Maui android TapGestureRecognizer problem issue

Question

Hello all. the problem is in the this section InputTB.Text = "''; not work inside task but work outside task pleas what wrong thank you . Finally I change to bool answer = await DisplayAlert() if(answer) {...} and that works ok but I still curious why in the task no works

      answer.ContinueWith(async task =>
      {
          if (task.Result)
          {
              saveForAWhile += InputTB.Text; // this not work
              InputTB.Text = " "; // this not work
          }
      });

 <Label HorizontalOptions="Center" VerticalOptions="End"
     FontAttributes="Bold" Text="Puzzle Window" >

    <Label.GestureRecognizers>
           <TapGestureRecognizer Tapped="OnTapClearPuzzleWindow"
                   NumberOfTapsRequired="2" />
     </Label.GestureRecognizers>

 </Label>



     <Label x:Name="Open"  Text="Open" FontAttributes="Bold"
         HorizontalOptions="Start" VerticalOptions="Center"
         Grid.Row="0" Grid.Column="1" >

         <Label.GestureRecognizers>
           <TapGestureRecognizer Tapped="OnTapDeletePuzzlsList"
                   NumberOfTapsRequired="2" />
           </Label.GestureRecognizers>
     </Label>



    private void OnTapDeletePuzzlsList(object sender, TappedEventArgs e)
    { 
      string msg = "Delete Puzzles List file?";  
      Task<bool> answer = DisplayAlert("", msg, "Yes", "No");
      answer.ContinueWith(async task =>
      {
          if (task.Result)
          {
              string savetime = DateTime.Now.ToString();
              string targetFile = System.IO.Path.Combine(FileSystem.Current.AppDataDirectory, "PuzzlesList.txt");
              savedPuzzlesList = "\n Puzzles List: " + savetime + "\n\n";

              File.Delete(targetFile);

              // Write the file content to the app data directory  
              using FileStream outputStream = System.IO.File.OpenWrite(targetFile);
              using StreamWriter streamWriter = new StreamWriter(outputStream);
              await streamWriter.WriteAsync(savedPuzzlesList);
          }
      });

    }



    private void OnTapClearPuzzleWindow(object sender, TappedEventArgs e)
    { 
      
      string msg = "Clear Puzzle Window?";  
      Task<bool> answer = DisplayAlert("", msg, "Yes", "No");
      answer.ContinueWith(async task =>
      {
          if (task.Result)
          {
              saveForAWhile += InputTB.Text;
              InputTB.Text = " ";
          }
      });

    }

              
    

Answer 1

Hello,

If you want to operate the UI control, you need to invoke this part of code in the main thread. You can use MainThread.BeginInvokeOnMainThread like following code.

answer.ContinueWith(async task =>
        {
            if (task.Result)
            {
                MainThread.BeginInvokeOnMainThread(() => {
                    saveForAWhile += InputTB.Text;
                    InputTB.Text = " ";
                });
             }
        });

Best Regards,

Leon Lu

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