systemUI之statusBar

systemUI之statusbar

看标题应该能猜出来这会是一个系列，不管写的咋样，就当是小结吧。因为是第一篇，所以会先说下systemUI是嘛，然后从view的角度认识一下systemUI的各个部件，重点分析一下statusbar的布局结构；最后是statusbar的加载流程。

一，文件目录

systemUI相对锁屏什么的它算是很规矩了，标准的android工程，安静的待在：

.\frameworks\base\packages\SystemUI目录下，可以直接单编译成apk，注意要push到system/app下面重启验证效果。

二，视图部件

上面的图简单的表示了systemUI的结构，其实这个从我们的代码目录也可以知道个大概，那么啥是systemUI，干嘛独独要把这些放在一起弄个番号呢？个人本着细心学习，大胆推测的精神得到以下证据：1，它们都非常勤快，至少都是赶在launcher前面打卡；2不知疲倦，常驻内存，随时可以响应用户的使唤.有这些共性说它们是一奶同胞也就有论据了，如果你够耐心看下去会发现确实都是由一个systemUI服务孵化的。

因为该文的主角是statusbar，所以我们多花些笔墨解析一下它。statusbar在手机上其实分两个view：StatusBar和StatusBarExpanded，就拿StatusBar作典型进行分析吧：

从上面的层次图可以看出icon和ticker是两个平行frameLayout，一般时候都是icon布局显示，当有notification进来时ticker显示，为了方便研究分别给它们加了background color：

三，statusbar启动流程

我们知道了statusbar是啥，混了个脸熟后就可以对它的生平以及来龙去脉考究一番。为了描述方便，我试着把一个连贯的过程分成以下四步：

1， systemUI是个服务

看一个android工程我们都会从AndroidManifest.xml文件开始分析，这个也不例外。从manifest文件中我们找到SystemUIService这个重要的服务，整个systemUI就是由它而起。通过简单的find命令，在systemserver.java里面找到了SystemUIService的启动代码。

2， systemServer相关

systemServer的水其实非常深，它起于Zygote，负责Android系统所有的service注册登记，生和死。系统的分析需要另起篇幅，这里我们使用查找直接找到systemUIService的启动代码：

3， systemUIservice

接上面，我们直接看onCreate方法，主要作用就是根据机器硬件配置决定是实例化statusbar还是systembar。并启动相应的start方法。

public void onCreate() {// Pick status bar or system bar.//1.aidl远程调用windowmanager实例IWindowManager wm = IWindowManager.Stub.asInterface(ServiceManager.getService(Context.WINDOW_SERVICE));try {//2.在PhoneWindowManager里面进行判定是phone还是tablet或其他。SERVICES[0] = wm.canStatusBarHide()? R.string.config_statusBarComponent: R.string.config_systemBarComponent;} catch (RemoteException e) {Slog.w(TAG, "Failing checking whether status bar can hide", e);}//3.实例化statusbar。final int N = SERVICES.length;mServices = new SystemUI[N];for (int i=0; i<N; i++) {Class cl = chooseClass(SERVICES[i]);Slog.d(TAG, "loading: " + cl);try {mServices[i] = (SystemUI)cl.newInstance();} catch (IllegalAccessException ex) {throw new RuntimeException(ex);} catch (InstantiationException ex) {throw new RuntimeException(ex);}//4.启动statusbar。mServices[i].mContext = this;Slog.d(TAG, "running: " + mServices[i]);mServices[i].start();}}

通过查看systemUI的资源文件找到以下定义

<!-- Component to be usedas the status bar service.  Mustimplement the IStatusBarinterface. This name is in the ComponentName flattened format (package/class)  --><string name="config_statusBarComponent"translatable="false">com.android.systemui.statusbar.phone.PhoneStatusBar</string><!--Component to be used as the system bar service. Must implement the IStatusBarinterface. This name is in the ComponentName flattened format (package/class)  -->
<string name="config_systemBarComponent" translatable="false">com.android.systemui.statusbar.tablet.TabletStatusBar</string>

所以实际上起的是PhoneStatusBar.java的start（）。

4，PhoneStatusBar

前面的都是铺垫，到这里终于要来实际的了。分析的顺序是PhoneStatusBar.start() => StatusBar.start()=>PhoneStatusBar.makeStatusBarView()。

public void start() {mDisplay = ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();mWindowManager = IWindowManager.Stub.asInterface(ServiceManager.getService(Context.WINDOW_SERVICE));
//调用父类statusBar的start方法。super.start();
//加载导航条。addNavigationBar();//addIntruderView();// 最后调用policy加载更新图标mIconPolicy = new PhoneStatusBarPolicy(mContext);
}

