本文主要是介绍Android Priority Job Queue 入门,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
1. 简介
Android Priority Job Queue是一款专门为Android平台编写,实现了Job Queue的后台任务队列类库,能够轻松的在后台执行定时任务,提高用户体验和应用的稳定性。
github地址:https://github.com/path/android-priority-jobqueue
2. 背景
几乎所有的应用程序都存在后台线程工作。这些“背景任务”需要保持应用程序响应性和鲁棒性,特别是在不利的情况下(如有限的网络连接)。在安卓应用中,有几种方法来实现后台工作:
1) 异步任务:
使用异步任务是最简单的方法,但它与activity生命周期紧密耦合。如果Activity生命周期发生了改变,比如用户旋转了它的屏幕,那么Activity重新加载,那么后台任务可能会被停止。
2) 使用service:
使用服务可以很好地处理界面逻辑,但是,随着事物的增加,可能需要一个线程池来安排队列请求道磁盘中,而且需要考虑任务的优先级和并发时的并发问题
作业队列提供了一个很好的框架来完成上述所有的工作。当确定了你的后台任务的工作时,将它们作为Job添加到你jobmanager实例。Job Manage会照顾优先级,持久性,负载平衡,延迟,网络控制,分组等,它还提供了一个很好的生命周期,为工作提供一个更好的,一致的用户体验。
3. 使用(基于android studio)
1.添加依赖
compile 'com.birbit:android-priority-jobqueue:1.3.5'
2.创建Application并配置JobManager
public class AppApplication extends Application {private JobManager jobManager;public static AppApplication instance;@Overridepublic void onCreate() {super.onCreate();configureJobManager();}public AppApplication(){instance=this;}public JobManager getJobManager() {return jobManager;}public static AppApplication getInstance() {return instance;}private void configureJobManager() {Configuration configuration = new Configuration.Builder(this).customLogger(new CustomLogger() {private static final String TAG = "JOBS";@Overridepublic boolean isDebugEnabled() {return true;}@Overridepublic void d(String text, Object... args) {Log.d(TAG, String.format(text, args));}@Overridepublic void e(Throwable t, String text, Object... args) {Log.e(TAG, String.format(text, args), t);}@Overridepublic void e(String text, Object... args) {Log.e(TAG, String.format(text, args));}}).minConsumerCount(1)//always keep at least one consumer alive.maxConsumerCount(3)//up to 3 consumers at a time.loadFactor(3)//3 jobs per consumer.consumerKeepAlive(120)//wait 2 minute.build();jobManager = new JobManager(this, configuration);}
}
3.创建Job任务
public class MJob extends Job {public static final int PRIORITY = 1;private String text;public MJob(String text) {// This job requires network connectivity,// and should be persisted in case the application exits before job is completed.super(new Params(Integer.parseInt(text)).requireNetwork().persist());this.text = text;Log.i("job",text+" goin");}@Overridepublic void onAdded() {// Job has been saved to disk.// This is a good place to dispatch a UI event to indicate the job will eventually run.// In this example, it would be good to update the UI with the newly posted tweet.Log.i("job",text+" Onadded");}@Overridepublic void onRun() throws Throwable {// Job logic goes here. In this example, the network call to post to Twitter is done here.// All work done here should be synchronous, a job is removed from the queue once// onRun() finishes.Log.i("job",text+" onRun");}@Overrideprotected RetryConstraint shouldReRunOnThrowable(Throwable throwable, int runCount,int maxRunCount) {// An error occurred in onRun.// Return value determines whether this job should retry or cancel. You can further// specify a backoff strategy or change the job's priority. You can also apply the// delay to the whole group to preserve jobs' running order.return RetryConstraint.createExponentialBackoff(runCount, 1000);}@Overrideprotected void onCancel() {}
}
任务调用执行Job时会依次执行onAdded(),onRun().
4.MainActivity
public class MainActivity extends AppCompatActivity {private JobManager jobManager;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);jobManager = AppApplication.getInstance().getJobManager();Button btn_start = (Button)findViewById(R.id.btn_start);btn_start.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {jobManager.addJobInBackground(new MJob("1"));jobManager.addJobInBackground(new MJob("2"));jobManager.addJobInBackground(new MJob("3"));jobManager.addJobInBackground(new MJob(""));jobManager.addJobInBackground(new MJob(""));jobManager.addJobInBackground(new MJob(""));}});
4.执行结果
初始化所有的job
执行前三个Job的Onadd()方法,同时执行Job1的OnRun()方法。
在执行完一个onAdd()方法后接着会调用队列中的第一个的OnAdd()方法。
5.分析
从Log中可以看到这个框架有一套自己的调度算法:
事实上,感觉这套框架其实跟Java的线程池差不多,都是来安排队列任务的优先级,调度方案,不过这套框架使用比较简单。
推荐一个Android的线程池博客:http://www.xuanyusong.com/archives/2439
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