Jetpack-WorkManager

JetpackWorkManager.kt

import android.content.Context
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
import androidx.work.*

/**
 *  Created by jixiaoyong1995@gmail.com
 *  Data: 2019/11/21.
 *  Description: WorkManager使用示例
 *
 *  参考链接：
 *  https://medium.com/androiddevelopers/workmanager-basics-beba51e94048
 *  http://hukai.me/google-io-2018-android-jetpack-workmanager/
 *
 *  需要先添加依赖:
 *   implementation "android.arch.work:work-runtime-ktx:$work_version"
 *
 */
class JetPackWorkManager {

    private val observer: Observer<WorkInfo> = Observer {
        //这里传来的是downloadWorkRequest任务的状态信息
        it.state //状态
        it.outputData //数据
    }

    private var downloaderWatcher: LiveData<WorkInfo>? = null

    fun start() {

        /**
         * 这里使用到了[Data] ( Data, which is essentially a map of primitive types and arrays.)
         * 用来在Worker间传递基本类型的数据及由其组成的数组
         * 有大小限制（10KB）
         */
        val data = Data.Builder()
            .putString("KEY1", "在构建任务的时候传入Data")
            .putInt("KEY1", 1)
            .build()

        /**
         * 约束
         * 只有当约束指定的条件满足时，才会执行对应的任务
         * 当[Worker]返回值为[Result.retry()]时，会根据约束判断是否重试
         */
        val constraints = Constraints.Builder()
            .setRequiredNetworkType(NetworkType.CONNECTED)
            .build()

        /**
         * WorkRequest defines how and when work should be run.
         */
        val downloadWorkRequest = OneTimeWorkRequestBuilder<DownloadWorker>()
            .setInputData(data)
            .setConstraints(constraints)
            .build()

        val saveWorkRequest = OneTimeWorkRequestBuilder<SaveWorker>()
            .build()

        //24小时循环一次
//        val saveWorkPeriodicRequest = PeriodicWorkRequestBuilder<SaveWorker>(
//            Duration.ofHours(24L)
//        ).build()
//        WorkManager.getInstance().enqueue(saveWorkPeriodicRequest)

        /**
         * Running work
         * 1.子线程 2.保证得到执行 3.根据API选择具体实现
         * 内部实现：
         * Internal TaskExecutor  管理enqueue到WorkManager的WorkRequest
         * WorkManager database 保存Worker的信息和状态，保证在设备重启等情况下仍然可以读取到任务信息
         * WorkerFactory 创建Worker实例
         * Default Executor 管理并保证任务在子线程运行
         */
        WorkManager.getInstance()
            .beginWith(downloadWorkRequest)
            .then(saveWorkRequest)
            .enqueue()

        downloaderWatcher =
            WorkManager.getInstance().getWorkInfoByIdLiveData(downloadWorkRequest.id)
        downloaderWatcher?.observeForever(observer)
    }

    class DownloadWorker(context: Context, workerParameters: WorkerParameters) :
        Worker(context, workerParameters) {

        private val inData = inputData.getString("KEY1")// "在构建任务的时候传入Data"

        override fun doWork(): Result {
            //do work
            val outData = Data.Builder()
                .putString("KEY2", "传给外部/下游worker的值（beginWith-then关系中）")
                .build()
            return Result.success(outData)
        }

    }

    class SaveWorker(context: Context, workerParameters: WorkerParameters) :
        Worker(context, workerParameters) {

        private val inData = inputData.getString("KEY2")// "传给外部/下游worker的值（beginWith-then关系中）"

        override fun doWork(): Result {
            //do work
            val outData = Data.Builder().putAll(inputData).build()
            return Result.success(outData)
        }

    }

}