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Android 8.0 Settings流程分析与变动

程序员文章站 2022-05-23 19:57:11
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开! 场!  白! 好! 难! 写!

一,相比Android Settings 7.0

    如下图,在7.0的基础上,去掉了7.0新加的侧滑菜单(可能是觉得有点鸡肋吧)。多加了一级页面,把原来类别标题变成的第一级菜单的子项。在代码架构也稍加变动,并引入架构组件之LifeCycle(生命周期感知,本文不作介绍)。

Android 8.0 Settings流程分析与变动

二,第一级菜单的加载

浏览源码,大多数我们从程序的AndroidManifest.xml入手,这次也不列外。

packages\apps\Settings\AndroidManifest.xml:

<activity-alias android:name="Settings"
                android:taskAffinity="com.android.settings"
                android:label="@string/settings_label_launcher"
                android:launchMode="singleTask"
                android:targetActivity="Settings">
            <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>

找到<category android:name="android.intent.category.LAUNCHER" />所属的类,Settings.java。但打开Settings.java类看,除了大量静态类继承SettingsActivity,就没什么东西了。那再去父类SettingsActivity.java找找。

packages\apps\Settings\src\com\android\settings\SettingsActivity.java:

首先当然是onCreate()->

@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();
        // 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();
        ... ...
        //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);
        ... ...
        //当前类是否为Settings.class,即进入方式为点击launcher上的图标进入的主设置界面
        mIsShowingDashboard = className.equals(Settings.class.getName());
        ... ...
        setContentView(mIsShowingDashboard ?
                R.layout.settings_main_dashboard : R.layout.settings_main_prefs);
        mContent = findViewById(R.id.main_content);
        getFragmentManager().addOnBackStackChangedListener(this);
        if (savedState != null) {
          ... ...
        } else {
            //加载布局
            launchSettingFragment(initialFragmentName, isSubSettings, intent);
        }

        ... ...
    }


launchSettingFragment()->

 @VisibleForTesting
    void launchSettingFragment(String initialFragmentName, boolean isSubSettings, Intent intent) {
        if (!mIsShowingDashboard && initialFragmentName != null) {
            ... ...
            switchToFragment(initialFragmentName, initialArguments, true, false,
                mInitialTitleResId, mInitialTitle, false);
        } else {
            // Show search icon as up affordance if we are displaying the main Dashboard
            mDisplayHomeAsUpEnabled = true;
            mInitialTitleResId = R.string.dashboard_title;
            //进入主页走的这里,替换目标Fragment
            switchToFragment(DashboardSummary.class.getName(), null /* args */, false, false,
                mInitialTitleResId, mInitialTitle, false);
        }
    }

继续,我们看看DashboardSummary.java,对于它我们主要是想知道它的数据加载,它是怎么加载自己的子项的。

packages\apps\Settings\src\com\android\settings\dashboard\DashboardSummary.java:

对子项的数据获取在updateCategoryAndSuggestion()中得到实现。

@VisibleForTesting
    void updateCategoryAndSuggestion(List<Tile> suggestions) {
        final Activity activity = getActivity();
        if (activity == null) {
            return;
        }
        /*根据"com.android.settings.category"的值查询子项数据,这里的值为"com.android.settings.category.ia.homepage"。
        具体获取办法追踪到frameworks\base\packages\SettingsLib\src\com\android\settingslib\drawer\TileUtils.java中。
        通过PackageManager查询所有在AndroidManifest.xml中定义<meta-data/>中含有该值的类。注意:会过滤掉非系统级应用的数据!
        有兴趣的自行研究,这里不深究。*/
        final DashboardCategory category = mDashboardFeatureProvider.getTilesForCategory(
                CategoryKey.CATEGORY_HOMEPAGE);
        if (category == null) {
            return;
        }
        mSummaryLoader.updateSummaryToCache(category);
        if (suggestions != null) {
            mAdapter.setCategoriesAndSuggestions(category, suggestions);
        } else {
            //数据的绑定在适配器中,->packages\apps\Settings\src\com\android\settings\dashboard\DashboardAdapter.java
            mAdapter.setCategory(category);
        }
    }

对于第一级菜单的加载。在AndroidManifest.xml中的配置如下列图:

Android 8.0 Settings流程分析与变动

三,第二级菜单的加载

    以上我们知道第一级菜单是完全动态的加载,但二级菜单则是动态加载和静态xml布局文件,就拿“系统”这项为例。

packages\apps\Settings\AndroidManifest.xml:

