Android4.4 systemui 启动流程
Android4.4SystemUI代码启动流程
转载http://blog.csdn.net/yihongyuelan
1.初始SystemUI
什么是SystemUI？你或许会觉得这个问题很幼稚，界面上的布局UI显示？系统的UI？如果你是这么想的，那么就大错特错了。我们知道Android4.4ICS同时适用于Phone和Tablet(TV)，因此，对于Phone来说SystemUI指的是：StatusBar(状态栏)、NavigationBar(导航栏)。而对于Tablet或者是TV来说SystemUI指的是：CombinedBar(包括了StatusBar和NavigationBar)。
根据上面的介绍，我想大家应该知道SystemUI的具体作用了吧！也就是说我们的Phone的信号，蓝牙标志，Wifi标志等等这些状态显示标志都会在StatusBar上显示。当我们的设备开机后，首先需要给用户呈现的就是各种界面同时也包括了我们的SystemUI，因此对于整个Android系统来说，SystemUI都有举足轻重的作用，那接下来就来看看它的启动流程吧！
2.启动流程
这里只是单单的分析启动流程，实际上SystemUI启动过程中涉及到很多东西的调用，这里暂时不分支去介绍，后续会有相关文章的详细分析。那么对于这种分析我还是将自己的分析思路写出来，而不是直接展现已经分析好的结果，当然结果会在最后展示出来。这样做一方面有利于锻炼自己的分析能力，另一方面各位看官也可以找出分析中的利与弊从而更好的取舍。
首先来看看SystemUI的代码位置，路径：SourceCode/frameworks/base/packages/SystemUI；其次看看它的代码梗概：
图 2.1
在Android4.4中，Google整合了Phone和Tablet(TV)的SystemUI，也就说可以根据设备的类型自动匹配相应的SystemUI。这一点是在Android2.3中是没有的。那么接下来怎么分析呢？打开AndroidManifest.xml可以看到：
[html]viewplaincopyprint?
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package="com.android.systemui"
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coreApp="true"
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android:sharedUserId="android.uid.system"
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android:process="system"
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>
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-
-
-
-
-
-
-
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android:persistent="true"
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android:allowClearUserData="false"
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android:allowBackup="false"
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android:hardwareAccelerated="true"
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android:label="@string/app_label"
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android:icon="@drawable/ic_launcher_settings">
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android:exported="true"
/>
android:process=":screenshot"
android:exported="false"/>
android:exported="true"/>
android:permission="android.permission.BIND_WALLPAPER"
android:exported="true"/>
......
根据以上代码我们可以发现这其中注册了很多Service，同时也包括了广播。但这里我们只关注SystemUIService，这才是本文的主旨啊。那么首先要找到SystemUIService是如何启动的。对于Service的启动，在我以前的博文中已有提到，这里就不多说了，不外乎startService(intent)和bindService(intent)，它们都是以intent为对象，那intent的声明也需要SystemUIService啊，因此我们可以据此搜索关键词"SystemUIService"。
经过漫长的搜索和比对之后发现，原来，SystemUIService是在SystemServer.java中被启动的，如下所示：
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static final void startSystemUi(Context context) {
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Intent intent = new Intent();
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intent.setComponent(new ComponentName("com.android.systemui",
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"com.android.systemui.SystemUIService"));
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Slog.d(TAG, "Starting service: " + intent);
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context.startService(intent);
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}
staticfinal void startSystemUi(Context context) {
Intentintent = new Intent();
intent.setComponent(newComponentName("com.android.systemui",
"com.android.systemui.SystemUIService"));
Slog.d(TAG,"Starting service: " + intent);
context.startService(intent);
}
这里的startSystemUi()方法则在ServerThread的run()方法中被调用。这里提到SystemServer就不得不提及Android的启动流程，这里不会展开详细讨论具体的流程，只是简单的介绍一下大概流程，用以表明SystemServer所处的位置。Android的启动分为内核启动、Android启动、launcher启动，我们的SystemServer就处于Android启动中，以下是大致流程图：
init->ServiceManager->Zygote->SystemServer->......
