安卓开发 类似于扣扣 删除消息 时，滑动调出选项的功能实现

package com.example.sjd.danmu;

import android.content.Context;
import android.graphics.Color;
import android.support.v4.view.ViewConfigurationCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

/**
* Created by sjd on 2017/2/15.
*/

public class ScrollerLayout extends ViewGroup {
private static final String TAG = "ScrollerLayout";
Scroller mScroller;
int touchSlop;
private int vLeft;
private int vRight;
/**
* 手机按下时的屏幕坐标
*/
private float mXDown;

/**
* 手机当时所处的屏幕坐标
*/
private float mXMove;

/**
* 上次触发ACTION_MOVE事件时的屏幕坐标
*/
private float mXLastMove;
private int dx;

public ScrollerLayout(Context context, AttributeSet attrs) {

super(context, attrs);
mScroller=new Scroller(context);
ViewConfiguration viewConfiguration=ViewConfiguration.get(context);
touchSlop= viewConfiguration.getScaledPagingTouchSlop();
setBackgroundColor(Color.GREEN);

}

public ScrollerLayout(Context context) {
super(context,null);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
for (int i = 0; i < getChildCount(); i++) {
measureChild(getChildAt(i),widthMeasureSpec,heightMeasureSpec);
}
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if(changed){

for (int i = 0; i < getChildCount(); i++) {
View v= getChildAt(i);
if(i==1){
v.layout(getWidth(), 0, (i + 2) * v.getMeasuredWidth(), v.getMeasuredHeight());
}else {
v.layout(i * v.getMeasuredWidth(), 0, (i + 1) * v.getMeasuredWidth(), v.getMeasuredHeight());
}
Log.i(TAG, "onLayout:"+ i*v.getMeasuredWidth()  +"       " +  (i+1)*v.getMeasuredWidth()   + "       "  +   v.getMeasuredHeight() );
}
vLeft=getChildAt(0).getLeft();
vRight=getChildAt(getChildCount()-1).getRight();
}

}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
Log.i(TAG, "onInterceptTouchEvent:1 ");
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
mXDown = ev.getRawX();
mXLastMove = mXDown;
break;
case MotionEvent.ACTION_MOVE:
mXMove = ev.getRawX();
float diff = Math.abs(mXMove - mXDown);
mXLastMove = mXMove;
// 当手指拖动值大于TouchSlop值时，认为应该进行滚动，拦截子控件的事件
if (diff > touchSlop) {
return true;
}
break;
}
return super.onInterceptTouchEvent(ev);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
Log.i(TAG, "onTouchEvent: ");
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
return true;
case MotionEvent.ACTION_MOVE:
mXMove = event.getRawX();
int scrolledX = (int) (mXLastMove - mXMove);
if (getScrollX() + scrolledX < vLeft) {
scrollTo(vLeft, 0);
Log.i(TAG, "onTouchEvent1: "+vLeft);
return true;
} else if (getScrollX() + getWidth() + scrolledX > vRight) {
scrollTo(vRight - getWidth(), 0);
Log.i(TAG, "onTouchEvent2: "+(vRight - getWidth()));
return true;
}
scrollBy(scrolledX, 0);
Log.i(TAG, "onTouchEvent3: "+scrolledX);
mXLastMove = mXMove;
break;
case MotionEvent.ACTION_UP:
// 当手指抬起时，根据当前的滚动值来判定应该滚动到哪个子控件的界面
int targetIndex = (getScrollX() + getWidth() / 2) / getWidth();
dx = targetIndex * getWidth() - getScrollX();
// 第二步，调用startScroll()方法来初始化滚动数据并刷新界面
if(getScrollX()<660){
mScroller.startScroll(getScrollX(), 0, dx, 0);
}
else {
mScroller.startScroll(getScrollX(), 0, 0, 0);
}
Log.i(TAG, "onTouchEvent4: "+getScrollX()+   "    "+getWidth());
invalidate();
break;
}
return super.onTouchEvent(event);
}

void outSlide() {
scrollTo(dx,0);
mScroller.startScroll(dx,0,-dx,0);
}

@Override
public void computeScroll() {
// 第三步，重写computeScroll()方法，并在其内部完成平滑滚动的逻辑
if (mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
invalidate();
}
}

 public void scroll(View view) {scrollerLayout= (ScrollerLayout) findViewById(R.id.sc);Toast.makeText(this,((TextView)view).getText(),Toast.LENGTH_SHORT).show();scrollerLayout.outSlide();}