我的實現思路就是自定義一個layout SwipeLayout繼承自FrameLayout。SwipeLayout包含兩個子view,第一個子view是內容區域,第二個子view是操作區域。滑動效果的控制,主要就是通過檢測SwipeLayout的touch事件來實現,這裏我不想自己去通過監聽touch事件來實現滑動效果,那是一個很繁瑣的過程。Android support庫裏其實已經提供了一個很好的工具類來幫我們做這件事情ViewDragHelper。如果你看過Android原生的DrawerLayout的代碼,就會發現DrawerLayout的滑動效果也是通過ViewDragHelper類實現的。
下面先介紹一下ViewDragHelper類的使用。
首先需要在容器中創建一個ViewDragHelper類的對象。
- mDragHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback());
- @Override
- public boolean onInterceptTouchEvent(MotionEvent event) {
- if (mDragHelper.shouldInterceptTouchEvent(event)) {
- return true;
- }
- return super.onInterceptTouchEvent(event);
- }
- @Override
- public boolean onTouchEvent(MotionEvent event) {
- mDragHelper.processTouchEvent(event);
- return true;
- }
ViewDragHelper對象來決定motion event是否是屬於拖動過程。如果motion event屬於拖動過程,那麼觸摸事件就交給ViewDragHelper來處理,ViewDragHelper在處理拖動過程的時候,會調用ViewDragHelper.Callback對象的一系列方法。
我們可以通過ViewDragHelper.Callback來監聽以下幾種事件:
1.拖動的狀態改變
2.被拖動的view的位置改變
3.被拖動的view被放開的時間和位置
ViewDragHelper.Callback還提供了幾個方法用來影響拖動過程。
1.控制view可以拖動的範圍
2.確定某個view是否可以拖動
好了,直接看代碼分析吧。
在SwipeLayout的inflate事件中,獲取到contentView和actionView。
- @Override
- protected void onFinishInflate() {
- contentView = getChildAt(0);
- actionView = getChildAt(1);
- actionView.setVisibility(GONE);
- }
在SwipeLayout的measure事件中,設置拖動的距離爲actionView的寬度。
- @Override
- protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
- super.onMeasure(widthMeasureSpec, heightMeasureSpec);
- dragDistance = actionView.getMeasuredWidth();
- }
DragHelperCallback的tryCaptureView方法,用來確定contentView和actionView是可以拖動的
- @Override
- public boolean tryCaptureView(View view, int i) {
- return view == contentView || view == actionView;
- }
- @Override
- public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
- draggedX = left;
- if (changedView == contentView) {
- actionView.offsetLeftAndRight(dx);
- } else {
- contentView.offsetLeftAndRight(dx);
- }
- if (actionView.getVisibility() == View.GONE) {
- actionView.setVisibility(View.VISIBLE);
- }
- invalidate();
- }
- @Override
- public int clampViewPositionHorizontal(View child, int left, int dx) {
- if (child == contentView) {
- final int leftBound = getPaddingLeft();
- final int minLeftBound = -leftBound - dragDistance;
- final int newLeft = Math.min(Math.max(minLeftBound, left), 0);
- return newLeft;
- } else {
- final int minLeftBound = getPaddingLeft() + contentView.getMeasuredWidth() - dragDistance;
- final int maxLeftBound = getPaddingLeft() + contentView.getMeasuredWidth() + getPaddingRight();
- final int newLeft = Math.min(Math.max(left, minLeftBound), maxLeftBound);
- return newLeft;
- }
- }
- @Override
- public int getViewHorizontalDragRange(View child) {
- return dragDistance;
- }
- @Override
- public void onViewReleased(View releasedChild, float xvel, float yvel) {
- super.onViewReleased(releasedChild, xvel, yvel);
- boolean settleToOpen = false;
- if (xvel > AUTO_OPEN_SPEED_LIMIT) {
- settleToOpen = false;
- } else if (xvel < -AUTO_OPEN_SPEED_LIMIT) {
- settleToOpen = true;
- } else if (draggedX <= -dragDistance / 2) {
- settleToOpen = true;
- } else if (draggedX > -dragDistance / 2) {
- settleToOpen = false;
- }
- final int settleDestX = settleToOpen ? -dragDistance : 0;
- viewDragHelper.smoothSlideViewTo(contentView, settleDestX, 0);
- ViewCompat.postInvalidateOnAnimation(SwipeLayout.this);
- }
代碼下載
github地址:https://github.com/lzyzsd/SwipeLayout
原文:http://blog.csdn.net/lzyzsd/article/details/41492783