Question

I want to rotate the canvas circularly on its center axis based on user touch.

Like a old phone dialer .

i want to rotate based on center

but

Now its rotating based on top left corner .so i am able to see only 1/4 for rotation of image.

I have tried like as follows

onDraw(Canvas canvas){
  canvas.save();
  // do my rotation
  canvas.rotate(rotation,0,0);
  canvas.drawBitmap( ((BitmapDrawable)d).getBitmap(),0,0,p );
  canvas.restore();
}

@Override
        public boolean onTouchEvent(MotionEvent e) {
                  float x = e.getX();
              float y = e.getY();
              updateRotation(x,y);
              mPreviousX = x;
              mPreviousY = y;
            invalidate();
        }

  private void updateRotation(float x, float y) {

          double r = Math.atan2(x - centerX, centerY - y);
            rotation = (int) Math.toDegrees(r);
        }

Answer 1

You need to add this to your custom view methods

@Override     
public void onSizeChanged (int w, int h, int oldw, int oldh){ 
  super.onSizeChanged(w, h, oldw, oldh);         

  screenW = w;         
  screenH = h; 
}

This method will give you the canvas size then use

canvas.rotate(rotation, screenW / 2, screenH / 2);