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Android 10.0 Settings 加载流程(一)

2022-07-12  本文已影响0人  孤街酒客0911

学习笔记:参考资源:https://blog.csdn.net/Otaku_627/article/details/108618647
了解更多:https://blog.csdn.net/Otaku_627/article/details/108843487

一、系统设置首页

代码路径:packages/app/Settings/

1 主界面加载:
        <!-- Alias for launcher activity only, as this belongs to each profile. -->
        <activity-alias android:name="Settings"
                android:label="@string/settings_label_launcher"
                android:launchMode="singleTask"
                android:targetActivity=".homepage.SettingsHomepageActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            <meta-data android:name="android.app.shortcuts" android:resource="@xml/shortcuts"/>
        </activity-alias>

Settings的主界面是Settings.java,但是从Settings.java来看,除了大量的静态类继承SettingsActivity,就无其他有效信息了。但看其xml定义可以发现targetActivity属性,实质应是SettingsHomepageActivity.java。
先看其xml配置:

        <activity android:name=".homepage.SettingsHomepageActivity"
                  android:label="@string/settings_label_launcher"
                  android:theme="@style/Theme.Settings.Home"
                  android:launchMode="singleTask">
            <intent-filter android:priority="1">
                <action android:name="android.settings.SETTINGS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
            <meta-data android:name="com.android.settings.PRIMARY_PROFILE_CONTROLLED"
                       android:value="true" />
        </activity>

SettingsHomepageActivity.java,主要从onCreate()方法开始:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.settings_homepage_container);
    final View root = findViewById(R.id.settings_homepage_container);
    root.setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_LAYOUT_STABLE);

    setHomepageContainerPaddingTop();

    final Toolbar toolbar = findViewById(R.id.search_action_bar);
    FeatureFactory.getFactory(this).getSearchFeatureProvider()
            .initSearchToolbar(this /* activity */, toolbar, SettingsEnums.SETTINGS_HOMEPAGE);

    final ImageView avatarView = findViewById(R.id.account_avatar);
    final AvatarViewMixin avatarViewMixin = new AvatarViewMixin(this, avatarView);
    getLifecycle().addObserver(avatarViewMixin);

    if (!getSystemService(ActivityManager.class).isLowRamDevice()) {
        // Only allow contextual feature on high ram devices.
        showFragment(new ContextualCardsFragment(), R.id.contextual_cards_content);
    }
    showFragment(new TopLevelSettings(), R.id.main_content);
    ((FrameLayout) findViewById(R.id.main_content))
            .getLayoutTransition().enableTransitionType(LayoutTransition.CHANGING);
}

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

<androidx.coordinatorlayout.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/settings_homepage_container"
    android:fitsSystemWindows="true"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.core.widget.NestedScrollView
        android:id="@+id/main_content_scrollable_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="com.android.settings.widget.FloatingAppBarScrollingViewBehavior">

        <LinearLayout
            android:id="@+id/homepage_container"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:descendantFocusability="blocksDescendants">

            <FrameLayout
                android:id="@+id/contextual_cards_content"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="@dimen/contextual_card_side_margin"
                android:layout_marginEnd="@dimen/contextual_card_side_margin"/>

            <FrameLayout
                android:id="@+id/main_content"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:animateLayoutChanges="true"
                android:background="?android:attr/windowBackground"/>

        </LinearLayout>
    </androidx.core.widget.NestedScrollView>

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <include layout="@layout/search_bar"/>
    </com.google.android.material.appbar.AppBarLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>

主界面布局中主要包含三部分:两个FrameLayout,一个顶部快捷搜索栏。其中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。.homepage.SettingsHomepageActivity 中的逻辑并不复杂,直接加载了TopLevelSettings这个Fragment。

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

TopLevelSettings通过AndroidX的Preference来展示设置项列表,设置项列表的内容通过静态配置+动态添加的方式获取。

后面分开分析:SettingsActivity.java、DashboardFragment.java。

2 SettingsActivity.java

Settings 继承了 SettingsActivity,有着大量的静态类,但其中并没有实现任何逻辑,那它是怎么加载到自己应有的布局的呢?

