gitProject/src/main/java/net/micode/notes/gtask/remote/GTaskSyncService.java

/*
 * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
 *
 * 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 net.micode.notes.gtask.remote;

import android.app.Activity;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.IBinder;

//由Service组件扩展而来，作用是提供GTask的同步服务
public class GTaskSyncService extends Service {
    //定义了一系列静态变量，用来表示同步操作的状态。
    public final static String ACTION_STRING_NAME = "sync_action_type";

    //用数字0、1、2分别表示开始同步、取消同步、同步无效
    public final static int ACTION_START_SYNC = 0;

    public final static int ACTION_CANCEL_SYNC = 1;

    public final static int ACTION_INVALID = 2;

    //服务广播的名称
    public final static String GTASK_SERVICE_BROADCAST_NAME = "net.micode.notes.gtask.remote.gtask_sync_service";

    //表示广播正在同步
    public final static String GTASK_SERVICE_BROADCAST_IS_SYNCING = "isSyncing";

    //GTask 广播服务消息
    public final static String GTASK_SERVICE_BROADCAST_PROGRESS_MSG = "progressMsg";

    private static GTaskASyncTask mSyncTask = null;

    private static String mSyncProgress = "";

    //开始一个同步工作
    private void startSync() {
        //若当前没有同步工作，申请一个task并把指针指向新任务，广播后执行
        if (mSyncTask == null) {
            mSyncTask = new GTaskASyncTask(this, new GTaskASyncTask.OnCompleteListener() {
                public void onComplete() {
                    mSyncTask = null;
                    sendBroadcast("");
                    stopSelf();
                }
            });
            sendBroadcast("");
            mSyncTask.execute();
        }
    }

    //取消同步
    private void cancelSync() {
        // 如果有同步任务，则取消
        if (mSyncTask != null) {
            mSyncTask.cancelSync();
        }
    }

    @Override
    //初始化任务，直接把mSyncTask指针的值置为空
    public void onCreate() {
        mSyncTask = null;
    }

    @Override
    //onStartCommand会告诉系统如何重启服务，如判断是否异常终止后重新启动，在何种情况下异常终止。返回值是一个(int)整形，有四种返回值。参数的flags表示启动服务的方式
    public int onStartCommand(Intent intent, int flags, int startId) {
        Bundle bundle = intent.getExtras();
        //判断当前的同步状态，根据开始或取消，执行对应操作
        if (bundle != null && bundle.containsKey(ACTION_STRING_NAME)) {
            switch (bundle.getInt(ACTION_STRING_NAME, ACTION_INVALID)) {
                case ACTION_START_SYNC:
                    startSync();
                    break;
                case ACTION_CANCEL_SYNC:
                    cancelSync();
                    break;
                default:
                    break;
            }
            return START_STICKY;
        }
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    //发送广播
    public void onLowMemory() {
        if (mSyncTask != null) {
            mSyncTask.cancelSync();
        }
    }

    //用于绑定操作的函数
    public IBinder onBind(Intent intent) {
        return null;
    }

    //发送广播内容
    public void sendBroadcast(String msg) {
        mSyncProgress = msg;
        Intent intent = new Intent(GTASK_SERVICE_BROADCAST_NAME);
        intent.putExtra(GTASK_SERVICE_BROADCAST_IS_SYNCING, mSyncTask != null);
        intent.putExtra(GTASK_SERVICE_BROADCAST_PROGRESS_MSG, msg);
        sendBroadcast(intent);
    }

    //对变量activity事件进行同步操作
    public static void startSync(Activity activity) {
        GTaskManager.getInstance().setActivityContext(activity);
        Intent intent = new Intent(activity, GTaskSyncService.class);
        intent.putExtra(GTaskSyncService.ACTION_STRING_NAME, GTaskSyncService.ACTION_START_SYNC);
        activity.startService(intent);
    }

    //取消同步
    public static void cancelSync(Context context) {
        Intent intent = new Intent(context, GTaskSyncService.class);
        intent.putExtra(GTaskSyncService.ACTION_STRING_NAME, GTaskSyncService.ACTION_CANCEL_SYNC);
        context.startService(intent);
    }

    //判断当前是否处于同步状态
    public static boolean isSyncing() {
        return mSyncTask != null;
    }

    //返回当前同步状态
    public static String getProgressString() {
        return mSyncProgress;
    }
}