💺 👨🏿‍🏭 📮 协程和改造2的经验 📎 🛒 🏇

这是什么

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Jetbrain写道：

协程简化了异步编程，将所有复杂性留在了库中。程序的逻辑可以在协程中顺序表达，而基库将为我们异步实现它。该库可以将用户代码的相应部分包装在订阅相应事件的回调中，并将执行分派到不同的线程（甚至到不同的机器！）。该代码将保持简单，就像严格按顺序执行一样。

简单来说，这是一个用于同步/异步代码执行的库。

怎么了

因为RxJava不再流行（只是在开玩笑）。

首先，我想尝试一些新的东西，其次，我碰到了一篇文章 -比较Corutin和其他方法的速度。

例子

例如，您需要在后台执行操作。

首先-添加对corutin的build.gradle依赖项：

dependencies {
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.1.1"
....
}

view raw build.gradle hosted with ❤ by GitHub

我们在代码中使用该方法：

suspend fun <T> withContext(
context: CoroutineContext,
block: suspend CoroutineScope.() -> T
)

view raw gistfile1.txt hosted with ❤ by GitHub

在上下文中-我们指定了所需的线程池-在简单情况下，它们是IO，Main和Default

IO-用于使用API进行简单操作，使用数据库进行操作，共享优先级等。
Main-UI线程，从中可以访问视图
默认-适用于CPU负载高的繁重操作
（本文更多）

块-我们要执行的Lambda

var result = 1.0
withContext(IO) {
for (i in 1..1000) {
result += i * i
}
}
Log.d("coroutines example", "result = $result")

view raw Example.kt hosted with ❤ by GitHub

原则上，就是这样，我们得到的平方和的结果是1到1000，同时我们不阻塞主线程，这意味着没有ANR

但是，如果协程执行了20秒，并且在此期间我们旋转了设备2次，则将有3个同时运行的程序段。哎呀

而且，如果我们将指向活动的链接传递给该块-则是泄漏，并且缺乏在旧块中执行视图操作的能力。两次

那该怎么办呢？

做得更好

private var viewModelJob = Job()
private val viewModelScope = CoroutineScope(Dispatchers.Main + viewModelJob)
fun doWork() {
var result = 1.0
viewModelScope.launch {
withContext(IO) {
for (i in 1..1000) {
result += i * i
}
}
}
Log.d("coroutines example", " result = $result")
}
fun cancelJob() {
viewModelJob.cancel()
}

view raw Example.kt hosted with ❤ by GitHub

因此，例如，当屏幕旋转时，我们能够停止流中代码的执行。

CoroutineScope使合并所有嵌套协程的范围成为可能，并且在调用job.cancel（）时停止了它们的执行

如果您打算在停止执行后重用作用域，则需要使用job.cancelChildren（）而不是job.cancel（）感谢Neikist的评论

同时，我们仍然有机会控制流量：

fun doWork() {
var result = 1.0
var result2 = 1.0
viewModelScope.launch {
withContext(IO) {
for (i in 1..1000) {
result += i * i
}
}
withContext(Default) {
for (i in 1..1000) {
result2 += i * i
}
}
}
Log.d("coroutines example", "running result = $result, result 2 = $result2")
}
fun cancelJob() {
viewModelJob.cancel()
}

view raw Example.kt hosted with ❤ by GitHub

我们连接改造2

将依赖项添加到冰雹中：

dependencies {
implementation "com.squareup.retrofit2:retrofit:$retrofitVersion"
implementation "com.squareup.retrofit2:converter-moshi:$converterMoshiVersion"
implementation "com.jakewharton.retrofit:retrofit2-kotlin-coroutines-adapter:$retrofitCoroutinesVersion"
...
}

view raw build.gradle hosted with ❤ by GitHub

我们以钢笔https://my-json-server.typicode.com/typicode/demo/posts为例

我们描述改造接口：

interface RetrofitPosts {
@GET("posts")
fun getPosts(): Deferred<Response<List<Post>>>
}

view raw RetrofitPosts.kt hosted with ❤ by GitHub

描述返回的Post模型：

data class Post(val id: Int, val title: String)

view raw Post.kt hosted with ❤ by GitHub

我们的基本资料库：

abstract class BaseRepository<Params, Result> {
abstract suspend fun doWork(params: Params): Result
}

view raw BaseRepository.kt hosted with ❤ by GitHub

PostsRepository的实现：

class PostsRepository :
BaseRepository<PostsRepository.Params, PostsRepository.Result>() {
override suspend fun doWork(params: Params): Result {
val retrofitPosts = Retrofit
.Builder()
.baseUrl("https://jsonplaceholder.typicode.com")
.addConverterFactory(MoshiConverterFactory.create())
.addCallAdapterFactory(CoroutineCallAdapterFactory())
.build()
.create(RetrofitPosts::class.java)
val result = retrofitPosts
.getPosts()
.await()
return Result(result.body())
}
class Params
data class Result(val posts: List<Post>?)
}

