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分析Android 11.0Settings源码之主界面加载
来源：jb51　　时间：2021/4/12 19:00:22　　对本文有异议

本篇主要记录AndroidR Settings源码主界面加载流程，方便后续工作调试其流程。

Settings代码路径：

packages/app/Settings/

Settings代码获取：

Setting 源码下载地址：https://github.com/aosp-mirror/platform_packages_apps_settings
git地址：https://github.com/aosp-mirror/platform_packages_apps_settings.git

主界面加载：

首先我们来看 Settings 模块中的 AndroidManifest.xml 文件，找到默认启动入口Activity信息：

  1. <activity android:name=".homepage.SettingsHomepageActivity"
  2.       android:label="@string/settings_label_launcher"
  3.       android:theme="@style/Theme.Settings.Home"
  4.       android:taskAffinity="com.android.settings.root"
  5.       android:launchMode="singleTask"
  6.       android:configChanges="keyboard|keyboardHidden">
  7. <intent-filter android:priority="1">
  8.     <action android:name="android.settings.SETTINGS" />
  9.     <category android:name="android.intent.category.DEFAULT" />
  10. </intent-filter>
  11. <meta-data android:name="com.android.settings.PRIMARY_PROFILE_CONTROLLED"
  12.            android:value="true" />
  13. </activity>
  14. //activity-alias可用来设置某个Activity的快捷入口，可以放在桌面上或者通过该别名被其他组件快速调起。                   
  15. //android:targetActivity为目标Activity. 
  16. <!-- Alias for launcher activity only, as this belongs to each profile. -->
  17. <activity-alias android:name="Settings"
  18.     android:label="@string/settings_label_launcher"
  19.     android:taskAffinity="com.android.settings.root"
  20.     android:launchMode="singleTask"
  21.     android:targetActivity=".homepage.SettingsHomepageActivity">
  22. <intent-filter>
  23.     <action android:name="android.intent.action.MAIN" />
  24.     <category android:name="android.intent.category.DEFAULT" />
  25.     <category android:name="android.intent.category.LAUNCHER" />
  26. </intent-filter>
  27. <meta-data android:name="android.app.shortcuts" android:resource="@xml/shortcuts"/>
  28. </activity-alias>

可以看到Settings的桌面图标启动的主界面是Settings.java，但其xml定义了targetActivity属性，实质应是SettingsHomepageActivity.java，从onCreate()方法开始:

  1. @Override
  2. protected void onCreate(Bundle savedInstanceState) {
  3.     super.onCreate(savedInstanceState);
  4.  
  5.     setContentView(R.layout.settings_homepage_container);
  6.     final View root = findViewById(R.id.settings_homepage_container);
  7.     root.setSystemUiVisibility(
  8.             View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_LAYOUT_STABLE);
  9.  
  10.     setHomepageContainerPaddingTop();
  11.  
  12.     final Toolbar toolbar = findViewById(R.id.search_action_bar);
  13.     FeatureFactory.getFactory(this).getSearchFeatureProvider()
  14.             .initSearchToolbar(this /* activity */, toolbar, SettingsEnums.SETTINGS_HOMEPAGE);
  15.  
  16.     final ImageView avatarView = findViewById(R.id.account_avatar);
  17.     getLifecycle().addObserver(new AvatarViewMixin(this, avatarView));
  18.     getLifecycle().addObserver(new HideNonSystemOverlayMixin(this));
  19.  
  20.     if (!getSystemService(ActivityManager.class).isLowRamDevice()) {
  21.         // Only allow contextual feature on high ram devices.
  22.         showFragment(new ContextualCardsFragment(), R.id.contextual_cards_content);
  23.     }
  24.     showFragment(new TopLevelSettings(), R.id.main_content);
  25.     ((FrameLayout) findViewById(R.id.main_content))
  26.             .getLayoutTransition().enableTransitionType(LayoutTransition.CHANGING);
  27. }

可以看到主界面的layout为settings_homepage_container.xml:

  1. <androidx.coordinatorlayout.widget.CoordinatorLayout
  2.     xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     android:id="@+id/settings_homepage_container"
  5.     android:fitsSystemWindows="true"
  6.     android:layout_width="match_parent"
  7.     android:layout_height="match_parent">
  8.  
  9.     <androidx.core.widget.NestedScrollView
  10.         android:id="@+id/main_content_scrollable_container"
  11.         android:layout_width="match_parent"
  12.         android:layout_height="match_parent"
  13.         app:layout_behavior="com.android.settings.widget.FloatingAppBarScrollingViewBehavior">
  14.  
  15.         <LinearLayout
  16.             android:id="@+id/homepage_container"
  17.             android:layout_width="match_parent"
  18.             android:layout_height="wrap_content"
  19.             android:orientation="vertical">
  20.  
  21.             <FrameLayout
  22.                 android:id="@+id/contextual_cards_content"
  23.                 android:layout_width="match_parent"
  24.                 android:layout_height="wrap_content"
  25.                 android:layout_marginStart="@dimen/contextual_card_side_margin"
  26.                 android:layout_marginEnd="@dimen/contextual_card_side_margin"/>
  27.  
  28.             <FrameLayout
  29.                 android:id="@+id/main_content"
  30.                 android:layout_width="match_parent"
  31.                 android:layout_height="wrap_content"
  32.                 android:animateLayoutChanges="true"
  33.                 android:background="?android:attr/windowBackground"/>
  34.  
  35.         </LinearLayout>
  36.     </androidx.core.widget.NestedScrollView>
  37.  
  38.     <com.google.android.material.appbar.AppBarLayout
  39.         android:layout_width="match_parent"
  40.         android:layout_height="wrap_content"
  41.         android:touchscreenBlocksFocus="false"
  42.         android:keyboardNavigationCluster="false">
  43.         <include layout="@layout/search_bar"/>
  44.     </com.google.android.material.appbar.AppBarLayout>
  45. </androidx.coordinatorlayout.widget.CoordinatorLayout>

主界面布局中主要包含两部分：一个顶部快捷搜索栏，一个Id为main_content的FrameLayout就是用来显示主设置内容的，即Settings的一级菜单项界面。
回到onCreate()方法：

  1. showFragment(new TopLevelSettings(), R.id.main_content);

可以看到一级菜单启动的是TopLevelSettings，TopLevelSettings继承于DashboardFragment.java：

  1. public class TopLevelSettings extends DashboardFragment implements
  2. PreferenceFragmentCompat.OnPreferenceStartFragmentCallback

TopLevelSettings的构造方法：

  1. public TopLevelSettings() {
  2.     final Bundle args = new Bundle();
  3.     // Disable the search icon because this page uses a full search view in actionbar.
  4.     args.putBoolean(NEED_SEARCH_ICON_IN_ACTION_BAR, false);
  5.     setArguments(args);
  6. }

可以看到通过构造方法传递了一个参数，从注释中可以看出，该参数的用意是由于主界面使用完整的搜索视图所以在主界面的actionbar中隐藏了搜索图标。然后再根据framgments生命周期先来看onAttach()方法:

  1. @Override
  2. public void onAttach(Context context) {
  3.     super.onAttach(context);
  4.     use(SupportPreferenceController.class).setActivity(getActivity());
  5. }

调用父类DashboardFragment.java的onAttach()方法：

  1. @Override
  2. public void onAttach(Context context) {
  3.     super.onAttach(context);
  4.     mSuppressInjectedTileKeys = Arrays.asList(context.getResources().getStringArray(
  5.             R.array.config_suppress_injected_tile_keys));
  6.     mDashboardFeatureProvider = FeatureFactory.getFactory(context).
  7.             getDashboardFeatureProvider(context);
  8.     // Load preference controllers from code
  9.     final List<AbstractPreferenceController> controllersFromCode =
  10.             createPreferenceControllers(context);
  11.     // Load preference controllers from xml definition
  12.     final List<BasePreferenceController> controllersFromXml = PreferenceControllerListHelper
  13.             .getPreferenceControllersFromXml(context, getPreferenceScreenResId());
  14.     // Filter xml-based controllers in case a similar controller is created from code already.
  15.     final List<BasePreferenceController> uniqueControllerFromXml =
  16.             PreferenceControllerListHelper.filterControllers(
  17.                     controllersFromXml, controllersFromCode);
  18.  
  19.     // Add unique controllers to list.
  20.     if (controllersFromCode != null) {
  21.         mControllers.addAll(controllersFromCode);
  22.     }
  23.     mControllers.addAll(uniqueControllerFromXml);
  24.  
  25.     // And wire up with lifecycle.
  26.     final Lifecycle lifecycle = getSettingsLifecycle();
  27.     uniqueControllerFromXml.forEach(controller -> {
  28.         if (controller instanceof LifecycleObserver) {
  29.             lifecycle.addObserver((LifecycleObserver) controller);
  30.         }
  31.     });
  32.  
  33.     // Set metrics category for BasePreferenceController.
  34.     final int metricCategory = getMetricsCategory();
  35.     mControllers.forEach(controller -> {
  36.         if (controller instanceof BasePreferenceController) {
  37.             ((BasePreferenceController) controller).setMetricsCategory(metricCategory);
  38.         }
  39.     });
  40.  
  41.     mPlaceholderPreferenceController =
  42.             new DashboardTilePlaceholderPreferenceController(context);
  43.     mControllers.add(mPlaceholderPreferenceController);
  44.     for (AbstractPreferenceController controller : mControllers) {
  45.         addPreferenceController(controller);
  46.     }
  47. }