在SystemServer中，初始化了Android系统中的Java层服务，如PowerManagerService、WindowManagerService等等，当然也包括了SystemUIService，它们通过ServiceManager的addService()方法，添加到ServiceManager的管理中。实际上，根据后面的分析这里add了一个很重要的StatusBarManagerService。这个Service在后面会用到的。
既然到这里SystemUIService已经启动，那么我们就继续跟踪该Service吧。
1).首先查看其onCreate()方法，如下：
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public void onCreate() {
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// Pick status bar or system bar.
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IWindowManager wm = IWindowManager.Stub.asInterface(
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ServiceManager.getService(Context.WINDOW_SERVICE));
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try {
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SERVICES[0] = wm.canStatusBarHide()//根据wm.canStatusBarHide()判断设备类型
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? R.string.config_statusBarComponent
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: R.string.config_systemBarComponent;
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} catch (RemoteException e) {
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Slog.w(TAG, "Failing checking whether status bar can hide", e);
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}
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final int N = SERVICES.length;
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mServices = new SystemUI[N];
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for (int i=0; i
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Class cl = chooseClass(SERVICES[i]);
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Slog.d(TAG, "loading: " + cl);
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try {
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mServices[i] = (SystemUI)cl.newInstance();
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} catch (IllegalAccessException ex) {
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throw new RuntimeException(ex);
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} catch (InstantiationException ex) {
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throw new RuntimeException(ex);
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}
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mServices[i].mContext = this;
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Slog.d(TAG, "running: " + mServices[i]);
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mServices[i].start();
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}
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}
publicvoid onCreate() {
//Pick status bar or system bar.
IWindowManagerwm = IWindowManager.Stub.asInterface(
ServiceManager.getService(Context.WINDOW_SERVICE));
try{
SERVICES[0]= wm.canStatusBarHide()//根据wm.canStatusBarHide()判断设备类型
?R.string.config_statusBarComponent
:R.string.config_systemBarComponent;
}catch (RemoteException e) {
Slog.w(TAG,"Failing checking whether status bar can hide", e);
}
finalint N = SERVICES.length;
mServices= new SystemUI[N];
for(int i=0; i
Classcl = chooseClass(SERVICES[i]);
Slog.d(TAG,"loading: " + cl);
try{
mServices[i]= (SystemUI)cl.newInstance();
}catch (IllegalAccessException ex) {
thrownew RuntimeException(ex);
}catch (InstantiationException ex) {
thrownew RuntimeException(ex);
}
mServices[i].mContext= this;
Slog.d(TAG,"running: " + mServices[i]);
mServices[i].start();
}
}
在这段代码中，通过AIDL的方式获取了WindowManager的对象wm，并调用其方法canStatusBarHide()来判断当前设备的类型，也就是说如果我们使用的Phone那么后续就会加载StatusBar和NivagationBar；而如果我们设备类型是Tablet(TV)之类的(可以在配置文档里面配置)，就会加载CombiedBar。这里的canStatusBarHide()方法的具体实现是在：frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java。为什么会是这里呢？我们在Eclipse中导入源码之后，找到SystemUIService.java中的wm.canStatusBarHide()方法，通过openImplementation直接跳转到WindowsManagerService中：
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public boolean canStatusBarHide() {
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return mPolicy.canStatusBarHide();
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}
publicboolean canStatusBarHide() {
returnmPolicy.canStatusBarHide();
}
但这里我们发现canStatusBarHide()实际上是WindowManagerPolicy的对象调用的方法，而WindowManagerPolicy只是一个接口类，根据以往分析的经验可以知道，这里的WindowManagerPolicy对象所调用的canStatusBartHide()方法一定是其实现类中的方法。因此，继续通过openImplementation跳转，来到了PhoneWindownManager中：[java]viewplaincopyprint?
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public boolean canStatusBarHide() {
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return mStatusBarCanHide;
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}
publicboolean canStatusBarHide() {
returnmStatusBarCanHide;
}
继续查看mSatuBarCanHide的实现，如下所示：[java]viewplaincopyprint?
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// Determine whether the status bar can hide based on the size
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// of the screen. We assume sizes > 600dp are tablets where we
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// will use the system bar.
