關于對話框，主要實現了讓用戶查看當前軟件的版本、軟件信息和檢查升級的功能。因此這個類主要繼續 ChromeViews::View 類、 ChromeViews::DialogDelegate 和 GoogleUpdateStatusListener 。其中 ChromeViews::View 實現窗口的布局和顯示問題， ChromeViews::DialogDelegate 實現了事件響應，或者窗口某時是否可以顯示按鈕的問題， GoogleUpdateStatusListener 是用來實現接收更新程序狀態信息。

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這個類的聲明如下：

class AboutChromeView : public ChromeViews::View,

??????????????????????? public ChromeViews::DialogDelegate,

??????????????????????? public GoogleUpdateStatusListener {

? public:

? explicit AboutChromeView(Profile* profile);

? virtual ~AboutChromeView();

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? // Initialize the controls on the dialog.

? void Init();

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? // Overridden from ChromeViews::View:

? virtual void GetPreferredSize(CSize *out);

? virtual void Layout();

? virtual void ViewHierarchyChanged(bool is_add,

????????????????????????????????? ?? ChromeViews::View* parent,

??????????????????????????????????? ChromeViews::View* child);

?

? // Overridden from ChromeViews::DialogDelegate:

? virtual int GetDialogButtons() const;

? virtual std::wstring GetDialogButtonLabel(DialogButton button) const;

? ? virtual bool IsDialogButtonEnabled(DialogButton button) const;

? virtual bool IsDialogButtonVisible(DialogButton button) const;

? virtual bool CanResize() const;

? virtual bool CanMaximize() const;

? virtual bool IsAlwaysOnTop() const;

? virtual bool HasAlwaysOnTopMenu() const;

? virtual bool IsModal() const;

? virtual std::wstring GetWindowTitle() const;

? virtual bool Accept();

? virtual ChromeViews::View* GetContentsView();

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? // Overridden from GoogleUpdateStatusListener:

? virtual void OnReportResults(GoogleUpdateUpgradeResult result,

?????????????????????????????? GoogleUpdateErrorCode error_code,

?????????????????????????????? const std::wstring& version);

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? private:

? // The visible state of the Check For Updates button.

? enum CheckButtonStatus {

? ?? CHECKBUTTON_HIDDEN = 0,

??? CHECKBUTTON_DISABLED,

??? CHECKBUTTON_ENABLED,

? };

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? // Update the UI to show the status of the upgrade.

? void UpdateStatus(GoogleUpdateUpgradeResult result,

??????????????????? GoogleUpdateErrorCode error_code);

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? Profile* profile_;

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? // UI elements on the dialog.

? ChromeViews::ImageView* about_dlg_background_;

? ChromeViews::Label* about_title_label_;

? ChromeViews::TextField* version_label_;

? ChromeViews::TextField* main_text_label_;

? // UI elements we add to the parent view.

? scoped_ptr<ChromeViews::Throbber> throbber_;

? ChromeViews::ImageView success_indicator_;

? ChromeViews::ImageView update_available_indicator_;

? ChromeViews::ImageView timeout_indicator_;

? ChromeViews::Label update_label_;

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? // Keeps track of the visible state of the Check For Updates button.

? CheckButtonStatus check_button_status_;

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? // The class that communicates with Google Update to find out if an update is

? // available and asks it to start an upgrade.

? GoogleUpdate* google_updater_;

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? // Our current version.

? std::wstring current_version_;

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? // The version Google Update reports is available to us.

? std::wstring new_version_available_;

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? DISALLOW_EVIL_CONSTRUCTORS(AboutChromeView);

};

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通過關于對話框的分析，可以理解到 chrome 瀏覽器窗口基本組成，以及窗口繼承關系，還有事件的響應方式。前面三次分析，主要是入門的分析，也是了解這么一個大工程的一種手段。比如測試整個工程是否可以編譯，是否可以修改代碼等等。后面的分析會以瀏覽器輸入 HTTP 連接開始，直到打開網頁顯示為一個主線，做一個基本的分析。

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谷歌瀏覽器的源碼分析(4)