view raw PostsRepository.kt hosted with ❤ by GitHub

我们的BaseUseCase：

abstract class BaseUseCase<Params, Result> {
abstract suspend fun doWork(params: Params): Result
}

view raw BaseUseCase.kt hosted with ❤ by GitHub

GetPostsListUseCase的实现：

class GetListOfPostsUseCase
: BaseUseCase<GetListOfPostsUseCase.Params, GetListOfPostsUseCase.Result>() {
override suspend fun doWork(params: Params): Result {
return Result(
PostsRepository()
.doWork(PostsRepository.Params())
.response
.posts
)
}
class Params
class Result(val posts: List<Post>?)
}

view raw GetListOfPostsUseCase.kt hosted with ❤ by GitHub

结果如下：

fun doWork() {
val useCase = GetListOfPostsUseCase()
viewModelScope.launch {
withContext(Dispatchers.IO) {
val result = useCase.doWork(
GetListOfPostsUseCase.Params()
)
Log.d("coroutines example", "get list of posts = ${result.posts}")
}
}
}
fun cancelJob() {
viewModelJob.cancel()
}

view raw Example.kt hosted with ❤ by GitHub

变得更好

我是一个懒惰的人，每次我不想拖动整个代码表时，都在BaseViewModel中进行了必要的方法：

abstract class BaseViewModel : ViewModel() {
private var viewModelJob = Job()
private val viewModelScope = CoroutineScope(Dispatchers.Main + viewModelJob)
private var isActive = true
// Do work in IO
fun <P> doWork(doOnAsyncBlock: suspend CoroutineScope.() -> P) {
doCoroutineWork(doOnAsyncBlock, viewModelScope, IO)
}
// Do work in Main
// doWorkInMainThread {...}
fun <P> doWorkInMainThread(doOnAsyncBlock: suspend CoroutineScope.() -> P) {
doCoroutineWork(doOnAsyncBlock, viewModelScope, Main)
}
// Do work in IO repeately
// doRepeatWork(1000) {...}
// then we need to stop it calling stopRepeatWork()
fun <P> doRepeatWork(delay: Long, doOnAsyncBlock: suspend CoroutineScope.() -> P) {
isActive = true
viewModelScope.launch {
while (this@BaseViewModel.isActive) {
withContext(IO) {
doOnAsyncBlock.invoke(this)
}
if (this@BaseViewModel.isActive) {
delay(delay)
}
}
}
}
fun stopRepeatWork() {
isActive = false
}
override fun onCleared() {
super.onCleared()
isActive = false
viewModelJob.cancel()
}
private inline fun <P> doCoroutineWork(
crossinline doOnAsyncBlock: suspend CoroutineScope.() -> P,
coroutineScope: CoroutineScope,
context: CoroutineContext
) {
coroutineScope.launch {
withContext(context) {
doOnAsyncBlock.invoke(this)
}
}
}
}

view raw BaseViewModel.kt hosted with ❤ by GitHub

现在获取帖子列表如下所示：

class PostViewModel : BaseViewModel() {
val lengthOfPostsList = MutableLiveData<String>()
fun getListOfPosts() {
doWork {
val result = GetListOfPostsUseCase()
.doWork(GetListOfPostsUseCase.Params())
Log.d("coroutines example", "get list of posts = ${result.posts}")
lengthOfPostsList.postValue(result.posts?.size.toString())
}
}

view raw PostViewModel.kt hosted with ❤ by GitHub

结论

我在产品中使用了协程，结果证明代码确实更简洁易读。

UPD：
改造异常处理说明，请参见注释

	dependencies {
	implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1"
	implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.1.1"
	....
	}

	suspend fun <T> withContext(
	context: CoroutineContext,
	block: suspend CoroutineScope.() -> T
	)

	var result = 1.0
	withContext(IO) {
	for (i in 1..1000) {
	result += i * i
	}
	}
	Log.d("coroutines example", "result = $result")

	private var viewModelJob = Job()
	private val viewModelScope = CoroutineScope(Dispatchers.Main + viewModelJob)

	fun doWork() {
	var result = 1.0
	viewModelScope.launch {
	withContext(IO) {
	for (i in 1..1000) {
	result += i * i
	}
	}
	}
	Log.d("coroutines example", " result = $result")
	}

