(翻译) Android SDK文档之Drawable Mutations

Drawable star = context.getResources().getDrawable(R.drawable.star);
if (book.isFavorite()) {
  star.mutate().setAlpha(255); // opaque
} else {
  star. mutate().setAlpha(70); // translucent
}

public class ConstantStateActivity extends ListActivity {

	private ListAdapter mAdapter;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		mAdapter = new MyListAdapter(this, R.layout.my_adatper, R.id.textView1, Arrays.asList("and-aa", "iphone-b"));
		getListView().setAdapter(mAdapter);
	}
	
	static class MyListAdapter extends ArrayAdapter<String> {
		private int mRes;
		private List<String> mData;
		
		public MyListAdapter(Context context, int resource,
				int textViewResourceId, List<String> objects) {
			super(context, resource, textViewResourceId, objects);
			this.mRes = resource;
			this.mData = objects;
		}
		
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			
			View view = convertView;
			if (null == view) {
				LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(LAYOUT_INFLATER_SERVICE);
				view = inflater.inflate(mRes, parent, false);
				
				ImageView icon = (ImageView) view.findViewById(R.id.imageView1);
				MyLog.i(icon + "");
				
				if (mData.get(position).startsWith("and")) {
					icon.getDrawable().setAlpha(0);
//					icon.getDrawable().mutate().setAlpha(0);
				}
			}
			return view;
		}
		
	}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="fill_parent" android:layout_height="fill_parent"
	android:gravity="center_vertical">
	<ImageView android:layout_height="wrap_content" android:src="@drawable/icon"
		android:layout_width="wrap_content" android:id="@+id/imageView1"></ImageView>
	<TextView android:text="TextView" android:id="@+id/textView1"
		android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView>

</LinearLayout>