[英]How to bind Instanceproperty to viewmodel, view is not updated
問題:
我的 Viewmodel 創建了一個控制器mycontroller
的實例,並且屬性Busy
應傳遞給 View 並根據控制器狀態在 View 中更新,但我的 View 不會更新。 另一個屬性Busy2
根據當前狀態更新。 Bindablebase 實現了 I
題:
為什么 ViewModel 中的Busy
屬性沒有更新? mycontroller.Busy 屬性正在更新,但不是視圖。
框架和工具:
棱鏡 6.3.0
Fody.Propertychanged
看法:
<TextBlock Text="{Binding Path=Busy}"></TextBlock>
<TextBlock Text="{Binding Path=Busy2}"></TextBlock>
視圖模型:
public class Controller
{
public bool Busy { get; private set; }
public async void GetValue()
{
Busy = true;
await Task.Delay(5000);
Busy = false;
}
}
public class MyViewModel : BindableBase
{
private readonly Controller _mycontroller;
public DelegateCommand<string> RunCommand { get; private set; }
// This property is not updated in the view
public bool Busy
{
get { return _mycontroller.Busy; }
}
// Works as aspected
public bool Busy2 { get; set; }
public MyViewModel()
{
_mycontroller = new Controller();
RunCommand = new DelegateCommand<string>(Run, Canrun).ObservesProperty((() => _mycontroller.Busy));
}
private bool Canrun(string arg)
{
return _mycontroller.Busy != true;
}
private void Run(string obj)
{
Busy2 = true;
_mycontroller.GetValue();
}
}
更新:
我從 Prism 添加了 Bindablebase,因為它實現了 INotifyPropertyChanged,但視圖仍未更新。 我重構了代碼並設置了一個斷點來設置{ SetProperty(ref _busy, value); }
{ SetProperty(ref _busy, value); }
並且斷點從未達到。
我也刪除了 Propertychanged.Fody nuget 包。
視圖模型:
public class Controller : BindableBase
{
private bool _busy;
public bool Busy
{
get { return _busy; }
set { SetProperty(ref _busy, value); }
}
public Controller()
{
}
public void DoWork1()
{
for (var i = 0; i < 10; i++)
{
Thread.Sleep(1000);
_busy = !_busy;
Debug.WriteLine(_busy.ToString());
}
}
public void DoWork2()
{
_busy = !_busy;
}
}
public class MainWindowViewModel : BindableBase
{
private Controller mycontroller;
private string _title = "Prism Unity Application";
public DelegateCommand RunCommand { get; private set; }
public string Title
{
get { return _title; }
set { SetProperty(ref _title, value); }
}
public bool Busy
{
get { return mycontroller.Busy; }
}
public MainWindowViewModel()
{
RunCommand = new DelegateCommand(Execute);
mycontroller = new Controller();
}
private void Execute()
{
mycontroller.DoWork1();
}
}
看法:
<Window x:Class="PropertytestPrism.Views.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:prism="http://prismlibrary.com/"
prism:ViewModelLocator.AutoWireViewModel="True"
Title="{Binding Title}" Height="350" Width="525">
<StackPanel>
<Button Command="{Binding RunCommand}" Content="Run"></Button>
<TextBlock Text="{Binding Busy}"></TextBlock>
</StackPanel>
</Window>
更新 2
視圖仍未更新,原因是我的 Delegatecommandmethod 執行 mycontroller.DoWork1();
題:
為什么視圖沒有更新? 如果我在 DelegateCommandmethod 中執行該方法?
您應該通過Controller
類實現INotifyPropertyChanged
。 在Controller
類中更改了屬性,應將此更改通知:
public class Controller : INotifyPropertyChanged
{
private bool _busy;
public bool Busy
{
get
{
return _busy;
}
private set
{
SetField(ref _busy, value, "Busy"); }
}
}
public async void GetValue()
{
Busy = true;
await Task.Delay(5000);
Busy = false;
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
protected bool SetField<T>(ref T field, T value, string propertyName)
{
if (EqualityComparer<T>.Default.Equals(field, value))
{
return false;
}
field = value;
OnPropertyChanged(propertyName);
return true;
}
}
試着讓你的綁定像這樣工作。
<TextBlock Text="{Binding Busy,Mode=OneWay}"></TextBlock>.
默認綁定是一次性的,因此即使在屬性更改通知中它們也不會更新。
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