实现拖拽删除的TouchListener

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。

实现拖拽删除的TouchListener

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