使用 Kotlin 1.3 在 Android 中迁移到 Kotlin 协程 [英] Migrate to Kotlin coroutines in Android with Kotlin 1.3

问题描述

我应该在我的 build.gradle 文件中更改什么或在类中导入以在我的带有 Kotlin 1.3 的 Android 项目中使用稳定的协程函数?

What should I change in my build.gradle file or import in classes to use stable coroutine functions in my Android project with Kotlin 1.3 ?

我的build.gradle

实现org.jetbrains.kotlin:kotlin-coroutines-core:$coroutines_version"实现org.jetbrains.kotlin:kotlin-coroutines-android:$coroutines_version"

当然我用的是 Android Studio 3.3 预览版

Of course I use Android Studio 3.3 Preview

推荐答案

在 build.gradle 中将一个库更改为

In build.gradle change a library to

实现'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1'.

删除，如果已添加:

kotlin {
    experimental {
        coroutines "enable"
    }
}

在代码中将 launch 更改为 GlobalScope.launch(Dispatchers.IO) 或 GlobalScope.launch(Dispatchers.Main).

In code change launch to GlobalScope.launch(Dispatchers.IO) or GlobalScope.launch(Dispatchers.Main).

更新

请使用本地协程上下文而不是全局范围(例如，请参见 http://kotlinlang.org/docs/reference/coroutines/coroutine-context-and-dispatchers.html).

Please, use local coroutine context instead of global scope (see, for instance, http://kotlinlang.org/docs/reference/coroutines/coroutine-context-and-dispatchers.html).

对于活动

参见 https://github.com/Kotlin/kotlinx.coroutines/blob/master/ui/coroutines-guide-ui.md.

实现CoroutineScope:

class YourActivity : AppCompatActivity(), CoroutineScope {

添加局部变量job并初始化:

Add a local variable job and initialize it:

private lateinit var job: Job

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    job = Job()
}

创建一个协程上下文并在 Activity destroy 时取消它:

Create a coroutine context and cancel it on Activity destroy:

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

override val coroutineContext: CoroutineContext
    get() = Dispatchers.Main + job

对于 Fragment(与 Activity 中的相同)

实现 CoroutineScope:

Implement CoroutineScope:

class YourFragment : Fragment(), CoroutineScope {

创建一个局部变量job并在onCreate()中初始化它.(我试图编写 private val job: Job = Job()，但遇到了在 ViewPager 中你将创建 Fragment 和它们的作业.因为我们会在 ViewPager 中滑动时取消 onDestroy() 中的 job，所以我们应该重新创建作业.

Create a local variable job and initialize it in onCreate(). (I tried to write private val job: Job = Job(), but bumped into problem that in ViewPager you will create Fragments and their jobs. As we will cancel the job in onDestroy() during swiping in ViewPager, we should recreate the job).

private lateinit var job: Job

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    ...
    job = Job()
}

创建一个协程上下文并在 Fragment destroy 时取消它:

Create a coroutine context and cancel it on Fragment destroy:

override val coroutineContext: CoroutineContext
    get() = Dispatchers.Main + job // You can use different variants here. 

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

启动示例

照常使用launch:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    launch {
        // Wait for result of I/O operation without blocking the main thread.
        withContext(Dispatchers.IO) {
            interactor.getCountry().let {
                countryName = it.name
            }
        }

        // Update views in the UI thread.
        country.updateCaption(countryName)
    }
}

就我而言，当我使用带有通常回调的 API 请求时出现问题.回调中的 launch 内部没有被调用.所以我用交互器重写了那个代码.

In my case a problem occured when I used API requests with usual callbacks. A launch interior inside a callback hasn't been called. So I rewrote that code with interactors.

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