TransitionUtil.java

package com.kaichunlin.transition.util;

import android.app.Activity;
import android.os.Build;
import android.support.annotation.IdRes;
import android.support.annotation.NonNull;
import android.support.v7.view.menu.ActionMenuItemView;
import android.support.v7.widget.ActionMenuView;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewTreeObserver;

import java.util.ArrayList;
import java.util.List;

/**
 * Support utility methods.
 */
public class TransitionUtil {

    /**
     * Get the list of visible MenuItems
     *
     * @param toolbar
     * @return the list of visible MenuItems
     */
    public static List<MenuItem> getVisibleMenuItemList(@NonNull Toolbar toolbar) {
        List<MenuItem> list = new ArrayList<>();
        for (int i = 0; i < toolbar.getChildCount(); i++) {
            final View v = toolbar.getChildAt(i);
            if (v instanceof ActionMenuView) {
                int childCount = ((ActionMenuView) v).getChildCount();
                for (int j = 0; j < childCount; j++) {
                    final View innerView = ((ActionMenuView) v).getChildAt(j);
                    if (innerView instanceof ActionMenuItemView) {
                        list.add(((ActionMenuItemView) innerView).getItemData());
                    }
                }
            }
        }
        return list;
    }

    /**
     * Search for a particular menu
     *
     * @param toolbar
     * @param menuId
     * @return the corresponding MenuItem, or null if not found
     */
    public static MenuItem getMenuItem(@NonNull Toolbar toolbar, @IdRes int menuId) {
        View v;
        int childCount;
        View innerView;
        MenuItem menuItem;
        for (int i = 0; i < toolbar.getChildCount(); i++) {
            v = toolbar.getChildAt(i);
            if (v instanceof ActionMenuView) {
                childCount = ((ActionMenuView) v).getChildCount();
                for (int j = 0; j < childCount; j++) {
                    innerView = ((ActionMenuView) v).getChildAt(j);
                    if (innerView instanceof ActionMenuItemView) {
                        menuItem = ((ActionMenuItemView) innerView).getItemData();
                        if (menuItem.getItemId() == menuId) {
                            return menuItem;
                        }
                    }
                }
            }
        }
        return null;
    }

    /**
     * Helper that removes the drudgery of using ViewTreeObserver
     *
     * @param view
     * @param listener
     */
    public static void executeOnGlobalLayout(@NonNull final View view, @NonNull final ViewTreeObserver.OnGlobalLayoutListener listener) {
        ViewTreeObserver vto = view.getViewTreeObserver();
        vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
                    view.getViewTreeObserver()
                            .removeGlobalOnLayoutListener(this);
                } else {
                    view.getViewTreeObserver()
                            .removeOnGlobalLayoutListener(this);
                }

                listener.onGlobalLayout();
            }
        });
    }

    /**
     * Helper that removes the drudgery of using ViewTreeObserver
     *
     * @param activity used to retrieve a View that can be
     * @param listener
     */
    public static void executeOnGlobalLayout(@NonNull final Activity activity, @NonNull final ViewTreeObserver.OnGlobalLayoutListener listener) {
        executeOnGlobalLayout(activity.getWindow().getDecorView().findViewById(android.R.id.content), listener);
    }
}