kotlin--SharedFlow运用

Flow为上流发射，下流接收，是一对一的，而SharedFlow可以一对多，发射一次，多端接收

效果：

1.定义一个类，来对MutableSharedFlow对象作操作

package com.aruba.flowapplyapplication.commonimport kotlinx.coroutines.flow.MutableSharedFlow/*** Created by aruba on 2021/9/21.*/
object LocalEventBus {val event = MutableSharedFlow<Event>()suspend fun postEvent(e: Event) {event.emit(e)}}data class Event(val timestamp: Long)

2.定义ViewModel，来开启和停止SharedFLow发射

package com.aruba.flowapplyapplication.viewmodelimport android.view.View
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.aruba.flowapplyapplication.common.Event
import com.aruba.flowapplyapplication.common.LocalEventBus
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.flow.SharedFlow
import kotlinx.coroutines.launch/*** Created by aruba on 2021/9/21.*/
class SharedFlowViewModel : ViewModel() {private lateinit var job: Jobfun start(v: View) {job = viewModelScope.launch(Dispatchers.IO) {while (true) {LocalEventBus.postEvent(Event(System.currentTimeMillis()))}}}fun stop(v: View) {job.cancel()}
}

3.父Fragment中绑定ViewModel

package com.aruba.flowapplyapplicationimport android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.ViewModelProvider
import com.aruba.flowapplyapplication.databinding.FragmentSharedFlowBinding
import com.aruba.flowapplyapplication.viewmodel.SharedFlowViewModelclass SharedFlowFragment : Fragment() {override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {val binding: FragmentSharedFlowBinding = DataBindingUtil.inflate(inflater,R.layout.fragment_shared_flow,container, false)val sharedFlowViewModel = ViewModelProvider(this,ViewModelProvider.AndroidViewModelFactory(requireActivity().application)).get(SharedFlowViewModel::class.java)binding.sharedFlowViewModel = sharedFlowViewModelreturn binding.root}}

布局文件:

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"><FrameLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"tools:context=".SharedFlowFragment"><androidx.appcompat.widget.LinearLayoutCompatandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><fragmentandroid:id="@+id/timeFragment1"android:name="com.aruba.flowapplyapplication.TimeFragment"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1" /><fragmentandroid:id="@+id/timeFragment2"android:name="com.aruba.flowapplyapplication.TimeFragment"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1" /><fragmentandroid:id="@+id/timeFragment3"android:name="com.aruba.flowapplyapplication.TimeFragment"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1" /></androidx.appcompat.widget.LinearLayoutCompat><com.google.android.material.floatingactionbutton.FloatingActionButtonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="left|bottom"android:layout_margin="10dp"android:onClick="@{sharedFlowViewModel.start}"android:src="@drawable/ic_baseline_play_arrow_24" /><com.google.android.material.floatingactionbutton.FloatingActionButtonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="right|bottom"android:layout_margin="10dp"android:onClick="@{sharedFlowViewModel.stop}"android:src="@drawable/ic_baseline_stop_24" /></FrameLayout><data><variablename="sharedFlowViewModel"type="com.aruba.flowapplyapplication.viewmodel.SharedFlowViewModel" /></data>
</layout>

4.子Fragment中对SharedFlow收集

package com.aruba.flowapplyapplicationimport android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.lifecycleScope
import com.aruba.flowapplyapplication.common.LocalEventBus
import com.aruba.flowapplyapplication.databinding.FragmentTimeBinding
import kotlinx.coroutines.flow.collectclass TimeFragment : Fragment() {override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {val binding = DataBindingUtil.inflate<FragmentTimeBinding>(inflater,R.layout.fragment_time,container,false)lifecycleScope.launchWhenCreated {LocalEventBus.event.collect {binding.textView3.text = it.timestamp.toString()}}return binding.root}
}

布局文件就一个TextView

Demo地址：https://gitee.com/aruba/flow-apply-application.git