Question

我有一个简单的代码，我检查了其他问题，但还没有。

我有一个应用程序，它从Web检索到的xml文件中加载一些数据，然后将它显示在longlistselector中。

我做到了，它有效，现在我想添加一个不确定的进度条，它一直保持活动状态，直到我完成数据加载。

我将进度条包含在我的longlistselector之前的stackpanel中，并且我将其可见性限制在函数ProgressBarVisibility中（参见下面的代码）。

        <phone:PivotItem Header="Status">
            <StackPanel>
            <ProgressBar Value ="0" IsIndeterminate="True" Visibility="{Binding ProgressBarVisibility}"/>
            <phone:LongListSelector Margin="0,0,-12,0" ItemsSource="{Binding PivotOne}">
                <phone:LongListSelector.ItemTemplate>
                    <!-- lots of code here -->
                </phone:LongListSelector.ItemTemplate>
            </phone:LongListSelector>
            </StackPanel>
        </phone:PivotItem>

在MainViewModel.cs中，这就是我写这个东西的方式。

    using System.Windows;


    public class MainViewModel : INotifyPropertyChanged
    {
    public MainViewModel()
    {
        this.PivotOne = new ObservableCollection<ItemViewModel>();
        this.PivotTwo = new ObservableCollection<ItemViewModel>();
        this.PivotThree = new ObservableCollection<ItemViewModel>();
    }

    /// <summary>
    /// A collection for ItemViewModel objects.
    /// </summary>
    public ObservableCollection<ItemViewModel> PivotOne { get; private set; }
    public ObservableCollection<ItemViewModel> PivotTwo { get; private set; }
    public ObservableCollection<ItemViewModel> PivotThree { get; private set; }

    private string _detailPageTitle = "Default";
    /// <summary>
    /// DetailPageTitle ritorna il titolo della pagina di dettaglio. Viene settato nella funzione che carica la pagina secondaria
    /// </summary>
    /// <returns></returns>
    public string DetailPageTitle
    {
        get
        {
            return _detailPageTitle;
        }
        set
        {
            if (value != _detailPageTitle)
            {
                _detailPageTitle = value;
                NotifyPropertyChanged("DetailPageTitle");
            }
        }
    }

    public bool IsDataLoaded
    {
        get;
        private set;
    }


    private Visibility _progressBarVisibility = Visibility.Collapsed;

    public Visibility ProgressBarVisibility
    {
        get
        {
            return _progressBarVisibility;
        }
        set
        {
            if (value != _progressBarVisibility)
            {
                _progressBarVisibility = value;
                NotifyPropertyChanged("ProgressBarVisibility");
            }
        }
    }


    private Visibility _progressBarVisibility = Visibility.Visible;

    public Visibility ProgressBarVisibility
    {
        get
        {
            return _progressBarVisibility;
        }
        set
        {
            if (value != _progressBarVisibility)
            {
                _progressBarVisibility = value;
                NotifyPropertyChanged("ProgressBarVisibility");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (null != handler)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    public void LoadData()
    {
        //progressbar is visible, data not loaded
        this.IsDataLoaded = false;
        ProgressBarVisibility = Visibility.Visible;

        // Load Static and dynamic data -- populate the different pivots
        LoadStaticData();
        LoadXMLFile();

        // data loaded, progressbar collapsed
        this.IsDataLoaded = true;
        ProgressBarVisibility = Visibility.Collapsed;
    }

所以我包含了system.windows库，并使用了可见性类。无论如何，当加载完成时，我无法让进度条消失，它会继续运行。

有什么建议吗？我在哪里做错了？

提前致谢！

解决方案：在应用程序激活时执行loaddata，因此此时内容甚至无法呈现。

Answer 1

您需要报告对视图所做的更改：

更改

public Visibility ProgressBarVisibility { get; set; }

通过

private Visibility _progressBarVisibility;
public Visibility ProgressBarVisibility
{
    get { return _progressBarVisibility;}
    set { _progressBarVisibility = value; RaisePropertyChanged("ProgressBarVisibility");}
}

确保实现INotifyPropertyChanged或实现它的基本ViewModel（MVVMLigth：ViewModelBase）。

Answer 2

您的MainViewModel必须实现INotifyPropertyChanged以向View发信号通知其中一个属性已更改。此外，当您更改ProgressBarVisibility属性时，它应触发PropertyChanged事件。

有一些MVVM frameworks带有一些INotifyPropertyChanged的实现，但您可以自己轻松实现something simple。

WP8 - 绑定ProgressBar可见性

2 个答案: