SystemUI-StatusBar啟動過程簡單分析

SystemUI的啟動

SystemUI本質(zhì)上是一個app爆雹，在系統(tǒng)中對應的源碼路徑為：
frameworks/base/packages/SystemUI

在源碼中編譯后會生成
out/target/product/product_name/system/priv-app/SystemUI/SystemUI.apk夯缺。

在system/priv-app下意味著SystemUI開機就會被安裝，SystemUI并不是自己啟動的捣域，它是在SystemServer進程創(chuàng)建過程中被開啟的，SystemServer進程啟動時會啟動各種系統(tǒng)服務（如AMS、PMS等）SystemUI的啟動就在這一流程中酝惧，下面以源碼中流程代碼來分析這一啟動過程：

以下源碼基于MT2712 MR2004 Android9.0版本源碼，流程代碼中省略了一些內(nèi)容

platform/frameworks/base/services/java/com/android/server/SystemServer.java

public final class SystemServer {
    ....
    // SystemServer進程啟動入口
    public static void main(String[] args) {
        new SystemServer().run();
    }
    private void run() {
        ....
        // 啟動各種系統(tǒng)服務
        try {
            startBootstrapServices();
            startCoreServices();
            // SystemUI的啟動在其他服務的啟動過程中
            startOtherServices();
            SystemServerInitThreadPool.shutdown();
        } catch (Throwable ex) {
           ....
        } finally {
            traceEnd();
        }
        ....
        // Loop forever.
        Looper.loop();
    }
    ....
    private void startOtherServices() {
        ....
        final WindowManagerService windowManagerF1 = wm;
        traceBeginAndSlog("StartSystemUI");
        try {
            // 啟動SystemUI入口
            startSystemUi(context, windowManagerF1);
        } catch (Throwable e) {
            reportWtf("starting System UI", e);
        }
        ....
    }
    
    static final void startSystemUi(Context context, WindowManagerService windowManager) {
        Intent intent = new Intent();
        intent.setComponent(new ComponentName("com.android.systemui",
                    "com.android.systemui.SystemUIService"));
        intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);
        context.startServiceAsUser(intent, UserHandle.SYSTEM);
        windowManager.onSystemUiStarted();
    }
}

通過最后調(diào)用到的startSystemUi可以看出伯诬，最后通過創(chuàng)建Intent晚唇，啟動SystemUIService。

SystemUI的加載

這里進入frameworks/basepackages/SystemUI/src/com/android/systemui/SystemUIService.java源碼中查看啟動后執(zhí)行了什么

public class SystemUIService extends Service {
    @Override
    public void onCreate() {
        super.onCreate();
        ((SystemUIApplication) getApplication()).startServicesIfNeeded();
        ....
    }
}

在onCreate中獲取了SystemUIApplication并調(diào)用了其startServicesIfNeeded方法

platform/frameworks/base/packages/SystemUI/src/com/android/systemui/SystemUIApplication.java

public class SystemUIApplication extends Application implements SysUiServiceProvider {
    ....
    public void startServicesIfNeeded() {
        String[] names = getResources().getStringArray(R.array.config_systemUIServiceComponents);
        startServicesIfNeeded(names);
    }
    
    private void startServicesIfNeeded(String[] services) {
        if (mServicesStarted) {
            return;
        }
        mServices = new SystemUI[services.length];
        ....
        final int N = services.length;
        for (int i = 0; i < N; i++) {
            String clsName = services[i];
            ....
            Class cls;
            try {
                // 通過反射調(diào)組件類啟動
                cls = Class.forName(clsName);
                mServices[i] = (SystemUI) cls.newInstance();
            } catch(ClassNotFoundException ex){
                throw new RuntimeException(ex);
            } catch (IllegalAccessException ex) {
                throw new RuntimeException(ex);
            } catch (InstantiationException ex) {
                throw new RuntimeException(ex);
            }

            mServices[i].mContext = this;
            mServices[i].mComponents = mComponents;
            mServices[i].start();
            ....
            if (mBootCompleted) {
                mServices[i].onBootCompleted();
            }
        }
        ....
        mServicesStarted = true;
    }


}

在方法內(nèi)創(chuàng)建了一個字符數(shù)組names盗似，讀取res/values/config.xml文件中定義的數(shù)組config_systemUIServiceComponents里面包含了各種SystemUI的各個組件和服務類的完整路徑哩陕，之后通過循環(huán)和反射調(diào)用各個組件的start方法，并將它們放入一個SystemUI數(shù)組管理赫舒；

