Using generics to find a View by Class

Question

This works but feels clunky - any suggestions for improvement?

public static <T extends View> T findViewByClassReference(View rootView, Class<T> classReference){
  if(classReference.isInstance(rootView)){
    return classReference.cast(rootView);
  }
  if(rootView instanceof ViewGroup){
    ViewGroup viewGroup = (ViewGroup) rootView;
    for(int i = 0; i < viewGroup.getChildCount(); i++){
      View child = viewGroup.getChildAt(i);
      View match = findViewByClassReference(child, classReference);
      if(match != null){
        return classReference.cast(match);
      }
    }
  }
  return null;
}

janos · Accepted Answer · 2016-05-27 06:43:40Z

This works but feels clunky

This seems fine. It does the job well. I don't see how this can be done simpler, and I'm not aware of other existing method in the SDK that can help simplify this.

any suggestions for improvement?

I have only minor suggestions:

The method uses depth first search to find a view. Depending on the actual tree of views in the application, this might be slow, for example when you have very deep trees but the class you're looking for is at a shallow level. In such case a breadth first search would perform better. This is not something to "fix", just something to keep in mind, and adjust to your actual application as necessary
Another point to keep in mind is that the method will return the first view with matching class. When there are multiple views of the same class, a user might not get the one expected
As with any utility method, it's good to add a nice javadoc. That will be a good place to mention about the previous points (search algorithm used, returns first match).
A common name for Class instances is clazz. I suggest to use that name to make the code look more familiar to other developers, and it's shorter too than classReference
The "ByClassReference" in the method name is redundant, because this is implied by the method signature
The formatting could be slightly more readable if you apply auto reformat in Android Studio

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