Android TouchListener实现拖拽删实例代码

Android TouchListener实现拖拽删实例代码

如果为一个控件设置了该触摸监听， 控件会随着用户的拖动而移动， 如果拖动的距离大过设置的临界值， 那么当松开手指时会有回调onDragComplete, 用户可在该方法中将该控件从父布局中删除， 或这进行其他操作。 如果用户拖拽的距离小于临界值， 那么当用户松开手指时控件会回谈到原来的初始位置。这时会触发onDragRebound回调。 如果用户触摸控件之后没有拖拽而是直接松开手指， 会触发onClick回调， 这样用户就不用为该控件设置onClick监听。

源码如下：

import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup; 

/**
 * Created by zhangjg on 14-10-10.
 */
public class DragTouchListener implements View.OnTouchListener { 

  /**
   * drag directions
   */
  public static final int DIRECTION_UP = 0;
  public static final int DIRECTION_DOWN = 1;
  public static final int DIRECTION_LEFT = 2;
  public static final int DIRECTION_RIGHT = 3; 

  private int mDragDirection = -1;
  private int mDragDistance = -1;
  private ViewGroup.MarginLayoutParams mParams;
  private ViewGroup.MarginLayoutParams mOriginParams; 

  private int viewOriginMargin = -1000; 

  private float mStartY = 0;
  private float mStartX = 0;
  private boolean isTouched = false; 

  public DragTouchListener(int dragDirection, int dragDistance){
    mDragDirection = dragDirection;
    mDragDistance = dragDistance;
  } 

  protected void onClick(View view){ 

  } 

  protected void onDragComplete(View view){ 

  } 

  protected void onDragRebound(View view){ 

  } 

  @Override
  public boolean onTouch(View view, MotionEvent motionEvent) { 

    if (viewOriginMargin == -1000){
      mParams = (ViewGroup.MarginLayoutParams)view.getLayoutParams();
      if (mDragDirection == DIRECTION_UP) {
        viewOriginMargin = mParams.bottomMargin;
      }else if (mDragDirection == DIRECTION_DOWN){
        viewOriginMargin = mParams.topMargin;
      }else if (mDragDirection == DIRECTION_LEFT){
        viewOriginMargin = mParams.rightMargin;
      }else if (mDragDirection == DIRECTION_RIGHT){
        viewOriginMargin = mParams.leftMargin;
      }
    } 

    int action = motionEvent.getAction();
    switch (action){
      case MotionEvent.ACTION_DOWN:
        isTouched = true;
        mStartY = motionEvent.getY();
        mStartX = motionEvent.getX();
        return true;
      case MotionEvent.ACTION_MOVE:
        float y = motionEvent.getY();
        float x = motionEvent.getX(); 

        if (mDragDirection == DIRECTION_UP){
          if(y < mStartY){
            mParams.bottomMargin = viewOriginMargin +(int) (mStartY - y);
          }
        }else if (mDragDirection == DIRECTION_DOWN){
          if (y > mStartY){
            mParams.topMargin = viewOriginMargin + (int) (y - mStartY);
          }
        }else if (mDragDirection == DIRECTION_LEFT){
          if (x < mStartX){
            mParams.rightMargin = viewOriginMargin + (int) (mStartX - x);
          }
        }else if (mDragDirection == DIRECTION_RIGHT){
          if (x > mStartX){
            mParams.leftMargin = viewOriginMargin + (int) (x - mStartX);
          }
        } 

        view.setLayoutParams(mParams);
        break;
      case MotionEvent.ACTION_UP:
        float nowY = motionEvent.getY();
        float nowX = motionEvent.getX(); 

        int deltaX = (int)nowX - (int)mStartX;
        int deltaY = (int)nowY - (int)mStartY; 

        if (isTouched && Math.abs(deltaX) < 5 && Math.abs(deltaY) < 5){
          onClick(view);
          break;
        } 

        if (mDragDirection == DIRECTION_UP){
          if (isTouched && mStartY - nowY > mDragDistance){ 

//            Log.i("test-drag", "direction up , startY = " + mStartY + ", nowY = " + nowY +
//                ", startY - nowY = " + (mStartY - nowY) + ", dragDistance : " + mDragDistance);
            onDragComplete(view); 

          }else if (mStartY - nowY > 0 && mStartY - nowY < mDragDistance ){
            mParams.bottomMargin = viewOriginMargin;
            view.setLayoutParams(mParams);
            onDragRebound(view);
          }
        }else if (mDragDirection == DIRECTION_DOWN){ 

          if (isTouched && nowY - mStartY > mDragDistance){
            onDragComplete(view);
          }else if ( nowY - mStartY > 0 && nowY - mStartY < mDragDistance ){
            mParams.topMargin = viewOriginMargin;
            view.setLayoutParams(mParams);
            onDragRebound(view);
          }
        }else if (mDragDirection == DIRECTION_LEFT){
          if (isTouched && mStartX - nowX > mDragDistance){
            onDragComplete(view);
          }else if ( mStartX - nowX > 0 && mStartX - nowX < mDragDistance ){
            mParams.rightMargin = viewOriginMargin;
            view.setLayoutParams(mParams);
            onDragRebound(view);
          }
        }else if (mDragDirection == DIRECTION_RIGHT){
          if (isTouched && nowX - mStartX > mDragDistance){
            onDragComplete(view);
          }else if ( nowX - mStartX > 0 && nowX - mStartX < mDragDistance ){
            mParams.leftMargin = viewOriginMargin;
            view.setLayoutParams(mParams);
            onDragRebound(view);
          }
        } 

        isTouched = false; 

        break;
    }
    return false;
  }
}

在使用时继承该类， 并覆盖三个回调方法， 就可以在合适的时机得到回调。

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