    <string-array name="config_systemUIServiceComponents" translatable="false">
        <item>com.android.systemui.Dependency</item>
        <item>com.android.systemui.Dependency</item>
        <item>com.android.systemui.util.NotificationChannels</item>
        <item>com.android.systemui.statusbar.CommandQueue$CommandQueueStart</item>
        <item>com.android.systemui.keyguard.KeyguardViewMediator</item>
        <item>com.android.systemui.SystemBars</item>
        <item>com.android.systemui.volume.VolumeUI</item>
        <item>com.android.systemui.usb.StorageNotification</item>
        <item>com.android.systemui.power.PowerUI</item>
        <item>com.android.systemui.media.RingtonePlayer</item>
        <item>com.android.systemui.keyboard.KeyboardUI</item>
        <item>com.android.systemui.pip.PipUI</item>
        <item>com.android.systemui.shortcut.ShortcutKeyDispatcher</item>
        <item>@string/config_systemUIVendorServiceComponent</item>
        <item>com.android.systemui.util.leak.GarbageMonitor$Service</item>
        <item>com.android.systemui.LatencyTester</item>
        <item>com.android.systemui.globalactions.GlobalActionsComponent</item>
        <item>com.android.systemui.ScreenDecorations</item>
        <item>com.android.systemui.fingerprint.FingerprintDialogImpl</item>
        <item>com.android.systemui.SliceBroadcastRelayHandler</item>
    </string-array>

這里分析以com.android.systemui.SystemBars為主悍及。

StatusBars的加載

platform/frameworks/base/packages/SystemUI/src/com/android/systemui/SystemBars.java

public class SystemBars extends SystemUI {
    ....
    @Override
    public void start() {
        createStatusBarFromConfig();
    }
    .... 
    private void createStatusBarFromConfig() {
        // 讀取res/values/config.xml獲取config_statusBarComponent屬性
        // 這里讀到的時com.android.systemui.statusbar.phone.StatusBar
        final String clsName = mContext.getString(R.string.config_statusBarComponent);
        ....
        Class<?> cls = null;
        try {
            cls = mContext.getClassLoader().loadClass(clsName);
        } catch (Throwable t) {
            throw andLog("Error loading status bar component: " + clsName, t);
        }
        try {
            mStatusBar = (SystemUI) cls.newInstance();
        } catch (Throwable t) {
            throw andLog("Error creating status bar component: " + clsName, t);
        }
        mStatusBar.mContext = mContext;
        mStatusBar.mComponents = mComponents;
        mStatusBar.start();
    }

}

這里與上衣過程類似，也是從config.xml文件中讀取一個完整路徑接癌，然后通過反射調(diào)用其start方法心赶，這里調(diào)用到StatusBar.java類的start方法。
platform/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBar.java

public class StatusBar extends SystemUI implements DemoMode,
        DragDownHelper.DragDownCallback, ActivityStarter, OnUnlockMethodChangedListener,
        OnHeadsUpChangedListener, CommandQueue.Callbacks, ZenModeController.Callback,
        ColorExtractor.OnColorsChangedListener, ConfigurationListener, NotificationPresenter {
        ....
        
    protected StatusBarWindowView mStatusBarWindow;
    protected StatusBarWindowManager mStatusBarWindowManager;
    
    @Override
    public void start() {
        ....

        mWindowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);

        mDisplay = mWindowManager.getDefaultDisplay();
        updateDisplaySize();
        ....
        // 1.這里開始加載StatusBar布局并添加到界面上
        createAndAddWindows();
        ....
    }
    
    public void createAndAddWindows() {
        // 2
        addStatusBarWindow();
    }

    private void addStatusBarWindow() {
        // 3.構(gòu)造SatusBarView
        makeStatusBarView();
        ....
        // 6.將mStatusBarWindow加載到系統(tǒng)界面上
        // getStatusBarHeight()對應的高度值在下方的updateResources()內(nèi)進行加載
        mStatusBarWindowManager.add(mStatusBarWindow, getStatusBarHeight());
    }

    protected void makeStatusBarView() {
        ....
        updateResources();//包含一些狀態(tài)欄高度等資源的加載
        ....
        // 4.通過inflate將布局加載給mStatusBarWindow
        inflateStatusBarWindow();
        // 5.將CollapsedStatusBarFragment加載進mStatusBarWindow扔涧，對應的就是顯示在頂部的狀態(tài)欄
        FragmentHostManager.get(mStatusBarWindow)
                .addTagListener(CollapsedStatusBarFragment.TAG, (tag, fragment) -> {
                    CollapsedStatusBarFragment statusBarFragment =
                            (CollapsedStatusBarFragment) fragment;
                    statusBarFragment.initNotificationIconArea(mNotificationIconAreaController);
                    mStatusBarView = (PhoneStatusBarView) fragment.getView();
                    // mStatusBarView的一些設置
                    ....

                    setAreThereNotifications();
                    checkBarModes();
                }).getFragmentManager()
                .beginTransaction()
                .replace(R.id.status_bar_container, new CollapsedStatusBarFragment(),
                        CollapsedStatusBarFragment.TAG)
                .commit();
        ....

