Android listview 右滑删除

这次交大家使用listview的右滑删除，其实也非常简单， 

首先需要自定义listview,具体代码如下：

package com.example.myapp;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Scroller;


public class SlideListView extends ListView {

    private int slidePosition;

    private int downY;

    private int downX;

    private int screenWidth;

    private View itemView;

    private Scroller scroller;
    private static final int SNAP_VELOCITY = 600;

    private VelocityTracker velocityTracker;

    private boolean isSlide = false;

    private int mTouchSlop;

    private RemoveListener mRemoveListener;

    private boolean isRemove = false;

    private RemoveDirection removeDirection;


    public enum RemoveDirection {
        RIGHT, LEFT, NONE;
    }


    public SlideListView(Context context) {
        this(context, null);
    }

    public SlideListView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public SlideListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        screenWidth = ((WindowManager) context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getWidth();
        scroller = new Scroller(context);
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }


    public void setRemoveListener(RemoveListener removeListener) {
        this.mRemoveListener = removeListener;
    }


    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN: {
            addVelocityTracker(event);


            if (!scroller.isFinished()) {
                return false;
            }
            downX = (int) event.getX();
            downY = (int) event.getY();

            slidePosition = pointToPosition(downX, downY);


            if (slidePosition == AdapterView.INVALID_POSITION) {
                return super.dispatchTouchEvent(event);
            }


            itemView = getChildAt(slidePosition - getFirstVisiblePosition());
            break;
        }
        case MotionEvent.ACTION_MOVE: {
            if (Math.abs(getScrollVelocity()) > SNAP_VELOCITY
                    || (Math.abs(event.getX() - downX) > mTouchSlop && Math
                            .abs(event.getY() - downY) < mTouchSlop)) {
                isSlide = true;

            }
            break;
        }
        case MotionEvent.ACTION_UP:
            recycleVelocityTracker();
            break;
        }

        return super.dispatchTouchEvent(event);
    }


    private void scrollRight() {
        removeDirection = RemoveDirection.RIGHT;
        final int delta = (screenWidth + itemView.getScrollX());
                scroller.startScroll(itemView.getScrollX(), 0, -delta, 0,
                Math.abs(delta));
        postInvalidate();
    }


    private void scrollLeft() {
        removeDirection = RemoveDirection.LEFT;
        final int delta = (screenWidth - itemView.getScrollX());

        scroller.startScroll(itemView.getScrollX(), 0, delta, 0,
                Math.abs(delta));
        postInvalidate();
    }


    private void scrollBack(){
        removeDirection = RemoveDirection.NONE;
        scroller.startScroll(itemView.getScrollX(), 0, -itemView.getScrollX(), 0,
                Math.abs(itemView.getScrollX()));
        postInvalidate();
    }


    private void scrollByDistanceX() {

        if (itemView.getScrollX() >= screenWidth / 2) {
            scrollLeft();
        } else if (itemView.getScrollX() <= -screenWidth / 2) {
            scrollRight();
        } else {

            scrollBack();
        }

    }


    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (isSlide && slidePosition != AdapterView.INVALID_POSITION) {
            requestDisallowInterceptTouchEvent(true);
            addVelocityTracker(ev);
            final int action = ev.getAction();
            int x = (int) ev.getX();
            switch (action) {
            case MotionEvent.ACTION_DOWN:
                System.out.println("touch-->" + "down");
                break;
            case MotionEvent.ACTION_MOVE:
                System.out.println("touch-->" + "move");
                MotionEvent cancelEvent = MotionEvent.obtain(ev);
                cancelEvent.setAction(MotionEvent.ACTION_CANCEL |
                           (ev.getActionIndex()<< MotionEvent.ACTION_POINTER_INDEX_SHIFT));
                onTouchEvent(cancelEvent);

                int deltaX = downX - x;


                itemView.scrollTo(deltaX, 0);

                itemView.setAlpha(1f - Math.abs((float)deltaX/screenWidth));

                return true;
            case MotionEvent.ACTION_UP:

                isSlide = false;
                int velocityX = getScrollVelocity();
                if (velocityX > SNAP_VELOCITY) {
                    scrollRight();
                } else if (velocityX < -SNAP_VELOCITY) {
                    scrollLeft();
                } else {
                    scrollByDistanceX();
                }

                recycleVelocityTracker();

                break;
            }
        }


        return super.onTouchEvent(ev);
    }

    @Override
    public void computeScroll() {

        if (scroller.computeScrollOffset()) {

            itemView.scrollTo(scroller.getCurrX(), scroller.getCurrY());

            itemView.setAlpha(1f - Math.abs((float)scroller.getCurrX()/screenWidth));

            postInvalidate();


            if (scroller.isFinished() && removeDirection != RemoveDirection.NONE) {
                if (mRemoveListener == null) {
                    throw new NullPointerException("RemoveListener is null, we should called setRemoveListener()");
                }
                itemView.scrollTo(0, 0);
                itemView.setAlpha(1f);
                mRemoveListener.removeItem(removeDirection, slidePosition);
            }
        }
    }


    private void addVelocityTracker(MotionEvent event) {
        if (velocityTracker == null) {
            velocityTracker = VelocityTracker.obtain();
        }

        velocityTracker.addMovement(event);
    }


    private void recycleVelocityTracker() {
        if (velocityTracker != null) {
            velocityTracker.recycle();
            velocityTracker = null;
        }
    }


    private int getScrollVelocity() {
        velocityTracker.computeCurrentVelocity(1000);
        int velocity = (int) velocityTracker.getXVelocity();
        return velocity;
    }


    public interface RemoveListener {
        public void removeItem(RemoveDirection direction, int position);
    }

}

然后使用SlideListView .setRemoveListener listview的这个方法就可以实现listview的右滑删除了。