从系统屏幕检测返回

Question

在某个时候，我的应用程序需要在可用网络列表中显示，这没有问题：

private void ShowConnectionSettings()
{
    Debug.WriteLine("ShowConnectionSettings()");

    //Use the ConnectionSettingsTask to bring up the connection settings
    var connectionSettings = new ConnectionSettingsTask();

    // We are using the Connection Settings page for AirplaneMode.
    connectionSettings.ConnectionSettingsType = ConnectionSettingsType.WiFi;
    connectionSettings.Show();
}

但是，当用户再次移除屏幕时，我该如何检测呢？我需要一个OnReturnFromSystemScreen事件或类似的事情。

我做了一些测试：

private void PhoneApplicationPage_GotFocus(object sender, RoutedEventArgs e)
{
   txtHeader.Text = DateTime.Now.ToLongTimeString();
}

private void PhoneApplicationPage_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
    txtHeader.Text = DateTime.Now.ToLongTimeString();
}

    private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
    {
        txtHeader.Text = DateTime.Now.ToLongTimeString();

    }

但这还不够。所以任何想法都是有帮助的。

Answer 1

我错过了最明显的激活和停用事件

// Code to execute when the application is activated (brought to foreground)
// This code will not execute when the application is first launched
private void Application_Activated(object sender, ActivatedEventArgs e)
{
   //do stuff
}

// Code to execute when the application is deactivated (sent to background)
// This code will not execute when the application is closing
private void Application_Deactivated(object sender, DeactivatedEventArgs e)
{
   //do stuff
}

当显示我的系统屏幕时，将调用停用，当我返回时，调用已激活。

Answer 2

我认为不存在从系统屏幕返回的事件，最接近的可能是使用OnNavigatedTo并检查NavigationEventArgs.NavigationMode的值Back，这将指示您是否使用back导航导航回页面。然后检查IsNavigationInitiator，这表明导航是否在应用程序中启动。如下所示：

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    if (e.NavigationMode == NavigationMode.Back && e.IsNavigationInitiator == false)
    {
        txtHeader.Text = DateTime.Now.ToLongTimeString();
    }
}

还请参阅http://msdn.microsoft.com/en-us/library/system.windows.navigation.navigationmode(v=vs.95).aspx中NavigationMode的所有值。

Answer 3

你的测试结果我不清楚。如果您在自己的代码中引发事件时遇到了困难：

“通常事件由类处理程序标记，而GotFocus事件不会引发以供该控件上的任何用户代码处理程序处理。”

您需要显式地覆盖OnGotFocus连体。

http://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.uielement.gotfocus.aspx http://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.controls.control.ongotfocus.aspx