android compose viewmodel更新数据方式

1.界面数据与viewmodel中数据的同步更新方法

第一种采用自定义一个UIState的StateFlow，第二种，对界面上每一个数据定义一个StateFlow。

2.采用UIState类的StateFlow方法。

2.1 UIState定义

//定义一个数据类
data class AppSettings(
    var id: Boolean = true,
    var Num: Boolean = true,
    var Date1: Boolean = true,
    var ProductName: Boolean = true,
    var RealNum: Boolean = true,
    var Price: Boolean = true,
    var CustomName: Boolean = true,
    var ScopeName: Boolean = true,

) {
    companion object {
        fun default() = AppSettings()
    }
}

2.2 在viewmodel中定义stateFlow

    private var _AppSettings = MutableStateFlow<AppSettings>(AppSettings())
    val appSettings = _AppSettings.asStateFlow()

2.3 在UI中定义Collect

    var appSettings = appViewModel.settingViewModel.appSettings.collectAsState()

2.4 在UI中应用Collect，包含数据更新

            Checkbox(
                checked =appSettings.value.id,
                onCheckedChange = {
                    //数据更新
                    appViewModel.settingViewModel.UpdateAppSettings(it,1)
                },
                modifier = Modifier.weight(0.5f)
            )

2.5在viewmodel中实现数据更新

    fun UpdateAppSettings(value: Boolean,type:Int){
        when(type)
        {
            1->_AppSettings.update { it.copy(id = value) }
            2->_AppSettings.update { it.copy(Num = value) }
            3->_AppSettings.update { it.copy(Date1 = value) }
            4->_AppSettings.update { it.copy(ProductName = value) }
            5->_AppSettings.update { it.copy(RealNum=value) }
            6->_AppSettings.update { it.copy(Price = value) }
            7->_AppSettings.update { it.copy(CustomName = value) }
            8->_AppSettings.update { it.copy(ScopeName = value) }
            else-> return
        }
    }

3.采用对界面上每一个数据定义一个StateFlow的方法

3.1 在viewmodel中定义一个变量的StateFlow

//声明一个StateFlowVariable

data class MutableStateFlowVariable(
    private var _data: MutableStateFlow<String> = MutableStateFlow<String>("")
){
    val Data = _data.asStateFlow()
    fun UpdateData(str:String){
        _data.value = str
    }
}

//在viewModel中定义
var ProductMount = MutableStateFlowVariable()

3.2 在UI中定义Collect

    var productMount = appViewModel.addNewViewModel.ProductMount.Data.collectAsState()

3.3在UI中使用Collect

        Row(
            horizontalArrangement = Arrangement.Center,
            verticalAlignment = Alignment.CenterVertically,
            modifier = Modifier.padding(top = 8.dp, bottom = 4.dp).fillMaxWidth()
        ) {
            //Text("数量：", textAlign = TextAlign.Right, modifier = Modifier.weight(1.0f))
            TextField(
                value = productMount.value,//selectedItem.value.Mount,
                onValueChange = {appViewModel.addNewViewModel.ProductMount.UpdateData(it)},
                placeholder = {Text("请输入数量")},
                keyboardOptions = KeyboardOptions(
                    keyboardType= KeyboardType.Decimal,
                    imeAction = ImeAction.Next
                ),
                modifier = Modifier.width(widthRow)
            )
        }

3.4在viewmodel中实现数据更新

//TextField(
//                value = productMount.value,//selectedItem.value.Mount,
                onValueChange = {appViewModel.addNewViewModel.ProductMount.UpdateData(it)},
//                placeholder = {Text("请输入数量")},
//                keyboardOptions = KeyboardOptions(
//                    keyboardType= KeyboardType.Decimal,
//                    imeAction = ImeAction.Next
//                ),
//                modifier = Modifier.width(widthRow)
//            )