如何使用Xamarin.Forms等待模态表单解雇? [英] How can I await modal form dismissal using Xamarin.Forms?

问题描述

使用Xamarin.Forms，如何使用make等待表单关闭的异步方法?如果我使用

Using Xamarin.Forms how can I use make an async method that waits for the form to dismiss? If I use

await Navigation.PushModalAsync(page);

它会在动画完成后返回，而不是在关闭页面时返回.

it will return once the animation is finished not when the page is dismissed.

我想要创建一个模式化Task SignInAsync方法，如果登录成功，该方法将返回true.

I want a to create modal Task SignInAsync method that return true if sign-in is successful.

推荐答案

您可以通过在登录页面中触发一个事件并在继续之前侦听该事件来实现此目的，但是您需要完整的TAP支持，我在那儿支持了您.这是一个简单但可以正常使用的2页应用程序，可以执行此操作.显然，您会想使用ContentPage自定义子类，并拥有适当的方法来代替我的快速Command，但是您知道了，并且节省了我的输入.

You can do this by triggering an event in your login page and listen for that event before going on, but you want the full TAP support and I second you there. Here's a simple yet working 2 page app that does just this. You'll obviously want to use ContentPage custom subclass and have proper methods instead of my quick Commands, but you get the idea, and it saves me typing.

public static Page GetFormsApp ()
{
    NavigationPage navpage = null;
    return navpage = new NavigationPage (new ContentPage { 
        Content = new Button {
            Text = "Show Login dialog",
            Command = new Command (async o => {
                Debug.WriteLine ("Showing sign in dialog");
                var result = await SignInAsync (navpage);
                Debug.WriteLine (result);
            })
        }
    });
}

static Task<bool> SignInAsync (NavigationPage navpage)
{
    Random rnd = new Random ();
    var tcs = new TaskCompletionSource<bool> ();
    navpage.Navigation.PushModalAsync (new ContentPage {
        Content = new Button {
            Text = "Try login",
            Command = new Command ( o => {
                var result = rnd.Next (2) == 1;
                navpage.Navigation.PopModalAsync ();
                tcs.SetResult (result);
            })
        }
    });
    return tcs.Task;
}

次要缺点是Task<bool>在弹出模式动画结束之前返回，但这是:

The minor drawback is that the Task<bool> returns before the end of the pop modal animation, but that's:

1. 易于修复
2. 这只是一个问题，如果您正在等待结果推送新的模态Page.否则，继续吧.

1. easy to fix
2. only an issue if you're awaiting that result to push a new modal Page. Otherwise, meh, just go on.

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