如何强制显示忙碌指示器? (WPF) [英] How can I force my busy indicator to display? (WPF)

问题描述

我创建了一个忙碌指示器-基本上是徽标旋转的动画.我已将其添加到登录窗口，并将Visibility属性绑定到我的视图模型的BusyIndi​​catorVisibility属性.

I've created a busy indicator - basically an animation of a logo spinning. I've added it to a login window and bound the Visibility property to my viewmodel's BusyIndicatorVisibility property.

当我单击登录时，我希望微调框出现在登录发生时(它调用Web服务以确定登录凭据是否正确).但是，当我将可见性设置为visible，然后继续登录时，直到完成登录后，微调框才会出现.在Winforms老式编码中，我将添加一个Application.DoEvents.如何使微调框出现在MVVM应用程序的WPF中?

When I click login, I want the spinner to appear whilst the login happens (it calls a web service to determine whether the login credentials are correct). However, when I set the visibility to visible, then continue with the login, the spinner doesn't appear until the login is complete. In Winforms old fashioned coding I would have added an Application.DoEvents. How can I make the spinner appear in WPF in an MVVM application?

代码是:

        private bool Login()
        {
            BusyIndicatorVisibility = Visibility.Visible;
            var result = false;
            var status = GetConnectionGenerator().Connect(_model);
            if (status == ConnectionStatus.Successful)
            {
                result = true;
            }
            else if (status == ConnectionStatus.LoginFailure)
            {
                ShowError("Login Failed");
                Password = "";
            }
            else
            {
                ShowError("Unknown User");
            }
            BusyIndicatorVisibility = Visibility.Collapsed;
            return result;
        }

推荐答案

您必须使登录名异步.您可以使用 BackgroundWorker 来执行此操作.像这样:

You have to make your login async. You can use the BackgroundWorker to do this. Something like:

BusyIndicatorVisibility = Visibility.Visible; 
// Disable here also your UI to not allow the user to do things that are not allowed during login-validation
BackgroundWorker bgWorker = new BackgroundWorker() ;
bgWorker.DoWork += (s, e) => {
    e.Result=Login(); // Do the login. As an example, I return the login-validation-result over e.Result.
};
bgWorker.RunWorkerCompleted += (s, e) => {
   BusyIndicatorVisibility = Visibility.Collapsed;  
   // Enable here the UI
   // You can get the login-result via the e.Result. Make sure to check also the e.Error for errors that happended during the login-operation
};
bgWorker.RunWorkerAsync();

仅出于完善目的::可以在登录之前给UI刷新时间.这是通过调度程序完成的.但是，这是一个黑客，绝不应该使用IMO.但是，如果您对此感兴趣，可以在StackOverflow中搜索 wpf doevents .

Only for completness: There is the possibility to give the UI the time to refresh before the login takes place. This is done over the dispatcher. However this is a hack and IMO never should be used. But if you're interested in this, you can search StackOverflow for wpf doevents.

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