android里每个服务启动时context

1.android里每个服务启动时context到底从哪里来的呢？？？？以mountservice的context为例在SystemServer.java的run函数中有如下代码 context = ActivityManagerService.main(factoryTest);......if...

1.android里每个服务启动时context到底从哪里来的呢？？？？以mountservice的context为例

在SystemServer.java的run函数中有如下代码

context = ActivityManagerService.main(factoryTest);

......

if (!"0".equals(SystemProperties.get("system_init.startmountservice"))) {

try {

/*

* NotificationManagerService is dependant on MountService,

* (for media / usb notifications) so we must start MountService first.

*/

Slog.i(TAG, "Mount Service");

mountService = new MountService(context);

ServiceManager.addService("mount", mountService);

} catch (Throwable e) {

reportWtf("starting Mount Service", e);

}

}

由此可知，由systemserver启动的服务的context都来自ActivityManagerService

ActivityManagerService.java

public static final Context main(int factoryTest) {

......

ActivityThread at = ActivityThread.systemMain();

......

Context context = at.getSystemContext();

......

return context;

}

由上可知，该context是由ActivityThread 创建的

ActivityThread .java

public ContextImpl getSystemContext() {

synchronized (this) {

if (mSystemContext == null) {

ContextImpl context =

ContextImpl.createSystemContext(this);

LoadedApk info = new LoadedApk(this, "android", context, null,

CompatibilityInfo.DEFAULT_COMPATIBILITY_INFO);

context.init(info, null, this);

context.getResources().updateConfiguration(

getConfiguration(), getDisplayMetricsLocked(

Display.DEFAULT_DISPLAY,

CompatibilityInfo.DEFAULT_COMPATIBILITY_INFO));

mSystemContext =
context;

//Slog.i(TAG, "Created system resources " + context.getResources()

// + ": " + context.getResources().getConfiguration());

}

}

return mSystemContext;

}

在ContextImpl .java中

static ContextImpl createSystemContext(ActivityThread mainThread) {

final ContextImpl context = new ContextImpl();

context.init(Resources.getSystem(), mainThread, Process.myUserHandle());

return context;

}

由此可知所有systemserver启动的服务的context对象实际为一个ContextImpl对象

即ServerThread::run<-ActivityManagerService.main<-ActivityThread::getSystemContext<-ContextImpl.createSystemContext

2.对于一个apk中的context一般直接指向这个activity本身，因为activity本身即继承自context