code: @TargetApi(11)
      public void setStatusBarAlpha(float alpha) {
          if (mStatusBarAvailable && Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
              mStatusBarTintView.setAlpha(alpha);
          }
      }
docs: Apply the specified alpha to the system status bar.
  
  @param alpha The alpha to use