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windows phone 7 app.xaml启动过程

12-12-16 来源：[db:作者]

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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>

<shell:PhoneApplicationService

Launching="Application_Launching" Closing="Application_Closing"

Activated="Application_Activated" Deactivated="Application_Deactivated"/>

</Application.ApplicationLifetimeObjects>

————————————————————————————–

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.windowNonUserCodeAttribute()]

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.windowNonUserCodeAttribute()]

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.window.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'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'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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