SystemServer程序源碼分析之一

1, 基本概念

SystemServer是三大核心步驟中的最後一個,主要是各種服務的注冊和啟動。SystemServer程序由Zygote程序啟動。zygoteInit的startSystemServer部分方法如下,

String args[] = { // SystemServer服務程序的資訊
            "--setuid=1000", // uid
            "--setgid=1000", // gid
            "--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1032,3001,3002,3003,3006,3007",
            "--capabilities=" + capabilities + "," + capabilities,
            "--nice-name=system_server", // 程序名
            "--runtime-args",
            "com.android.server.SystemServer", // 包名
        };
           

在Zygote文章中已經分析了SystemServer程序的啟動流程,在此就不多論述了,直接看SystemServer的main方法。

2, SystemServer

SystemServer的main方法如下,

public static void main(String[] args) {
        new SystemServer().run();
    }
           

Main函數很簡單,僅僅構造一個SystemServer對象,然後調用run方法

run方法比較長,還是看大體步驟

1,調整時間

if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
            Slog.w(TAG, "System clock is before 1970; setting to 1970.");
            SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
        }
           

2,設定系統相關屬性

if (!SystemProperties.get("persist.sys.language").isEmpty()) {
            final String languageTag = Locale.getDefault().toLanguageTag();

            SystemProperties.set("persist.sys.locale", languageTag);
            SystemProperties.set("persist.sys.language", "");
            SystemProperties.set("persist.sys.country", "");
            SystemProperties.set("persist.sys.localevar", "");
        }
public static void main(String[] args) {
        new SystemServer().run();
}
           

3,設定環境

VMRuntime.getRuntime().setTargetHeapUtilization(0.8f); // 虛拟機堆棧的大小
        Build.ensureFingerprintProperty(); // 初始化binder
        Environment.setUserRequired(true);
        BinderInternal.disableBackgroundScheduling(true);

        // Prepare the main looper thread (this thread).
        android.os.Process.setThreadPriority(       // Binder,消息機制
                android.os.Process.THREAD_PRIORITY_FOREGROUND);
        android.os.Process.setCanSelfBackground(false);
        Looper.prepareMainLooper();

        // Initialize native services.
        System.loadLibrary("android_servers"); // 加載JNI運作庫
           

4,建立程序上下文

createSystemContext();
           

5,建立SystemServiceManager

mSystemServiceManager = new SystemServiceManager(mSystemContext);
        LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
           

6,啟動各種服務

// Start services.
        try {
            startBootstrapServices();
            startCoreServices();
            startOtherServices();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        }
           

7,開始循環處理消息。

Looper.loop();
           

3, 啟動各種服務

服務分三類啟動:

3.1 startBootstrapServices

ActivityManagerService	PowerManagerService	LightsService
DisplayManagerService	RegionalizationService	PackageManagerService
SensorService

3.2 startCoreServices

BatteryService

UsageStatsService

WebViewUpdateService

3.3 startOtherServices

SchedulingPolicyService	TelecomLoaderService	telephonyRegistry
CameraService	AccountManagerService	ContentService
VibratorService	ConsumerIrService	AlarmManagerService
Watchdog	InputManagerService	WindowManagerService
BluetoothService	InputMethodManagerService	MountService
UiModeManagerService	LockSettingsService	DeviceIdleController
StatusBarManagerService	ClipboardService	WifiP2pService
NetworkScoreService	NetworkStatsService	WifiService
WifiScanningService	RttService	EthernetService
ConnectivityService	NsdService	UpdateLockService
LocationManagerService	CountryDetectorService	SearchManagerService
DropBoxManagerService	WallpaperManagerService	AudioService
DockObserver	WiredAccessoryManager	MidiService
UsbService	SerialService	TwilightService
JobSchedulerService	BackupManagerService	AppWidgetService
GestureLauncherService	DiskStatsService	SamplingProfilerService
CertBlacklister	DreamManagerService	AssetAtlasService
PrintManagerService	MediaSessionService	HdmiControlService
MediaRouterService	TrustManagerService	FingerprintService
LauncherAppsService	MmsServiceBroker

AccessibilityManagerService   PersistentDataBlockService   DevicePolicyManagerService

NetworkManagementService  TextServicesManagerService  NetworkPolicyManagerService

NotificationManagerService   DeviceStorageMonitorService  VoiceInteractionManagerService

NetworkTimeUpdateService   CommonTimeManagementService  GraphicsStatsService

RestrictionsManagerService   TvInputManagerService      MediaProjectionManagerService

果然,一切皆服務啊!

4,小結

SystemServer程序是android中一個很重要的程序由Zygote程序啟動

SystemServer程序主要用于啟動系統中的服務