title: invalidate only works in custom view
body: <p>so i created a view called "drawable view"</p>
  
  <pre><code> class DrawableView extends View{
          Context mContext;
  
          int touches=0,k,Xoffs,clicks=0;
  
  
    double x_1 = 0,x_2=0;
  
          private float mLastTouchX, mLastTouchY;
  
          public DrawableView(Context context) {
          super(context);
          mContext = context;
          }
  
  ....
      @Override
      protected void onDraw(Canvas canvas){
  
          Paint myPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
  
  canvas.drawColor(Color.BLUE);
  myPaint.setColor(Color.WHITE);
  
  canvas.drawCircle(200, 100, 20, myPaint);
  
  
      }
  
  ..... more code....
  
  }
  </code></pre>
  
  <p>and it can only be invalidated within the ondraw command! ie: calling "invalidate();" at the end of the ondraw command causes it to loop.</p>
  
  <p>I have tried many times to call g_draw.invalidate(); or g_draw.postInvalidate(); (g_draw is the name of the created Drawable View)from other classes and even the main activity class and it doesnt work. why and how can i fix it?</p>
  
  <p>thanks </p>