Android 可拖拽的GridView效果实现, 长按可拖拽和item实时交换

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修复点击空白处滑动crash的bug.

case MotionEvent.ACTION_MOVE:

if (mDragPosition == AdapterView.INVALID_POSITION) {

return super.dispatchTouchEvent(ev);

}

int moveX = (int) ev.getX();

int moveY = (int) ev.getY();

//如果我们在按下的item上面移动，只要不超过item的边界我们就不移除mRunnable

if (!isTouchInItem(mStartDragItemView, moveX, moveY)) {

mHandler.removeCallbacks(mLongClickRunnable);

}

break;

case MotionEvent.ACTION_UP:

if (mDragPosition == AdapterView.INVALID_POSITION) {

return super.dispatchTouchEvent(ev);

}

mHandler.removeCallbacks(mLongClickRunnable);

mHandler.removeCallbacks(mScrollRunnable);

break;

}

return super.dispatchTouchEvent(ev);

}

//用来处理是否为长按的Runnable

private Runnable mLongClickRunnable = new Runnable() {

@Override

public void run() {

isDrag = true; //设置可以拖拽

mVibrator.vibrate(50); //震动一下

if (mStartDragItemView != null) {

mStartDragItemView.setVisibility(View.INVISIBLE);//隐藏该item

//根据我们按下的点显示item镜像

createDragImage(mDragBitmap, mDownX, mDownY);

}

}

};