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();
        }
    }
}


<?xml version="1.0" encoding="utf-8"?>
<com.example.sjd.danmu.ScrollerLayout
    android:id="@+id/sc"
    android:descendantFocusability="beforeDescendants"
    xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
    android:layout_height="match_parent">
<TextView
    android:onClick="scroll"
    android:gravity="center"
    android:textSize="18sp"
    android:text="哈哈哈哈哈"
    android:layout_width="match_parent"
    android:layout_height="100dp" />
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="200dp"
        android:layout_height="100dp">
    <TextView
        android:onClick="scroll"

        android:layout_weight="1"
        android:gravity="center"
        android:text="删除"
        android:background="@color/colorAccent"
        android:layout_width="wrap_content"
        android:layout_height="100dp" />
        <TextView
            android:onClick="scroll"
            android:layout_weight="1"
            android:gravity="center"
            android:text="置顶"
            android:background="@color/colorPrimaryDark"
            android:layout_width="wrap_content"
            android:layout_height="100dp" />
    </LinearLayout>
</com.example.sjd.danmu.ScrollerLayout>


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

    }