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int shortSizeDp = shortSize
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* DisplayMetrics.DENSITY_DEFAULT
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/ DisplayMetrics.DENSITY_DEVICE;
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mStatusBarCanHide = shortSizeDp < 600;
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mStatusBarHeight = mContext.getResources().getDimensionPixelSize(
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mStatusBarCanHide
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? com.android.internal.R.dimen.status_bar_height
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: com.android.internal.R.dimen.system_bar_height);
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mHasNavigationBar = mContext.getResources().getBoolean(
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com.android.internal.R.bool.config_showNavigationBar);
//Determine whether the status bar can hide based on the size
//of the screen. We assume sizes > 600dp are tablets where we
//will use the system bar.
intshortSizeDp = shortSize
*DisplayMetrics.DENSITY_DEFAULT
/DisplayMetrics.DENSITY_DEVICE;
mStatusBarCanHide= shortSizeDp < 600;
mStatusBarHeight= mContext.getResources().getDimensionPixelSize(
mStatusBarCanHide
?com.android.internal.R.dimen.status_bar_height
:com.android.internal.R.dimen.system_bar_height);
mHasNavigationBar= mContext.getResources().getBoolean(
com.android.internal.R.bool.config_showNavigationBar);
这里通过shortSizeDp来判断当前设备的类型，如果当前屏幕的shortSizeDp<600dp，则系统会认为该设备是Phone反之则认为是Tablet。根据mStatusBarCanHide的值，设定StatusBar或者SystemBar(CombinedBar)的高度，以及是否显示NavigationBar。继续回到我们的SystemUIService.java的onCreate()方法中，根据前面对canStatusBarHide()的判断，SERVICE[0]中将存放R.string.config_statusBarComponent或者R.string.config_systemBarComponent。它们的值具体是：
[html]viewplaincopyprint?
因为我的测试设备是Phone，那么现在SERVICE[0]中存放的就是com.android.systemui.statusbart.phone.PhoneStatusBar。查看以下代码：[java]viewplaincopyprint?
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final int N = SERVICES.length;
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mServices = new SystemUI[N];
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for (int i=0; i
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Class cl = chooseClass(SERVICES[i]);
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Slog.d(TAG, "loading: " + cl);
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try {
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mServices[i] = (SystemUI)cl.newInstance();
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} catch (IllegalAccessException ex) {
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throw new RuntimeException(ex);
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} catch (InstantiationException ex) {
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throw new RuntimeException(ex);
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}
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mServices[i].mContext = this;
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Slog.d(TAG, "running: " + mServices[i]);
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mServices[i].start();
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}
finalint N = SERVICES.length;
mServices= new SystemUI[N];
for(int i=0; i
Classcl = chooseClass(SERVICES[i]);
Slog.d(TAG,"loading: " + cl);
try{
mServices[i]= (SystemUI)cl.newInstance();
}catch (IllegalAccessException ex) {
thrownew RuntimeException(ex);
}catch (InstantiationException ex) {
thrownew RuntimeException(ex);
}
mServices[i].mContext= this;
Slog.d(TAG,"running: " + mServices[i]);
mServices[i].start();
}
这些方法会分别启动两个方法，这两个方法可以从log中知道，分别是PhoneStatusBar.start()和PowerUI.start()。而我们的目的是要弄清SystemUI的启动，因此现关注PhoneStatusBar.start()方法。log信息：
06-0413:23:15.379: DEBUG/SystemUIService(396): loading: classcom.android.systemui.statusbar.phone.PhoneStatusBar
06-0413:23:16.739: DEBUG/SystemUIService(396): loading: classcom.android.systemui.power.PowerUI
来到PhoneStatusBar.start()方法中，位于：SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java，代码如下：
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@Override
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public void start() {
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mDisplay = ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
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.getDefaultDisplay();
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mWindowManager = IWindowManager.Stub.asInterface(
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ServiceManager.getService(Context.WINDOW_SERVICE));
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super.start(); // calls makeStatusBarView()
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addNavigationBar();
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//addIntruderView();
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// Lastly, call to the icon policy to install/update all the icons.
