简介
Android系统中有3个非常重要的应用，分别是SystemUI，launcher,Setting
- Setting：显示需要用户知道的设置项目，以前让用户配置自己系统的设置
- launcher：显示所有的应用，展示应用入口
- SystemUI：显示重要的信息，比如信号，电量，供用户操作的导航栏
Android 的 SystemUI 其实就是 Android 的系统界面，它包括了界面上方的状态栏 status bar，下方的导航栏Navigation Bar，锁屏界面 Keyguard ，电源界面 PowerUI，近期任务界面 Recent Task 等等。对于用户而言，SystemUI 的改动是最能直观感受到的。因此，每个 Android 版本在 SystemUI 上都有比较大的改动。而对开发者而言，理解 Android SystemUI 对优化Android系统界面，改善用户体验十分重要。
SystemUI的启动
Android系统在启动系统服务器SystemService的时候，会启动各个服务器，而在启动这个服务器之后会启动launcher和SystemUI
frameworks/base/services/java/com/android/server/SystemServer.java
public final class SystemServer {
private void run() {
startBootstrapServices();
startCoreServices();
startOtherServices();
}
private void startOtherServices() {
// We now tell the activity manager it is okay to run third party
// code. It will call back into us once it has gotten to the state
// where third party code can really run (but before it has actually
// started launching the initial applications), for us to complete our
// initialization.
mActivityManagerService.systemReady(() -> {
startSystemUi(context, windowManagerF);
}
}
｝
可以看出在系统在启动所有服务器之后，监听mActivityManagerService状态，如果“systemReady”后，启动SytemUI，AMS的systemReady先启动SystemUI之后启动launcher，我们这里只关注SystemUI
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);
//Slog.d(TAG, "Starting service: " + intent);
context.startServiceAsUser(intent, UserHandle.SYSTEM);
windowManager.onSystemUiStarted();
}
可以看见启动的是SystemUI的服务，然后调用 windowManager.onSystemUiStarted();
windowManager.onSystemUiStarted();执行了下面的流程
- windowManagerSerivce#onSystemUiStarted
- PhoneWindoiwManager#onSystemUiStarted
- KeyguardServiceDelegate#KeyguardServiceDelegate
public void bindService(Context context) {
context.bindServiceAsUser(intent, mKeyguardConnection,//注1
Context.BIND_AUTO_CREATE, mHandler, UserHandle.SYSTEM)
}
注1：这里的intent是SystemUI的keygaurdServUC儿，通过获取SystemUI的keyguard，控制SystemU的锁屏。
SystemService启动SystemUIService
SystemUIService类十分简短，下面基本就是他全部的代码，
public class SystemUIService extends Service {
@Override
public void onCreate() {
super.onCreate();
((SystemUIApplication) getApplication()).startServicesIfNeeded();
}
@Override
public IBinder onBind(Intent intent) {
return null;
}
}
他只是调用SystemUIApplication的startServicesIfNeeded方法
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];
if (DEBUG) Log.d(TAG, "loading: " + clsName);
log.traceBegin("StartServices" + clsName);
long ti = System.currentTimeMillis();
Class cls;
try {
cls = Class.forName(clsName);
mServices[i] = (SystemUI) cls.newInstance();//new it
} 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;
}
｝
可以看到他通过反射实例化config_systemUIServiceComponents数组对应的“service”，然后调用start方法。
config_systemUIServiceComponents有哪些呢？
<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>
这些类继承SystemUI，SystemUI类又是干什么的呢？
这个应用主要界面都是显示在Android屏幕部分区域，这些界面没有通过Activity控制，SystemUI类具有管理的功能，如在屏幕旋转会调用onConfigurationChanged方法，各个界面就可以做出相应的显示，调用onstar启动相应的模块。
启动SystemBars
各个模块比较多，已SystemBars为例进行分析。在startServicesIfNeeded方法中会实例化这个模块，然后调用其start方法。
SystemBars类（去除不重要的代码，以及log）
public class SystemBars extends SystemUI {
@Override
public void start() {
createStatusBarFromConfig();
}
private void createStatusBarFromConfig() {
//
final String clsName =com.android.systemui.statusbar.phone.StatusBar mContext.getString(R.string.config_statusBarComponent);
Class<?> cls = null;
cls = mContext.getClassLoader().loadClass(clsName);
mStatusBar = (SystemUI) cls.newInstance();
mStatusBar.mContext = mContext;
mStatusBar.mComponents = mComponents;
mStatusBar.start();
}
}
SystemBars实例化了R.string.config_statusBarComponent对应的com.android.systemui.statusbar.phone.StatusBar这个类,并调用其start方法。
public class StatusBar extends SystemUI｛
@Override
public void start() {
createAndAddWindows();
｝
public void createAndAddWindows() {
addStatusBarWindow();
}
private void addStatusBarWindow() {
makeStatusBarView();
mStatusBarWindowManager = Dependency.get(StatusBarWindowManager.class);
mRemoteInputManager.setUpWithPresenter(this, mEntryManager, this,
new RemoteInputController.Delegate() {
public void setRemoteInputActive(NotificationData.Entry entry,
boolean remoteInputActive) {
mHeadsUpManager.setRemoteInputActive(entry, remoteInputActive);
entry.row.notifyHeightChanged(true /* needsAnimation */);
updateFooter();
}
public void lockScrollTo(NotificationData.Entry entry) {
mStackScroller.lockScrollTo(entry.row);
}
public void requestDisallowLongPressAndDismiss() {
mStackScroller.requestDisallowLongPress();
mStackScroller.requestDisallowDismiss();
}
});
mRemoteInputManager.getController().addCallback(mStatusBarWindowManager);
mStatusBarWindowManager.add(mStatusBarWindow, getStatusBarHeight());
}
protected void inflateStatusBarWindow(Context context) {
mStatusBarWindow = (StatusBarWindowView) View.inflate(context,
R.layout.super_status_bar, null);
}
｝
最后通过inflateStatusBarWindow获取view，然后mStatusBarWindowManager添加这个view，并显示出来。
SystemBars加载各个视图
SystemBars加载基本全部SystemUI的界面显示，由于布局太多，查找起来十分麻烦，我从其他人那里copy过来，链接:++https://www.jianshu.com/p/2e0f403e5299++