无法从 Xamarin 表单中的对象更新数据绑定

Question

我正在尝试从我的视图模型中的对象更新我的 xamarin 绑定。我究竟做错了什么。 当我看到页面并查看“用户”时，我看到我的用户对象在那里。

页面：

  <StackLayout BindableLayout.ItemsSource="{Binding User}"
             Orientation="Horizontal">
            <BindableLayout.ItemTemplate>
                <DataTemplate x:DataType="model:User">
                    
                    <StackLayout>
                        <Label Text="{Binding Name, Mode=OneWay}"/>
                        <Label Text="{Binding PhoneNumber, Mode=OneWay}"/>
                        <Label Text="{Binding Adress, Mode=OneWay}"/>
                        <Label Text="{Binding Email, Mode=OneWay}"/>
                    </StackLayout>
                 

                </DataTemplate>
            </BindableLayout.ItemTemplate>
        </StackLayout>

您需要了解的有关使用 mvvhelpers 的 Viewmodel 的知识

public User User { get; set; }

 public MyProfileViewModel()
        {
            
            Title = "MyProfile";



            RefreshCommand = new AsyncCommand(Refresh);
            AddCommand = new AsyncCommand(Add);
            // RemoveCommand = new AsyncCommand<User>(Remove);

            User = new User();



        }

public async refrsh(){
 User = await MyProfileService.GetMyProfile(2);
            nameDisplay = User.Name;
}
  string nameDisplay;
        public string NameDisplay
        {
            get => nameDisplay;
            set => SetProperty(ref nameDisplay, value);

        }

Answer 1

根据Jason的意见，如果你只有一个User对象，就不需要使用BindableLayout和DataTemplate，可以直接将User Object绑定到StackLayout BindingContext。

 <StackLayout BindingContext="{Binding User}">
            <Label Text="{Binding Name, Mode=OneWay}" />
            <Label Text="{Binding PhoneNumber, Mode=OneWay}" />
            <Label Text="{Binding Adress, Mode=OneWay}" />
            <Label Text="{Binding Email, Mode=OneWay}" />
        </StackLayout>

如果你有 IEnumerable User 的集合，你可以使用 BindableLayout.ItemsSource 和 DataTemplate

你需要为用户属性实现INotifyPropertyChanged，它会通知数据变化。

public class ViewModelBase : INotifyPropertyChanged
{
    
    public event PropertyChangedEventHandler PropertyChanged;

     
    public void RaisePropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

完整代码：

 <StackLayout>
       
        <StackLayout BindingContext="{Binding User}">
            <Label Text="{Binding Name, Mode=OneWay}" />
            <Label Text="{Binding PhoneNumber, Mode=OneWay}" />
            <Label Text="{Binding Adress, Mode=OneWay}" />
            <Label Text="{Binding Email, Mode=OneWay}" />
        </StackLayout>
        <Button
            x:Name="btn1"
            Command="{Binding changecommand}"
            Text="change user data" />
    </StackLayout>

 public partial class Page27 : ContentPage
{

    public Page27()
    {
        InitializeComponent();
        this.BindingContext = new MyProfileViewModel();
    }
}

public class MyProfileViewModel
{ 
    public User User {   get;  set;}
    public ICommand changecommand { get; }
    public MyProfileViewModel()
    {
        User = new User();
        User.Name = "cherry";
        User.PhoneNumber = "123";
        User.Adress = "location 1";
        User.Email = "xxxxx.@outlook.com";

        changecommand = new Command(() =>
        {
            User.Name = "barry";

        });
    }
}
public class User:ViewModelBase
{
    private string _Name;
    public string Name
    {
        get { return _Name; }
        set
        {
            _Name = value;
           RaisePropertyChanged("Name");
        }
    }
    private string _PhoneNumber;
    public string PhoneNumber
    {
        get { return _PhoneNumber; }
        set
        {
            _PhoneNumber = value;
            RaisePropertyChanged("PhoneNumber");
        }
    }
    private string _Adress;
    public string Adress
    {
        get { return _Adress; }
        set
        {
            _Adress = value;
            RaisePropertyChanged("Adress");
        }
    }
    private string _Email;
    public string Email
    {
        get { return _Email; }
        set
        {
            _Email = value;
            RaisePropertyChanged("Email");
        }
    }

}