其实这些Activity的逻辑都是在SettingsActivity中实现。
在父类SettingsActivity的onCreate()中:

@Override  
    protected void onCreate(Bundle savedState) {  
        super.onCreate(savedState);  
        long startTime = System.currentTimeMillis();  
        //工厂类实现方法com.android.settings.overlay.FeatureFactoryImpl.java  
        final FeatureFactory factory = FeatureFactory.getFactory(this);  
        //获取菜单信息的工厂类,实现类为DashboardFeatureProviderImpl.java  
        mDashboardFeatureProvider = factory.getDashboardFeatureProvider(this);  
        mMetricsFeatureProvider = factory.getMetricsFeatureProvider();  
 // 第一步    从intent信息中获取<meta-data/>标签名为"com.android.settings.FRAGMENT_CLASS"的值(下文用于加载Fragment的类名)  
        getMetaData();  

 // 第二步
      final Intent intent = getIntent();
      if (intent.hasExtra(EXTRA_UI_OPTIONS)) {
          getWindow().setUiOptions(intent.getIntExtra(EXTRA_UI_OPTIONS, 0));
      }
      
        //获取上面getMetaData()得到的类名  
        final String initialFragmentName = intent.getStringExtra(EXTRA_SHOW_FRAGMENT);  
        //是否为快捷进入方式(如从其它的应用进入Settings的某个设置项)  
        mIsShortcut = isShortCutIntent(intent) || isLikeShortCutIntent(intent) ||  
                intent.getBooleanExtra(EXTRA_SHOW_FRAGMENT_AS_SHORTCUT, false);  
        ... ...  
     
        if (savedState != null) {  
          ... ...  
        } else {  
 //  第三步   加载布局  
            launchSettingFragment(initialFragmentName, isSubSettings, intent);  
        }  
  
        ... ...  
    } 

第一步:
首先通过getMetaData()获取该Activity在manifest中配置的fragment, 并赋值给mFragmentClass。

private void getMetaData() {
        try {
            ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
                    PackageManager.GET_META_DATA);
            if (ai == null || ai.metaData == null) return;
            mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
        } catch (NameNotFoundException nnfe) {
            // No recovery
            Log.d(LOG_TAG, "Cannot get Metadata for: " + getComponentName().toString());
        }
    }

第二步:
通过getIntent()方法、getStartingFragmentClass()方法筛选出要启动的Fragment。

第三步:
通过launchSettingFragment()启动对应Fragment,这里的initialFragmentName参数就是第二步Intent中包含的EXTRA_SHOW_FRAGMENT参数,mFragmentClass不为空的情况下传入的就是mFragmentClass。

3 DashboardFragment.java

通过上面知道,SettingsHomepageActivity 直接加载了TopLevelSettings这个Fragment。而该Fragment继承了DashboardFragment,先来看TopLevelSettings的构造方法:

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

可以看到构造方法中仅设置了个标志位,再根据framgments生命周期先来看onAttach()方法:

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        use(SupportPreferenceController.class).setActivity(getActivity());
    }

调用父类DashboardFragment.java的onAttach()方法,此方法主要是完成mPreferenceControllers的加载。
接着看onCreate()方法,因为TopLevelSettings未重写父类的方法,所以直接看父类DashboardFragment的onCreate()方法。

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

根据log定位发现,其后调用DashboardFragment.java的onCreatePreferences()方法:这里我也不知道怎么调用到这来的,哈哈。

    @Override
    public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
        refreshAllPreferences(getLogTag());
    }
    /**
     * Refresh all preference items, including both static prefs from xml, and dynamic items from
     * DashboardCategory.
     */
    private void refreshAllPreferences(final String TAG) {
        final PreferenceScreen screen = getPreferenceScreen();
        // First remove old preferences.
        if (screen != null) {
            // Intentionally do not cache PreferenceScreen because it will be recreated later.
            screen.removeAll();
        }

