Android9.0 SystemUI 简介篇 （一）

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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();
}

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public void onCreate() {
    super.onCreate();
    // Set the application theme that is inherited by all services. Note that setting the
    // application theme in the manifest does only work for activities. Keep this in sync with
    // the theme set there.
    // 设置主题
    setTheme(R.style.Theme_SystemUI);

    SystemUIFactory.createFromConfig(this);

    if (Process.myUserHandle().equals(UserHandle.SYSTEM)) {
        // SYSTEM 用户
        // 监听开机广播
        IntentFilter bootCompletedFilter = new IntentFilter(Intent.ACTION_BOOT_COMPLETED);
        // 设置优先级
        bootCompletedFilter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
        // 注册开机广播接收器
        registerReceiver(new BroadcastReceiver() {
                @Override
                public void onReceive(Context context, Intent intent) {
                    if (mBootCompleted) return;
                    // 移除本接收器
                    unregisterReceiver(this);
                    mBootCompleted = true;
                    if (mServicesStarted) {
                        final int N = mServices.length;
                        for (int i = 0; i < N; i++) {
                            mServices[i].onBootCompleted();
                        }
                    }


                }
            }, bootCompletedFilter);
        // 监听语言改变并更新  SystemUi 的通知渠道
        IntentFilter localeChangedFilter = new IntentFilter(Intent.ACTION_LOCALE_CHANGED);
        registerReceiver(new BroadcastReceiver() {
                @Override
                public void onReceive(Context context, Intent intent) {
                    if (Intent.ACTION_LOCALE_CHANGED.equals(intent.getAction())) {
                        if (!mBootCompleted) return;
                        // Update names of SystemUi notification channels
                        NotificationChannels.createAll(context);
                    }
                }
            }, localeChangedFilter);
    } else {
        // We don't need to startServices for sub-process that is doing some tasks.
        // (screenshots, sweetsweetdesserts or tuner ..)
        String processName = ActivityThread.currentProcessName();
        ApplicationInfo info = getApplicationInfo();
        if (processName != null && processName.startsWith(info.processName + ":")) {
            return;
        }
        // For a secondary user, boot-completed will never be called because it has already
        // been broadcasted on startup for the primary SystemUI process.  Instead, for
        // components which require the SystemUI component to be initialized per-user, we
        // start those components now for the current non-system user.
        // 第二用户启动的服务
        startSecondaryUserServicesIfNeeded();
    }
}

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public void onCreate() {
    super.onCreate();
    ((SystemUIApplication) getApplication()).startServicesIfNeeded();
    // ......
}

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public void startServicesIfNeeded() {
    // 获取  SystemUI 所有服务类名，后面看看这个数组
    String[] names = getResources().getStringArray(R.array.config_systemUIServiceComponents);
    startServicesIfNeeded(names);
}

private void startServicesIfNeeded(String[] services) {
    if (mServicesStarted) {
        return;
    }
    mServices = new SystemUI[services.length];

    if (!mBootCompleted) {
        // check to see if maybe it was already completed long before we began
        // see ActivityManagerService.finishBooting()
        if ("1".equals(SystemProperties.get("sys.boot_completed"))) {
            mBootCompleted = true;
        }
    }

    final int N = services.length;
    for (int i = 0; i < N; i++) {
        String clsName = services[i];
        long ti = System.currentTimeMillis();
        Class cls;
        try {
            // 通过反射获取服务对象
            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);
        }

        // 填充对象信息并启动服务
        mServices[i].mContext = this;
        mServices[i].mComponents = mComponents;
        mServices[i].start();

        // Warn if initialization of component takes too long
        // 如果服务加载时间过程发出警告
        ti = System.currentTimeMillis() - ti;
        if (ti > 1000) {
            Log.w(TAG, "Initialization of " + cls.getName() + " took " + ti + " ms");
        }
        if (mBootCompleted) {
            mServices[i].onBootCompleted();
        }
    }
    // 插件相关
    Dependency.get(PluginManager.class).addPluginListener(new PluginListener<OverlayPlugin>() {
            private ArraySet<OverlayPlugin> mOverlays;

