Android Kotlin SharedFlow

Posted 2022-09-12 安果移不动

SharedFlow 会从其中收集值得所有使用方法中发出数据

、

简而言之就是 像普通的流只可以一方发送。一方接受

而这个流可以一方发送。多方接受

下面上代码演示

SharedFlowFragment

package com.example.android_flow_practice.fragment

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.fragment.app.viewModels
import com.example.android_flow_practice.databinding.FragmentSharedFlowBinding
import com.example.android_flow_practice.viewmodel.SharedFlowViewModel


class SharedFlowFragment : Fragment() 
    private val TAG = "ArticleFragment"
    private val viewModel: SharedFlowViewModel by viewModels()

    private val mBinding: FragmentSharedFlowBinding by lazy 
        FragmentSharedFlowBinding.inflate(layoutInflater)
    

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
    ): View? 
        // Inflate the layout for this fragment
        return mBinding.root
    


    override fun onActivityCreated(savedInstanceState: Bundle?) 
        super.onActivityCreated(savedInstanceState)
        mBinding.btnStart.setOnClickListener 
            viewModel.startRefresh()
        
        mBinding.btnStop.setOnClickListener 
            viewModel.stopRefresh()
        
    

布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".fragment.TextFragment">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <fragment
            android:id="@+id/fragment_1"
            android:name="com.example.android_flow_practice.fragment.TextFragment"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />

        <fragment
            android:id="@+id/fragment_2"
            android:name="com.example.android_flow_practice.fragment.TextFragment"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />

        <fragment
            android:id="@+id/fragment_3"
            android:name="com.example.android_flow_practice.fragment.TextFragment"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />

    </LinearLayout>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/btn_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|start"
        android:layout_marginStart="8dp"
        android:layout_marginBottom="8dp"
        android:src="@android:drawable/ic_media_play"


        />


    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/btn_stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_marginStart="8dp"
        android:layout_marginBottom="8dp"
        android:src="@android:drawable/ic_notification_overlay"

        />



</FrameLayout>

TextFragment

package com.example.android_flow_practice.fragment

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.viewModels
import androidx.lifecycle.lifecycleScope
import com.example.android_flow_practice.R
import com.example.android_flow_practice.common.LocalEventBus
import com.example.android_flow_practice.databinding.FragmentSharedFlowBinding
import com.example.android_flow_practice.databinding.FragmentTextBinding
import com.example.android_flow_practice.viewmodel.ArticleViewModel
import kotlinx.coroutines.flow.collect


class TextFragment : Fragment() 

    private val mBinding: FragmentTextBinding by lazy 
        FragmentTextBinding.inflate(layoutInflater)
    

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
    ): View? 
        // Inflate the layout for this fragment
        return mBinding.root
    


    override fun onActivityCreated(savedInstanceState: Bundle?) 
        super.onActivityCreated(savedInstanceState)
        lifecycleScope.launchWhenCreated 
            LocalEventBus.events.collect 
                mBinding.tvText.text = it.timestamp.toString()
            
        

    

布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".fragment.TextFragment">

    <TextView
        android:layout_gravity="center"
        android:id="@+id/tv_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</FrameLayout>

核心代码

package com.example.android_flow_practice.common

import kotlinx.coroutines.flow.MutableSharedFlow

object LocalEventBus 
    val events = MutableSharedFlow<Event>()

    suspend fun postEvent(event: Event) 
        events.emit(event)
    


data class Event(val timestamp: Long)

package com.example.android_flow_practice.viewmodel

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.example.android_flow_practice.common.Event
import com.example.android_flow_practice.common.LocalEventBus
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.launch

class SharedFlowViewModel : ViewModel() 
    private lateinit var job: Job

    fun startRefresh() 
        job = viewModelScope.launch(Dispatchers.IO) 
            while (true) 
                LocalEventBus.postEvent(Event(System.currentTimeMillis()))
            

        
    

    fun stopRefresh() 
        if(::job.isInitialized)
            job.cancel()

        
    

点击启动三个fragment同事开始打印当前时间

点击停止 就停止打印 非常的好用