	fun cancelJob() {
	viewModelJob.cancel()
	}

	fun doWork() {
	var result = 1.0
	var result2 = 1.0
	viewModelScope.launch {
	withContext(IO) {
	for (i in 1..1000) {
	result += i * i
	}
	}
	withContext(Default) {
	for (i in 1..1000) {
	result2 += i * i
	}
	}
	}
	Log.d("coroutines example", "running result = $result, result 2 = $result2")
	}

	fun cancelJob() {
	viewModelJob.cancel()
	}


	dependencies {
	implementation "com.squareup.retrofit2:retrofit:$retrofitVersion"
	implementation "com.squareup.retrofit2:converter-moshi:$converterMoshiVersion"
	implementation "com.jakewharton.retrofit:retrofit2-kotlin-coroutines-adapter:$retrofitCoroutinesVersion"
	...
	}

	interface RetrofitPosts {

	@GET("posts")
	fun getPosts(): Deferred<Response<List<Post>>>

	}

	abstract class BaseRepository<Params, Result> {

	abstract suspend fun doWork(params: Params): Result

	}

	class PostsRepository :
	BaseRepository<PostsRepository.Params, PostsRepository.Result>() {

	override suspend fun doWork(params: Params): Result {
	val retrofitPosts = Retrofit
	.Builder()
	.baseUrl("https://jsonplaceholder.typicode.com")
	.addConverterFactory(MoshiConverterFactory.create())
	.addCallAdapterFactory(CoroutineCallAdapterFactory())
	.build()
	.create(RetrofitPosts::class.java)
	val result = retrofitPosts
	.getPosts()
	.await()

	return Result(result.body())
	}

	class Params
	data class Result(val posts: List<Post>?)
	}

	abstract class BaseUseCase<Params, Result> {

	abstract suspend fun doWork(params: Params): Result

	}

	class GetListOfPostsUseCase
	: BaseUseCase<GetListOfPostsUseCase.Params, GetListOfPostsUseCase.Result>() {

	override suspend fun doWork(params: Params): Result {
	return Result(
	PostsRepository()
	.doWork(PostsRepository.Params())
	.response
	.posts
	)
	}

	class Params
	class Result(val posts: List<Post>?)
	}

	fun doWork() {
	val useCase = GetListOfPostsUseCase()
	viewModelScope.launch {
	withContext(Dispatchers.IO) {

	val result = useCase.doWork(
	GetListOfPostsUseCase.Params()
	)
	Log.d("coroutines example", "get list of posts = ${result.posts}")
	}
	}

	}

	fun cancelJob() {
	viewModelJob.cancel()
	}

	abstract class BaseViewModel : ViewModel() {

	private var viewModelJob = Job()
	private val viewModelScope = CoroutineScope(Dispatchers.Main + viewModelJob)
	private var isActive = true

	// Do work in IO
	fun <P> doWork(doOnAsyncBlock: suspend CoroutineScope.() -> P) {
	doCoroutineWork(doOnAsyncBlock, viewModelScope, IO)
	}

	// Do work in Main
	// doWorkInMainThread {...}
	fun <P> doWorkInMainThread(doOnAsyncBlock: suspend CoroutineScope.() -> P) {
	doCoroutineWork(doOnAsyncBlock, viewModelScope, Main)
	}

	// Do work in IO repeately
	// doRepeatWork(1000) {...}
	// then we need to stop it calling stopRepeatWork()
	fun <P> doRepeatWork(delay: Long, doOnAsyncBlock: suspend CoroutineScope.() -> P) {
	isActive = true
	viewModelScope.launch {
	while (this@BaseViewModel.isActive) {
	withContext(IO) {
	doOnAsyncBlock.invoke(this)
	}
	if (this@BaseViewModel.isActive) {
	delay(delay)
	}
	}
	}
	}

	fun stopRepeatWork() {
	isActive = false
	}

	override fun onCleared() {
	super.onCleared()
	isActive = false
	viewModelJob.cancel()
	}

	private inline fun <P> doCoroutineWork(
	crossinline doOnAsyncBlock: suspend CoroutineScope.() -> P,
	coroutineScope: CoroutineScope,
	context: CoroutineContext
	) {
	coroutineScope.launch {
	withContext(context) {
	doOnAsyncBlock.invoke(this)
	}
	}
	}
	}

	class PostViewModel : BaseViewModel() {

	val lengthOfPostsList = MutableLiveData<String>()

	fun getListOfPosts() {
	doWork {
	val result = GetListOfPostsUseCase()
	.doWork(GetListOfPostsUseCase.Params())
	Log.d("coroutines example", "get list of posts = ${result.posts}")
	lengthOfPostsList.postValue(result.posts?.size.toString())
	}
	}

协程和改造2的经验

这是什么

怎么了

例子

做得更好

我们连接改造2

变得更好

结论

More articles: