design/src/android/support/design/widget/DrawableUtils.java

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.design.widget;

import android.graphics.drawable.Drawable;
import android.graphics.drawable.DrawableContainer;
import android.os.Build;
import android.util.Log;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

/**
 * Caution. Gross hacks ahead.
 */
class DrawableUtils {

    private static final String LOG_TAG = "DrawableUtils";

    private static Method sSetConstantStateMethod;
    private static boolean sSetConstantStateMethodFetched;

    private static Field sDrawableContainerStateField;
    private static boolean sDrawableContainerStateFieldFetched;

    private DrawableUtils() {}

    static boolean setContainerConstantState(DrawableContainer drawable,
            Drawable.ConstantState constantState) {
        if (Build.VERSION.SDK_INT >= 9) {
            // We can use getDeclaredMethod() on v9+
            return setContainerConstantStateV9(drawable, constantState);
        } else {
            // Else we'll just have to set the field directly
            return setContainerConstantStateV7(drawable, constantState);
        }
    }

    private static boolean setContainerConstantStateV9(DrawableContainer drawable,
            Drawable.ConstantState constantState) {
        if (!sSetConstantStateMethodFetched) {
            try {
                sSetConstantStateMethod = DrawableContainer.class.getDeclaredMethod(
                        "setConstantState", DrawableContainer.DrawableContainerState.class);
                sSetConstantStateMethod.setAccessible(true);
            } catch (NoSuchMethodException e) {
                Log.e(LOG_TAG, "Could not fetch setConstantState(). Oh well.");
            }
            sSetConstantStateMethodFetched = true;
        }
        if (sSetConstantStateMethod != null) {
            try {
                sSetConstantStateMethod.invoke(drawable, constantState);
                return true;
            } catch (Exception e) {
                Log.e(LOG_TAG, "Could not invoke setConstantState(). Oh well.");
            }
        }
        return false;
    }

    private static boolean setContainerConstantStateV7(DrawableContainer drawable,
            Drawable.ConstantState constantState) {
        if (!sDrawableContainerStateFieldFetched) {
            try {
                sDrawableContainerStateField = DrawableContainer.class
                        .getDeclaredField("mDrawableContainerStateField");
                sDrawableContainerStateField.setAccessible(true);
            } catch (NoSuchFieldException e) {
                Log.e(LOG_TAG, "Could not fetch mDrawableContainerStateField. Oh well.");
            }
            sDrawableContainerStateFieldFetched = true;
        }
        if (sDrawableContainerStateField != null) {
            try {
                sDrawableContainerStateField.set(drawable, constantState);
                return true;
            } catch (Exception e) {
                Log.e(LOG_TAG, "Could not set mDrawableContainerStateField. Oh well.");
            }
        }
        return false;
    }

}