拖动按钮要离开屏幕了吗？

Question

我有一个按钮，可以拖到屏幕的任意位置，但是拖的时候会到屏幕外，所以怎么只拖到屏幕里面，才不会拖到屏幕外

Button.setOnTouchListener(new TextView.OnTouchListener() {
        public boolean onTouch(View view, MotionEvent event) {              

            X_button = (int) event.getRawX();
            Y_button= (int) event.getRawY();


            switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:

                RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                _xDelta = X_button - lParams.leftMargin;
                _yDelta = Y_button - lParams.topMargin;
                break;
            case MotionEvent.ACTION_UP:                 
                 if(!isMoving)
                 {
                    view.performClick();                        
                 }  

                 isMoving=false;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                break;
            case MotionEvent.ACTION_POINTER_UP:
                break;
            case MotionEvent.ACTION_MOVE:                   
                isMoving=true;                  
                RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
                        .getLayoutParams();
                layoutParams.leftMargin = X_button - _xDelta;
                layoutParams.topMargin = Y_button - _yDelta;
                layoutParams.rightMargin = -250;
                layoutParams.bottomMargin = -250;
                view.setLayoutParams(layoutParams);

                break;
            }
            return true;
        }
    });

Answer 1

将 OnTouch 监听器部分修改为：

 DisplayMetrics displaymetrics = new DisplayMetrics();
 getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
 screenHight = displaymetrics.heightPixels;
 screenWidth = displaymetrics.widthPixels;

  @SuppressLint("NewApi") @Override
  public boolean onTouch(View view, MotionEvent event) {


       float newX, newY;

    switch (event.getActionMasked()) {
      case MotionEvent.ACTION_DOWN:

        dX = view.getX() - event.getRawX();
        dY = view.getY() - event.getRawY();
        lastAction = MotionEvent.ACTION_DOWN;
        break;

      case MotionEvent.ACTION_MOVE:

          newX = event.getRawX() + dX;
          newY = event.getRawY() + dY;

      // check if the view out of screen
          if ((newX <= 0 || newX >= screenWidth-view.getWidth()) || (newY <= 0 || newY >= screenHight-view.getHeight()))
          {
              lastAction = MotionEvent.ACTION_MOVE;
              break;      
          }

        view.setX(newX);
        view.setY(newY);

        lastAction = MotionEvent.ACTION_MOVE;

        break;

      case MotionEvent.ACTION_UP:
        if (lastAction == MotionEvent.ACTION_DOWN)
          Toast.makeText(DraggableView.this, "Clicked!", Toast.LENGTH_SHORT).show();
        break;

      default:
        return false;
    }
    return true;
  }

请参考此解决方案，当拖动图像时，图像会停留在屏幕上。 https://stackoverflow.com/a/36417605/4324288

Answer 2

首先，使用View.setX()、View.setY()、View.setTranslateX()、View.setTranslateY()方法在屏幕上移动视图，而不是更新LayoutParams的边距。我发现它们的表现更流畅。

其次，为了将视图限制为可用窗口，请使用以下函数获取可用窗口大小：

DisplayMetrics metrics = getResources().getDisplayMetrics();
int windowWidth = metrics.widthPixels;
int windowHeight = metrics.heightPixels

接下来，在您的 onTouch 方法中，计算目标位置是否超过上述尺寸。例如：

if( currentXLocation + deltaX > windowWidth ){

    // this will ensure that target location 
    // is always <= windowHeight
    deltaX = windowWidth - currentXLocation; 

} else if( currentXLocation + deltaX < 0){

    deltaX = -(currentXLocation);

} else if (...){

    // perform similar calculations for the rest 

}

Answer 3

注册只是为了回答这个问题，因为在整个互联网上发现相同的，不幸的是错误的答案感到沮丧。

要处理在视图之外绘制的对象，请为对象设置 OnDragListener，然后从那里调用处理程序 - 如果不使用处理程序，它将崩溃 - 并将视图 ID 传递给处理程序。除了，我发现您的用户还可以通过同时触摸两个按钮来搞砸工作，并且当您切换活动时，如果用户正在触摸屏幕，那么您也可以通过这种方式丢失对象 - 所以最有效的是我的从拖动侦听器 ACTION_DRAG_ENDED 调用处理程序，触摸侦听器 ACTION_UP 只是确保应该可见的所有内容都是。这样，每次用户停止触摸屏幕时，它都会修复他/她所做的一切。

private final class MyTouchListener implements OnTouchListener {
    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        switch (motionEvent.getAction()) {
            case MotionEvent.ACTION_DOWN:
                ClipData data = ClipData.newPlainText("", "");
                DragShadowBuilder shadowBuilder = new DragShadowBuilder(view);
                view.startDrag(data, shadowBuilder, view, 0);
                view.setVisibility(View.INVISIBLE);
                return true;
            case MotionEvent.ACTION_UP:
                drophandler.sendEmptyMessage(0);
            case MotionEvent.ACTION_MOVE:
                return true;
            default:
                break;
            }
        return true;
    }
}

class MyDragListener implements OnDragListener {
    @Override
    public boolean onDrag(View v, DragEvent event) {
        View view = (View) event.getLocalState();
        Button drag = (Button) view;
        int action = event.getAction();

        switch (event.getAction()) {
            case DragEvent.ACTION_DRAG_STARTED:
                break;
            case DragEvent.ACTION_DRAG_ENTERED:
                break;
            case DragEvent.ACTION_DRAG_EXITED:
                break;
            case DragEvent.ACTION_DROP:
                Button target = (Button) v;
                //do stuff
                return true;
            case DragEvent.ACTION_DRAG_ENDED:
                drophandler.sendEmptyMessage(0);
                return true;
            default:
                break;
        }
        return true;
    }
}

private Handler drophandler = new Handler() {
    public void handleMessage(android.os.Message msg) {
        for(int x = 0; x < 3 + difficulty; x++){
            for(int y = 0; y < 5 + difficulty; y++){
                if (buttons[x][y] != null){
                    buttons[x][y].setVisibility(View.VISIBLE);
                }
            }
        }
    }
};