通过方法注释可以得知此方法主要是完成preference controllers的加载。
DashboardFragment.java的onCreate()方法：

  1. @Override
  2. public void onCreate(Bundle icicle) {
  3.     super.onCreate(icicle);
  4.     // Set ComparisonCallback so we get better animation when list changes.
  5.     getPreferenceManager().setPreferenceComparisonCallback(
  6.             new PreferenceManager.SimplePreferenceComparisonCallback());
  7.     if (icicle != null) {
  8.         // Upon rotation configuration change we need to update preference states before any
  9.         // editing dialog is recreated (that would happen before onResume is called).
  10.         updatePreferenceStates();
  11.     }
  12. }

设置ComparisonCallback，以便在列表更改时获得更好的动画效果。
第一次进入时，icicle为null，根据log定位发现，其后调用DashboardFragment.java的onCreatePreferences()方法：

  1. @Override
  2. public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
  3.     checkUiBlocker(mControllers);
  4.     refreshAllPreferences(getLogTag());
  5.     mControllers.stream()
  6.             .map(controller -> (Preference) findPreference(controller.getPreferenceKey()))
  7.             .filter(Objects::nonNull)
  8.             .forEach(preference -> {
  9.                 // Give all controllers a chance to handle click.
  10.                 preference.getExtras().putInt(CATEGORY, getMetricsCategory());
  11.             });
  12. }

调用refreshAllPreferences()：

  1. /**
  2.  * Refresh all preference items, including both static prefs from xml, and dynamic items from
  3.  * DashboardCategory.
  4.  */
  5. private void refreshAllPreferences(final String tag) {
  6.     final PreferenceScreen screen = getPreferenceScreen();
  7.     // First remove old preferences.
  8.     if (screen != null) {
  9.         // Intentionally do not cache PreferenceScreen because it will be recreated later.
  10.         screen.removeAll();
  11.     }
  12.  
  13.     // Add resource based tiles.
  14.     displayResourceTiles();
  15.  
  16.     refreshDashboardTiles(tag);
  17.  
  18.     final Activity activity = getActivity();
  19.     if (activity != null) {
  20.         Log.d(tag, "All preferences added, reporting fully drawn");
  21.         activity.reportFullyDrawn();
  22.     }
  23.  
  24.     updatePreferenceVisibility(mPreferenceControllers);
  25. }

刷新所有preference items，包括来自xml的静态preference和来自DashboardCategory的动态preference，静态xml定义的prefs(调用displayResourceTiles()方法)，动态DashboardCategory动态加载(调用refreshDashboardTiles(TAG)方法，其中TAG为 “TopLevelSettings”)。
displayResourceTiles()：此方法主要是从xml资源文件中加载显示prefs：

  1. /**
  2.  * Displays resource based tiles.
  3.  */
  4. private void displayResourceTiles() {
  5.     final int resId = getPreferenceScreenResId();
  6.     if (resId <= 0) {
  7.         return;
  8.     }
  9.     addPreferencesFromResource(resId);
  10.     final PreferenceScreen screen = getPreferenceScreen();
  11.     screen.setOnExpandButtonClickListener(this);
  12.     displayResourceTilesToScreen(screen);
  13. }
  14. /**
  15.  * Perform {@link AbstractPreferenceController#displayPreference(PreferenceScreen)}
  16.  * on all {@link AbstractPreferenceController}s.
  17.  */
  18. protected void displayResourceTilesToScreen(PreferenceScreen screen) {
  19.     mPreferenceControllers.values().stream().flatMap(Collection::stream).forEach(
  20.             controller -> controller.displayPreference(screen));
  21. }

