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xamarin - 如何将入口参数传递给 Xamarin MVVM viewmodel

转载 作者:行者123 更新时间:2023-12-03 10:12:43 29 4
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我一直在寻找通过单击带有命令参数的按钮(在 View 中)将入口参数(用户名、密码)传递给 Xamarin MVVM View 模型的最佳方法。

最佳答案

这是在 Xamarin MVVM 模式中传递用户名和密码的示例。它工作正常:

1) 创建一个包含您的命令的 LoginViewModel。确保 ViewModel 实现了 INotifyPropertyChanged:

public class LoginViewModel:INotifyPropertyChanged
{
private ObservableCollection<CredentialsModel> _listOfItems=new
ObservableCollection<CredentialsModel>();
public ObservableCollection<CredentialsModel> ListOfItems
{
get { return _listOfItems; }
set
{
if (_listOfItems != value)
{
_listOfItems = value;
RaisePropertyChanged();
}
}
}
private string username = null;
private string password = null;
private string loginMessage = null;
public string Username { get { return username; } set { username =
value; } }
public string Password { get { return password; } set { password =
value; } }
public string LoginMessage { get { return loginMessage; } set {
loginMessage = value; RaisePropertyChanged(); } }

public event PropertyChangedEventHandler PropertyChanged;

protected void RaisePropertyChanged([CallerMemberName]string caller="")
{
if(PropertyChanged!=null)
{
PropertyChanged(this, new PropertyChangedEventArgs(caller));
}
}

public ICommand LoginCommand
{
get;
private set;
}

public LoginViewModel()
{
ListOfItems.Add(new CredentialsModel());
LoginCommand = new Command((e) =>
{
var item = (e as CredentialsModel);
//TODO: LOGIN TO YOUR SYSTEM
loginMessage = string.Concat("Login successful for user: ",
item.Username);
});
}
}

2) 在您的 LoginView 标记中,为您的 ListView 分配一个名称,以便您可以从列表项访问 LoginCommand

3) 将 Button 的 Command 属性绑定(bind)到 LoginView 中的 LoginCommand。确保将其命令源设置为 ListView 使用的 BindingContext,它将指向 LoginViewModel。并将 Button 的 CommandParameter 绑定(bind)到当前列表项:

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class LoginView : ContentPage
{
public LoginView()
{
InitializeComponent();
BindingContext = new LoginViewModel();
}

}


<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.View.LoginView">
<ContentPage.Content>
<StackLayout>
<control:MenuView />
<ListView x:Name="LoginList" ItemsSource="{Binding ListOfItems,
Mode=TwoWay}" SeparatorVisibility="None">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout Orientation="Horizontal">
<Entry Placeholder="Enter user name" Text="
{Binding Username, Mode=TwoWay}"
x:Name="Username"/>
<Entry Placeholder="Enter password" Text="
{Binding Password, Mode=TwoWay}"
x:Name="Password" />
<Button Text="Login"
Command="{Binding
Path=BindingContext.LoginCommand,
Source={x:Reference LoginList}}"
CommandParameter="{Binding}">
</Button>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Label Text="{Binding LoginMessage}"></Label>
</StackLayout>
</ContentPage.Content>
</ContentPage>

关于xamarin - 如何将入口参数传递给 Xamarin MVVM viewmodel,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/46552891/

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