android 如何实现边缘拖动侧滑

据需求需要自己自定义一个ListView来实现该功能，接下来先贴出代码再讲解具体的实现
package comexampleslidecutlistview;

import androidcontentContext;
import androidutilAttributeSet;
import androidviewMotionEvent;
import androidviewVelocityTracker;
import androidviewView;
import androidviewViewConfiguration;
import androidviewWindowManager;
import androidwidgetAdapterView;
import androidwidgetListView;
import androidwidgetScroller;

/
@blog http://blogcsdnnet/xiaanming

@author xiaanming

/
public class SlideCutListView extends ListView {
/
当前滑动的ListView　position
/
private int slidePosition;
/
手指按下X的坐标
/
private int downY;
/
手指按下Y的坐标
/
private int downX;
/
屏幕宽度
/
private int screenWidth;
/
ListView的item
/
private View itemView;
/
滑动类
/
private Scroller scroller;
private static final int SNAP_VELOCITY = 600;
/
速度追踪对象
/
private VelocityTracker velocityTracker;
/
是否响应滑动，默认为不响应
/
private boolean isSlide = false;
/
认为是用户滑动的最小距离
/
private int mTouchSlop;
/
移除item后的回调接口
/
private RemoveListener mRemoveListener;
/
用来指示item滑出屏幕的方向,向左或者向右,用一个枚举值来标记
/
private RemoveDirection removeDirection;

// 滑动删除方向的枚举值
public enum RemoveDirection {
RIGHT, LEFT;
}
public SlideCutListView(Context context) {
this(context, null);
}

public SlideCutListView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public SlideCutListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
screenWidth = ((WindowManager) contextgetSystemService(ContextWINDOW_SERVICE))getDefaultDisplay()getWidth();
scroller = new Scroller(context);
mTouchSlop = ViewConfigurationget(getContext())getScaledTouchSlop();
}

/
设置滑动删除的回调接口
@param removeListener
/
public void setRemoveListener(RemoveListener removeListener) {
thismRemoveListener = removeListener;
}

/
分发事件，主要做的是判断点击的是那个item, 以及通过postDelayed来设置响应左右滑动事件
/
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
switch (eventgetAction()) {
case MotionEventACTION_DOWN: {
addVelocityTracker(event);

// 假如scroller滚动还没有结束，我们直接返回
if (!scrollerisFinished()) {
return superdispatchTouchEvent(event);
}
downX = (int) eventgetX();
downY = (int) eventgetY();

slidePosition = pointToPosition(downX, downY);

// 无效的position, 不做任何处理
if (slidePosition == AdapterViewINVALID_POSITION) {
return superdispatchTouchEvent(event);
}

// 获取我们点击的item view
itemView = getChildAt(slidePosition - getFirstVisiblePosition());
break;
}
case MotionEventACTION_MOVE: {
if (Mathabs(getScrollVelocity()) > SNAP_VELOCITY
|| (Mathabs(eventgetX() - downX) > mTouchSlop && Math
abs(eventgetY() - downY) < mTouchSlop)) {
isSlide = true;
}
break;
}
case MotionEventACTION_UP:
recycleVelocityTracker();
break;
}

return superdispatchTouchEvent(event);
}

/
往右滑动，getScrollX()返回的是左边缘的距离，就是以View左边缘为原点到开始滑动的距离，所以向右边滑动为负值
/
private void scrollRight() {
removeDirection = RemoveDirectionRIGHT;
final int delta = (screenWidth + itemViewgetScrollX());
// 调用startScroll方法来设置一些滚动的参数，我们在computeScroll()方法中调用scrollTo来滚动item
scrollerstartScroll(itemViewgetScrollX(), 0, -delta, 0,
Mathabs(delta));
postInvalidate(); // 刷新itemView
}

/
向左滑动，根据上面我们知道向左滑动为正值
/
private void scrollLeft() {
removeDirection = RemoveDirectionLEFT;
final int delta = (screenWidth - itemViewgetScrollX());
// 调用startScroll方法来设置一些滚动的参数，我们在computeScroll()方法中调用scrollTo来滚动item
scrollerstartScroll(itemViewgetScrollX(), 0, delta, 0,
Mathabs(delta));
postInvalidate(); // 刷新itemView
}

/
根据手指滚动itemView的距离来判断是滚动到开始位置还是向左或者向右滚动
/
private void scrollByDistanceX() {
// 如果向左滚动的距离大于屏幕的三分之一，就让其删除
if (itemViewgetScrollX() >= screenWidth / 3) {
scrollLeft();
} else if (itemViewgetScrollX() <= -screenWidth / 3) {
scrollRight();
} else {
// 滚回到原始位置,为了偷下懒这里是直接调用scrollTo滚动
itemViewscrollTo(0, 0);
}

}

/
处理我们拖动ListView item的逻辑
/
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (isSlide && slidePosition != AdapterViewINVALID_POSITION) {
addVelocityTracker(ev);
final int action = evgetAction();
int x = (int) evgetX();
switch (action) {
case MotionEventACTION_MOVE:
int deltaX = downX - x;
downX = x;

// 手指拖动itemView滚动, deltaX大于0向左滚动，小于0向右滚
itemViewscrollBy(deltaX, 0);
break;
case MotionEventACTION_UP:
int velocityX = getScrollVelocity();
if (velocityX > SNAP_VELOCITY) {
scrollRight();
} else if (velocityX < -SNAP_VELOCITY) {
scrollLeft();
} else {
scrollByDistanceX();
}

recycleVelocityTracker();
// 手指离开的时候就不响应左右滚动
isSlide = false;
break;
}

return true; // 拖动的时候ListView不滚动
}

//否则直接交给ListView来处理onTouchEvent事件
return superonTouchEvent(ev);
}

@Override
public void computeScroll() {
// 调用startScroll的时候scrollercomputeScrollOffset()返回true，
if (scrollercomputeScrollOffset()) {
// 让ListView item根据当前的滚动偏移量进行滚动
itemViewscrollTo(scrollergetCurrX(), scrollergetCurrY());

postInvalidate();

// 滚动动画结束的时候调用回调接口
if (scrollerisFinished()) {
if (mRemoveListener == null) {
throw new NullPointerException(RemoveListener is null, we should called setRemoveListener());
}

itemViewscrollTo(0, 0);
mRemoveListenerremoveItem(removeDirection, slidePosition);
}
}
}

/
添加用户的速度跟踪器

@param event
/
private void addVelocityTracker(MotionEvent event) {
if (velocityTracker == null) {
velocityTracker = VelocityTrackerobtain();
}

velocityTrackeraddMovement(event);
}

/
移除用户速度跟踪器
/
private void recycleVelocityTracker() {
if (velocityTracker != null) {
velocityTrackerrecycle();
velocityTracker = null;
}
}

/
获取X方向的滑动速度,大于0向右滑动，反之向左

@return
/
private int getScrollVelocity() {
velocityTrackercomputeCurrentVelocity(1000);
int velocity = (int) velocityTrackergetXVelocity();
return velocity;
}

/

当ListView item滑出屏幕，回调这个接口
我们需要在回调方法removeItem()中移除该Item,然后刷新ListView

@author xiaanming

/
public interface RemoveListener {
public void removeItem(RemoveDirection direction, int position);
}

}

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