Why there is no DoubleTapped event in GestureRecognizer

Question

I want to add double-tap to zoom feature to our application. I've told the gesture recognizer to recognize the double tap gesture along with other gestures with the code

    m_gestureRecognizer = ref new GestureRecognizer;

    // specify which gestures the application supports
    m_gestureRecognizer->GestureSettings = 
        GestureSettings::DoubleTap                    | // normal zoom
        GestureSettings::ManipulationScale            | // smooth zoom
        GestureSettings::ManipulationTranslateX       | // pan
        GestureSettings::ManipulationTranslateY       |
        GestureSettings::ManipulationTranslateInertia |
        GestureSettings::RightTap; // bring up context controls

When I register gesture event handlers, I am surprised to find that there is DoubleTapped event in GestureRecognizer. So what can I do to handle double-tap gesture? Thanks.

Answer 1

Check CanBeDoubleTap in your Tapped event handler.

--Rob

Answer 2

Thanks Rob. But the CanBeDoubleTap method always returns true for both single tap and double tap. This method requires a PointerPoint parameter. As I cannot get this parameter from the input parameters of the Tapped event handler, I obtain it from the OnPointerPress event handler. Here is my code:

// header file
ref class TouchME : public Windows::ApplicationModel::Core::IFrameworkView
{
......
    Windows::UI::Input::GestureRecognizer^ m_gestureRecognizer; 
    Windows::UI::Input::PointerPoint^ m_pointerPoint;
};

// implementation file
void TouchME::OnPointerPressed(_In_ CoreWindow^, _In_ PointerEventArgs^ args)
{
    unsigned int pointerId = args->CurrentPoint->PointerId;
    m_pointerPoint = PointerPoint::GetCurrentPoint(pointerId);
    m_gestureRecognizer->ProcessDownEvent(m_pointerPoint);
}

void TouchME::initGestureRecognizer()
{
    m_gestureRecognizer = ref new GestureRecognizer;
    m_pointerPoint = nullptr;

    // specify which gestures the application supports
    m_gestureRecognizer->GestureSettings = 
        GestureSettings::Tap                          | // normal zoom
        GestureSettings::DoubleTap                    | 
        GestureSettings::ManipulationScale            | // smooth zoom
        GestureSettings::ManipulationTranslateX       | // pan
        GestureSettings::ManipulationTranslateY       |
        GestureSettings::ManipulationTranslateInertia |
        GestureSettings::RightTap; // bring up thumbnails and context controls

    // Register all the gesture event handlers
    _tokenTapped = m_gestureRecognizer->Tapped::add(
        ref new TypedEventHandler<GestureRecognizer^, TappedEventArgs^>(
                this, &TouchME::OnTapped));
......
}

void TouchME::OnTapped(_In_ GestureRecognizer^ sender, _In_ TappedEventArgs^ args)
{
    if ( m_gestureRecognizer->CanBeDoubleTap(m_pointerPoint) ) {
        OutputDebugString(TEXT("DoubleTap gesture detected\n"));
    }
}

I couldn't find the cause that makes CanBeDoubleTap return incorrect result. Please give me some help, thanks.

Answer 3

I want to add double-tap to zoom feature to my app. I use CanBeDoubleTap inside the OnTapped event handler to detect double-tap as suggested in the post (http://social.msdn.microsoft.com/Forums/en-US/winappswithnativecode/thread/fe938ad4-373a-4cdb-876e-c06180c65756). However, this method always returns true for both single and double tap. I notice this method requires a PointerPoint parameter. As I cannot get this parameter from the input parameters of the OnTapped event handler, I obtain it from the OnPointerPress event handler. Here is my code:

// header file
ref class TouchME : public Windows::ApplicationModel::Core::IFrameworkView
{
......
    Windows::UI::Input::GestureRecognizer^ m_gestureRecognizer; 
    Windows::UI::Input::PointerPoint^ m_pointerPoint;
};

// implementation file
void TouchME::OnPointerPressed(_In_ CoreWindow^, _In_ PointerEventArgs^ args)
{
    unsigned int pointerId = args->CurrentPoint->PointerId;
    m_pointerPoint = PointerPoint::GetCurrentPoint(pointerId);
    m_gestureRecognizer->ProcessDownEvent(m_pointerPoint);
}

void TouchME::initGestureRecognizer()
{
    m_gestureRecognizer = ref new GestureRecognizer;
    m_pointerPoint = nullptr;

    // specify which gestures the application supports
    m_gestureRecognizer->GestureSettings = 
        GestureSettings::Tap                          | // normal zoom
        GestureSettings::DoubleTap                    | 
        GestureSettings::ManipulationScale            | // smooth zoom
        GestureSettings::ManipulationTranslateX       | // pan
        GestureSettings::ManipulationTranslateY       |
        GestureSettings::ManipulationTranslateInertia |
        GestureSettings::RightTap; // bring up thumbnails and context controls

    // Register all the gesture event handlers
    _tokenTapped = m_gestureRecognizer->Tapped::add(
        ref new TypedEventHandler<GestureRecognizer^, TappedEventArgs^>(
                this, &TouchME::OnTapped));
......
}

void TouchME::OnTapped(_In_ GestureRecognizer^ sender, _In_ TappedEventArgs^ args)
{
    if ( m_gestureRecognizer->CanBeDoubleTap(m_pointerPoint) ) { // issue: the condition is always true
        OutputDebugString(TEXT("DoubleTap gesture detected\n"));
    }
}

Answer 4

void TouchME::OnTapped(_In_ GestureRecognizer^ sender, _In_ TappedEventArgs^ args)
{
    if (args->TapCount == 2 ) { // issue: the condition is always true
        OutputDebugString(L"DoubleTap gesture detected\n"));
    }
}

Answer 5

Thank you. It works.