JetPack之WorkManager 管理后台任务

【链接】
【背景】作为 Android Jetpack 中的新组件，WorkManager 负责用来管理后台任务，它和一个异步任务以及 Service 有什么区别呢？看完你就知道了。

【1】 继承worker，实现doWork，类似于异步任务

public class MyWorker extends Worker {

/**
 * 必须有一个构造函数，调用基类的构造函数
 *
 * @param context
 * @param workerParams
 */
public MyWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
    super(context, workerParams);
}

//1、创建worker，执行任务的执行者
@NonNull
@Override
public Result doWork() {
    //在workRequest中传递来的data，
    Data data = getInputData();
    String name = data.getString("name");
    int age = data.getInt("age", 0);
    //do some work
    Log.i("test", "worker doWork() name: " + name + " age: " + age);
    //返回任务的结果数据，
    Data out = new Data.Builder()
            .putString("result", "哈哈哈，真的可以返回呀")
            .putInt("status", 200)
            .build();
    return Result.success(out);
}

}

【2】workmanager使用

public class WorkActivity extends AppCompatActivity {

private String name = "tmc";
private int age = 18;
//类似于intent的bundle
Data data = new Data.Builder()
        .putString("name", name)
        .putInt("age", age)
        .build();

//todo 这里workmanager的request有个高级用法，就是添加环境约束 ，比如网络、电量等
Constraints constraints = new Constraints.Builder()
        .setRequiredNetworkType(NetworkType.CONNECTED)//联网状态
        .setRequiresBatteryNotLow(true)//低电量不操作
        .setRequiresCharging(true)//充电时候才开始
  //     .setRequiresDeviceIdle(true)//待机状态下才执行，api 23 以上
        .setRequiresStorageNotLow(true)//存储空间不能太小
        .build();

//2、创建一个workrequest 这里有onetime,还有个PeriodicWorkRequest
private WorkRequest workRequest = new OneTimeWorkRequest.Builder(MyWorker.class)
        .setConstraints(constraints)//添加约束
        .setInputData(data)//传递data到worker中
        .build();

//todo worker的角色定位用于特殊的任务操作，可以脱离于本App的进程，所以这里的定期任务，做了最小限制，间隔至少15分钟，最小弹性伸缩时间为5分钟
private WorkRequest request = new PeriodicWorkRequest.Builder(MyWorker.class, 15, TimeUnit.MINUTES)
        .setBackoffCriteria(BackoffPolicy.LINEAR, 20, TimeUnit.MINUTES)
        .build();

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_work);
    //3、加入任务管理，但不是执行，执行的代码稍后
    WorkManager.getInstance().enqueue(workRequest);
    //4、通过workRequest的唯一标记id，来操作request，并获取返回数据
    //todo 这里因为在oncreate中执行，会先与work执行，toast会弹出未执行work的空结果，work变化后，还会显示出成功后的结果。这是因为observe监测worker的status变化 enqueued、RUNNING、successed、retry、failure等
    WorkManager.getInstance().getWorkInfoByIdLiveData(workRequest.getId())
            .observe(this, workStatus -> {
                //接收从worker中返回的任务结果,最好在这里判断status为success再做具体操作
                if (workStatus.getState() == WorkInfo.State.SUCCEEDED) {
                    Data data = workStatus.getOutputData();
                    String result = data.getString("result");
                    int status = data.getInt("status", 0);
                    Toast.makeText(WorkActivity.this, "result: " + result + " status: " + status, Toast.LENGTH_SHORT).show();
                    Log.i("WorkActivity", "workStatus: " + workStatus.getState().name());
                }
            });
}

//<editor-folder desc="工作流 演示">
/*{
    OneTimeWorkRequest workA = null, workB = null, workC = null, workD = null, workE = null;
    //串行
    WorkManager.getInstance().beginWith(workA)
            .then(workB)
            .then(workC)
            .enqueue();
    //并行合流
    WorkManager.getInstance().beginWith(workA, workB)
            .then(workC)
            .enqueue();
    //分支 合并
    WorkContinuation chainA = WorkManager.getInstance().beginWith(workA).then(workB);
    WorkContinuation chainB = WorkManager.getInstance().beginWith(workC).then(workD);
    WorkContinuation.combine(chainA, chainB)
            .then(workE)
            .enqueue();//合并 A->B  C->D 两个之流后，再执行workE

    //避免任务的重复添加，保持唯一性
    WorkManager.getInstance()
            //使用unique，配置策略
            .beginUniqueWork("unique name",ExistingWorkPolicy.REPLACE,workA)
            .enqueue();
}*/
//</editor-folder>

@Override
protected void onDestroy() {
    super.onDestroy();
    WorkManager.getInstance().cancelWorkById(workRequest.getId());
     }
}