Confirmation Dialog on back button press event Xamarin.Forms - xamarin

Question

I am stuck at one point in Xamarin.Forms application
On Back button press simply I want to ask user to confirm whether he really wants to exit or not,
"OnBackButtonPressed" I want to show Alert dialog and proceed as user response.
But "OnBackButtonPressed" is not Async I cannot write await DisplayAlert...
Please direct me how should i implement this feature?
I am using ContentPage as my root Page of NavigationPage
public class frmHome : ContentPage
Here is the code :
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

Here's the code that worked for me
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 3

Easy way to override hardware back button and show a confirmation dialog box to user
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 4

If you are on Mainpage and want to exit your app then this code will help you.
In your 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;
}
Also create an Interface (in your UI PCL):
public interface IAndroidMethods
{
void CloseApp();
}
Now implement the Android-specific logic in your Android project:
[assembly: Xamarin.Forms.Dependency(typeof(AndroidMethods))]
namespace Your.Namespace
{
public class AndroidMethods : IAndroidMethods
{
public void CloseApp()
{
var activity = (Activity)Forms.Context;
activity.FinishAffinity();
}
}
}

Answer 5

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 6

I am done like this
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
}
}

Answer 7

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
{
}
}