我们在前面已经知道activity和service的启动流程，activity和service本质上也是一个Context对象，在其启动过程中会创建一个与之关联的Context对象
1：Activity的Context创建流程
当我们在启动activity的过程是调用的方法都是startActivity,我们知道这是一个跨进程的过程，涉及到binder调用，在AMS端Activity是以ActivityRecord形式存在的，被TaskRecord以栈的形式管理，在启动activity的过程中会根据intent和flag信息为其找到合适的Stack和Task,我们都知道主线程，ActivityThread便是Android应用程序的主线程，它是有应用程序进程创建过程中由zyote进程反射调用的，在Activity启动过程中会调用handleLaunchActivity来启动一个activity, 在其内部会调用performLaunchActivity来完成Activity的启动
1.1:handleLaunchActivity
// Initialize before creating the activity
if (!ThreadedRenderer.sRendererDisabled) {
GraphicsEnvironment.earlyInitEGL();
}
WindowManagerGlobal.initialize();
final Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
if (!r.activity.mFinished && pendingActions != null) {
pendingActions.setOldState(r.state);
pendingActions.setRestoreInstanceState(true);
pendingActions.setCallOnPostCreate(true);
}
} else {
// If there was an error, for any reason, tell the activity manager to stop us.
try {
ActivityManager.getService()
.finishActivity(r.token, Activity.RESULT_CANCELED, null,
Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
1.2:performLaunchActivity的具体实现
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
ActivityInfo aInfo = r.activityInfo;
if (r.packageInfo == null) {
r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent();-------->intent中有没有指定组件名称
if (component == null) {
component = r.intent.resolveActivity(
mInitialApplication.getPackageManager());
r.intent.setComponent(component);
}
if (r.activityInfo.targetActivity != null) {
component = new ComponentName(r.activityInfo.packageName,
r.activityInfo.targetActivity);
}
ContextImpl appContext = createBaseContextForActivity(r);------->为activity创建ContextImpl对象
Activity activity = null;
try {
java.lang.ClassLoader cl = appContext.getClassLoader();
activity = mInstrumentation.newActivity(--------->通过classLoader创建一个Activity对象
cl, component.getClassName(), r.intent);
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to instantiate activity " + component
+ ": " + e.toString(), e);
}
}
try {
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (activity != null) {
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {
config.updateFrom(r.overrideConfig);
}
if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
+ r.activityInfo.name + " with config " + config);
Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
window = r.mPendingRemoveWindow;
r.mPendingRemoveWindow = null;
r.mPendingRemoveWindowManager = null;
}
appContext.setOuterContext(activity);----->将创建的activity对象和ContextImpl对象关联起来
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window, r.configCallback);
1.3:Activity的attch方法
final void attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
Application application, Intent intent, ActivityInfo info,
CharSequence title, Activity parent, String id,
NonConfigurationInstances lastNonConfigurationInstances,
Configuration config, String referrer, IVoiceInteractor voiceInteractor,
Window window, ActivityConfigCallback activityConfigCallback) {
attachBaseContext(context);------>关联ContextImpl对象
mFragments.attachHost(null /*parent*/);
mWindow = new PhoneWindow(this, window, activityConfigCallback);---->创建PhoneWindow对象
mWindow.setWindowControllerCallback(this);
mWindow.setCallback(this);--------------------->将this也就是activity和PhoneWindow关联起来
mWindow.setOnWindowDismissedCallback(this);
mWindow.getLayoutInflater().setPrivateFactory(this);
...................................................
}
1.4:attachBaseContext的实现
protected void attachBaseContext(Context newBase) {
super.attachBaseContext(newBase);
if (newBase != null) {
newBase.setAutofillClient(this);
}
}
1.5:attachBaseContext
@Override
protected void attachBaseContext(Context newBase) {
super.attachBaseContext(newBase);
}
protected void attachBaseContext(Context base) {
if (mBase != null) {
throw new IllegalStateException("Base context already set");
}
mBase = base;--------------->mBase的数据类型是Context
}
由于Activity是继承ContextThemeWrapper，ContextThemeWrapper是ContextWrapper的子类，这样便将上面的ContextImpl和Activity的成员变量mBase关联起来了
2.Service的Context创建过程
service的context创建流程和activity的context创建流程大致上是一致的
public final void scheduleCreateService(IBinder token,
ServiceInfo info, CompatibilityInfo compatInfo, int processState) {
updateProcessState(processState, false);
CreateServiceData s = new CreateServiceData();
s.token = token;
s.info = info;
s.compatInfo = compatInfo;
sendMessage(H.CREATE_SERVICE, s);
}
最终的方法是handleCreateService
private void handleCreateService(CreateServiceData data) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
LoadedApk packageInfo = getPackageInfoNoCheck(
data.info.applicationInfo, data.compatInfo);
Service service = null;
try {
java.lang.ClassLoader cl = packageInfo.getClassLoader();
service = packageInfo.getAppFactory()----------->创建一个service对象
.instantiateService(cl, data.info.name, data.intent);
} catch (Exception e) {
if (!mInstrumentation.onException(service, e)) {
throw new RuntimeException(
"Unable to instantiate service " + data.info.name
+ ": " + e.toString(), e);
}
}
try {
if (localLOGV) Slog.v(TAG, "Creating service " + data.info.name);
ContextImpl context = ContextImpl.createAppContext(this, packageInfo);----->创建一个ContextImpl对象
context.setOuterContext(service);------>将service对象和ContextImpl对象关联起来
Application app = packageInfo.makeApplication(false, mInstrumentation);
service.attach(context, this, data.info.name, data.token, app,
ActivityManager.getService());-------------------->调用attach方法
service.onCreate();----------------------------------------->回调其生命周期
mServices.put(data.token, service);
try {
ActivityManager.getService().serviceDoneExecuting(
data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
} catch (Exception e) {
if (!mInstrumentation.onException(service, e)) {
throw new RuntimeException(
"Unable to create service " + data.info.name
+ ": " + e.toString(), e);
}
}
}
2.1service的attach方法实现
public final void attach(
Context context,
ActivityThread thread, String className, IBinder token,
Application application, Object activityManager) {
attachBaseContext(context);----------------->关联ContextImpl对象
mThread = thread; // NOTE: unused - remove?
mClassName = className;
mToken = token;
mApplication = application;
mActivityManager = (IActivityManager)activityManager;
mStartCompatibility = getApplicationInfo().targetSdkVersion
< Build.VERSION_CODES.ECLAIR;
}
这样service的context对象便关联和创建