静态加载

首先调用getPreferenceScreenResId()方法获取所要加载的xml的ID，然后调用子类TopLevelSettings.java的getPreferenceScreenResId()方法：

  1. @Override
  2. protected int getPreferenceScreenResId() {
  3.     return R.xml.top_level_settings;
  4. }

可以看到Settings主界面加载的xml文件是top_level_settings：

  1. <PreferenceScreen
  2.     xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:settings="http://schemas.android.com/apk/res-auto"
  4.     android:key="top_level_settings">
  5.  
  6.     <Preference
  7.         android:key="top_level_network"
  8.         android:title="@string/network_dashboard_title"
  9.         android:summary="@string/summary_placeholder"
  10.         android:icon="@drawable/ic_homepage_network"
  11.         android:order="-120"
  12.         android:fragment="com.android.settings.network.NetworkDashboardFragment"
  13.         settings:controller="com.android.settings.network.TopLevelNetworkEntryPreferenceController"/>
  14.  
  15.     <Preference
  16.         android:key="top_level_connected_devices"
  17.         android:title="@string/connected_devices_dashboard_title"
  18.         android:summary="@string/summary_placeholder"
  19.         android:icon="@drawable/ic_homepage_connected_device"
  20.         android:order="-110"
  21.         android:fragment="com.android.settings.connecteddevice.ConnectedDeviceDashboardFragment"
  22.         settings:controller="com.android.settings.connecteddevice.TopLevelConnectedDevicesPreferenceController"/>
  23.  
  24.     <Preference
  25.         android:key="top_level_apps_and_notifs"
  26.         android:title="@string/app_and_notification_dashboard_title"
  27.         android:summary="@string/app_and_notification_dashboard_summary"
  28.         android:icon="@drawable/ic_homepage_apps"
  29.         android:order="-100"
  30.         android:fragment="com.android.settings.applications.AppAndNotificationDashboardFragment"/>
  31.  
  32.     <Preference
  33.         android:key="top_level_battery"
  34.         android:title="@string/power_usage_summary_title"
  35.         android:summary="@string/summary_placeholder"
  36.         android:icon="@drawable/ic_homepage_battery"
  37.         android:fragment="com.android.settings.fuelgauge.PowerUsageSummary"
  38.         android:order="-90"
  39.         settings:controller="com.android.settings.fuelgauge.TopLevelBatteryPreferenceController"/>
  40.  
  41.     <Preference
  42.         android:key="top_level_display"
  43.         android:title="@string/display_settings"
  44.         android:summary="@string/summary_placeholder"
  45.         android:icon="@drawable/ic_homepage_display"
  46.         android:order="-80"
  47.         android:fragment="com.android.settings.DisplaySettings"
  48.         settings:controller="com.android.settings.display.TopLevelDisplayPreferenceController"/>
  49.  
  50.     <Preference
  51.         android:key="top_level_sound"
  52.         android:title="@string/sound_settings"
  53.         android:summary="@string/sound_dashboard_summary"
  54.         android:icon="@drawable/ic_homepage_sound"
  55.         android:order="-70"
  56.         android:fragment="com.android.settings.notification.SoundSettings"/>
  57.  
  58.     <Preference
  59.         android:key="top_level_storage"
  60.         android:title="@string/storage_settings"
  61.         android:summary="@string/summary_placeholder"
  62.         android:icon="@drawable/ic_homepage_storage"
  63.         android:order="-60"
  64.         android:fragment="com.android.settings.deviceinfo.StorageSettings"
  65.         settings:controller="com.android.settings.deviceinfo.TopLevelStoragePreferenceController"/>
  66.  
  67.     <Preference
  68.         android:key="top_level_privacy"
  69.         android:title="@string/privacy_dashboard_title"
  70.         android:summary="@string/privacy_dashboard_summary"
  71.         android:icon="@drawable/ic_homepage_privacy"
  72.         android:order="-55"
  73.         android:fragment="com.android.settings.privacy.PrivacyDashboardFragment"/>
  74.  
  75.     <Preference
  76.         android:key="top_level_location"
  77.         android:title="@string/location_settings_title"
  78.         android:summary="@string/location_settings_loading_app_permission_stats"
  79.         android:icon="@drawable/ic_homepage_location"
  80.         android:order="-50"
  81.         android:fragment="com.android.settings.location.LocationSettings"
  82.         settings:controller="com.android.settings.location.TopLevelLocationPreferenceController"/>
  83.  
  84.     <Preference
  85.         android:key="top_level_security"
  86.         android:title="@string/security_settings_title"
  87.         android:summary="@string/summary_placeholder"
  88.         android:icon="@drawable/ic_homepage_security"
  89.         android:order="-40"
  90.         android:fragment="com.android.settings.security.SecuritySettings"
  91.         settings:controller="com.android.settings.security.TopLevelSecurityEntryPreferenceController"/>
  92.  
  93.     <Preference
  94.         android:key="top_level_accounts"
  95.         android:title="@string/account_dashboard_title"
  96.         android:summary="@string/summary_placeholder"
  97.         android:icon="@drawable/ic_homepage_accounts"
  98.         android:order="-30"
  99.         android:fragment="com.android.settings.accounts.AccountDashboardFragment"
  100.         settings:controller="com.android.settings.accounts.TopLevelAccountEntryPreferenceController"/>
  101.  
  102.     <Preference
  103.         android:key="top_level_accessibility"
  104.         android:title="@string/accessibility_settings"
  105.         android:summary="@string/accessibility_settings_summary"
  106.         android:icon="@drawable/ic_homepage_accessibility"
  107.         android:order="-20"
  108.         android:fragment="com.android.settings.accessibility.AccessibilitySettings"
  109.         settings:controller="com.android.settings.accessibility.TopLevelAccessibilityPreferenceController"/>
  110.  
  111.     <Preference
  112.         android:key="top_level_system"
  113.         android:title="@string/header_category_system"
  114.         android:summary="@string/system_dashboard_summary"
  115.         android:icon="@drawable/ic_homepage_system_dashboard"
  116.         android:order="10"
  117.         android:fragment="com.android.settings.system.SystemDashboardFragment"/>
  118.  
  119.     <Preference
  120.         android:key="top_level_about_device"
  121.         android:title="@string/about_settings"
  122.         android:summary="@string/summary_placeholder"
  123.         android:icon="@drawable/ic_homepage_about"
  124.         android:order="20"
  125.         android:fragment="com.android.settings.deviceinfo.aboutphone.MyDeviceInfoFragment"
  126.         settings:controller="com.android.settings.deviceinfo.aboutphone.TopLevelAboutDevicePreferenceController"/>
  127.  
  128.     <Preference
  129.         android:key="top_level_support"
  130.         android:summary="@string/support_summary"
  131.         android:title="@string/page_tab_title_support"
  132.         android:icon="@drawable/ic_homepage_support"
  133.         android:order="100"
  134.         settings:controller="com.android.settings.support.SupportPreferenceController"/>
  135.  
  136. </PreferenceScreen>

