1、概述
本篇博客的產生呢,是因爲,羣裏的哥們暖暖給我發了個效果圖,然後問我該如何實現頂部ViewPager指示器的字體變色,該效果圖是這樣的:
大概是今天頭條的app,神奇的地方就在於,切換ViewPager頁面的時候,頂部指示器改成了字體顏色的變化,個人覺得還是不錯的。
那麼核心的地方就是做一個支持字體這樣逐漸染色就可以了,我大概想了32s,掃描了一些可能實現的方案,最終定位了一個靠譜的,下面我就帶大家開始實現的征程。
實現之前貼一下我們的效果圖:
2、效果圖
1、簡單使用
效果如上圖了,關於顏失色的改變我添加了兩個方向,一個是左方向,一個是有方向。
單純的使用,可能覺得沒什麼意思,下面看結合ViewPager使用的一個例子。
2、結合ViewPager使用
可以看到我們切換頁面的時候,上面的指示器的效果,棒棒噠~~~
當然了,學會了原理,你可以擴展,可以做個性的進度條,可以將字體變色改爲背景色變色,可以把方向改爲上下,太多了,自己去摳腳想把。
3、原理
看完效果圖,有木有什麼思路~花幾分鐘想想,因爲原理很簡單
我大致想了下,目測繪製半個字估計不行,那麼就在繪製範圍上下功夫,你可以全部繪製,但是我控制顯示的範圍,所以上述效果:
其實是繪製了兩遍字體,但是呢,分別控制了繪製的顯示範圍,實現了逐漸變色的效果,那麼對於範圍的控制,有什麼方便的API麼,顯然是有的
canvas有個clipRect的方法~ok,原理分析完畢
4、實現
說到實現,那第一步肯定又是自定義屬性,我們這裏的屬性,需要text,textSize,textOriginColor,textChangeColor,progress,大致看一下,應該都能看出來作用吧,看不出來沒事,結合下面的代碼。tip:我們的View叫做ColorTrackView,感謝小七的命名。
1、自定義屬性和獲取
attr.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<attr name="text" format="string" />
<attr name="text_size" format="dimension" />
<attr name="text_origin_color" format="color|reference" />
<attr name="text_change_color" format="color|reference" />
<attr name="progress" format="float" />
<attr name="direction">
<enum name="left" value="0" />
<enum name="right" value="1" />
</attr>
<declare-styleable name="ColorTrackView">
<attr name="text" />
<attr name="text_size" />
<attr name="text_origin_color" />
<attr name="text_change_color" />
<attr name="progress" />
<attr name="direction" />
</declare-styleable>
</resources>
然後在我們的ColorTrackView的構造方法中進行獲取這些個渣渣屬性:
/**
*
* @author zhy
*
*/
public class ColorTrackView extends View
{
private int mTextStartX;
public enum Direction
{
LEFT , RIGHT ;
}
private int mDirection = DIRECTION_LEFT;
private static final int DIRECTION_LEFT = 0 ;
private static final int DIRECTION_RIGHT= 1 ;
public void setDirection(int direction)
{
mDirection = direction;
}
private String mText = "張鴻洋";
private Paint mPaint;
private int mTextSize = sp2px(30);
private int mTextOriginColor = 0xff000000;
private int mTextChangeColor = 0xffff0000;
private Rect mTextBound = new Rect();
private int mTextWidth;
private int mRealWidth;
private float mProgress;
public ColorTrackView(Context context)
{
super(context, null);
}
public ColorTrackView(Context context, AttributeSet attrs)
{
super(context, attrs);
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
TypedArray ta = context.obtainStyledAttributes(attrs,
R.styleable.ColorTrackView);
mText = ta.getString(R.styleable.ColorTrackView_text);
mTextSize = ta.getDimensionPixelSize(
R.styleable.ColorTrackView_text_size, mTextSize);
mTextOriginColor = ta.getColor(
R.styleable.ColorTrackView_text_origin_color,
mTextOriginColor);
mTextChangeColor = ta.getColor(
R.styleable.ColorTrackView_text_change_color,
mTextChangeColor);
mProgress = ta.getFloat(R.styleable.ColorTrackView_progress, 0);
mDirection = ta.getInt(R.styleable.ColorTrackView_direction, mDirection);
ta.recycle();
mPaint.setTextSize(mTextSize);
measureText();
}
private void measureText()
{
mTextWidth = (int) mPaint.measureText(mText);
mPaint.getTextBounds(mText, 0, mText.length(), mTextBound);
}
可以看到我同時貼出了成員變量,大家簡單看下就行了,都比較簡單。
獲取了屬性,初始化完成一些成員變量以後,那麼應該走向我們的measure之旅了~~
2、onMeasure
[java] view plaincopy在CODE上查看代碼片派生到我的代碼片
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
int width = measureWidth(widthMeasureSpec);
int height = measureHeight(heightMeasureSpec);
setMeasuredDimension(width, height);
mRealWidth = getMeasuredWidth() - getPaddingLeft() - getPaddingRight();
mTextStartX = mRealWidth / 2 - mTextWidth / 2;
}
private int measureHeight(int measureSpec)
{
int mode = MeasureSpec.getMode(measureSpec);
int val = MeasureSpec.getSize(measureSpec);
int result = 0;
switch (mode)
{
case MeasureSpec.EXACTLY:
result = val;
break;
case MeasureSpec.AT_MOST:
case MeasureSpec.UNSPECIFIED:
result = mTextBound.height();
break;
}