<activity android:name=".Settings$SystemDashboardActivity"
                  android:label="@string/header_category_system"
                  android:icon="@drawable/ic_settings_about">
            <intent-filter android:priority="-1">
                <action android:name="com.android.settings.action.SETTINGS"/>
            </intent-filter>
            <meta-data android:name="com.android.settings.category"
                       android:value="com.android.settings.category.ia.homepage"/>
            <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
                       android:value="com.android.settings.system.SystemDashboardFragment"/>
            <meta-data android:name="com.android.settings.summary"
                       android:resource="@string/system_dashboard_summary"/>
        </activity>

SystemDashboardFragment.java继承DashboardFragment.java。我们主要观察这个类。

packages\apps\Settings\src\com\android\settings\dashboard\DashboardFragment.java:

1,静态加载部分:

静态加载部分的实现方法为displayResourceTiles()->

	/**
     * Displays resource based tiles.
     */
    private void displayResourceTiles() {
		//获取xml布局文件的id(DashboardFragment.java实现该方法)
        final int resId = getPreferenceScreenResId();
        if (resId <= 0) {
            return;
        }
        addPreferencesFromResource(resId);
        final PreferenceScreen screen = getPreferenceScreen();
		/** 实现布局文件中的子项控件的业务逻辑
		 *  DashboardFragment.java的子类实现getPreferenceControllers()方法,该方法加载继承于AbstractPreferenceController.java的实现业务逻辑类
		 */
        Collection<AbstractPreferenceController> controllers = mPreferenceControllers.values();
        for (AbstractPreferenceController controller : controllers) {
            controller.displayPreference(screen);
        }
    }

2,动态加载部分:

动态加载部分的实现方法refreshDashboardTiles()->

/**
     * Refresh preference items backed by DashboardCategory.
     */
    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
    void refreshDashboardTiles(final String TAG) {
        final PreferenceScreen screen = getPreferenceScreen();
		/* 获取子项 
		 * getCategoryKey()从DashboardFragmentRegistry.PARENT_TO_CATEGORY_KEY_MAP中获取Category值。
		 * 该值通过类名获取
		 * 存:PARENT_TO_CATEGORY_KEY_MAP.put(SystemDashboardFragment.class.getName(), CategoryKey.CATEGORY_SYSTEM);
		 * CATEGORY_SYSTEM = "com.android.settings.category.ia.system";
		 */
        final DashboardCategory category =
                mDashboardFeatureProvider.getTilesForCategory(getCategoryKey());
        ... ...
        // Install dashboard tiles.
        for (Tile tile : tiles) {
            ... ...
            if (mDashboardTilePrefKeys.contains(key)) {
                ... ...
            } else {
                // Don't have this key, add it.
                final Preference pref = new Preference(getPrefContext());
				/*在这里进行绑定,加载
				 *packages\apps\Settings\src\com\android\settings\dashboard\DashboardFeatureProviderImpl.java->bindPreferenceToTile()
				 */
                mDashboardFeatureProvider.bindPreferenceToTile(getActivity(), getMetricsCategory(),
                        pref, tile, key, mPlaceholderPreferenceController.getOrder());
                mProgressiveDisclosureMixin.addPreference(screen, pref);
                mDashboardTilePrefKeys.add(key);
            }
            remove.remove(key);
        }
        // Finally remove tiles that are gone.
        for (String key : remove) {
            mDashboardTilePrefKeys.remove(key);
            mProgressiveDisclosureMixin.removePreference(screen, key);
        }
        mSummaryLoader.setListening(true);
    }

该文的Settings加载流程就差不多到这里了。

四,顺便说说

下拉菜单栏时长按设置图标进入设置,在系统项里面会多一个《系统界面调节工具》。那么这是怎么显示和隐藏的了?

frameworks\base\packages\SystemUI\src\com\android\systemui\tuner\TunerService.java

->setTunerEnabled():

public static final void setTunerEnabled(Context context, boolean enabled) {
		//隐藏应用图标,隐藏某个组件启动也可以使用该方法
        userContext(context).getPackageManager().setComponentEnabledSetting(
                new ComponentName(context, TunerActivity.class),
                enabled ? PackageManager.COMPONENT_ENABLED_STATE_ENABLED
                        : PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
    }