从使用协程进行网络调用的服务内部发送广播

Posted 2023-04-19

【中文标题】从使用协程进行网络调用的服务内部发送广播

【英文标题】：sendBroadcast from inside Service which uses Coroutine for network call

【发布时间】：2020-09-09 15:01:48

【问题描述】：

我有一个 JobIntentService，它应该进行 API 调用并在结果可用后进行广播。

我正在使用协程通过 Retrofit 进行网络调用。 但是，如果我在 CoroutineScope 中执行 sendBroadcast，它不会触发 BroadcastReceiver

这是我的服务代码 -

MyService.kt

class MyService : JobIntentService() 

    private val TAG = MyService::class.java.simpleName
    private var databaseHelper: DatabaseHelper = DatabaseHelper(this)
    private var imageFetcher: ImageFetcher = ImageFetcher(this)
    private var imageSaver: ImageSaver = ImageSaver(this)
    private val receiver = ServiceBroadcastReceiver()


    override fun onHandleWork(intent: Intent) 
        val filter = IntentFilter()
        filter.addAction("ACTION_FINISHED_SERVICE")
        registerReceiver(receiver, filter)

        when (intent.action) 
            "ACTION_FETCH_FROM_API" -> 
                handleFetchFromAPI()
            
        
    

    override fun onDestroy() 
        super.onDestroy()
        unregisterReceiver(receiver)
    

    private fun handleFetchFromAPI() 
        val API = ServiceBuilder.buildWebService(WebService::class.java)
        CoroutineScope(IO).launch 
            try 
                var apiSuccess : Boolean = false
                val apiResponse = API.getImageOfTheDay()
                if (apiResponse.isSuccessful) 
                    apiSuccess = true
                    val imageAPIResponse = apiResponse.body()
                    val bitmap = imageFetcher.getImageBitmapFromURL(imageAPIResponse.url)
                    val filePath = imageSaver.saveBitmapToFile(bitmap, "image.jpg")
                    withContext(Main) 
                        databaseHelper.saveImageInRoom(imageAPIResponse, filePath)
                    
                
                if(apiSuccess)
                    val broadCastIntent = Intent()
                    broadCastIntent.action = "ACTION_FINISHED_SERVICE"
                    sendBroadcast(broadCastIntent)
                 
             catch (exception: Exception) 
                Log.d(TAG, "Exception occurred $exception.message")
            
        
    

    companion object 
        private const val JOB_ID = 2
        @JvmStatic
        fun enqueueWork(context: Context, intent: Intent) 
            enqueueWork(context, MyService::class.java, JOB_ID, intent)
        
    

ServiceBroadcastReceiver.kt 类 ServiceBroadcastReceiver : BroadcastReceiver()

private val TAG = ServiceBroadcastReceiver::class.java.simpleName
private lateinit var _mNotificationManager: NotificationManager
private val _notificationId = 0
private val _primaryChannelId = "primary_notification_channel"

override fun onReceive(context: Context, intent: Intent) 
    _mNotificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
    when (intent.action) 
        "ACTION_FINISHED_SERVICE" -> 
            deliverNotification(context)
        
    


private fun deliverNotification(context: Context) 
    val contentIntent = Intent(context, MainActivity::class.java)
    val pendingIntent = PendingIntent.getActivity(context,_notificationId,contentIntent,
            PendingIntent.FLAG_UPDATE_CURRENT)
    val builder = NotificationCompat.Builder(context,_primaryChannelId)
    builder.setSmallIcon(R.mipmap.ic_launcher)
    builder.setContentTitle("Hi There")
    builder.setContentText("Service finished its job")
    builder.setContentIntent(pendingIntent)
    builder.priority = NotificationCompat.PRIORITY_HIGH
    builder.setAutoCancel(true)
    builder.setDefaults(NotificationCompat.DEFAULT_ALL)
    _mNotificationManager.notify(_notificationId,builder.build())

getImageOfTheDay() 是 WebService.kt 中的挂起函数

@Headers("Content-Type: application/json")
@GET("/v1/getImageOfTheDay")
suspend fun getImageOfTheDay(): Response<ImageAPIResponse>

如果我将代码移到协程范围之外，则广播会正确发送。 我该如何解决这个问题？

【参考方案1】：

你不应该在这里使用协程。 onHandleWork 方法在后台线程上调用，从该方法返回表示工作已完成并且可以终止服务。

当您使用 launch 启动协程时，onHandleWork 立即返回并且您的服务终止。

您应该直接调用您的网络 API，而不是在协程中，因为 JobIntentService 已经设计为以这种方式工作。

【讨论】：

如何直接调用 API.getImageOfTheDay() 方法？它是一个带有挂起修饰符的函数，因此必须在协程中调用。

在这种情况下将其包裹在runBlocking中。