后退按钮按下事件的确认对话框 Xamarin.Forms

Question

我卡在 Xamarin.Forms 应用程序的某一点上

在后退按钮上按下只是想问用户确认他是否真的想退出， "OnBackButtonPressed" 我想显示警报对话框并根据用户响应继续。

但是 "OnBackButtonPressed" 不是 Async 我不能写 await DisplayAlert... 请指导我应该如何实现此功能？

我使用 ContentPage 作为 NavigationPage 的根页面

    public class frmHome : ContentPage

这是代码：

protected override bool OnBackButtonPressed()
{
    var result = await  this.DisplayAlert("Alert!", "Do you really want to exit?", "Yes", "No");

    if (result)
        {
            //user wants to exit
            //Terminate application
        }
        else
        {
            //Dont do anything
        }
}

Answer 1

    protected override bool OnBackButtonPressed()
    {
        Device.BeginInvokeOnMainThread(async() => {
            var result = await this.DisplayAlert("Alert!", "Do you really want to exit?", "Yes", "No");
            if (result) await this.Navigation.PopAsync(); // or anything else
        });

        return true;
    }

Answer 2

覆盖硬件后退按钮并向用户显示确认对话框的简单方法

protected override bool OnBackButtonPressed()
{
    Device.BeginInvokeOnMainThread(async () =>
    {
        if (await DisplayAlert("Alert", "Are you sure you want to go back ?", "Yes", "No"))
        {
            base.OnBackButtonPressed();

            await Navigation.PopAsync();
         }
    });

    return true;
}

Answer 3

public override void OnBackPressed()
{
    RunOnUiThread(
        async () =>
        {
            var isCloseApp = await AlertAsync(this, "NameOfApp", "Do you want to close this app?", "Yes", "No");

            if (isCloseApp)
            {
                var activity = (Activity)Forms.Context;
                activity.FinishAffinity();
            }
        });
}

public Task<bool> AlertAsync(Context context, string title, string message, string positiveButton, string negativeButton)
{
    var tcs = new TaskCompletionSource<bool>();

    using (var db = new AlertDialog.Builder(context))
    {
        db.SetTitle(title);
        db.SetMessage(message);
        db.SetPositiveButton(positiveButton, (sender, args) => { tcs.TrySetResult(true); });
        db.SetNegativeButton(negativeButton, (sender, args) => { tcs.TrySetResult(false); });
        db.Show();
    }

    return tcs.Task;
}

Xamarin.Android await AlertDialog.Builder

Answer 4

 private async void OnDelete(object sender, EventArgs e)
        {
            var result = await this.DisplayAlert("Alert!", "Do you really want to exit?", "Yes", "No");
            if (result)
            {

                var menuitem = sender as MenuItem;
                string name = menuitem.BindingContext as string;

                lielements.Remove(name);
            }
            else
            {


            }

        }

Answer 5

如果您在 Mainpage 上并想退出您的应用程序，那么此代码将帮助您。

在你的 UI (PCL)

  protected override bool OnBackButtonPressed()
            {

                Device.BeginInvokeOnMainThread(new Action(async () => {
                    var result = await this.DisplayAlert("Alert!", "Do you really want to exit?", "Yes", "No");

                    if (result)
                    {
                        if (Device.RuntimePlatform == Device.Android)
                            DependencyService.Get<IAndroidMethods>().CloseApp();
                    }
                }));
                return true;
            }

同时创建一个接口（在您的 UI PCL 中）：

public interface IAndroidMethods
{
    void CloseApp();
}

现在在您的 Android 项目中实现 Android 特定的逻辑：

[assembly: Xamarin.Forms.Dependency(typeof(AndroidMethods))]
namespace Your.Namespace
{
   public class AndroidMethods : IAndroidMethods
   {
       public void CloseApp()
       {
             var activity = (Activity)Forms.Context;
            activity.FinishAffinity();
       }
   }
}

Answer 6

这是对我有用的代码

protected override bool OnBackButtonPressed()
    {
        Device.BeginInvokeOnMainThread(async () =>
        {
            var result = await this.DisplayAlert("Alert!", "Do you really want to exit?", "Yes", "No");

            if (result)
            {
                System.Diagnostics.Process.GetCurrentProcess().CloseMainWindow(); // Or anything else
            }
        });
        return true;
    }

Answer 7

这样就搞定了

protected override bool OnBackButtonPressed()
{
    var result = await  this.DisplayAlert("Alert!", "Do you really want to exit?", "Yes", "No");

    if (result)
        {
            Process.GetCurrentProcess().CloseMainWindow();
            Process.GetCurrentProcess().Close();
        }
        else
        {
            //Dont do anything
        }
}

后退按钮按下事件的确认对话框 Xamarin.Forms

Confirmation Dialog on back button press event Xamarin.Forms

xamarin

xamarin.forms