        // Add resource based tiles.
        displayResourceTiles();

        refreshDashboardTiles(TAG);

        final Activity activity = getActivity();
        if (activity != null) {
            Log.d(TAG, "All preferences added, reporting fully drawn");
            activity.reportFullyDrawn();
        }

        updatePreferenceVisibility(mPreferenceControllers);
    }

以看到此方法主要是用来加载显示的preference items,主要分为两部分,一个是静态xml定义的prefs(调用displayResourceTiles()方法),另一部分是从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:

    /**
     * Displays resource based tiles.
     */
    private void displayResourceTiles() {
        final int resId = getPreferenceScreenResId();
        if (resId <= 0) {
            return;
        }
        addPreferencesFromResource(resId);
        final PreferenceScreen screen = getPreferenceScreen();
        screen.setOnExpandButtonClickListener(this);
        mPreferenceControllers.values().stream().flatMap(Collection::stream).forEach(
                controller -> controller.displayPreference(screen));
    }

首先调用getPreferenceScreenResId()方法获取所要加载的xml的ID:

    @Override
    protected abstract int getPreferenceScreenResId();

最终回调用到子类TopLevelSettings.java的getPreferenceScreenResId()方法:

    @Override
    protected int getPreferenceScreenResId() {
        return R.xml.top_level_settings;
    }

此主要是调用androidX Preference的addPreferencesFromResource()方法。此方法主要是将preferenceScreen下所有Preference添加到ArrayList中,然后再根据此集合构建生成PreferenceGroupAdapter,最后将此adapter设置到listview中,完成数据绑定,从而完成界面加载。在这里就要明白mPreferenceControllers是什么,在哪初始化的?
我们很快就可以找到:在onAttach()中添加的。

        final List<AbstractPreferenceController> controllers = new ArrayList<>();
        // Load preference controllers from code
        final List<AbstractPreferenceController> controllersFromCode =
                createPreferenceControllers(context);
        // Load preference controllers from xml definition
        final List<BasePreferenceController> controllersFromXml = PreferenceControllerListHelper
                .getPreferenceControllersFromXml(context, getPreferenceScreenResId());
        // Filter xml-based controllers in case a similar controller is created from code already.
        final List<BasePreferenceController> uniqueControllerFromXml =
                PreferenceControllerListHelper.filterControllers(
                        controllersFromXml, controllersFromCode);

        // Add unique controllers to list.
        if (controllersFromCode != null) {
            controllers.addAll(controllersFromCode);
        }
        controllers.addAll(uniqueControllerFromXml);

        // And wire up with lifecycle.
        final Lifecycle lifecycle = getSettingsLifecycle();
        uniqueControllerFromXml
                .stream()
                .filter(controller -> controller instanceof LifecycleObserver)
                .forEach(
                        controller -> lifecycle.addObserver((LifecycleObserver) controller));

        mPlaceholderPreferenceController =
                new DashboardTilePlaceholderPreferenceController(context);
        controllers.add(mPlaceholderPreferenceController);
        for (AbstractPreferenceController controller : controllers) {
            addPreferenceController(controller);
        }

可以发现:1、从代码中加载preference controllers,调用createPreferenceControllers()方法;2、从xml定义中加载preference controllers,调用getPreferenceControllersFromXml()方法。3、过滤重复定义的controller等,赋值填充mPreferenceControllers。

再回到displayResourceTiles()方法中的:

mPreferenceControllers.values().stream().flatMap(Collection::stream).forEach(
                controller -> controller.displayPreference(screen));

此语句主要就是调用各个controller的displayPreference()方法。
以网络和互联网菜单项为例,xml中配置的controller为"com.android.settings.network.TopLevelNetworkEntryPreferenceController",查看TopLevelNetworkEntryPreferenceController.java发现,其内并未实现displayPreference()方法,查看继承关系:是继承BasePreferenceController的,接着查看BasePreferenceController中的displayPreference()方法。

    /**
     * Displays preference in this controller.
     */
    @Override
    public void displayPreference(PreferenceScreen screen) {
        super.displayPreference(screen);
        if (getAvailabilityStatus() == DISABLED_DEPENDENT_SETTING) {
            // Disable preference if it depends on another setting.
            final Preference preference = screen.findPreference(getPreferenceKey());
            if (preference != null) {
                preference.setEnabled(false);
            }
        }
    }