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mIconPolicy = new PhoneStatusBarPolicy(mContext);
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}
@Override
publicvoid start() {
mDisplay= ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
.getDefaultDisplay();
mWindowManager= IWindowManager.Stub.asInterface(
ServiceManager.getService(Context.WINDOW_SERVICE));
super.start();// calls makeStatusBarView()
addNavigationBar();
//addIntruderView();
//Lastly, call to the icon policy to install/update all the icons.
mIconPolicy= new PhoneStatusBarPolicy(mContext);
}
这里的重心主要是在super.start()和addNavigationBar()上。目前市面上很多手机已经刷入了ICS，但是大多数是没有NavigationBar的，也就是说自己修改了源码，屏蔽了NavigationBar。继续跟踪super.start()方法，来到/SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBar.java的start()方法中，代码如下：[java]viewplaincopyprint?
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public void start() {
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// First set up our views and stuff.
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View sb = makeStatusBarView();
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// Connect in to the status bar manager service
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StatusBarIconList iconList = new StatusBarIconList();
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ArrayList
notificationKeys = new ArrayList (); -
ArrayList
notifications = new ArrayList (); -
mCommandQueue = new CommandQueue(this, iconList);
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mBarService = IStatusBarService.Stub.asInterface(
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ServiceManager.getService(Context.STATUS_BAR_SERVICE));
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int[] switches = new int[7];
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ArrayList
binders = new ArrayList (); -
try {
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mBarService.registerStatusBar(mCommandQueue, iconList, notificationKeys, notifications,
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switches, binders);
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} catch (RemoteException ex) {
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// If the system process isn't there we're doomed anyway.
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}
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disable(switches[0]);
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setSystemUiVisibility(switches[1]);
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topAppWindowChanged(switches[2] != 0);
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// StatusBarManagerService has a back up of IME token and it's restored here.
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setImeWindowStatus(binders.get(0), switches[3], switches[4]);
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setHardKeyboardStatus(switches[5] != 0, switches[6] != 0);
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// Set up the initial icon state
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int N = iconList.size();
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int viewIndex = 0;
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for (int i=0; i
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StatusBarIcon icon = iconList.getIcon(i);
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if (icon != null) {
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addIcon(iconList.getSlot(i), i, viewIndex, icon);
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viewIndex++;
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}
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}
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// Set up the initial notification state
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N = notificationKeys.size();
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if (N == notifications.size()) {
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for (int i=0; i
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addNotification(notificationKeys.get(i), notifications.get(i));
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}
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} else {
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Log.wtf(TAG, "Notification list length mismatch: keys=" + N
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+ " notifications=" + notifications.size());
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}
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// Put up the view
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final int height = getStatusBarHeight();
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final WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
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ViewGroup.LayoutParams.MATCH_PARENT,
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height,
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WindowManager.LayoutParams.TYPE_STATUS_BAR,
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WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
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| WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
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| WindowManager.LayoutParams.FLAG_SPLIT_TOUCH,
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// We use a pixel format of RGB565 for the status bar to save memory bandwidth and
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// to ensure that the layer can be handled by HWComposer. On some devices the
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// HWComposer is unable to handle SW-rendered RGBX_8888 layers.
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PixelFormat.RGB_565);
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// the status bar should be in an overlay if possible
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final Display defaultDisplay
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= ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
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.getDefaultDisplay();
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// We explicitly leave FLAG_HARDWARE_ACCELERATED out of the flags. The status bar occupies
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// very little screen real-estate and is updated fairly frequently. By using CPU rendering
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// for the status bar, we prevent the GPU from having to wake up just to do these small
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// updates, which should help keep power consumption down.
-
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lp.gravity = getStatusBarGravity();
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lp.setTitle("StatusBar");
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lp.packageName = mContext.getPackageName();
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lp.windowAnimations = R.style.Animation_StatusBar;
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WindowManagerImpl.getDefault().addView(sb, lp);
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if (SPEW) {
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Slog.d(TAG, "Added status bar view: gravity=0x" + Integer.toHexString(lp.gravity)
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+ " icons=" + iconList.size()
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+ " disabled=0x" + Integer.toHexString(switches[0])
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+ " lights=" + switches[1]
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+ " menu=" + switches[2]
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+ " imeButton=" + switches[3]
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);
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}
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mDoNotDisturb = new DoNotDisturb(mContext);
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}
publicvoid start() {
//First set up our views and stuff.
