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.common

import kotlinx.coroutines.flow.MutableSharedFlow

/**
 * Created by aruba on 2021/9/21.
 */
object LocalEventBus {
    val event = MutableSharedFlow()

    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:

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(
            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