result = mode == MeasureSpec.AT_MOST ? Math.min(result, val) : result;
return result + getPaddingTop() + getPaddingBottom();
}
private int measureWidth(int measureSpec)
{
int mode = MeasureSpec.getMode(measureSpec);
int val = MeasureSpec.getSize(measureSpec);
int result = 0;
switch (mode)
{
case MeasureSpec.EXACTLY:
result = val;
break;
case MeasureSpec.AT_MOST:
case MeasureSpec.UNSPECIFIED:
// result = mTextBound.width();
result = mTextWidth;
break;
}
result = mode == MeasureSpec.AT_MOST ? Math.min(result, val) : result;
return result + getPaddingLeft() + getPaddingRight();
}
關於測量,也是比較傳統的寫法,根據傳入的widthMeasureSpec、heightMeasureSpec,利用MeasureSpec分別獲取模式和值,如何是EXACTLY萬事大吉,如果是AT_MOST、UNSPECIFIED那麼就進行自己測量需要的空間,當然了,最好注意如果是AT_MOST不應該大於父類傳入的值。
這裏提一下,如果偷懶的話,可以選擇繼承TextView,然後測量就不需要寫了,TextView默認幫你實現了,還能利用TextView的一些屬性,不過咱們這個例子比較簡單,我最終還是選擇了繼承View,繼承View有種everything under control 的感覺。
測量完成以後,不用說都是繪製了。
3、onDraw
@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
int r = (int) (mProgress* mTextWidth +mTextStartX );
if(mDirection == DIRECTION_LEFT)
{
drawChangeLeft(canvas, r);
drawOriginLeft(canvas, r);
}else
{
drawOriginRight(canvas, r);
drawChangeRight(canvas, r);
}
}
private void drawChangeRight(Canvas canvas, int r)
{
drawText(canvas, mTextChangeColor, (int) (mTextStartX +(1-mProgress)*mTextWidth), mTextStartX+mTextWidth );
}
private void drawOriginRight(Canvas canvas, int r)
{
drawText(canvas, mTextOriginColor, mTextStartX, (int) (mTextStartX +(1-mProgress)*mTextWidth) );
}
private void drawChangeLeft(Canvas canvas, int r)
{
drawText(canvas, mTextChangeColor, mTextStartX, (int) (mTextStartX + mProgress * mTextWidth) );
}
private void drawOriginLeft(Canvas canvas, int r)
{
drawText(canvas, mTextOriginColor, (int) (mTextStartX + mProgress * mTextWidth), mTextStartX +mTextWidth );
}
private void drawText(Canvas canvas , int color , int startX , int endX)
{
mPaint.setColor(color);
canvas.save(Canvas.CLIP_SAVE_FLAG);
canvas.clipRect(startX, 0, endX, getMeasuredHeight());
canvas.drawText(mText, mTextStartX, getMeasuredHeight() / 2
+ mTextBound.height() / 2, mPaint);
canvas.restore();
}
繪製的核心就在於利用mProgress和方向去計算應該clip的範圍,具體的參考代碼,沒什麼難點。有了範圍以後,無非就是drawText~~~
該View的完整代碼:ColorTrackView
主要的方法介紹完畢,我們就該測試了。
5、測試
1、簡單測試
佈局文件
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:zhy="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.zhy.view.ColorTrackView
android:id="@+id/id_changeTextColorView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:background="#44ff0000"
android:padding="10dp"
zhy:progress="0"
zhy:text="張鴻洋"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="60sp" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="@+id/id_left"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="startLeftChange"
android:text="StartLeft" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/id_left"
android:onClick="startRightChange"
android:text="StartRight" />
</LinearLayout>
</RelativeLayout>
注意我們的自定義屬性的命名空間,該佈局就一個ColorTrackView,然後兩個按鈕來控制進度。
SimpleUseActivity:
package com.zhy.viewpagerIndicator;
import android.animation.ObjectAnimator;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import com.zhy.view.ColorTrackView;
public class SimpleUseActivity extends Activity
{
ColorTrackView mView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_simple_main);
mView = (ColorTrackView) findViewById(R.id.id_changeTextColorView);
}
@SuppressLint("NewApi")
public void startLeftChange(View view)
{
mView.setDirection(0);
ObjectAnimator.ofFloat(mView, "progress", 0, 1).setDuration(2000)
.start();
}
@SuppressLint("NewApi")
public void startRightChange(View view)
{
mView.setDirection(1);
ObjectAnimator.ofFloat(mView, "progress", 0, 1).setDuration(2000)
.start();
}
}
這裏拿屬性動畫進行的測試,沒有導入3.0以下兼容包,有需要自己導入。
效果圖,見上效果圖1。
2、結合ViewPager
