android 多个viewmodel之间通信

       多个viewmodel之间的通信有多种方法，比如通过resposity将sharedviewmodel作为参数传递，进而完成数据通信，也可以通过一个公共的全局变量进行数据传递。本文中提供一个以singleton单例的方式进行。

1.创建单例的resposity类。

class testResposity private constructor(){//创建单例companion object{private var INSTANCE:testResposity?=null@Synchronizedfun getInstance():testResposity{if(INSTANCE==null)INSTANCE = testResposity()return INSTANCE!!}}//以下为业务逻辑val data = MutableStateFlow<String>("")val _counter1 = MutableStateFlow<Int>(0)val counter1 = _counter1.asStateFlow()fun updateCounter1(){_counter1.value++if(_counter1.value==2){data.value = "second"}else if(_counter1.value == 3){data.value = "third"}}
}

2.创建测试的viewmodel1

class TestViewModel1:ViewModel() {//获取resposity单例private val resposity = testResposity.getInstance()val data = resposity.data//调用测试逻辑public fun updateCounter1(){resposity.updateCounter1()}
}

3.按照相同的方式，创建测试的viewmodel2

class TestViewModel2:ViewModel() {private val resposity = testResposity.getInstance()val counter = resposity.counter1public fun updateCounter(){resposity.updateCounter1()}
}

4.测试的compose

@Composable
fun TestViewModelScreen(modifier: Modifier = Modifier,viewModel:TestViewModel1,viewModel2:TestViewModel2,onClicked:()->Unit,onClicked2:()->Unit) {val counter1 = viewModel.data.collectAsState()val counter2 = viewModel2.counter.collectAsState();Column {Text(text = counter1.value.toString())Text(text = counter2.value.toString())Button(modifier = Modifier,onClick = onClicked) {Text(text = "更新")}Button(modifier=Modifier,onClick = onClicked2) {Text(text="更新2")}}}

5.Activity中调用代码

var viewModel1=ViewModelProvider(this).get(TestViewModel1::class.java)var viewModel2 = ViewModelProvider(this).get(TestViewModel2::class.java)TestViewModelTheme {Surface(modifier = Modifier.fillMaxSize(),){Row (modifier = Modifier.fillMaxSize(),verticalAlignment = Alignment.CenterVertically,horizontalArrangement = Arrangement.Center){TestViewModelScreen(viewModel = viewModel1,viewModel2=viewModel2,onClicked = {viewModel1.updateCounter1()},onClicked2 = {viewModel2.updateCounter()})}}}

6.结果

通过两个不同的viewModel，可以对仓库类中的一个变量进行操作，并同步可显示双方操作结果。