Question

我正在尝试在mvvmcross中使用UIActivityIndicatorView的自定义绑定，但我无法使其正常工作。我遵循了建议here。所以我创建了自定义绑定类：

public class ActivityIndicatorViewHiddenTargetBinding : MvxConvertingTargetBinding
{
    public ActivityIndicatorViewHiddenTargetBinding(UIActivityIndicatorView target)
        : base(target)
    {
        if (target == null)
        {
            MvxBindingTrace.Trace(
                MvxTraceLevel.Error,
                "Error - UIActivityIndicatorView is null in ActivityIndicatorViewHiddenTargetBinding");
        }
    }

    public override MvxBindingMode DefaultMode
    {
        get { return MvxBindingMode.OneWay; }
    }

    public override System.Type TargetType
    {
        get { return typeof(bool); }
    }

    protected UIActivityIndicatorView View
    {
        get { return Target as UIActivityIndicatorView; }
    }

    protected override void SetValueImpl(object target, object value)
    {
        var view = (UIActivityIndicatorView)target;
        if (view == null)
        {
            return;
        }

        view.Hidden = (bool)value;

        if (view.Hidden)
        {
            view.StopAnimating();
        }
        else
        {
            view.StartAnimating();
        }
    }
}

我试着注册。

public class Setup : MvxIosSetup
{
    // ...

    protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry)
    {
        registry.RegisterPropertyInfoBindingFactory(
           typeof(ActivityIndicatorViewHiddenTargetBinding),
           typeof(UIActivityIndicatorView), "Hidden");

        base.FillTargetFactories(registry);
    }

    // ...
}

设置绑定的代码：

public override void ViewDidLoad()
{
    base.ViewDidLoad();

          var bindingSet = this.CreateBindingSet<LoginView, LoginViewModel>();
          bindingSet.Bind(Username).To(vm => vm.Username);
          bindingSet.Bind(Password).To(vm => vm.Password);
          bindingSet.Bind(LoginButton).To(vm => vm.LoginCommand);

          //Progress is UIActivityIndicator
          bindingSet.Bind(Progress)
                  .For(p => p.Hidden)
                  .To(vm => vm.IsLoading);
              .WithConversion("Inverse");

    bindingSet.Apply();
}

正在调用服务器的PCL库中的代码：

public class LoginViewModel : MvxViewModel
{
    // ...
    private bool _isLoading;
    public bool IsLoading
    {
        get { return _isLoading; }
        set { SetProperty(ref _isLoading, value);}
    }

    private IMvxCommand _loginCommand;
    public virtual IMvxCommand LoginCommand
    {
        get
        {
            _loginCommand = _loginCommand ?? new MvxAsyncCommand(AttemptLogin, CanExecuteLogin);
            return _loginCommand;
        }
    }

    private async Task AttemptLogin()
    {
        IsLoading = true;
        try
        {
            await Task.Run(async () =>
            {
                await _loginService.LogIn(Username, Password);
            });

            ShowViewModel<MainViewModel>();
        }
        catch (SecurityClientException exc)
        {
            _dialogService.Alert(exc.Message, "Login Failed", "OK");
        }
        catch (Exception exc)
        {
            _dialogService.Alert($"Unknown error: {exc.Message}", "Login Failed", "OK");
        }
        finally
        {
            IsLoading = false;
        }
    }

    // ...
}

但是我遇到了以下无法解决的问题：

加载视图时，微调器可见并设置动画
执行命令时，微调器不可见（我正在尝试使用和不使用.WithConversion("Inverse");的代码版本
当我在ActivityIndicatorViewHiddenTargetBinding类中将断点放入SetValueImpl方法时，未被命中。

我是mvvmcross和Xamarin的新手。有没有人知道代码有什么问题？

如何在mvvmcross中正确注册自定义绑定？

0 个答案: