Data binding 将数据从Main发送到Detail，并在MainViewMode中更新对象_Data Binding_Xamarin_Xamarin.android_Mvvmcross

Data binding 将数据从Main发送到Detail，并在MainViewMode中更新对象

data-binding xamarin xamarin.android

Data binding 将数据从Main发送到Detail，并在MainViewMode中更新对象,data-binding,xamarin,xamarin.android,mvvmcross,Data Binding,Xamarin,Xamarin.android,Mvvmcross,我有下面的recyclerview，其中包含TestViewModel对象列表。在这个对象中，我有年龄、性别和姓名属性。我试图实现当用户单击列表项时，它将用户带到详细视图，用户可以在其中更新并单击保存按钮，然后更新所选项的属性问题： <MvxRecyclerView android:id="@+id/TestRecyclerView" android:scrollbars="vertical" android:layout_width="match_parent"

我有下面的

recyclerview

，其中包含

TestViewModel

对象列表。在这个对象中，我有

年龄

、

性别

和

姓名

属性。我试图实现当用户单击列表项时，它将用户带到详细视图，用户可以在其中更新并单击保存按钮，然后更新所选项的属性

问题：

<MvxRecyclerView
    android:id="@+id/TestRecyclerView"
    android:scrollbars="vertical"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    local:MvxBind="ItemsSource TestsViews; ; ItemClick ItemSelected" />

在

MainViewModel

中，当用户在细节中输入值并更新每个属性时，我从

DetailViewModel

接收消息的下面一段代码将起作用

private void OnMessageReceived(TestMessage obj)
{
    _selectedItem.Age = obj.messageTest.Age;
    _selectedItem.Name = obj.messageTest.Name;
    _selectedItem.Gender = obj.messageTest.Gender;
}

但是下面的代码在我试图直接更新对象时不起作用

private void OnMessageReceived(TestMessage obj)
{
    _selectedItem= obj.messageTest;
    RaisePropertyChanged(() => SelectedItem);
}

代码实现如下：

<MvxRecyclerView
    android:id="@+id/TestRecyclerView"
    android:scrollbars="vertical"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    local:MvxBind="ItemsSource TestsViews; ; ItemClick ItemSelected" />

DetailViewModel

public TestViewModel EditTest
{
    get { return _editTest; }
    set
    {
        _editTest = value;
        RaisePropertyChanged(() => EditTest);
    }
}

public DetailViewModel(IMvxMessenger messenger)
{
    _messenger = messenger;
}

public void Save()
{
    UpdateValues();
}

public void UpdateValues()
{
    var message = new TestMessage(this, _editTest);
    _messenger.Publish(message, typeof(TestMessage));
}

public void Init(Parameter param)
{
    _editTest = new TestViewModel();
    _editTest.Age = param.Age;
    _editTest.Name = param.Name;
    _editTest.Gender = param.Gender;

public class Parameter
{
    public double Age { get; set; }
    public int Gender { get; set; }
    public string Name { get; set; }
}

<EditText
    style="@style/InputNumbersEditText"
    android:layout_weight="1"
    android:layout_width="0dp"
    android:layout_height="44dp"
    android:gravity="center_vertical|right"
    android:hint="00.000"
    local:MvxBind="Text EditTest.Age, Converter=Nullable;" />

详细视图xml

public TestViewModel EditTest
{
    get { return _editTest; }
    set
    {
        _editTest = value;
        RaisePropertyChanged(() => EditTest);
    }
}

public DetailViewModel(IMvxMessenger messenger)
{
    _messenger = messenger;
}

public void Save()
{
    UpdateValues();
}

public void UpdateValues()
{
    var message = new TestMessage(this, _editTest);
    _messenger.Publish(message, typeof(TestMessage));
}

public void Init(Parameter param)
{
    _editTest = new TestViewModel();
    _editTest.Age = param.Age;
    _editTest.Name = param.Name;
    _editTest.Gender = param.Gender;

public class Parameter
{
    public double Age { get; set; }
    public int Gender { get; set; }
    public string Name { get; set; }
}

<EditText
    style="@style/InputNumbersEditText"
    android:layout_weight="1"
    android:layout_width="0dp"
    android:layout_height="44dp"
    android:gravity="center_vertical|right"
    android:hint="00.000"
    local:MvxBind="Text EditTest.Age, Converter=Nullable;" />

NullableValueConverter

public MainViewModel SelectedItem
{
    get { return _selectedItem; }
    set
    {
        _selectedItem = value;
        ShowViewModel<DetailViewModel>(
        new DetailViewModel.Parameter
        {
            Age = _selectedItem.Age,
            Name = _selectedItem.Name,
            Gender = _selectedItem.Gender,
        });
        RaisePropertyChanged(() => SelectedItem);
    }
}

public virtual ICommand ItemSelected
{
   get
    {
      return new MvxCommand<TestViewModel>(item =>
      {
          SelectedItem = item;
      });
     }
}

private void OnMessageReceived(TestMessage obj)
{
    _selectedItem.Age= obj.messageTest.Age;
    _selectedItem.Name= obj.messageTest.Name;
    _selectedItem.Gender= obj.messageTest.Gender;
 }

public class TestMessage : MvxMessage
{
    public MainModel messageTest { get; set; }

    public TestMessage(object sender, MainModel editTest) : base(sender)
    {
        messageTest = editTest;
    }
}

public class TestViewModel : BaseViewModel
{
    public string? Name { get; set; }
    public double? Age { get; set; }
    public int? Gender { get; set; }
}

public class NullableValueConverter : MvxValueConverter
{
    public override object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (string.IsNullOrEmpty(value?.ToString()))
        {
            return parameter;
        }
        return value;
    }

    public override object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null || string.IsNullOrEmpty(value.ToString()))
        {
            return null;
        }

        return value;
    }
}

更新的答案

为

\u selectedItem

分配一个新的

TestViewModel

会断开它与

TestsViews

数据源列表中的

TestViewModel

的参考链接。分配各个属性时，会在

TestsViews

列表中维护对原始

TestViewModel

的引用

原始答案

更新支持字段时，

\u selectedItem

，因此当您收到消息事件时，

selectedItem

属性集中定义的

RaisePropertyChanged

事件将永远不会运行。您必须手动触发

RaisePropertyChanged

，才能触发绑定更新

尝试更改当前的方法：

private void OnMessageReceived(TestMessage obj)
{
    _selectedItem= obj.messageTest;
}

要引发属性更改事件，请执行以下操作：

private void OnMessageReceived(TestMessage obj)
{
    _selectedItem = obj.messageTest;
    RaisePropertyChanged(() => SelectedItem);
}