Android 实现左滑出现删除选项

滑动删除的部分主要包含两个部分， 一个是内容区域（用于放置正常显示的view），另一个是操作区域（用于放置删除按钮）。默认情况下，操作区域是不显示的，内容区域的大小是填充整个容 器，操作区域始终位于内容区域的右面。当开始滑动的时候，整个容器中的所有子view都像左滑动，如果操作区域此时是不可见的，设置为可见。

实现思路就是自定义一个layout SwipeLayout继承自FrameLayout。SwipeLayout包含两个子view，第一个子view是内容区域，第二个子view是操作 区域。滑动效果的控制，主要就是通过检测SwipeLayout的touch事件来实现，Android support库里其实已经提供了ViewDragHelper来进行监听touch事件。

1、首先需要对LinearLayout进行重载

具体分析看注解

package com.example.Mac.agriculturemanagement;import android.content.Context;import android.support.annotation.Nullable;import android.support.v4.view.ViewCompat;import android.support.v4.widget.ViewDragHelper;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import android.widget.LinearLayout;//条目滑动效果public class SlideLayout extends LinearLayout {  private ViewDragHelper mDragHelper;  private View contentView;  private View actionView;  private int dragDistance;  private final double AUTO_OPEN_SPEED_LIMIT = 800.0;  private int draggedX;  public SlideLayout(Context context) {    super(context);    init();  }  public SlideLayout(Context context, @Nullable AttributeSet attrs) {    super(context, attrs);    init();  }  public SlideLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    init();  }  //初始化  public void init (){    mDragHelper = ViewDragHelper.create(this, new DragHelperCallback());  }  @Override  public boolean callOnClick() {    return super.callOnClick();  }     //把容器的事件处理委托给ViewDragHelper对象  @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;  }  @Override  protected void onFinishInflate() {    contentView = getChildAt(0);    actionView = getChildAt(1);    actionView.setVisibility(GoNE);  }   //设置拖动的距离为actionView的宽度   @Override   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    dragDistance = actionView.getMeasuredWidth();    //System.out.println("rightTop"+actionView.getTop());   }  private class DragHelperCallback extends ViewDragHelper.Callback {    //用来确定contentView和actionView是可以拖动的    @Override    public boolean tryCaptureView(View view, int i) {      return view == contentView || view == actionView;    }    //被拖动的view位置改变的时候调用，如果被拖动的view是contentView，    // 我们需要在这里更新actionView的位置    @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);      }      //actionView 是否可见      //0  --------  VISIBLE  可见      //4  --------  INVISIBLE  不可见但是占用布局空间      //8  --------  GONE  不可见也不占用布局空间      if (actionView.getVisibility() == View.GONE) {        actionView.setVisibility(View.VISIBLE);      }      if (left==25)      {        actionView.setVisibility(View.GONE);      }      invalidate(); //刷新View    }    //用来限制view在x轴上拖动    //@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), 25);        //System.out.println("content "+newLeft);        return newLeft;      } else {        //getMeasuredWidth()获取全部长度 包括隐藏的        final int minLeftBound = getPaddingLeft() + contentView.getMeasuredWidth() - dragDistance;        final int maxLeftBound = getPaddingLeft() + contentView.getMeasuredWidth() + getPaddingRight();        final int newLeft = Math.min(Math.max(left, minLeftBound), maxLeftBound);        System.out.println("action "+newLeft);        return newLeft;      }    }    @Override    public int clampViewPositionVertical(View child, int top, int dy) {      //System.out.println("top "+top);      if(top!=25)      {        top=25;      }      return top;    }    //用来限制view可以拖动的范围    //@Override    public int getViewHorizontalDragRange(View child) {      return dragDistance;    }    @Override    public int getViewVerticalDragRange(View child) {      return 0;    }    //根据滑动手势的速度以及滑动的距离来确定是否显示actionView。    // smoothSlideViewTo方法用来在滑动手势之后实现惯性滑动效果    //@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;      mDragHelper.smoothSlideViewTo(contentView, settleDestX, 0);      ViewCompat.postInvalidateOnAnimation(SlideLayout.this);    }  }}