Coroutines and Lifecycle in Kotlin

一、前言

kotlinCoroutines in sometimes very convenient.jetpackProvides enough compatible,Here to record some of its

二、引入依赖

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.fragment:fragment-ktx:1.5.0'
    implementation 'androidx.activity:activity-ktx:1.5.0'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.5.1'
     implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.5.1'

三、代码示例

1、基础用法

凡是实现了LifecycleOwnerInterface class can use the following way open coroutines,例如Fragment、ComponentActivity及其子类

	//You can use the following way open association degree,Advantage is not to deal with page after the closing
	   lifecycleScope.launch {
    
        }

ViewModel

 viewModelScope.launch {
     
            
        }

2、repeatOnLifecycle

If there is a demand according to the page life cycle must be,比如说onStartWhen start coroutines,onStopTime to stop coroutines,可以使用以下方式.The life cycle is calledCan restart the life cycle of perceptual coroutines

override fun onCreate(savedInstanceState: Bundle?) {
    
	lifecycleListener()
}
    private fun lifecycleListener(){
    
        lifecycleScope.launch {
    
            repeatOnLifecycle(Lifecycle.State.STARTED){
    
                while (isActive){
    
                    delay(1000)
                    Log.e("YM---->","线程运行中....")
                }
            }
        }
    }

3、flowWithLifecycle

If it is only on a data streamFlow进行监听,可以使用以下方式

    private fun lifecycleListener(){
    
        lifecycleScope.launch {
    
            (1..9).asFlow().flowWithLifecycle(lifecycle,Lifecycle.State.STARTED).collect{
    
                println("YM---->value:$it")
            }

        }
    }

由于flowWithLifecycle是Flow的函数,So it can be hung on in heatStateFlow或ShareFlow上面.Multiple streams can also use the aboverepeatOnLifecycle的方式

4、lifecycle.whenCreated、lifecycle.whenStarted 和 lifecycle.whenResumed

repeatOnLifecycleActivities can be limited within a certain range,But this will come as the life cycle of repeated repeated start,但是假如,Only use a word you don't need so much,可以使用以下方式,

class MyFragment: Fragment {
    
    init {
    
        lifecycleScope.launch {
    
            whenStarted {
    }
        }
        //或者
        lifecycleScope.launchWhenCreated {
     
            
        }
    }
}

5、协程与LiveData

在使用LiveData时候,We sometimes need to asynchronous access to content,Usually is to createLiveData,然后在onCreate()To take the initiative to load the data,This way can simplify the operation

    private val user: LiveData<Int> = liveData {
    
// val data = database.loadUser() // loadUser is a suspend function.
        //delay(5000)
        emit(10)
    }
 override fun onCreate(savedInstanceState: Bundle?) {
    
	 lifecycleListener()
 }
 private fun lifecycleListener(){
    
        user.observe(this){
    
            Log.e("YM---->"," 参数:$it")
        }
    }

以下引用自官网

当 LiveData 变为活动状态时,代码块开始执行;当 LiveData
变为非活动状态时,代码块会在可配置的超时过后自动取消.如果代码块在完成前取消,则会在 LiveData
再次变为活动状态后重启;如果在上次运行中成功完成,则不会重启.请注意,代码块只有在自动取消的情况下才会重启.如果代码块由于任何其他原因（例如,抛出
CancellationException）而取消,则不会重启.

当页面进入onStop时候,Will not send until the restore data page,才会发送数据,需要注意的是,实际测试中,Logic does not perform again,But in the next time the already loading the data sent directly

四、参考链接

1. kotlin协程Flow的StateFlow和SharedFlow(十二)
2. 将 Kotlin 协程与生命周期感知型组件一起使用
3. Jetpack之LifeCycle
4. kotlin协程Flow的StateFlow和SharedFlow(十二)