Question

我的绑定：

<local:MyContentView BindingContext="{Binding Source={x:Reference Root}, Path=BindingContext.Entity.Recipe, Mode=OneWay}"/>

更改配方时，将更新ContentView上的BindingContext，但是MyContentView内的控件未填充数据。如果Recipe是有效值，则最初将用数据填充MyContentView内的控件，但是如果Recipe以null开头并更改为有效目标，则即使BindingContext更改，控件也不会更新。

Answer 1

根据您的描述，您希望将contentview绑定到内容页面中，当数据源发生更改时数据不会更新，我想您可能没有为食谱实现 INotifypropertychanged ，您可以按照然后下一篇文章实现INotifyPropertyChanged。

https://xamarinhelp.com/xamarin-forms-binding/

使用 Bindableproperty 的另一种方法，我为您制作了一个示例，您可以看一下：

Contentview：

<ContentView.Content>
  <StackLayout>
        <Label x:Name="label1" Text="{Binding Text}" />

    </StackLayout>

public partial class mycontenview : ContentView
{


    public static BindableProperty TextProperty = BindableProperty.Create(
propertyName: "Text",
returnType: typeof(string),
declaringType: typeof(mycontenview),
defaultValue: string.Empty,
defaultBindingMode: BindingMode.OneWay,
propertyChanged: HandlePropertyChanged);


    public string Text
    {
        get
        {
            return (string)GetValue(TextProperty);
        }
        set
        {
            SetValue(TextProperty, value);
        }
    }
    private static void HandlePropertyChanged(BindableObject bindable, object oldValue, object newValue)
    {
        mycontenview contentview = bindable as mycontenview;
        contentview.label1.Text = newValue.ToString();

    }


    public mycontenview()
    {
        InitializeComponent();

    }
}

主页：

<StackLayout>
    <Label Text="welcome to xamarin world!"/>
    <Button x:Name="btn1" Text="btn1" Clicked="btn1_Clicked"/>
    <local:mycontenview  Text="{Binding str}"/>
</StackLayout>

public partial class MainPage : ContentPage, INotifyPropertyChanged
{

    private string _str;
    public string str
    {
        get { return _str; }
        set
        {
            _str = value;
            OnPropertyChanged("str");
        }
    }
    public MainPage()
    {
        InitializeComponent();
        m = new model1() { str = "test 1", str1 = "test another 1" };
        str = "cherry";
        this.BindingContext = this;
    }
    public event PropertyChangedEventHandler PropertyChanged;



    protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs((propertyName)));
    }



    protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName]string propertyName = null)
    {
        if (EqualityComparer<T>.Default.Equals(storage, value))
        {
            return false;
        }
        storage = value;
        OnPropertyChanged(propertyName);



        return true;
    }



    private void btn1_Clicked(object sender, EventArgs e)
    {
        str = "this is test!";
    }
}

绑定ContentView的BindingContext不会更新内部的控件

1 个答案: