Android自定义View实现可以拖拽的GridView

public class DragGridVeiw extends GridView {

 private final int PRESS_TIME = 1000;//长按时间

 private int mDownX;//触碰时的X坐标
 private int mDownY;//触碰时的Y坐标
 private int mMoveX;//移动时的X坐标
 private int mMoveY;//移动时的Y坐标

 private int mOffset2Top;//DragGridView距离屏幕顶部的偏移量
 private int mOffset2Left;//DragGridView距离屏幕左边的偏移量
 private int mPointToItemTop;//触碰点距离ItemView的上边距
 private int mPointToItemLeft;//触碰点距离ItemView的左边距
 private int mStatusHeight;//状态栏高度

 private boolean isDraging;//是否正在拖曳

 private Bitmap mBitmap;//ItemView的图片
 private int mTouchPostiion;//触碰的位置
 private View mTouchItemView;//触碰的ItemView

 private Vibrator mVibrator;//震动器
 private ImageView mDragImageView;//拖曳的View
 private WindowManager mWindowManager;//窗口管理器
 private WindowManager.LayoutParams mWindowLayoutParams;//窗口管理器布局

 private OnChanageListener onChanageListener;//交换事件监听器

 private Handler mHandler = new Handler();


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

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

 public DragGridVeiw(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  mStatusHeight = getStatusHeight(context);
  mVibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
  mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
 }


 @Override
 public boolean dispatchTouchEvent(MotionEvent ev) {
  switch (ev.getAction()) {
   case MotionEvent.ACTION_DOWN:
    //使用Handler延迟dragResponseMS执行mLongClickRunnable
    mHandler.postDelayed(mLongClickRunnable, PRESS_TIME);

    mDownX = (int) ev.getX();
    mDownY = (int) ev.getY();

    //根据按下的X,Y坐标获取所点击item的position
    mTouchPostiion = pointToPosition(mDownX, mDownY);

    if (mTouchPostiion == AdapterView.INVALID_POSITION) {
     return super.dispatchTouchEvent(ev);
    }

    //根据position获取该item所对应的View
    mTouchItemView = getChildAt(mTouchPostiion - getFirstVisiblePosition());

    //下面这几个距离大家可以参考我的博客上面的图来理解下
    mPointToItemTop = mDownY - mTouchItemView.getTop();
    mPointToItemLeft = mDownX - mTouchItemView.getLeft();

    mOffset2Top = (int) (ev.getRawY() - mDownY);
    mOffset2Left = (int) (ev.getRawX() - mDownX);

    //开启mDragItemView绘图缓存
    mTouchItemView.setDrawingCacheEnabled(true);
    //获取mDragItemView在缓存中的Bitmap对象
    mBitmap = Bitmap.createBitmap(mTouchItemView.getDrawingCache());
    //这一步很关键，释放绘图缓存，避免出现重复的镜像
    mTouchItemView.destroyDrawingCache();

    break;
   case MotionEvent.ACTION_MOVE:
    int moveX = (int) ev.getX();
    int moveY = (int) ev.getY();

    //拖曳点超出GridView区域则取消拖曳事件
    if (ev.getY() > getHeight() || ev.getY() < 0) {
     onStopDrag();
    }

    //如果我们在按下的item上面移动，只要超过item的边界就移除mRunnable
    if (!isTouchInItem(mTouchItemView, moveX, moveY)) {
     mHandler.removeCallbacks(mLongClickRunnable);
    }
    break;
   case MotionEvent.ACTION_UP:
    mHandler.removeCallbacks(mLongClickRunnable);
    break;
  }
  return super.dispatchTouchEvent(ev);
 }

 @Override
 public boolean onTouchEvent(MotionEvent ev) {
  if (isDraging && mDragImageView != null) {
   switch (ev.getAction()) {
    case MotionEvent.ACTION_MOVE:
     mMoveX = (int) ev.getX();
     mMoveY = (int) ev.getY();
     //拖动item
     onDragItem(mMoveX, mMoveY);
     break;
    case MotionEvent.ACTION_UP:
     onStopDrag();

     break;
   }
   return true;
  }
  return super.onTouchEvent(ev);
 }


 //处理长按事件的线程
 private Runnable mLongClickRunnable = new Runnable() {
  @Override
  public void run() {
   isDraging = true; //设置可以拖拽
   mVibrator.vibrate(50); //震动一下
   mTouchItemView.setVisibility(View.INVISIBLE);//隐藏该ItemView

   //根据我们按下的点显示ItemView镜像
   createDragView(mBitmap, mDownX, mDownY);
  }
 };


 //添加拖动View
 private void createDragView(Bitmap bitmap, int downX, int downY) {
  mWindowLayoutParams = new WindowManager.LayoutParams();
  mWindowLayoutParams.format = PixelFormat.TRANSLUCENT; //图片之外的其他地方透明
  mWindowLayoutParams.gravity = Gravity.TOP | Gravity.LEFT;
  mWindowLayoutParams.x = downX - mPointToItemTop + mOffset2Left;
  mWindowLayoutParams.y = downY - mPointToItemTop + mOffset2Top - mStatusHeight;
  mWindowLayoutParams.alpha = 0.6f; //透明度
  mWindowLayoutParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
  mWindowLayoutParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
  mWindowLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
    | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;

  mDragImageView = new ImageView(getContext());
  mDragImageView.setImageBitmap(bitmap);
  mWindowManager.addView(mDragImageView, mWindowLayoutParams);
 }


 private void removeDragView() {
  if (mDragImageView != null) {
   mWindowManager.removeView(mDragImageView);
   mDragImageView = null;
  }
 }

 //是否点击在GridView的item上面
 private boolean isTouchInItem(View dragView, int x, int y) {
  int leftOffset = dragView.getLeft();
  int topOffset = dragView.getTop();
  if (x < leftOffset || x > leftOffset + dragView.getWidth()) {
   return false;
  }
  if (y < topOffset || y > topOffset + dragView.getHeight()) {
   return false;
  }
  return true;
 }

 //拖动事件处理
 private void onDragItem(int moveX, int moveY) {
  mWindowLayoutParams.x = moveX - mPointToItemLeft + mOffset2Left;
  mWindowLayoutParams.y = moveY - mPointToItemTop + mOffset2Top - mStatusHeight;
  mWindowManager.updateViewLayout(mDragImageView, mWindowLayoutParams); //更新DragView的位置
  onSwapItem(moveX, moveY);//Item的相互交换
 }

 //交换item,并且控制item之间的显示与隐藏效果
 private void onSwapItem(int moveX, int moveY) {
  //获取我们手指移动到的那个item的position
  int tempPosition = pointToPosition(moveX, moveY);

  //假如tempPosition 改变了并且tempPosition不等于-1,则进行交换
  if (tempPosition != mTouchPostiion && tempPosition != AdapterView.INVALID_POSITION) {
   getChildAt(tempPosition - getFirstVisiblePosition()).setVisibility(View.INVISIBLE);//拖动到了新的item,新的item隐藏掉
   getChildAt(mTouchPostiion - getFirstVisiblePosition()).setVisibility(View.VISIBLE);//之前的item显示出来

   if (onChanageListener != null) {
    onChanageListener.onChange(mTouchPostiion, tempPosition);
   }

   mTouchPostiion = tempPosition;
  }
 }

 //停止拖拽我们将之前隐藏的item显示出来，并将DragView移除
 private void onStopDrag() {
  isDraging = false;
  getChildAt(mTouchPostiion - getFirstVisiblePosition()).setVisibility(View.VISIBLE);
  removeDragView();
 }

 //Item交换事件监听
 public void setOnChangeListener(OnChanageListener onChanageListener) {
  this.onChanageListener = onChanageListener;
 }

 //获取状态栏高度
 private int getStatusHeight(Context context) {
  int statusHeight = 0;
  Rect localRect = new Rect();
  ((Activity) context).getWindow().getDecorView().getWindowVisibleDisplayFrame(localRect);
  statusHeight = localRect.top;
  if (0 == statusHeight) {
   Class<?> localClass;
   try {
    localClass = Class.forName("com.android.internal.R$dimen");
    Object localObject = localClass.newInstance();
    int i5 = Integer.parseInt(localClass.getField("status_bar_height").get(localObject).toString());
    statusHeight = context.getResources().getDimensionPixelSize(i5);
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
  return statusHeight;
 }

 //当item交换位置的时候回调的方法，我们只需要在该方法中实现数据的交换即可
 public interface OnChanageListener {
  public void onChange(int from, int to);
 }
}

  List<HashMap<String, Object>> dataSourceList = new ArrayList<>();

  dragVeiw = (DragGridVeiw) findViewById(R.id.view_drag);

  for (int i = 0; i < 8; i++) {
   HashMap<String, Object> itemHashMap = new HashMap<>();
   itemHashMap.put("item_image", R.drawable.sample_1);
   itemHashMap.put("item_text", "拖拽 " + Integer.toString(i));
   dataSourceList.add(itemHashMap);
  }

  final SimpleAdapter mSimpleAdapter = new SimpleAdapter(this, dataSourceList,
    R.layout.item_drag, new String[]{"item_image", "item_text"},
    new int[]{R.id.item_image, R.id.item_text});

  dragVeiw.setAdapter(mSimpleAdapter);

  dragVeiw.setOnChangeListener(new DragGridVeiw.OnChanageListener() {
   @Override
   public void onChange(int from, int to) {
    HashMap<String, Object> temp = dataSourceList.get(from);
    //这里的处理需要注意下
    if (from < to) {
     for (int i = from; i < to; i++) {
      Collections.swap(dataSourceList, i, i + 1);
     }
    } else if (from > to) {
     for (int i = from; i > to; i--) {
      Collections.swap(dataSourceList, i, i - 1);
     }
    }

    dataSourceList.set(to, temp);
    mSimpleAdapter.notifyDataSetChanged();
   }
  });

Log.v("-->getWidth", String.valueOf(getWidth()));//DragView的宽度
Log.v("-->getHeight", String.valueOf(getHeight()));//DragView的高度
Log.v("-->getLeft", String.valueOf(getLeft()));//DragView左边距离屏幕左侧的长度
Log.v("-->getTop", String.valueOf(getTop()));///DragView上边距离屏幕顶部的长度
Log.v("-->getRawX", String.valueOf(ev.getRawX()));//触碰点相对于屏幕的X坐标
Log.v("-->getRawY", String.valueOf(ev.getRawY()));//触碰点相对于屏幕的Y坐标
Log.v("-->getX", String.valueOf(ev.getX()));//触碰点相对于DragView的X坐标
Log.v("-->getY", String.valueOf(ev.getY()));//触碰点相对于DragView的Y坐标

Log.v("-->getItemWidth", String.valueOf(mTouchItemView.getWidth()));//DragView中ItemView的宽度
Log.v("-->getItemHeight", String.valueOf(mTouchItemView.getHeight()));//DragView中ItemView的高度
Log.v("-->getItemLeft", String.valueOf(mTouchItemView.getLeft()));//DragView中ItemView左边距离DragView左侧的长度
Log.v("-->getItemTop", String.valueOf(mTouchItemView.getTop()));//DragView中ItemView上边距离DragView顶部的长度