我们进入statusBar.start()一探究竟：

public void start(){// 1.First set up our views and stuff.View sb = makeStatusBarView();// 2.Connect in to the status bar manager service。。。。。。try {mBarService.registerStatusBar(mCommandQueue, iconList,notificationKeys, notifications,switches, binders);} catch (RemoteException ex) {// 3.If the system process isn't there we're doomed anyway.}disable(switches[0]);setSystemUiVisibility(switches[1]);topAppWindowChanged(switches[2] != 0);// 4.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);// 5.Set up the initial icon stateint N = iconList.size();int viewIndex = 0;for (int i=0; i<N; i++) {StatusBarIcon icon =iconList.getIcon(i);if (icon != null) {addIcon(iconList.getSlot(i), i,viewIndex, icon);viewIndex++;}}// 6.Set up the initial notification stateN = notificationKeys.size();if (N == notifications.size()) {for (int i=0; i<N; i++) {addNotification(notificationKeys.get(i), notifications.get(i));}} else {Log.wtf(TAG, "Notification list length mismatch: keys=" + N+ " notifications=" +notifications.size());}// 7.Put up the viewfinal int height = getStatusBarHeight();final WindowManager.LayoutParams lp = newWindowManager.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,PixelFormat.OPAQUE);// 8.the status bar should be in an overlay if possiblefinal Display defaultDisplay= ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();if (ActivityManager.isHighEndGfx(defaultDisplay)){lp.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;}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);
}

statusBar乃至整个systemUI的view是怎么创建起来的，我们必须进入第一步的makeStatusBarView()方法细看一下。

protected View makeStatusBarView() {。。。。
//1.加载ExpandedView。ExpandedView expanded = (ExpandedView)View.inflate(context,R.layout.status_bar_expanded, null);if (DEBUG) {expanded.setBackgroundColor(0x6000FF80);}expanded.mService = this;
//2.加载PhoneStatusBarView。PhoneStatusBarView sb = (PhoneStatusBarView)View.inflate(context,R.layout.status_bar, null);sb.mService = this;mStatusBarView = sb;
//3.决定是否加载NavigationBarView。try {boolean showNav = mWindowManager.hasNavigationBar();if (showNav) {mNavigationBarView = (NavigationBarView) View.inflate(context, R.layout.navigation_bar, null);mNavigationBarView.setDisabledFlags(mDisabled);}} catch (RemoteException ex) {// no window manager? good luck with that}
//4.加载statusBar的各个具体控件。// figure out which pixel-format to use for the status bar.mPixelFormat = PixelFormat.OPAQUE;mStatusIcons = (LinearLayout)sb.findViewById(R.id.statusIcons);mNotificationIcons = (IconMerger)sb.findViewById(R.id.notificationIcons);mIcons = (LinearLayout)sb.findViewById(R.id.icons);mTickerView = sb.findViewById(R.id.ticker);
//4.实例化各种控制器。mLocationController = new LocationController(mContext); // will post a notificationmBatteryController = new BatteryController(mContext);mBatteryController.addIconView((ImageView)sb.findViewById(R.id.battery));mNetworkController = new NetworkController(mContext);
//5.加载并更新RecentsPanelView。// RecentsPanelmRecentTasksLoader = new RecentTasksLoader(context);updateRecentsPanel();
//6.注册定制的监听器。// receive broadcastsIntentFilter filter = new IntentFilter();filter.addAction(Intent.ACTION_CONFIGURATION_CHANGED);filter.addAction(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);filter.addAction(Intent.ACTION_SCREEN_OFF);context.registerReceiver(mBroadcastReceiver, filter);return sb;}

以上大概就是就是整个systemUI的加载流程，主线就是statusBar，在加载它的时候顺便也把RecentsPanel，NavigationBarView等看起来没啥联系的东西也一块加载好，私以为这里的代码结构还可以更好，4.1可能会有所改善吧。

小结：

这些东西其实一个月前就想写了，断断续续的一直没有开始着手，一来总有很多琐事或看起来更重要的事来打扰，二来是总觉得自己看的肤浅，不敢写，也不想写。不过总算是写出第一篇了。systemUI这块是整个系统UI风格的关键也最大程度地影响着用户的日常体验，无论是优化还是现有的usb处理挂载流程都有很多东西值得去挖掘，日后陆续放出吧。