title: Android - Predraw canvas for onDraw
body: <p>I used to do my drawing in an ImageView in the onDraw method.
  However, I've learnt that's better to draw the canvas outside of the onDraw and just update the canvas in onDraw.</p>
  
  <p>I know this is clearly wrong (because it's not working) but how would I accomplish what I'm trying to do:</p>
  
  <pre><code>@Override 
  public void onDraw(Canvas c) {
    c = this.newCanvas;
    super.onDraw(c);
  }
  </code></pre>