androidandroid-drawableandroid-4.3-jelly-beanbitmapdrawable

Android: cannot cast BitmapDrawable to a ClipDrawable

I'm trying to implement a simple ClipDrawable using Android Jellybean (SDK 18). I don't understand why I'm getting the casting error for ImageView.getDrawable() when that returns a Drawable, not a BitmapDrawable

Here's my relevant code in the onCreate() of an activity:

    ImageView image = (ImageView) findViewById(R.id.guage_one);
    ClipDrawable drawable = (ClipDrawable) image.getDrawable();
    drawable.setLevel(10000);

Why would I get a ClassCastException for this? I know BitmapDrawable and ClipDrawable are subclasses of Drawable so you can't cast them to one another, I know that. But why is image.getDrawable() returning a BitmapDrawable and not just a drawable? Am I missing something in the documentation?

Solution

  • ClipDrawable does not inherit BitmapDrawable.

    This is it's inheritance tree:

    java.lang.Object

    ↳ android.graphics.drawable.Drawable

    ↳ android.graphics.drawable.DrawableWrapper

    ↳ android.graphics.drawable.ClipDrawable

    To convert a BitmapDrawable to ClipDrawable you can do the following:

    ImageView image = (ImageView) findViewById(R.id.guage_one);
ClipDrawable clipDrawable = new ClipDrawable(image.getDrawable(), Gravity.LEFT, ClipDrawable.HORIZONTAL);