Setting 的首页加载过程

<1> 在manifest.xml中可以知道settings类为入口类

setting.java:

public class Settings extends SettingsActivity {    /*    * Settings subclasses for launching independently.    */    public static class BluetoothSettingsActivity extends SettingsActivity { /* empty */ }........    public static class AppDrawOverlaySettingsActivity extends SettingsActivity { /* empty */ }    public static class AppWriteSettingsActivity extends SettingsActivity { /* empty */ }}

可以知道settings中定义了很多类，而没有具体的实现，settings类只是一个管理类，定义设置中的Activity,具体实现类是在其父类SettingsActivity 中

<2>SettingsActivity 加载主页的过程

SettingsActivity ：

@Override    protected void onCreate(Bundle savedState) {        super.onCreate(savedState);        final Intent intent = getIntent();        final ComponentName cn = intent.getComponent();        final String className = cn.getClassName();        mIsShowingDashboard = className.equals(Settings.class.getName());        setContentView(mIsShowingDashboard ?                R.layout.settings_main_dashboard : R.layout.settings_main_prefs);        mContent = (ViewGroup) findViewById(R.id.main_content);        if (savedState != null) {        } else {            if (!mIsShowingDashboard) {            } else {                switchToFragment(DashboardSummary.class.getName(), null, false, false, mInitialTitleResId, mInitialTitle, false);            }        }    }

可以看到settingActivity的onCreate（）方法（只留下主界面加载相关的逻辑代码），setting第一次启动时savedState=null,className =”Settings”，这就可以知道setting加载的是R.layout.settings_main_dashboard布局，切换到DashboardSummary的fragment，下面来看
settings_main_dashboard布局：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"             android:id="@+id/main_content"             android:layout_height="match_parent"             android:layout_width="match_parent"             />

布局就只有一个控件。所以界面元素实在DashboardSummary中加载的
DashboardSummary：

 private void rebuildUI(Context context) {        List<DashboardCategory> categories =                ((SettingsActivity) context).getDashboardCategories(true);        final int count = categories.size();        for (int n = 0; n < count; n++) {            DashboardCategory category = categories.get(n);            View categoryView = mLayoutInflater.inflate(R.layout.dashboard_category, mDashboard,                    false);            TextView categoryLabel = (TextView) categoryView.findViewById(R.id.category_title);            categoryLabel.setText(category.getTitle(res));            ViewGroup categoryContent =                    (ViewGroup) categoryView.findViewById(R.id.category_content);            final int tilesCount = category.getTilesCount();            for (int i = 0; i < tilesCount; i++) {                DashboardTile tile = category.getTile(i);                DashboardTileView tileView = new DashboardTileView(context);                updateTileView(context, res, tile, tileView.getImageView(),                        tileView.getTitleTextView(), tileView.getStatusTextView());                tileView.setTile(tile);                categoryContent.addView(tileView);            }            // Add the category            mDashboard.addView(categoryView);        }    }

通过分析代码可以知道，是通过rebuildUI方法加载界面的，而主界面的数据又是通过SettingsActivity的getDashboardCategories的方法获取的

<3>SettingsActivity 通过getDashboardCategories获取主页相关数据

public List<DashboardCategory> getDashboardCategories(boolean forceRefresh) {        if (forceRefresh || mCategories.size() == 0) {            buildDashboardCategories(mCategories);        }        return mCategories;    } private void buildDashboardCategories(List<DashboardCategory> categories) {        categories.clear();        loadCategoriesFromResource(R.xml.dashboard_categories, categories, this);        updateTilesList(categories);    } public static void loadCategoriesFromResource(int resid, List<DashboardCategory> target,            Context context) {            解析dashboard_categories.xml的数据｝

由上可知主页的相关数据都是保存在dashboard_categories.xml中，通过解析xml中的数据生成 List<DashboardCategory> 数据列表再在DashboardSummary的rebuildUI方法中将数据填充到界面里，感觉就像直接加载dashboard_categories布局一样

<4>dashboard_categories.xml的神秘面纱

<dashboard-categories        xmlns:android="http://schemas.android.com/apk/res/android">    <!-- WIRELESS and NETWORKS -->    <dashboard-category            android:id="@+id/wireless_section"            android:key="@string/category_key_wireless"            android:title="@string/header_category_wireless_networks" >        <!-- Wifi -->        <dashboard-tile                android:id="@+id/wifi_settings"                android:title="@string/wifi_settings_title"                android:fragment="com.android.settings.wifi.WifiSettings"                android:icon="@drawable/ic_settings_wireless"                />        <!-- Other wireless and network controls -->        <dashboard-tile                android:id="@+id/wireless_settings"                android:title="@string/radio_controls_title"                android:fragment="com.android.settings.WirelessSettings"                android:icon="@drawable/ic_settings_more"                />    </dashboard-category>    <!-- DEVICE -->    <dashboard-category            android:id="@+id/device_section"            android:key="@string/category_key_device"            android:title="@string/header_category_device" >        <!-- Manage users -->        <!-- <dashboard-tile                android:id="@+id/user_settings"                android:title="@string/user_settings_title"                android:fragment="com.android.settings.users.UserSettings"                android:icon="@drawable/ic_settings_multiuser"                /> -->        <!-- Manage NFC payment apps -->        <dashboard-tile                android:id="@+id/nfc_payment_settings"                android:title="@string/nfc_payment_settings_title"                android:fragment="com.android.settings.nfc.PaymentSettings"                android:icon="@drawable/ic_settings_nfc_payment"                />    </dashboard-category></dashboard-categories>

可以看到dashboard_categories由一些dashboard-category，dashboard-tile节点组成一个用于分类，一个是具体的项

<4>总结

setting加载主页是通过DashboardSummary的rebuildui方法将dashboard_categories的数据添加到view中，看起来像是直接加载dashboard_categories