Question

我在Windows Phone 10上的硬件后退按钮出现问题，当默认页面是BackgroundMusic页面时，该按钮不起作用。

App.cs

protected override void OnLaunched(LaunchActivatedEventArgs e)
        {
#if DEBUG
            if (System.Diagnostics.Debugger.IsAttached)
            {
                this.DebugSettings.EnableFrameRateCounter = true;
            }
#endif
            Frame rootFrame = Window.Current.Content as Frame;

            // Do not repeat app initialization when the Window already has content,
            // just ensure that the window is active
            if (rootFrame == null)
            {
                // Create a Frame to act as the navigation context and navigate to the first page
                rootFrame = new Frame();

                rootFrame.NavigationFailed += OnNavigationFailed;
                rootFrame.Navigated += RootFrame_Navigated;

                if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
                {
                    //TODO: Load state from previously suspended application
                }

                // Place the frame in the current Window
                Window.Current.Content = rootFrame;

                // Register a handler for BackRequested events and set the  
                // visibility of the Back button  
                SystemNavigationManager.GetForCurrentView().BackRequested += OnBackRequested;

                SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
                    rootFrame.CanGoBack ?
                    AppViewBackButtonVisibility.Visible :
                    AppViewBackButtonVisibility.Collapsed;
            }

            if (e.PrelaunchActivated == false)
            {
                if (rootFrame.Content == null)
                {
                    // 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(typeof(BackgroundMusic), e.Arguments);
                }
                // Ensure the current window is active
                Window.Current.Activate();
            }
        }

private void RootFrame_Navigated(object sender, NavigationEventArgs e)
        {
            // Each time a navigation event occurs, update the Back button's visibility  
            SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
                ((Frame)sender).CanGoBack ?
                AppViewBackButtonVisibility.Visible :
                AppViewBackButtonVisibility.Collapsed;
        }

        private void OnBackRequested(object sender, BackRequestedEventArgs e)
        {
            Frame rootFrame = Window.Current.Content as Frame;

            if (App.DetectPlatform() == Platform.WindowsPhone)
            {
                HardwareButtons.BackPressed += new EventHandler<BackPressedEventArgs>((s, a) =>
                {
                    if (rootFrame.CanGoBack)
                    {

                        rootFrame.GoBack();
                        a.Handled = true;
                    }
                });
            }
            else if (App.DetectPlatform() == Platform.Windows)
            {
                if (rootFrame.CanGoBack)
                {
                    e.Handled = true;
                    rootFrame.GoBack();
                }
            }
        }

        public static Platform DetectPlatform()
        {
            bool isHardwareButtonsAPIPresent = ApiInformation.IsTypePresent("Windows.Phone.UI.Input.HardwareButtons");

            if (isHardwareButtonsAPIPresent)
            {
                return Platform.WindowsPhone;
            }
            else
            {
                return Platform.Windows;
            }
        }

public static MediaElement GlobalMediaElement
        {
            get { return Current.Resources["MyPlayer"] as MediaElement; }
        }

        private void mediaended(object sender, RoutedEventArgs e)
        {
            var AppMediaElement = App.GlobalMediaElement;
            AppMediaElement.Position = TimeSpan.Zero;
            AppMediaElement.Play();
        }

BackgroundMusic.cs

const string soundTrackToken = "soundtrack";
    int flag = 1;


    public BackgroundMusic()
    {
        this.InitializeComponent();
    }

    protected async override void OnNavigatedTo(NavigationEventArgs e)
    {
        //navigationHelper.OnNavigatedTo(e);
        mainFrame.Navigate(typeof(MainPage));

        if (StorageApplicationPermissions.FutureAccessList.ContainsItem(soundTrackToken))
        {
            StorageFile audioFile = await StorageApplicationPermissions.FutureAccessList.GetFileAsync(soundTrackToken);
            if (audioFile != null)
            {
                await StartAudio(audioFile);
            }
        }
    }

如何处理？

注意： - 当默认页面是MainPage时，硬件返回按钮才能工作。但是当默认页面是BackgroundMusic页面时，硬件后退按钮不起作用 - BackgroundMusic页面是应用程序上的背景音乐页面（还有一个播放和停止按钮）。

Answer 1

你可以试试这个：

在

下

SystemNavigationManager.GetForCurrentView().BackRequested += OnBackRequested;

把

HardwareButtons.BackPressed += OnBackRequested:

然后在OnBackRequested

内删除此内容

HardwareButtons.BackPressed += new EventHandler<BackPressedEventArgs>((s, a) =>
            {

解释是您需要预先注册事件处理程序。在当前代码中，您只处理软件后退按钮。单击它并知道它是Phone平台，然后注册一个新的事件处理程序。所以，我建议你做的是预先注册处理程序与软件后退按钮相同，因此它处理相同的行为，如果以后是手机，你不需要添加新的事件处理程序。

Answer 2

首先，在Windows手机上你处理硬件后退按钮是这样的：

if (App.DetectPlatform() == Platform.WindowsPhone)
{
    HardwareButtons.BackPressed += new EventHandler<BackPressedEventArgs>((s, a) =>
    {
        if (rootFrame.CanGoBack)
        {
            rootFrame.GoBack();
            a.Handled = true;
        }
    });
}

这是不对的，就像处理后退按钮两次一样，当在移动设备上按下后退按钮时，BackStack的{{1}}中的两个项目将被删除。您可以像这样更改此代码：

rootFrame

其次，在if (App.DetectPlatform() == Platform.WindowsPhone) { if (rootFrame.CanGoBack) { rootFrame.GoBack(); e.Handled = true; } }的{{1}}事件中，我不知道你的OnNavigatedTo是什么，如果这是BackgroundMusic mainFrame 1}}页面，然后可以导航到Frame，BackgroundMusic的{{1}}将没有项目。如果此MainPage恰好是BackStack，那么导航将在rootFrame事件中导致失败，其中的项目为＆＃39}。 mainFrame的{{1}}次仍为0。

因此，如果您希望在rootFrame的默认网页为OnNavigatedTo时使用BackStack导航至rootFrame，则可以在rootFrame事件导航中导航以MainPage为例，例如：

rootFrame

Windows Phone 10上的硬件后退按钮无法正常工作

2 个答案: