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.common

import 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.viewmodel

import 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: Job
    
    fun 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.flowapplyapplication

import 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.SharedFlowViewModel

class 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 = sharedFlowViewModel
        
        return 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">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".SharedFlowFragment">

        <androidx.appcompat.widget.LinearLayoutCompat
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <fragment
                android:id="@+id/timeFragment1"
                android:name="com.aruba.flowapplyapplication.TimeFragment"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="1" />

            <fragment
                android:id="@+id/timeFragment2"
                android:name="com.aruba.flowapplyapplication.TimeFragment"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="1" />

            <fragment
                android: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.FloatingActionButton

            android: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.FloatingActionButton
            android: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>

        <variable
            name="sharedFlowViewModel"
            type="com.aruba.flowapplyapplication.viewmodel.SharedFlowViewModel" />
    </data>
</layout>

4.子Fragment中对SharedFlow收集

package com.aruba.flowapplyapplication

import 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.collect

class 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