可以看到主要配置的是一些Preference菜单项如网络和互联网、已连接的设备、应用和通知、电池等等，Preference的配置含义：

  • key：唯一性ID；
  • title：标题；
  • summary：简介；
  • ico：图标；
  • order：加载显示优先级，order为负时，绝对值越高，界面显示越靠前；order为正时，值越高，显示越靠后；
  • fragment：点击此preference所跳转的fragment界面；
  • controller：控制管理类。

动态加载

refreshDashboardTiles

总结：

  1. Settings的主Activity实质实现是在SettingsHomepageActivity.java内；
  2. Settings的主界面设置item的显示是在fragment上，fragment为TopLevelSettings.java，加载显示的布局为top_level_settings.xml；
  3. Settings主界面设置项item的加载显示主要分为两部分，一部分是xml定义的静态加载，xml为top_level_settings.xml；一部分是DashboardCategory来获取动态加载；
  4. 每个设置项item均为一个preference，通过xml定义加载时，必须要有一个controller，可以是在xml中定义"settings:controller"属性声明，名称必须与类的包名路径相同；也可直接在相关fragment中实现createPreferenceControllers()方法去调用构造相关controller。此二者存其一即可。
  5. xml中配置preference时，必须定义”android:key“属性；

以上就是分析Android 11.0Settings源码之主界面加载的详细内容，更多关于Android 11.0Settings源码的资料请关注w3xue其它相关文章！

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