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windows phone 7 app.xaml启动过程

2012-12-16

在网上找了一下基本没有人分析app.xaml的执行过程.只说是整个程序的生命周期而并没有深入.但是其实在app.xaml.cs的注释里面也说的很清楚了.我根据自己的理解翻译一下.首先有四个事件要注意,在app.xaml文件中的Ap...

在网上找了一下基本没有人分析app.xaml的执行过程.只说是整个程序的生命周期而并没有深入.
但是其实在app.xaml.cs的注释里面也说的很清楚了.我根据自己的理解翻译一下.
首先有四个事件要注意,在app.xaml文件中的Application.ApplicationLifetimeObjects节点定义
<Application.ApplicationLifetimeObjects>
<!--Required object that handles lifetime events for the application-->
<shell:PhoneApplicationService
Launching="Application_Launching" Closing="Application_Closing"
Activated="Application_Activated" Deactivated="Application_Deactivated"/>
</Application.ApplicationLifetimeObjects>
————————————————————————————&ndash;
这里多说一句,为什么在xaml文件定义的事件可以被程序知道.因为每个xaml.cs的构造函数都会调用一个InitializeComponent()函数.
这个函数是编译器自动生成的.内容如下
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public void InitializeComponent() {
if (_contentLoaded) {
return;
}
_contentLoaded = true;
System.Windows.Application.LoadComponent(this, new System.Uri("/PhoneSample;component/App.xaml", System.UriKind.Relative));
}
可以看到在这个函数里加载了xaml文件.如果你查看其他界面Page的InitializeComponent()函数.你可能会更明白xaml文件的作用
下面是来自Phone.Toolkit的MainPage的例子
internal System.Windows.Controls.Grid LayoutRoot;
internal System.Windows.Controls.StackPanel TitlePanel;
internal System.Windows.Controls.TextBlock ApplicationTitle;
internal System.Windows.Controls.TextBlock PageTitle;
internal System.Windows.Controls.Grid ContentPanel;
private bool _contentLoaded;
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public void InitializeComponent() {
if (_contentLoaded) {
return;
}
_contentLoaded = true;
System.Windows.Application.LoadComponent(this, new System.Uri("/PhoneToolkitSample;component/MainPage.xaml", System.UriKind.Relative));
this.LayoutRoot = ((System.Windows.Controls.Grid)(this.FindName("LayoutRoot")));
this.TitlePanel = ((System.Windows.Controls.StackPanel)(this.FindName("TitlePanel")));
this.ApplicationTitle = ((System.Windows.Controls.TextBlock)(this.FindName("ApplicationTitle")));
this.PageTitle = ((System.Windows.Controls.TextBlock)(this.FindName("PageTitle")));
this.ContentPanel = ((System.Windows.Controls.Grid)(this.FindName("ContentPanel")));
}
————————————————————
在这里注册了程序生命周期的四个事件,Launching,Closing,Activated,Deactivated
启动程序的时候会调用Application_Launching,退出程序的时候调用Application_Closing
启动别的程序时调用Application_Deactivated,返回到本程序时调用Application_Activated
1.App构造函数
public App()
{
// Global handler for uncaught exceptions.
//注册一个全局的异常处理handle,专门处理程序中没有处理的异常.
UnhandledException += Application_UnhandledException;
// Show graphics profiling information while debugging.
//下面这个是很有用的一个"宏",如果是出于调试状态则,IsAttached==true
if (System.Diagnostics.Debugger.IsAttached)
{
// Display the current frame rate counters.
//显示当前屏幕显示的帧率,如果不想显示可以去掉
Application.Current.Host.Settings.EnableFrameRateCounter = true;
// Show the areas of the app that are being redrawn in each frame.
//显示程序每一帧需要重绘的区域.
//Application.Current.Host.Settings.EnableRedrawRegions = true;
// Enable non-production analysis visualization mode,
// which shows areas of a page that are being GPU accelerated with a colored overlay.
//不懂
//Application.Current.Host.Settings.EnableCacheVisualization = true;
//在Application.Current.Host.Settings中还有其他参数.具体请参考Settings类.
}
// Standard Silverlight initialization
//标准Silverlight初始化,上面已经说过了.
InitializeComponent();
// Phone-specific initialization
//手机专有的初始化.后面介绍
InitializePhoneApplication();
}
2.InitializePhoneApplication函数的作用
// Avoid double-initialization
//防止2次初始化.
private bool phoneApplicationInitialized = false;
// Do not add any additional code to this method
private void InitializePhoneApplication()
{
if (phoneApplicationInitialized)
return;
// Create the frame but don&#39;t set it as RootVisual yet; this allows the splash
// screen to remain active until the application is ready to render.
//初始化程序框架,暂时不给RootVisual复制.这样可以让splash显示,知道在程序render完成
RootFrame = new TransitionFrame();
//加载完成事件,在这个事件中给RootVisual=RootFrame开始显示程序界面.
RootFrame.Navigated += CompleteInitializePhoneApplication;
// Handle navigation failures
//处理程序navigationg失败
RootFrame.NavigationFailed += RootFrame_NavigationFailed;
// Ensure we don&#39;t initialize again
//初始化完成.不再初始化
phoneApplicationInitialized = true;
}
在RootFrame加载完成后,把RootFrame赋值到程序的RootVisual,这样MainPage.xaml就得到显示了.
为什么显示的是MainPage?
这是在WMAppMainfest.xml中的节点定义的.你可以换成任意你喜欢的page.
到这里app的启动就算完成了.
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