RegisterClassCommandBinding不触发CanExecute

Question

In certain situations (I couldn't establish a pattern) the execution goes over

    System.Windows.Input.CommandManager.InvalidateRequerySuggested();
    var can = GlobalCommands.UpdateWindowTitle.CanExecute(title, null);
    GlobalCommands.UpdateWindowTitle.Execute(title, null);

without entering CanExecute nor Execute methods . Variable "can" is false (without executing CanExecute), and the command never fires. But sometimes it works as expected.

This is how the command is created and bound:

    var updateTitleBinding = new CommandBinding(GlobalCommands.UpdateWindowTitle,         UpdateWindowTitle, CanUpdateWindowTitle);
    CommandManager.RegisterClassCommandBinding(typeof(System.Windows.Window), updateTitleBinding);

I can't use

    Application.Current.MainWindow.CommandBindings.Add(
         new CommandBinding(_addCommand, ExecuteAddCommand, CanExecuteAddCommand));

because the calling class is not a visual element and doesn't have CommandBindings

I tried calling

    System.Windows.Input.CommandManager.InvalidateRequerySuggested();

before CanExecute and Execute calls, but this doesn't affect the behaviour.

--

Do you know what might be happening there? Are there any other patterns that I could use?

The problem looks similar to CanExecute method going to false problem but I'm not setting focus anywhere.

Thanks!

Answer 1

好吧，因为您为目标传递了null，这意味着框架将基于Keyboard.FocusedElement进行路由，因此要么为null（如果应用程序处于非活动状态或键盘焦点位于HwndHost之类的其他位置，则可能发生这种情况或MessageBox）或Keyboard.FocusedElement为非null，但不在Window的视觉/逻辑树内。