ViewGroupUtils.java

/*
 * Copyright (C) 2016 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 androidx.transition;

import android.os.Build;
import android.view.ViewGroup;

import androidx.annotation.NonNull;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Compatibility utilities for platform features of {@link ViewGroup}.
 */
class ViewGroupUtils {

    private static Method sGetChildDrawingOrderMethod;
    private static boolean sGetChildDrawingOrderMethodFetched;

    /**
     * Backward-compatible {@link ViewGroup#getOverlay()}.
     */
    static ViewGroupOverlayImpl getOverlay(@NonNull ViewGroup group) {
        if (Build.VERSION.SDK_INT >= 18) {
            return new ViewGroupOverlayApi18(group);
        }
        return ViewGroupOverlayApi14.createFrom(group);
    }

    /**
     * Provides access to the hidden ViewGroup#suppressLayout method.
     */
    static void suppressLayout(@NonNull ViewGroup group, boolean suppress) {
        if (Build.VERSION.SDK_INT >= 18) {
            ViewGroupUtilsApi18.suppressLayout(group, suppress);
        } else {
            ViewGroupUtilsApi14.suppressLayout(group, suppress);
        }
    }

    /**
     * Returns the index of the child to draw for this iteration.
     */
    static int getChildDrawingOrder(@NonNull ViewGroup viewGroup, int i) {
        if (!sGetChildDrawingOrderMethodFetched) {
            try {
                sGetChildDrawingOrderMethod = ViewGroup.class.getDeclaredMethod(
                        "getChildDrawingOrder", int.class, int.class);
                sGetChildDrawingOrderMethod.setAccessible(true);
            } catch (NoSuchMethodException ignore) {

            }
            sGetChildDrawingOrderMethodFetched = true;
        }
        if (sGetChildDrawingOrderMethod != null) {
            try {
                return (Integer) sGetChildDrawingOrderMethod.invoke(viewGroup,
                        viewGroup.getChildCount(), i);
            } catch (IllegalAccessException ignore) {
            } catch (InvocationTargetException ignore) {
            }
        }
        // fallback implementation
        return i;
    }


    private ViewGroupUtils() {
    }
}