我已按照此示例binding to observable collection设置了ListView的绑定,但是当我运行应用程序时,集合值不会显示在ListView中。
输出窗口没有抛出任何绑定错误,因此不确定绑定错误是什么。 此外,我在列表中设置了一个断点,然后将其发送到第二个VM并填充它,即不为空。
我的猜测是第二个VM中的列表为空,因为它在被传递后没有被正确初始化。
有人可以建议如何调试ListView为空吗?
这是视图中的绑定集:
namespace LC_Points.View
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class ViewSubjectGradePage : Page
{
private NavigationHelper navigationHelper;
private ViewSubjectGradeViewModel ViewModel;
public ViewSubjectGradePage()
{
this.InitializeComponent();
this.navigationHelper = new NavigationHelper(this);
this.navigationHelper.LoadState += this.NavigationHelper_LoadState;
this.navigationHelper.SaveState += this.NavigationHelper_SaveState;
ViewModel = new ViewSubjectGradeViewModel();
this.DataContext = ViewModel;
}
/// <summary>
/// Gets the <see cref="NavigationHelper"/> associated with this <see cref="Page"/>.
/// </summary>
public NavigationHelper NavigationHelper
{
get { return this.navigationHelper; }
}
/// <summary>
/// Populates the page with content passed during navigation. Any saved state is also
/// provided when recreating a page from a prior session.
/// </summary>
/// <param name="sender">
/// The source of the event; typically <see cref="NavigationHelper"/>
/// </param>
/// <param name="e">Event data that provides both the navigation parameter passed to
/// <see cref="Frame.Navigate(Type, Object)"/> when this page was initially requested and
/// a dictionary of state preserved by this page during an earlier
/// session. The state will be null the first time a page is visited.</param>
private void NavigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
}
/// <summary>
/// Preserves state associated with this page in case the application is suspended or the
/// page is discarded from the navigation cache. Values must conform to the serialization
/// requirements of <see cref="SuspensionManager.SessionState"/>.
/// </summary>
/// <param name="sender">The source of the event; typically <see cref="NavigationHelper"/></param>
/// <param name="e">Event data that provides an empty dictionary to be populated with
/// serializable state.</param>
private void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)
{
}
#region NavigationHelper registration
/// <summary>
/// The methods provided in this section are simply used to allow
/// NavigationHelper to respond to the page's navigation methods.
/// <para>
/// Page specific logic should be placed in event handlers for the
/// <see cref="NavigationHelper.LoadState"/>
/// and <see cref="NavigationHelper.SaveState"/>.
/// The navigation parameter is available in the LoadState method
/// in addition to page state preserved during an earlier session.
/// </para>
/// </summary>
/// <param name="e">Provides data for navigation methods and event
/// handlers that cannot cancel the navigation request.</param>
protected override void OnNavigatedTo(NavigationEventArgs e)
{
this.navigationHelper.OnNavigatedTo(e);
}
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
this.navigationHelper.OnNavigatedFrom(e);
}
#endregion
}
}
View的数据上下文在后面的代码中设置如下:
namespace LC_Points.ViewModel
{
public class ViewSubjectGradeViewModel
{
public ViewSubjectGradeViewModel()
{
}
/// <summary>
/// Initializes a new instance of the ViewSubjectGradeViewModel class.
/// </summary>
public ViewSubjectGradeViewModel(IEnumerable<ScoreModel> addedSubjectGradePairs)
{
this.AddedSubjectGradePairsCopy = addedSubjectGradePairs;
}
//Property for collection passed from MainViewModel
public IEnumerable<ScoreModel> AddedSubjectGradePairsCopy { get; set; }
}
}
通过构造函数接收ViewSubjectGradeVM中的列表:
namespace LC_Points.Model
{
public class ScoreModel : INotifyPropertyChanged
{
// The name of the subject.
public string Subject { get; set; }
// The points paired with each grade type.
public int Points { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
这是从MainVM传递到ViewSubjectGradeVM的List的支持模型:
{{1}}
答案 0 :(得分:2)
尝试这样的事情。当然,您的模型应该来自您应该映射到viewmodel的某些源。但这说明了设置正确的datacontext的方法。
app = gui.App()
top = gui.Container()
button = gui.Button("Start")
button.resize(200, 100)
top.add(button, 0, 0)
app.init(top, screen)