android autofocus fix

Adding camera.cancelAutoFocus(); some devices crashes

android/ZBarScannerActivity.java

@@ -219,6 +219,7 @@ implements SurfaceHolder.Callback {
     private AutoFocusCallback autoFocusCb = new AutoFocusCallback()
     {
         public void onAutoFocus(boolean success, Camera camera) {
+			camera.cancelAutoFocus();
             autoFocusHandler.postDelayed(doAutoFocus, autoFocusInterval);
         }
     };