RunBlocking 与 Dispatcher 通信不起作用

Question

I have switched my context to Dispatcher.Main to show UI but data fetched on runBlocking but unable to display in RecylerView

runBlocking {
            var fruits = fetchFruitList()
            withContext(Dispatchers.Main){
                recyclerView.adapter = FruitAdapter(fruits);
            }
        }

我做错了什么以及return数据从一个 Dispatcher 到另一个 Dispatcher 的正确方法是什么。

我试过另一种方法

GlobalScope.launch {
            withContext(Dispatchers.IO){
                var fruits = arrayOf("Grapes","Apple","Mango","TuttiFruit","PineApple",
                        "Pomegrante","Apple","Mango","TuttiFruit","PineApple",
                        "Pomegrante","Apple","Mango","TuttiFruit","PineApple").toList()
                return@withContext
            }
            recyclerView.adapter = FruitAdapter(fruits)
        }

但以上述方式 I have to declare fruits as global 而我不想让它在全球范围内工作。有没有办法 return 数据从一个 '调度程序队列到另一个

I have to fetch data from Api (IO operation) and display that data in RecyclerView(Main Thread Operation)

Answer 1

那是因为你必须在获取数据后切换上下文：

GlobalScope.launch(Dispatchers.IO){
       var fruits = arrayOf("Grapes","Apple","Mango","TuttiFruit","PineApple",
                    "Pomegrante","Apple","Mango","TuttiFruit","PineApple",
                    "Pomegrante","Apple","Mango","TuttiFruit","PineApple").toList()

       withContext(Dispatchers.MAIN){
           recyclerView.adapter = FruitAdapter(fruits)
       }        
}

根据评论编辑：

对于 runBlocking 查看文档第一段。

Runs a new coroutine and blocks the current thread interruptibly until its completion. This function should not be used from a coroutine. It is designed to bridge regular blocking code to libraries that are written in suspending style, to be used in main functions and in tests.

其次，您要求GlobalScope用法。是的，如果你在 Android 中执行协程，你应该避免这种情况。 Reasons here.

如何在AndroidActivity/Fragment中启动协程？

首先我建议在 ViewModel 或 Presenter 中使用，但如果你想在 Activity/Fragment 中启动协程，你将需要一种方法来控制和管理它取消以避免内存泄漏。解决方案是：

private val job: Job = Job()
                                              //or Dispatchers.IO
private val fragmentScope = CoroutineScope(Dispatchers.MAIN + job)

//launch a coroutine later in Activity/Fragment

fragmentScope.launch{
  //the default coroutine dispatcher would be the defined dispatcher above
}

override fun onDestroy(){
  super.onDestroy()
  fragmentScope.cancel()
}

关于你的问题：

what am I doing wrong and what is the appropriate way to return data from one Dispatcher to another

如果您想 return 来自不同上下文的值，您也可以尝试此解决方案：

someScope.launch(Dispatchers.MAIN){
 var data = withContext(Dispatchers.IO){
  val someData = fetchSomeData()
  return@withContext data
}
if(data.isAvailable()){ //for example
 //runing on the main thread
 }
}

RunBlocking 与 Dispatcher 通信不起作用

RunBlocking with Dispatcher communication not working

android

dispatcher

kotlin

kotlin-coroutines