8種機械鍵盤軸體對比
本人程序員，要買一個寫代碼的鍵盤，請問紅軸和茶軸怎么選？
一、SystemUI組成
SystemUI是Android的系統界面，包括狀態欄statusbar、鎖屏keyboard、任務列表recents等等，都繼承于SystemUI這個類，如鎖屏KeyguardViewMediator。
二、SystemUI啟動流程
SystemUI的啟動由SystemServer開始。SystemServer由Zygote fork生成的，進程名為system_server，該進程承載著framework的核心服務。Zygote啟動過程中會調用startSystemServer()。SystemUI的分析從SystemServer的main方法開始。SystemUI啟動的大致流程如下：
2.1 SystemServer
SystemServer在run方法中負責啟動系統的各種服務。
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15..........
// Start services.
try {
traceBeginAndSlog("StartServices");
startBootstrapServices();
startCoreServices();
startOtherServices();
SystemServerInitThreadPool.shutdown();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
} finally {
traceEnd();
}
在startOtherServices方法中先是創建并添加WindowManagerService、InputManagerService等service,并且調用startSystemUi方法，跳轉SystemUIService。
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25private void startOtherServices() {
//創建，注冊服務
...
WindowManagerService wm = null;
SerialService serial = null;
NetworkTimeUpdateService networkTimeUpdater = null;
CommonTimeManagementService commonTimeMgmtService = null;
InputManagerService inputManager = null;
...
traceBeginAndSlog("IpConnectivityMetrics");
mSystemServiceManager.startService(IpConnectivityMetrics.class);
traceEnd();
traceBeginAndSlog("NetworkWatchlistService");
mSystemServiceManager.startService(NetworkWatchlistService.Lifecycle.class);
traceEnd();
...
traceBeginAndSlog("StartSystemUI");
try {
startSystemUi(context, windowManagerF);
} catch (Throwable e) {
reportWtf("starting System UI", e);
}
啟動跳轉SystemUIService。
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9static 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();
}
2.2 SystemUIService
SystemUIService在onCreate中調用SystemUIApplication的startServicesIfNeeded方法。
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12@Override
public void onCreate() {
super.onCreate();
((SystemUIApplication) getApplication()).startServicesIfNeeded();
// For debugging RescueParty
if (Build.IS_DEBUGGABLE && SystemProperties.getBoolean("debug.crash_sysui", false)) {
throw new RuntimeException();
}
...
}
2.3 SystemUIApplication
SystemUIApplication先獲取配置的systemUI組件。
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4public void startServicesIfNeeded() {
String[] names = getResources().getStringArray(R.array.config_systemUIServiceComponents);
startServicesIfNeeded(names);
}
配置文件在/frameworks/base/packages/SystemUI/res/values/config.xml中，配置的systemui組件如圖：
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332 com.android.systemui.Dependency
333 com.android.systemui.util.NotificationChannels
334 com.android.systemui.statusbar.CommandQueue$CommandQueueStart
335 com.android.systemui.keyguard.KeyguardViewMediator
336 com.android.systemui.recents.Recents
337 com.android.systemui.volume.VolumeUI
338 com.android.systemui.stackdivider.Divider
339 com.android.systemui.SystemBars
340 com.android.systemui.usb.StorageNotification
341 com.android.systemui.power.PowerUI
342 com.android.systemui.media.RingtonePlayer
343 com.android.systemui.keyboard.KeyboardUI
344 com.android.systemui.pip.PipUI
345 com.android.systemui.shortcut.ShortcutKeyDispatcher
346 @string/config_systemUIVendorServiceComponent
347 com.android.systemui.util.leak.GarbageMonitor$Service
348 com.android.systemui.LatencyTester
349 com.android.systemui.globalactions.GlobalActionsComponent
350 com.android.systemui.ScreenDecorations
351 com.android.systemui.fingerprint.FingerprintDialogImpl
352 com.android.systemui.SliceBroadcastRelayHandler
353
在startServicesIfNeeded方法中，根據config配置創建SystemUI，并調用SystemUI的start方法。
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31private 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();
} 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;
if (DEBUG) Log.d(TAG, "running: " + mServices[i]);
mServices[i].start();
log.traceEnd();
...
}
2.4 SystemUI
SystemUI是一個抽象類，start()是抽象方法，具體實現在子類。
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16public abstract class SystemUI implements SysUiServiceProvider {
public Context mContext;
public Map, Object> mComponents;
public abstract void start();
protected void onConfigurationChanged(Configuration newConfig) {
}
public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
}
protected void onBootCompleted() {
}
...
}
)