又是调用BasePreferenceController父类AbstractPreferenceController中的displayPreference:

    /**
     * Displays preference in this controller.
     */
    public void displayPreference(PreferenceScreen screen) {
        final String prefKey = getPreferenceKey();
        if (TextUtils.isEmpty(prefKey)) {
            Log.w(TAG, "Skipping displayPreference because key is empty:" + getClass().getName());
            return;
        }
        if (isAvailable()) {
            setVisible(screen, prefKey, true /* visible */);
            if (this instanceof Preference.OnPreferenceChangeListener) {
                final Preference preference = screen.findPreference(prefKey);
                preference.setOnPreferenceChangeListener(
                        (Preference.OnPreferenceChangeListener) this);
            }
        } else {
            setVisible(screen, prefKey, false /* visible */);
        }
    }

1、getPreferenceKey()获取preference的key,会调用到子类BasePreferenceController.java的getPreferenceKey()方法:

    @Override
    public String getPreferenceKey() {
        return mPreferenceKey;
    }

而据上面分析到mPreferenceKey实质上即为xml中每个preference配置的android:key属性的值,即此处应为"top_level_network"。(以网络和互联网菜单项为例)

2、isAvailable();判断此preference是否可用即是否应该被显示。如果返回true,则被显示出来,反之则不被显示,最终也会调用到BasePreferenceController.java的isAvailable()方法:

    @Override
    public final boolean isAvailable() {
        final int availabilityStatus = getAvailabilityStatus();
        return (availabilityStatus == AVAILABLE
                || availabilityStatus == AVAILABLE_UNSEARCHABLE
                || availabilityStatus == DISABLED_DEPENDENT_SETTING);
    }

注意:看这里的BasePreferenceController.java中的isAvailable()方法中的getAvailabilityStatus(),一直跟进去,会发现调用的是:BasePreferenceController子类TopLevelNetworkEntryPreferenceController.java的getAvailabilityStatus()方法:

    @Override
    public int getAvailabilityStatus() {
        return Utils.isDemoUser(mContext) ? UNSUPPORTED_ON_DEVICE : AVAILABLE_UNSEARCHABLE;
    }

3、 调用setVisible()方法设置是否可被显示:setVisible(screen, prefKey, true /* visible */);

// frameworks/base/packages/SettingsLib/src/com/android/settingslib/core/AbstractPreferenceController.java
 protected final void setVisible(PreferenceGroup group, String key, boolean isVisible) {
        final Preference pref = group.findPreference(key);
        if (pref != null) {
            pref.setVisible(isVisible);
        }
    }

4、判断controller是否实现了Preference.OnPreferenceChangeListener接口,是,则设置监听。

综上,如果希望preference不被显示在界面上,可以通过实现相关preference的controller的getAvailabilityStatus()方法,使此方法的返回值不为AVAILABLE、AVAILABLE_UNSEARCHABLE、DISABLED_DEPENDENT_SETTING即可。

2、继续看查看BasePreferenceController.java的displayPreference()方法的剩余语句:

        if (getAvailabilityStatus() == DISABLED_DEPENDENT_SETTING) {
            // Disable preference if it depends on another setting.
            final Preference preference = screen.findPreference(getPreferenceKey());
            if (preference != null) {
                preference.setEnabled(false);
            }
        }

根据子类controller实现的getAvailabilityStatus()方法的返回值判断是否需要将此preference置为不可点击。

至此,DashboardFragment.java中displayResourceTiles()方法分析完成。

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;
6、需要隐藏不显示某个设置项时,一是可以直接在xml中注释其定义;二是可以在相关设置项preference的controller类中实现getAvailabilityStatus()方法,使此方法的返回值不为AVAILABLE、AVAILABLE_UNSEARCHABLE、DISABLED_DEPENDENT_SETTING即可;
7、如果需要某个设置项不可点击,一是可以直接调用setEnabled()。二是可以在相关设置项preference的controller类中实现getAvailabilityStatus()方法,使此方法的返回值为DISABLED_DEPENDENT_SETTING即可。

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