Windows Phone - 将视图绑定到视图模型
本文关键字：视图 绑定 模型 Phone Windows | 更新日期: 2023-09-27 17:55:20
所以，我正在学习Windows Phone的MVVM Pattern，并坚持如何将视图绑定到我的ViewModel。我现在构建的应用程序正在获取当前和未来 5 天的天气，并使用 UserControl 将其显示在 MainPage.xaml 上的一个全景项目中。
我不能简单地设置 Forecasts.ItemsSource = forecast;在我的 WeatherView 模型中，它说 Forecasts（WeatherView 中的 Listbox 元素名称）在当前上下文中不存在。
谁能教我如何绑定它？任何人都有Windows-Phone中MVVM模式的良好源代码/示例示例？谢谢之前。
编辑：
天气模型.cs
namespace JendelaBogor.Models
{
public class WeatherModel
{
public string Date { get; set; }
public string ObservationTime { get; set; }
public string WeatherIconURL { get; set; }
public string Temperature { get; set; }
public string TempMaxC { get; set; }
public string TempMinC { get; set; }
public string Humidity { get; set; }
public string WindSpeedKmph { get; set; }
}
}
天气视图模型.cs
namespace JendelaBogor.ViewModels
{
public class WeatherViewModel : ViewModelBase
{
private string weatherURL = "http://free.worldweatheronline.com/feed/weather.ashx?q=";
private const string City = "Bogor,Indonesia";
private const string APIKey = "APIKEY";
private IList<WeatherModel> _forecasts;
public IList<WeatherModel> Forecasts
{
get
{
if (_forecasts == null)
{
_forecasts = new List<WeatherModel>();
}
return _forecasts;
}
private set
{
_forecasts = value;
if (value != _forecasts)
{
_forecasts = value;
this.NotifyPropertyChanged("Forecasts");
}
}
}
public WeatherViewModel()
{
WebClient downloader = new WebClient();
Uri uri = new Uri(weatherURL + City + "&num_of_days=5&extra=localObsTime&format=xml&key=" + APIKey, UriKind.Absolute);
downloader.DownloadStringCompleted += new DownloadStringCompletedEventHandler(ForecastDownloaded);
downloader.DownloadStringAsync(uri);
}
private void ForecastDownloaded(object sender, DownloadStringCompletedEventArgs e)
{
if (e.Result == null || e.Error != null)
{
MessageBox.Show("Cannot load Weather Forecast!");
}
else
{
XDocument document = XDocument.Parse(e.Result);
var current = from query in document.Descendants("current_condition")
select new WeatherModel
{
ObservationTime = DateTime.Parse((string)query.Element("localObsDateTime")).ToString("HH:mm tt"),
Temperature = (string)query.Element("temp_C"),
WeatherIconURL = (string)query.Element("weatherIconUrl"),
Humidity = (string)query.Element("humidity"),
WindSpeedKmph = (string)query.Element("windspeedKmph")
};
this.Forecasts = (from query in document.Descendants("weather")
select new WeatherModel
{
Date = DateTime.Parse((string)query.Element("date")).ToString("dddd"),
TempMaxC = (string)query.Element("tempMaxC"),
TempMinC = (string)query.Element("tempMinC"),
WeatherIconURL = (string)query.Element("weatherIconUrl")
}).ToList();
}
}
}
}
天气视图.xaml
<UserControl x:Class="JendelaBogor.Views.WeatherView"
xmlns:vm="clr-namespace:JendelaBogor.ViewModels">
<UserControl.DataContext>
<vm:WeatherViewModel />
</UserControl.DataContext>
<Grid Margin="0,-10,0,0">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid x:Name="Current" Grid.Row="0" Height="150" VerticalAlignment="Top">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="150"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Image Grid.Column="0" delay:LowProfileImageLoader.UriSource="{Binding WeatherIconURL}" Width="120" Height="120" VerticalAlignment="Top"/>
<StackPanel Grid.Column="1" Height="200" VerticalAlignment="Top">
<TextBlock Text="{Binding Temperature}" FontSize="22"/>
<TextBlock Text="{Binding ObservationTime}" FontSize="22"/>
<TextBlock Text="{Binding Humidity}" FontSize="22"/>
<TextBlock Text="{Binding Windspeed}" FontSize="22"/>
</StackPanel>
</Grid>
<Grid Grid.Row="1" Height="300" VerticalAlignment="Bottom" Margin="10,0,0,0">
<StackPanel VerticalAlignment="Top">
<StackPanel Height="40" Orientation="Horizontal" Margin="0,0,0,0">
<TextBlock Text="Date" FontSize="22" Width="170"/>
<TextBlock Text="FC" FontSize="22" Width="60"/>
<TextBlock Text="Max" TextAlignment="Right" FontSize="22" Width="90"/>
<TextBlock Text="Min" TextAlignment="Right" FontSize="22" Width="90"/>
</StackPanel>
<StackPanel Orientation="Horizontal">
<ListBox ItemsSource="{Binding Forecasts}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Height="40" Orientation="Horizontal" Margin="0,10,0,0">
<TextBlock Text="{Binding Date}" FontSize="22" TextAlignment="Left" Width="170" />
<Image delay:LowProfileImageLoader.UriSource="{Binding WeatherIconURL}" Width="40" Height="40" />
<TextBlock Text="{Binding TempMaxC, StringFormat=''{0'} °C'}" TextAlignment="Right" FontSize="22" Width="90" />
<TextBlock Text="{Binding TempMinC, StringFormat=''{0'} °C'}" TextAlignment="Right" FontSize="22" Width="90" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</StackPanel>
</Grid>
</Grid>
</UserControl>
MainPage.xaml
<controls:PanoramaItem x:Name="Weather" Header="weather">
<views:WeatherView />
</controls:PanoramaItem>
您需要告诉视图您正在使用什么视图模型。加入
<UserControl
xmlns:vm="clr-namespace:JendelaBogor.ViewModels">
<UserControl.DataContext>
<vm:WeatherViewModel />
</UserControl.DataContext>
</UserControl>
所有{Binding}都映射到类WeatherViewModel。按照 Reed 的建议使用列表框上的 ItemsSource 属性，可以绑定通过属性公开的列表中的所有项。
如果在运行应用程序时更改了列表，请考虑使用ObservableCollection并清除它，并在收到新数据时添加所有新项目。如果这样做，您的 GUI 将随之更新。
ViewModel 不知道视图。
您需要在视图模型上创建一个Forecasts属性，并将 ItemsSource 从您的视图绑定到该属性。 在您看来，将ListBox更改为：
<!-- No need for a name - just add the binding -->
<ListBox ItemsSource="{Binding Forecasts}">
然后，在视图模型中，添加：
// Add a backing field
private IList<WeatherModel> forecasts;
// Add a property implementing INPC
public IList<WeatherModel> Forecasts
{
get { return forecasts; }
private set
{
forecasts = value;
this.RaisePropertyChanged("Forecasts");
}
}
然后，您可以在方法中进行此设置：
this.Forecasts = (from query in document.Descendants("weather")
select new WeatherModel
{
Date = DateTime.Parse((string)query.Element("date")).ToString("dddd"),
TempMaxC = (string)query.Element("tempMaxC"),
TempMinC = (string)query.Element("tempMinC"),
WeatherIconURL = (string)query.Element("weatherIconUrl")
})
.ToList(); // Turn this into a List<T>