Android自定义View实现可以拖拽的GridView

先看看效果图

主要思想：

1、监听触碰事件
2、用WindowManager添加拖曳的图片
3、用Collections.swap()交换List数据

自定义代码：

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);
  }
}

使用方法：

   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();
      }
    });

附录：

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

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