    }
    
    protected void inflateStatusBarWindow(Context context) {
        mStatusBarWindow = (StatusBarWindowView) View.inflate(context,
                R.layout.super_status_bar, null);
    }
            
}

針對StatusBar园担，當我們調(diào)用StatusBar的start方法后届谈，我們會加載狀態(tài)欄的一些資源（如高度），之后通過inflate將super_status_bar.xml對應的布局加載給mStatusBarWindow對象弯汰；

在super_status_bar.xml布局文件中有一個status_bar_container的FrameLayout艰山，之后會被用來放置CollapsedStatusBarFragment,這里存放了眾多的狀態(tài)欄View。這一步完成后就會將將mStatusBarWindow加載到系統(tǒng)界面上

StatusBar加載到系統(tǒng)界面

StatusBar通過StatusBarWindowManager.add加載到系統(tǒng)界面上咏闪，具體的源碼如下：
platform/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarWindowManager.java

 /**
     * 將狀態(tài)欄視圖添加到WindowMangager曙搬。
     *
     * @param statusBarView 
     * @param barHeight 折疊狀態(tài)下狀態(tài)欄高度
     */
    public void add(View statusBarView, int barHeight) {
        
        mWindowManager.getDefaultDisplay().getSize(mPoint);
        int navigationbarWidth = getNavigationBarWidth();
        mLp = new WindowManager.LayoutParams(
                mPoint.x - navigationbarWidth,
                barHeight,
                navigationbarWidth,
                0,
                WindowManager.LayoutParams.TYPE_STATUS_BAR,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                        | WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
                        | WindowManager.LayoutParams.FLAG_SPLIT_TOUCH
                        | WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH
                        | WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS,
                PixelFormat.TRANSLUCENT);
        mLp.token = new Binder();
        mLp.gravity = Gravity.TOP;
        mLp.softInputMode = WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE;
        mLp.setTitle("StatusBar");
        mLp.packageName = mContext.getPackageName();
        mLp.layoutInDisplayCutoutMode = LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS;
        mStatusBarView = statusBarView;
        mBarHeight = barHeight;
        mWindowManager.addView(mStatusBarView, mLp);
        mLpChanged = new WindowManager.LayoutParams();
        mLpChanged.copyFrom(mLp);
    }

這里傳入的mStatusBarWindow就通過WindowManager加載到相應的位置上了。

CollapsedStatusBarFragment擴展學習記錄

這里展示CollapsedStatusBarFragment的兩個生命周期鸽嫂。這里包含了布局和顯示內(nèi)容的加載
frameworks/base纵装、packages/SystemUI/src/com/android/systemui/statusbar/phone/CollapsedStatusBarFragment.java

public class CollapsedStatusBarFragment extends Fragment implements CommandQueue.Callbacks {
    ....
    private PhoneStatusBarView mStatusBar;
    private KeyguardMonitor mKeyguardMonitor;
    private NetworkController mNetworkController;
    private StatusBar mStatusBarComponent;
    ....

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
            Bundle savedInstanceState) {
        // 加載布局status_bar.xml
        return inflater.inflate(R.layout.status_bar, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        mStatusBar = (PhoneStatusBarView) view;
        if (savedInstanceState != null && savedInstanceState.containsKey(EXTRA_PANEL_STATE)) {
            mStatusBar.go(savedInstanceState.getInt(EXTRA_PANEL_STATE));
        }
        mDarkIconManager = new DarkIconManager(view.findViewById(R.id.statusIcons));
        mDarkIconManager.setShouldLog(true);
        Dependency.get(StatusBarIconController.class).addIconGroup(mDarkIconManager);
        // 用來顯示狀態(tài)欄圖標的區(qū)域（(藍牙、wifi据某、VPN橡娄、網(wǎng)卡、SIM卡信號癣籽、飛行模式等) 電池）
        mSystemIconArea = mStatusBar.findViewById(R.id.system_icon_area);
        mClockView = mStatusBar.findViewById(R.id.clock);
        showSystemIconArea(false);
        showClock(false);
        initEmergencyCryptkeeperText();
        initOperatorName();
    }
    
}

CollapsedStatusBarFragment內(nèi)還有一些Notification相關的內(nèi)容挽唉，之后有時間再

graph LR
A-->B

繼續(xù)分析。