佈局文件:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:zhy="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="horizontal" >
<com.zhy.view.ColorTrackView
android:id="@+id/id_tab_01"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
zhy:progress="1"
zhy:text="簡介"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="18sp" />
<com.zhy.view.ColorTrackView
android:id="@+id/id_tab_02"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
zhy:text="評價"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="18sp" />
<com.zhy.view.ColorTrackView
android:id="@+id/id_tab_03"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
zhy:text="相關"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="18sp" />
</LinearLayout>
<android.support.v4.view.ViewPager
android:id="@+id/id_viewpager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" >
</android.support.v4.view.ViewPager>
</LinearLayout>
3個ColorTrackView代表Tab,下面是ViewPager
ViewPagerUseActivity:
package com.zhy.viewpagerIndicator;
import java.util.ArrayList;
import java.util.List;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.Log;
import com.zhy.view.ColorTrackView;
public class ViewPagerUseActivity extends FragmentActivity
{
private String[] mTitles = new String[] { "簡介", "評價", "相關" };
private ViewPager mViewPager;
private FragmentPagerAdapter mAdapter;
private TabFragment[] mFragments = new TabFragment[mTitles.length];
private List<ColorTrackView> mTabs = new ArrayList<ColorTrackView>();
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_vp_main);
initViews();
initDatas();
initEvents();
}
private void initEvents()
{
mViewPager.setOnPageChangeListener(new OnPageChangeListener()
{
@Override
public void onPageSelected(int position)
{
}
@Override
public void onPageScrolled(int position, float positionOffset,
int positionOffsetPixels)
{
if (positionOffset > 0)
{
ColorTrackView left = mTabs.get(position);
ColorTrackView right = mTabs.get(position + 1);
left.setDirection(1);
right.setDirection(0);
Log.e("TAG", positionOffset+"");
left.setProgress( 1-positionOffset);
right.setProgress(positionOffset);
}
}
@Override
public void onPageScrollStateChanged(int state)
{
}
});
}
private void initDatas()
{
for (int i = 0; i < mTitles.length; i++)
{
mFragments[i] = (TabFragment) TabFragment.newInstance(mTitles[i]);
}
mAdapter = new FragmentPagerAdapter(getSupportFragmentManager())
{
@Override
public int getCount()
{
return mTitles.length;
}
@Override
public Fragment getItem(int position)
{
return mFragments[position];
}
};
mViewPager.setAdapter(mAdapter);
mViewPager.setCurrentItem(0);
}
private void initViews()
{
mViewPager = (ViewPager) findViewById(R.id.id_viewpager);
mTabs.add((ColorTrackView) findViewById(R.id.id_tab_01));
mTabs.add((ColorTrackView) findViewById(R.id.id_tab_02));
mTabs.add((ColorTrackView) findViewById(R.id.id_tab_03));
}
}
TabFragment
package com.zhy.viewpagerIndicator;
import java.util.Random;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class TabFragment extends Fragment
{
public static final String TITLE = "title";
private String mTitle = "Defaut Value";
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
if (getArguments() != null)
{
mTitle = getArguments().getString(TITLE);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
TextView tv = new TextView(getActivity());
tv.setTextSize(60);
Random r = new Random();
tv.setBackgroundColor(Color.argb(r.nextInt(120), r.nextInt(255),
r.nextInt(255), r.nextInt(255)));
tv.setText(mTitle);
tv.setGravity(Gravity.CENTER);
return tv;
}
public static TabFragment newInstance(String title)
{
TabFragment tabFragment = new TabFragment();
Bundle bundle = new Bundle();
bundle.putString(TITLE, title);
tabFragment.setArguments(bundle);
return tabFragment;
}
}
效果圖見上效果圖2。
本文轉自http://blog.csdn.net/lmj623565791/article/details/44098729,本文出自:【張鴻洋的博客】