            @Override
            public void onPluginConnected(OverlayPlugin plugin, Context pluginContext) {
                StatusBar statusBar = getComponent(StatusBar.class);
                if (statusBar != null) {
                    plugin.setup(statusBar.getStatusBarWindow(),
                                 statusBar.getNavigationBarView());
                }
                // Lazy init.
                if (mOverlays == null) mOverlays = new ArraySet<>();
                if (plugin.holdStatusBarOpen()) {
                    mOverlays.add(plugin);
                    Dependency.get(StatusBarWindowManager.class)
                        .setStateListener(b -> mOverlays.forEach(o -> o.setCollapseDesired(b)));
                    Dependency.get(StatusBarWindowManager.class)
                        .setForcePluginOpen(mOverlays.size() != 0);

                }
            }

            @Override
            public void onPluginDisconnected(OverlayPlugin plugin) {
                mOverlays.remove(plugin);
                Dependency.get(StatusBarWindowManager.class)
                    .setForcePluginOpen(mOverlays.size() != 0);
            }
        }, OverlayPlugin.class, true /* Allow multiple plugins */);

    mServicesStarted = true;
}

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<string-array name="config_systemUIServiceComponents" translatable="false">
<item>com.android.systemui.Dependency</item>
<item>com.android.systemui.util.NotificationChannels</item>
<item>com.android.systemui.statusbar.CommandQueue$CommandQueueStart</item>
<item>com.android.systemui.keyguard.KeyguardViewMediator</item>
<item>com.android.systemui.recents.Recents</item>
<item>com.android.systemui.volume.VolumeUI</item>
<item>com.android.systemui.stackdivider.Divider</item>
<item>com.android.systemui.SystemBars</item>
<item>com.android.systemui.usb.StorageNotification</item>
<item>com.android.systemui.power.PowerUI</item>
<item>com.android.systemui.media.RingtonePlayer</item>
<item>com.android.systemui.keyboard.KeyboardUI</item>
<item>com.android.systemui.pip.PipUI</item>
<item>com.android.systemui.shortcut.ShortcutKeyDispatcher</item>
<item>@string/config_systemUIVendorServiceComponent</item>
<item>com.android.systemui.util.leak.GarbageMonitor$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>

<string name="config_systemUIVendorServiceComponent" translatable="false">com.android.systemui.VendorServices</string>

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void startSecondaryUserServicesIfNeeded() {
    String[] names =
        getResources().getStringArray(R.array.config_systemUIServiceComponentsPerUser);
    startServicesIfNeeded(names);
}

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<string-array name="config_systemUIServiceComponentsPerUser" translatable="false">
<item>com.android.systemui.Dependency</item>
<item>com.android.systemui.util.NotificationChannels</item>
<item>com.android.systemui.recents.Recents</item>
</string-array>

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public abstract class SystemUI implements SysUiServiceProvider {
    public Context mContext;
    public Map<Class<?>, Object> mComponents;

    public abstract void start();

    protected void onConfigurationChanged(Configuration newConfig) {
    }

    public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
    }

    protected void onBootCompleted() {
    }

    @SuppressWarnings("unchecked")
    public <T> T getComponent(Class<T> interfaceType) {
        return (T) (mComponents != null ? mComponents.get(interfaceType) : null);
    }

    public <T, C extends T> void putComponent(Class<T> interfaceType, C component) {
        if (mComponents != null) {
            mComponents.put(interfaceType, component);
        }
    }

    public static void overrideNotificationAppName(Context context, Notification.Builder n,
                                                   boolean system) {
        final Bundle extras = new Bundle();
        String appName = system
            ? context.getString(com.android.internal.R.string.notification_app_name_system)
            : context.getString(com.android.internal.R.string.notification_app_name_settings);
        extras.putString(Notification.EXTRA_SUBSTITUTE_APP_NAME, appName);

        n.addExtras(extras);
    }
}

public interface SysUiServiceProvider {
    <T> T getComponent(Class<T> interfaceType);

    public static <T> T getComponent(Context context, Class<T> interfaceType) {
        return ((SysUiServiceProvider) context.getApplicationContext()).getComponent(interfaceType);
    }
}