Viewsb = makeStatusBarView();
//Connect in to the status bar manager service
StatusBarIconListiconList = new StatusBarIconList();
ArrayList
notificationKeys = new ArrayList (); ArrayList
notifications = new ArrayList (); mCommandQueue= new CommandQueue(this, iconList);
mBarService= IStatusBarService.Stub.asInterface(
ServiceManager.getService(Context.STATUS_BAR_SERVICE));
int[]switches = new int[7];
ArrayList
binders = new ArrayList (); try{
mBarService.registerStatusBar(mCommandQueue,iconList, notificationKeys, notifications,
switches,binders);
}catch (RemoteException ex) {
//If the system process isn't there we're doomed anyway.
}
disable(switches[0]);
setSystemUiVisibility(switches[1]);
topAppWindowChanged(switches[2]!= 0);
//StatusBarManagerService has a back up of IME token and it's restoredhere.
setImeWindowStatus(binders.get(0),switches[3], switches[4]);
setHardKeyboardStatus(switches[5]!= 0, switches[6] != 0);
//Set up the initial icon state
intN = iconList.size();
intviewIndex = 0;
for(int i=0; i
StatusBarIconicon = iconList.getIcon(i);
if(icon != null) {
addIcon(iconList.getSlot(i),i, viewIndex, icon);
viewIndex++;
}
}
//Set up the initial notification state
N= notificationKeys.size();
if(N == notifications.size()) {
for(int i=0; i
addNotification(notificationKeys.get(i),notifications.get(i));
}
}else {
Log.wtf(TAG,"Notification list length mismatch: keys=" + N
+" notifications=" + notifications.size());
}
//Put up the view
finalint height = getStatusBarHeight();
finalWindowManager.LayoutParams lp = new WindowManager.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
height,
WindowManager.LayoutParams.TYPE_STATUS_BAR,
WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
|WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
|WindowManager.LayoutParams.FLAG_SPLIT_TOUCH,
//We use a pixel format of RGB565 for the status bar to save memorybandwidth and
//to ensure that the layer can be handled by HWComposer. On somedevices the
//HWComposer is unable to handle SW-rendered RGBX_8888 layers.
PixelFormat.RGB_565);
//the status bar should be in an overlay if possible
finalDisplay defaultDisplay
=((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
.getDefaultDisplay();
//We explicitly leave FLAG_HARDWARE_ACCELERATED out of the flags. Thestatus bar occupies
//very little screen real-estate and is updated fairly frequently. Byusing CPU rendering
//for the status bar, we prevent the GPU from having to wake up just todo these small
//updates, which should help keep power consumption down.
lp.gravity= getStatusBarGravity();
lp.setTitle("StatusBar");
lp.packageName= mContext.getPackageName();
lp.windowAnimations= R.style.Animation_StatusBar;
WindowManagerImpl.getDefault().addView(sb,lp);
if(SPEW) {
Slog.d(TAG,"Added status bar view: gravity=0x" +Integer.toHexString(lp.gravity)
+" icons=" + iconList.size()
+" disabled=0x" + Integer.toHexString(switches[0])
+" lights=" + switches[1]
+" menu=" + switches[2]
+" imeButton=" + switches[3]
);
}
mDoNotDisturb= new DoNotDisturb(mContext);
}
在这里，完成了SystemUI的整个初始化以及设置过程，并最终呈现到界面上。在StatusBar中的start()方法主要完成了以下几个工作：首先获取需要在StatusBar上显示的各种icons。然后初始化一些属性。最后通过WindowManager的addView方法将StatusBar显示出来。分析到这里可能有人会问了，明明说分析的是SystemUI的嘛，怎么最后变成StatusBar了呢？如果你硬要说我跑题那我也没有办法，回过头去看看addNavigationBar()，你会发现和StatusBar的加载几乎一致，因此没必要再详述了。如果细心阅读了的朋友肯定会发现这句代码：mBarService=IStatusBarService.Stub.asInterface(ServiceManager.getService(Context.STATUS_BAR_SERVICE));
这不正是我们前面add的StatusBarManagerSerivce吗？这里通过AIDL的方式来获取它的对象。
整个代码执行的时序图如图2.2所示：
图2.2
3.总结
Android4.4的SystemUI加载启动的过程大致就是这样。
-