Question

I currently have something working where I can drag a box horizontally on the screen (what I want it to do). However, it works when you click ANYWHERE on the screen, and I want it to work only when the box has been clicked. I have tried implementing this in different ways, and I’ve looked all over the place and still remain lost. Can anybody help? I also can’t figure out how a bitmap is placed (I’m using a bitmap right now as I can’t for the life of me figure out how to implement the ImageView inside my SurfaceView). If I say my bitmap is placed at 0,0 will that place the bitmap according to its top left corner at 0,0? I also had an algorithm for stopping the box when it reached an edge, but I’ll just have to rewrite that as I must have deleted it. Please if you can offer your knowledge I would GREATLY appreciate it

public class BoardView extends SurfaceView implements SurfaceHolder.Callback{
    Context mContext;

    private BoardThread thread;
    private float box_x = 140;
    private float box_y = 378;
    ImageView i = (ImageView) findViewById(R.id.box_view);

    Bitmap box = 
        (BitmapFactory.decodeResource
                (getResources(), R.drawable.box));
    private float boxWidth = box.getWidth();
    private float boxHeight = box.getHeight();



    public BoardView(Context context){
        super(context);
        //surfaceHolder provides canvas that we draw on
        getHolder().addCallback(this);
        // controls drawings
        thread = new BoardThread(getHolder(),this);
        //intercepts touch events
        setFocusable(true);

    }


    @Override

    public void onDraw(Canvas canvas){
        canvas.drawColor(Color.WHITE);  


        //draw box and set start location
        canvas.drawBitmap(box, box_x - (boxWidth/2), 
                box_y - (boxHeight/2), null);






    }

    @Override
    public boolean onTouchEvent(MotionEvent event){

        //boolean mode = false;

        if(event.getAction() == MotionEvent.ACTION_DOWN){
            //int x = (int)event.getX();
            //int y = (int)event.getY();

            //if (x > box_x && x < box_x + 29 && y > box_y && y < box_y + 30){
                //mode = true;
                box_x = (int)event.getX();
            //}
        }

        if(event.getAction() == MotionEvent.ACTION_MOVE) {
            //int x = (int)event.getX();
            //int y = (int)event.getY();

            //if (mode == true){
                box_x = (int)event.getX();
            //}
        }

        invalidate();

        return true;
    }


    @Override
    public void surfaceChanged(SurfaceHolder holder, 
            int format, int width, int height ){

    }


    @Override
    public void surfaceCreated(SurfaceHolder holder){
        thread.startRunning(true);
        thread.start();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder){
        thread.startRunning(false);
        thread.stop();
    }



}

Answer 1

Simply check the touch event x and y coordinate, and check if this x,y-combination is within the box’s bounds. I can see you are on the right path by looking at your commented out code.

Do something like this:

RectF rect = new RectF(x,y, x + box.getWidth(), y+box.geHeight());

if(rect.contains(touchX, touchY)) {
    // You hit the box, allow dragging...
}