1 <Grid Background="#F5F5F5" DataContext="{Binding Path=MainPageViewModel, Source={StaticResource Locator}}">
2     <Grid Canvas.ZIndex="10000" Visibility="{Binding ExitNotificationVisible}" Height="30" Background="Red" VerticalAlignment="Top">
3         <TextBlock FontSize="14" Text="提示: 再按一次返回键退出支付宝" VerticalAlignment="Center" Margin="10 0 0 0" />
4     </Grid>
5     <ContentControl HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch" Content="{Binding DynamicContent}" />
6 </Grid>

1 using System;
2 using Windows.UI.Xaml;
3 using Windows.UI.Xaml.Controls;
4 using Windows.UI.Popups;

 1 public class MainPageViewModel : Core.ViewModelBase
 2 {
 3     public MainPageViewModel()
 4     {
 5         InitData();
 6         if(DynamicContent == null)
 7         {
 8             DynamicContent = ViewControlLocator.Instance.RegisterViewControl<HomePage, HomePageViewModel>(true);
 9         }
10         //---物理返回键api---
11         Windows.Phone.UI.Input.HardwareButtons.BackPressed += HardwareButtons_BackPressed;
12     }
13 
14     #region  attribute
15     //---计时器---
16     DispatcherTimer timer = null;
17     int timesToTick = 2;
18 
19     private UserControl m_DynamicContent;
20     public UserControl DynamicContent
21     {
22         get { return m_DynamicContent; }
23         set { m_DynamicContent = value; RaisePropertyChanged("DynamicContent"); }
24     }
25 
26     private Visibility m_ExitNotificationVisible;
27     public Visibility ExitNotificationVisible
28     {
29         get { return m_ExitNotificationVisible; }
30         set { m_ExitNotificationVisible = value; RaisePropertyChanged("ExitNotificationVisible"); }
31     }
32     #endregion
33     
34     #region  method
35     private void InitData()
36     {
37         ExitNotificationVisible = Visibility.Collapsed;
38     }
39 
40     //---关闭事件---
41     void HardwareButtons_BackPressed(object sender, Windows.Phone.UI.Input.BackPressedEventArgs e)
42     {
43         e.Handled = true;
44         if (ExitNotificationVisible == Visibility.Collapsed)
45         {
46             ExitNotificationVisible = Visibility.Visible;
47 
48             if(timer == null)
49             {
50                 timer = new DispatcherTimer();
51             }                
52             timer.Interval = TimeSpan.FromSeconds(2);
53             timer.Tick += timer_Tick;
54             timer.Start();
55         }
56         else
57         {
58             App.Current.Exit();
59         }
60     }
61 
62     //---到时没有执行关闭操作，隐藏关闭操作提示---
63     void timer_Tick(object sender, object e)
64     {
65         timesToTick--;
66         if (timesToTick == 0)
67         {
68             timesToTick = 2;
69             timer.Tick -= timer_Tick;
70             timer.Stop();
71             ExitNotificationVisible = Visibility.Collapsed;  
72         }
73     }
74     #endregion
75 }