Architecture -- WorkManager

1. WorkManager

1). 简介

其实就是"管理一些要在后台工作的任务, -- 即使你的应用没启动也能保证任务能被执行"，WorkManager在底层, 会根据你的设备情况, 选用JobScheduler, Firebase的JobDispatcher, 或是AlarmManager。WorkManager并不是为了那种在应用内的后台线程而设计出来的. 这种需求你应该使用ThreadPool。

2). 引入

• kolin

# Android Studio 3.0， 3.0以下版本请使用complie
  ext.work_version = "1.0.0-alpha02"
  // WorkManager
  implementation "android.arch.work:work-runtime:$work_version" // use -ktx for Kotlin
  // optional - Firebase JobDispatcher support
  implementation "android.arch.work:work-firebase:$work_version"
  // optional - Test helpers
  androidTestImplementation "android.arch.work:work-testing:$work_version"

• java

# 必须加入
implementation "android.arch.work:work-runtime:1.0.0-alpha01"

2. 用法

1). 执行一次的任务

• PullWorker.kt

/**
 * Pull 任务
 * 创建步骤：
 *      1. 继承Worker类
 *      2. 重写doWork()方法
 * Created by mazaiting on 2018/6/6.
 */
class PullWorker : Worker() {
    override fun doWork(): WorkerResult {
        // 模拟设置页面中的"是否接受推送"是否被勾选
        val isOkay = this.inputData.getBoolean("key_accept_bg_work", false)

        // 判断是否推送
        if (isOkay) {
            // 模拟长时间工作
            Thread.sleep(5000)
            // 获取数据
            val pulledResult = startPull()
            // 设置输出数据
            val output = Data.Builder().putString("key_pulled_result", pulledResult).build()
            // 存放数据
            outputData = output
            // 返回成功
            return WorkerResult.SUCCESS
        } else {
            // 返回失败
            return WorkerResult.FAILURE
        }
    }

    /**
     * 开始推送
     */
    private fun startPull(): String {
        return "[worker] pull messages from backend."
    }

}

• PullEngine.kt

/**
 * Pull 引擎
 * Created by mazaiting on 2018/6/6.
 */
class PullEngine {

    fun scheduleOneTimeWork(context: Context) {
        // 设置任务，执行一次
        val pullRequest = OneTimeWorkRequestBuilder<PullWorker>()
                .setInputData(
                        Data.Builder()
                                .putBoolean("key_accept_bg_work", true)
                                .build()
                )
                .build()
        WorkManager.getInstance().enqueue(pullRequest)
        // 将请求入列
        WorkManager.getInstance().enqueue(pullRequest)
        // 获取请求ID
        val pullRequestId = pullRequest.id
        // 存在SharedPreference中
        PreferenceManager
                .getDefaultSharedPreferences(context)
                .edit()
                .putString("pullId", pullRequestId.toString())
                .apply()
    }

}

• MainApplication.kt(注意在AndroidManifest.xml文件中配置)

class MainApplication : Application() {
    override fun onCreate() {
        super.onCreate()

        // 任务执行一次
        PullEngine().scheduleOneTimeWork(this.applicationContext)
    }
}

• MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        // UUID实现了Serializable接口，能由toString(),fromString()与String互转
        val uuid = UUID.fromString(
                PreferenceManager.getDefaultSharedPreferences(this.applicationContext)
                        .getString("pullId", "")
        )
        WorkManager.getInstance()
                // 获取状态ID
                .getStatusById(uuid)
                // 观察数据
                .observe(this, Observer<WorkStatus>{ status ->
                    if (null != status && status.state.isFinished) {
                        val pulledResult = status.outputData.getString("key_pulled_result","")
                        Log.e("MainActivity", pulledResult)
                    }
                })
    }
}

• 打印结果

  
  
  图1.png

2). 任务设置约束

    fun scheduleOneTimeWork(context: Context) {
        val constraints = Constraints.Builder()
                // 负荷
                .setRequiresCharging(true)
                .build()
        // 设置任务，执行一次
        val pullRequest = OneTimeWorkRequestBuilder<PullWorker>()
                // 设置约束
                .setConstraints(constraints)
                // 输入数据
                .setInputData(
                        Data.Builder()
                                .putBoolean("key_accept_bg_work", true)
                                .build()
                )
                .build()
        // 将请求入列
        WorkManager.getInstance().enqueue(pullRequest)
        // 获取请求ID
        val pullRequestId = pullRequest.id
        // 存在SharedPreference中
        PreferenceManager
                .getDefaultSharedPreferences(context)
                .edit()
                .putString("pullId", pullRequestId.toString())
                .apply()
    }

3). 取消任务

    // 获取请求ID
    val pullRequestId = pullRequest.id
    // 取消任务
    WorkManager.getInstance().cancelWorkById(pullRequestId)

4). 任务链

WorkManager.getInstance()
    .beginWith(workA)
        // Note: WorkManager.beginWith() returns a
        // WorkContinuation object; the following calls are
        // to WorkContinuation methods
    .then(workB)    // FYI, then() returns a new WorkContinuation instance
    .then(workC)
    .enqueue()

或

WorkManager.getInstance()
    // First, run all the A tasks (in parallel):
    .beginWith(workA1, workA2, workA3)
    // ...when all A tasks are finished, run the single B task:
    .then(workB)
    // ...then run the C tasks (in any order):
    .then(workC1, workC2)
    .enqueue()

再或

val chain1 = WorkManager.getInstance()
    .beginWith(workA)
    .then(workB)
val chain2 = WorkManager.getInstance()
    .beginWith(workC)
    .then(workD)
val chain3 = WorkContinuation
    .combine(chain1, chain2)
    .then(workE)
chain3.enqueue()

5). 定时任务

    /**
     * 执行任务
     */
    fun schedulePeriodicWork(context: Context) {
        val constraints = Constraints.Builder()
                // 负荷
                .setRequiresCharging(true)
                .build()
        // 设置任务执行时长，并设置输入参数
        // 长期任务，循环
        val pullRequest = PeriodicWorkRequestBuilder<PullWorker>(30, TimeUnit.SECONDS)
                            .setConstraints(constraints)
                            .setInputData(
                                Data.Builder()
                                        .putBoolean("key_accept_bg_work", true)
                                        .build()
                            )
                            .build()
        // 将请求入列
        WorkManager.getInstance().enqueue(pullRequest)
        // 获取请求ID
        val pullRequestId = pullRequest.id
        // 存在SharedPreference中
        PreferenceManager
                .getDefaultSharedPreferences(context)
                .edit()
                .putString("pullId", pullRequestId.toString())
                .apply()
    }

6). 原文地址

7). 代码下载