Reputation:
I am new to Windows 10 UWP apps and currently I am trying out various navigation techniques in apps. I have searched for the back button functionality in UWP apps but cant seem to understand that where do I have to put the "provided code" and how to execute it. I have also tried to do it on my own but it throws various errors in Visual Studio about identifier not found.
The first code is:
Windows::UI::Core::SystemNavigationManager::GetForCurrentView()->
BackRequested += ref new Windows::Foundation::EventHandler<
Windows::UI::Core::BackRequestedEventArgs^>(
this, &App::App_BackRequested);
The second piece of code is:
void App::App_BackRequested(
Platform::Object^ sender,
Windows::UI::Core::BackRequestedEventArgs^ e)
{
Frame^ rootFrame = dynamic_cast<Frame^>(Window::Current->Content);
if (rootFrame == nullptr)
return;
// Navigate back if possible, and if the event has not
// already been handled.
if (rootFrame->CanGoBack && e->Handled == false)
{
e->Handled = true;
rootFrame->GoBack();
}
}
Please help me in this matter and tell me how do I implement this code in my UWP App. Thanks
Source: https://msdn.microsoft.com/en-us/library/windows/apps/mt465734.aspx
Upvotes: 0
Views: 1358
Reputation: 3167
It should be like below:
This is OnLaunched method in App.xaml.cpp class:
Just before its end you should paste first fragment:
void App::OnLaunched(Windows::ApplicationModel::Activation::LaunchActivatedEventArgs^ e)
{
#if _DEBUG
// Show graphics profiling information while debugging.
if (IsDebuggerPresent())
{
// Display the current frame rate counters
DebugSettings->EnableFrameRateCounter = true;
}
#endif
auto rootFrame = dynamic_cast<Frame^>(Window::Current->Content);
// Do not repeat app initialization when the Window already has content,
// just ensure that the window is active
if (rootFrame == nullptr)
{
// Create a Frame to act as the navigation context and associate it with
// a SuspensionManager key
rootFrame = ref new Frame();
rootFrame->NavigationFailed += ref new Windows::UI::Xaml::Navigation::NavigationFailedEventHandler(this, &App::OnNavigationFailed);
if (e->PreviousExecutionState == ApplicationExecutionState::Terminated)
{
// TODO: Restore the saved session state only when appropriate, scheduling the
// final launch steps after the restore is complete
}
if (e->PrelaunchActivated == false)
{
if (rootFrame->Content == nullptr)
{
// When the navigation stack isn't restored navigate to the first page,
// configuring the new page by passing required information as a navigation
// parameter
rootFrame->Navigate(TypeName(MainPage::typeid), e->Arguments);
}
// Place the frame in the current Window
Window::Current->Content = rootFrame;
// Ensure the current window is active
Window::Current->Activate();
}
}
else
{
if (e->PrelaunchActivated == false)
{
if (rootFrame->Content == nullptr)
{
// When the navigation stack isn't restored navigate to the first page,
// configuring the new page by passing required information as a navigation
// parameter
rootFrame->Navigate(TypeName(MainPage::typeid), e->Arguments);
}
// Ensure the current window is active
Window::Current->Activate();
}
}
Windows::UI::Core::SystemNavigationManager::GetForCurrentView()->
BackRequested += ref new Windows::Foundation::EventHandler<
Windows::UI::Core::BackRequestedEventArgs^>(
this, &App::App_BackRequested);
}
Now under OnLaunched method please paste this handler:
void App::App_BackRequested(
Platform::Object^ sender,
Windows::UI::Core::BackRequestedEventArgs^ e)
{
Frame^ rootFrame = dynamic_cast<Frame^>(Window::Current->Content);
if (rootFrame == nullptr)
return;
// Navigate back if possible, and if the event has not
// already been handled.
if (rootFrame->CanGoBack && e->Handled == false)
{
e->Handled = true;
rootFrame->GoBack();
}
}
You need to also add below code to App.xaml.h:
ref class App sealed (Visual Studio can add it automatically): { protected: virtual void OnLaunched(Windows::ApplicationModel::Activation::LaunchActivatedEventArgs^ e) override;
void App_BackRequested(Platform::Object ^ sender, Windows::UI::Core::BackRequestedEventArgs ^ e);
internal:
App();
private:
void OnSuspending(Platform::Object^ sender, Windows::ApplicationModel::SuspendingEventArgs^ e);
void OnNavigationFailed(Platform::Object ^sender, Windows::UI::Xaml::Navigation::NavigationFailedEventArgs ^e);
};
Hope this will help you.
Upvotes: 1
Reputation:
I managed to get it right somehow, the first code was put in App.xaml code-behind file under the "OnLaunched" event. The second code was put in the last of the above file and it's forward declaration was put in the header file.
Upvotes: 0