SystemUI 7.0学习总结一-SystemUI的启动

来源：互联网发布：matlab 矩阵赋值编辑：程序博客网时间：2024/05/20 22:30

最近在学习并接触SystemUI模块的工作，Keyguard做为引入库也纳入了SystemUI的大家庭，所以整体感觉SystemUI模块还是挺大的，为了日后的查阅还是要写一下笔记。笔记记录过程中参考了许多网友的文章，在本文最后的文章参考会一一罗列，在此非常感谢他们的分享。

SystemUI概览

SystemUI属于系统级的apk，位置在frameworks\base\packages\SystemUI，主要功能有：

状态栏信息显示，比如电池，wifi信号，3G/4G等icon显示
通知面板，比如系统消息，第三方应用消息
近期任务栏显示面板，比如长按近期任务快捷键，显示近期使用的应用
截图服务
壁纸服务
……

SystemUI的启动流程

SystemServer启动后，会在Main Thread启动ActivityManagerService，当ActivityManagerService systemReady后，会去启动SystemUIService。
SystemServer路径:/base/services/java/com/android/server/SystemServer.java

    mActivityManagerService.systemReady(new Runnable() {            @Override            public void run() {                Slog.i(TAG, "Making services ready");                ......                Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartSystemUI");                try {                    startSystemUi(context);                } catch (Throwable e) {                    reportWtf("starting System UI", e);                }                Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);                ......            }                     });

在这个方法里启动一个SystemUIService服务，

static final void startSystemUi(Context context) {        Intent intent = new Intent();        intent.setComponent(new ComponentName("com.android.systemui",                    "com.android.systemui.SystemUIService"));        intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);        //Slog.d(TAG, "Starting service: " + intent);        context.startServiceAsUser(intent, UserHandle.SYSTEM);    }

通过startServiceAsUser，SystemUIService就启动了，即SystemUI进程开机启动。

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

在SystemUIService的onCreate方法中会调用SystemUIApplication的startServicesIfNeeded方法，这个方法会调用 startServicesIfNeeded(SERVICES)方法启动一系列服务(并不是真正的service,都继承自SystemUI)。

public class SystemUIApplication extends Application {    ......    /**     * The classes of the stuff to start.     */    private final Class<?>[] SERVICES = new Class[] {            com.android.systemui.tuner.TunerService.class,            com.android.systemui.keyguard.KeyguardViewMediator.class,            com.android.systemui.recents.Recents.class,            com.android.systemui.volume.VolumeUI.class,            Divider.class,            com.android.systemui.statusbar.SystemBars.class,            com.android.systemui.usb.StorageNotification.class,            com.android.systemui.power.PowerUI.class,            com.android.systemui.media.RingtonePlayer.class,            com.android.systemui.keyboard.KeyboardUI.class,            com.android.systemui.tv.pip.PipUI.class,            com.android.systemui.shortcut.ShortcutKeyDispatcher.class,            com.android.systemui.VendorServices.class    };    ......    public void startServicesIfNeeded() {        startServicesIfNeeded(SERVICES);    }}

startServicesIfNeeded方法会遍历SERVICES 这个数组,依次调用service的start方法启动服务。

private void startServicesIfNeeded(Class<?>[] services) {        if (mServicesStarted) {            return;        }        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;                if (DEBUG) Log.v(TAG, "BOOT_COMPLETED was already sent");            }        }        Log.v(TAG, "Starting SystemUI services for user " +                Process.myUserHandle().getIdentifier() + ".");        final int N = services.length;        for (int i=0; i<N; i++) {            Class<?> cl = services[i];            if (DEBUG) Log.d(TAG, "loading: " + cl);            try {                Object newService = SystemUIFactory.getInstance().createInstance(cl);                mServices[i] = (SystemUI) ((newService == null) ? cl.newInstance() : newService);            } catch (IllegalAccessException ex) {                throw new RuntimeException(ex);            } catch (InstantiationException ex) {                throw new RuntimeException(ex);            }            mServices[i].mContext = this;            mServices[i].mComponents = mComponents;            if (DEBUG) Log.d(TAG, "running: " + mServices[i]);            mServices[i].start();            if (mBootCompleted) {                mServices[i].onBootCompleted();            }        }        mServicesStarted = true;    }

看到这里，这么多文字可能不够直观，那就看看图吧，非常感谢参考文章中的分享。
这里以SERVICES 中com.android.systemui.keyguard.KeyguardViewMediator.class为例，

SystemUI Services启动后，根据各Services的功能，SystemUI的各个模块就开始正常工作起来了。

参考文章

http://blog.csdn.net/qq_31530015/article/details/53507968
http://blog.csdn.net/zhudaozhuan/article/details/50817180
http://blog.csdn.net/yj934672573/article/details/54571704
http://blog.csdn.net/Picasso_L/article/details/69388919
… …

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