src/com/android/launcher3/dynamicui/ExtractionUtils.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 com.android.launcher3.dynamicui;

import android.app.WallpaperManager;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;

import com.android.launcher3.Utilities;

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

/**
 * Contains helper fields and methods related to extracting colors from the wallpaper.
 */
public class ExtractionUtils {
    public static final String EXTRACTED_COLORS_PREFERENCE_KEY = "pref_extractedColors";
    public static final String WALLPAPER_ID_PREFERENCE_KEY = "pref_wallpaperId";

    private static final int FLAG_SET_SYSTEM = 1 << 0; // TODO: use WallpaperManager.FLAG_SET_SYSTEM

    /**
     * Extract colors in the :wallpaper-chooser process, if the wallpaper id has changed.
     * When the new colors are saved in the LauncherProvider,
     * Launcher will be notified in Launcher#onSettingsChanged(String, String).
     */
    public static void startColorExtractionServiceIfNecessary(final Context context) {
        // Run on a background thread, since the service is asynchronous anyway.
        Utilities.THREAD_POOL_EXECUTOR.execute(new Runnable() {
            @Override
            public void run() {
                if (hasWallpaperIdChanged(context)) {
                    context.startService(new Intent(context, ColorExtractionService.class));
                }
            }
        });
    }

    private static boolean hasWallpaperIdChanged(Context context) {
        if (!Utilities.isNycOrAbove()) {
            // TODO: update an id in sharedprefs in onWallpaperChanged broadcast, and read it here.
            return false;
        }
        final SharedPreferences sharedPrefs = Utilities.getPrefs(context);
        int wallpaperId = getWallpaperId(WallpaperManager.getInstance(context));
        int savedWallpaperId = sharedPrefs.getInt(ExtractionUtils.WALLPAPER_ID_PREFERENCE_KEY, -1);
        return wallpaperId != savedWallpaperId;
    }

    public static int getWallpaperId(WallpaperManager wallpaperManager) {
        // TODO: use WallpaperManager#getWallpaperId(WallpaperManager.FLAG_SET_SYSTEM) directly.
        try {
            Method getWallpaperId = WallpaperManager.class.getMethod("getWallpaperId", int.class);
            return (int) getWallpaperId.invoke(wallpaperManager, FLAG_SET_SYSTEM);
        } catch (InvocationTargetException | NoSuchMethodException | IllegalAccessException e) {
            return -1;
        }
    }
}