为什么在 UWP 的情况下，网格的 TapGesture 识别器响应缓慢，但在 Android 和 iOS 中工作正常？

Question

I have a Button and a Grid. Button is bind to ExecuteButtonCommand and TapGestureRecognizer for Grid is bind to ExecuteGridCommand. Now if I press button rapidly and fast, corrresponding label shows correct click counts for all the platforms ie the command code is getting executed for the number of times click happened.

But in case of Grid, although for android and iOS this works perfectly fine. But for UWP, not all the clicks are executing the command. Example: If I tap the grid rapidly and fast lets say 6 times, then the corresponding label shows only 3 or 4 counts which means command for tapgesture is getting executed less number of times than it actually should.

This is what I have in my ViewModel

<StackLayout HorizontalOptions="Center" VerticalOptions="Center">
        <!-- Place new controls here -->
        <Label Text="{Binding ButtonExecutionCount}" HorizontalOptions="Center"/>
        <Button x:Name="ClickButton" Text="ExecuteClick"  HorizontalOptions="Center"
                    Command="{Binding ExecuteButtonCommand}"
                />
        <Label Text="{Binding GridExecutionCount}" HorizontalOptions="Center"/>
        <Grid BackgroundColor="Aquamarine" VerticalOptions="Center" HorizontalOptions="Center">
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Label Text="Click this grid" Grid.Column="0" Grid.Row="0" HorizontalOptions="Center"/>
            <Grid.GestureRecognizers>
                <TapGestureRecognizer Command="{Binding ExecuteGridCommand}"></TapGestureRecognizer>
            </Grid.GestureRecognizers>
        </Grid>
    </StackLayout>

And here is the code of binding viewmodel that records and displays the click counts:

public class MainPageViewModel : INotifyPropertyChanged
    {
        public MainPageViewModel()
        {
            ExecuteGridCommand = new Command(ExecuteGridMethod);
            ExecuteButtonCommand = new Command(ExecuteButtonMethod);
        }

        private int _gridExecutionCount;
        public int GridExecutionCount
        {
            get => _gridExecutionCount;
            set
            {
                _gridExecutionCount = value;
                OnPropertyChanged();
            }
        }

        private int _buttonExecutionCount;
        public int ButtonExecutionCount
        {
            get => _buttonExecutionCount;
            set
            {
                _buttonExecutionCount = value;
                OnPropertyChanged();
            }
        }

        public Command ExecuteGridCommand { get; set; }

        public Command ExecuteButtonCommand { get; set; }


        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged([CallerMemberName] string name = "")
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }

        public void ExecuteGridMethod()
        {
            GridExecutionCount++;
        }

        public void ExecuteButtonMethod()
        {
            ButtonExecutionCount++;
        }
    }

Here I have cliked both 5 times and for button count is fine but for grid in UWP it is less that actual clicks.

Answer 1

Cause: The strange behavior in your project was caused by the version of Xamarin.Forms. It is an existing issue in the version 4.5.x .

Solution: The issue had been fixed in the latest version ( 4.7.x ). I tested your sample on it and works fine. So you just need to update the version of XF both in share project and platform projects to the latest version.