July 2020
Intermediate to advanced
235 pages
3h 37m
Chinese
Content preview from Kotlin 编程实践
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216
｜
第
13
章
➊
使用 coroutineContext 属性启动。
➋
为网络调用切换到 Dispatchers.IO。
➌
切换回 Dispatchers.Main 更新 UI。
一旦 activity 被销毁，任务也将被取消。
最新版本的 Android 架构组件提供了其他作用域，例如 viewModelScope，这些作用
域在清除 ViewModel 时会自动取消作业。这是 Android KTX 库的一部分，因此你需要
在构建中添加适当的依赖项：
dependencies {
// ... 与前面相同 ...
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:x.x.x"
}
这将添加 viewModelScope 属性，你可以使用该属性在任何调度器上启动协程。
13.6
协程调试
问题
如何获取运行中的协程的更多信息。
解决方案
使用 JVM 上的 -Dkotlinx.coroutines.debug 标记。
讨论
调试异步程序总是很困难的，因为可以同时运行多个任务。幸运的是，协程库包含一个
简单的调试功能。
要在调试模式下（在 JVM 上）执行协程，请使用系统属性 kotlinx.coroutines.
debug。
或者，你可以通过 Java 命令行上的 -ea（启用断言）标记启用调试。
协程与结构化并发
｜
217
调试模式为每个启动的协程都附加一个唯一的名称。为方便起见，在此处复制了示例
13-5，显示除主线程之外还启动了两个协程： ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.