li><li style="box-sizing: border-box; padding: 0px 5px;">101</li><li style="box-sizing: border-box; padding: 0px 5px;">102</li><li style="box-sizing: border-box; padding: 0px 5px;">103</li><li style="box-sizing: border-box; padding: 0px 5px;">104</li><li style="box-sizing: border-box; padding: 0px 5px;">105</li><li style="box-sizing: border-box; padding: 0px 5px;">106</li><li style="box-sizing: border-box; padding: 0px 5px;">107</li><li style="box-sizing: border-box; padding: 0px 5px;">108</li><li style="box-sizing: border-box; padding: 0px 5px;">109</li><li style="box-sizing: border-box; padding: 0px 5px;">110</li><li style="box-sizing: border-box; padding: 0px 5px;">111</li><li style="box-sizing: border-box; padding: 0px 5px;">112</li><li style="box-sizing: border-box; padding: 0px 5px;">113</li></ul>
佈局文件我們僅僅是換了下文本和背景色就不重複貼了。
第一個View基本沒做任何修改。
第二個View,我們在onLayout之後保存了最開啓的位置信息,最主要還是重寫了Callback中的onViewReleased
,我們在onViewReleased中判斷如果是mAutoBackView則調用settleCapturedViewAt
回到初始的位置。大家可以看到緊隨其後的代碼是invalidate();因爲其內部使用的是mScroller.startScroll,所以別忘了需要invalidate()以及結合computeScroll
方法一起。
第三個View,我們在onEdgeDragStarted
回調方法中,主動通過captureChildView
對其進行捕獲,該方法可以繞過tryCaptureView,所以我們的tryCaptureView雖然併爲返回true,但卻不影響。注意如果需要使用邊界檢測需要添加上mDragger.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT);
。
到此,我們已經介紹了Callback中常用的回調方法了,當然還有一些方法沒有介紹,接下來我們修改下我們的佈局文件,我們把我們的TextView全部加上clickable=true,意思就是子View可以消耗事件。再次運行,你會發現本來可以拖動的View不動了,(如果有拿Button測試的兄弟應該已經發現這個問題了,我希望你看到這了,而不是已經提問了,哈~)。
原因是什麼呢?主要是因爲,如果子View不消耗事件,那麼整個手勢(DOWN-MOVE*-UP)都是直接進入onTouchEvent,在onTouchEvent的DOWN的時候就確定了captureView。如果消耗事件,那麼就會先走onInterceptTouchEvent
方法,判斷是否可以捕獲,而在判斷的過程中會去判斷另外兩個回調的方法:getViewHorizontalDragRange
和getViewVerticalDragRange
,只有這兩個方法返回大於0的值才能正常的捕獲。
所以,如果你用Button測試,或者給TextView添加了clickable = true ,都記得重寫下面這兩個方法:
<code class="language-java hljs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getViewHorizontalDragRange</span>(View child) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getMeasuredWidth()-child.getMeasuredWidth(); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getViewVerticalDragRange</span>(View child) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getMeasuredHeight()-child.getMeasuredHeight(); }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>
方法的返回值應當是該childView橫向或者縱向的移動的範圍,當前如果只需要一個方向移動,可以只複寫一個。
到此,我們列一下所有的Callback方法,看看還有哪些沒用過的:
-
onViewDragStateChanged
當ViewDragHelper狀態發生變化時回調(IDLE,DRAGGING,SETTING[自動滾動時])
-
onViewPositionChanged
當captureview的位置發生改變時回調
-
onViewCaptured
當captureview被捕獲時回調
-
onViewReleased 已用
-
onEdgeTouched
當觸摸到邊界時回調。
-
onEdgeLock
true的時候會鎖住當前的邊界,false則unLock。
-
onEdgeDragStarted 已用
-
getOrderedChildIndex
改變同一個座標(x,y)去尋找captureView位置的方法。(具體在:findTopChildUnder方法中)
-
getViewHorizontalDragRange 已用
- getViewVerticalDragRange 已用
- tryCaptureView 已用
- clampViewPositionHorizontal 已用
- clampViewPositionVertical 已用
ok,至此所有的回調方法都有了一定的認識。
總結下,方法的大致的回調順序:
<code class="language-java hljs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">shouldInterceptTouchEvent: DOWN: getOrderedChildIndex(findTopChildUnder) ->onEdgeTouched MOVE: getOrderedChildIndex(findTopChildUnder) ->getViewHorizontalDragRange & getViewVerticalDragRange(checkTouchSlop)(MOVE中可能不止一次) ->clampViewPositionHorizontal& clampViewPositionVertical ->onEdgeDragStarted ->tryCaptureView ->onViewCaptured ->onViewDragStateChanged processTouchEvent: DOWN: getOrderedChildIndex(findTopChildUnder) ->tryCaptureView ->onViewCaptured ->onViewDragStateChanged ->onEdgeTouched MOVE: ->STATE==DRAGGING:dragTo ->STATE!=DRAGGING: onEdgeDragStarted ->getOrderedChildIndex(findTopChildUnder) ->getViewHorizontalDragRange& getViewVerticalDragRange(checkTouchSlop) ->tryCaptureView ->onViewCaptured ->onViewDragStateChanged </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li></ul>
ok,上述是正常情況下大致的流程,當然整個過程可能會存在很多判斷不成立的情況。
從上面也可以解釋,我們在之前TextView(clickable=false)的情況下,沒有編寫getViewHorizontalDragRange方法時,是可以移動的。因爲直接進入processTouchEvent的DOWN,然後就onViewCaptured、onViewDragStateChanged(進入DRAGGING狀態),接下來MOVE就直接dragTo了。
而當子View消耗事件的時候,就需要走shouldInterceptTouchEvent,MOVE的時候經過一系列的判斷(getViewHorizontalDragRange,clampViewPositionVertical等),才能夠去tryCaptureView。
ok,到此ViewDragHelper的入門用法我們就介紹結束了,下一篇,我們將使用ViewDragHelper
去自己實現一個DrawerLayout
。
有興趣的也可以根據本文,以及DrawerLayout
的源碼去實現了~