getSharedPreferences(String name, int mode) of Service的实现（转）

I found a method getSharedPreferences(String name, int mode) in Service class

than I want to see how it implements

first I got a abstrat method in Context class

/android_opensource/frameworks/base/core/java/android/content/Context.java

...
262     /**
263      * Retrieve and hold the contents of the preferences file 'name', returning
264      * a SharedPreferences through which you can retrieve and modify its
265      * values.  Only one instance of the SharedPreferences object is returned
266      * to any callers for the same name, meaning they will see each other's
267      * edits as soon as they are made.
268      *
269      * @param name Desired preferences file. If a preferences file by this name
270      * does not exist, it will be created when you retrieve an
271      * editor (SharedPreferences.edit()) and then commit changes (Editor.commit()).
272      * @param mode Operating mode.  Use 0 or {@link #MODE_PRIVATE} for the
273      * default operation, {@link #MODE_WORLD_READABLE}
274      * and {@link #MODE_WORLD_WRITEABLE} to control permissions.
275      *
276      * @return Returns the single SharedPreferences instance that can be used
277      *         to retrieve and modify the preference values.
278      *
279      * @see #MODE_PRIVATE
280      * @see #MODE_WORLD_READABLE
281      * @see #MODE_WORLD_WRITEABLE
282      */
283     public abstract SharedPreferences getSharedPreferences(String name,
284             int mode);
...

and Service extends ContextWrapper, ContextWrapper extends Context just implements from a new Context instance
/android_opensource/frameworks/base/core/java/android/content/ContextWrapper.java

...
132     @Override
133     public SharedPreferences getSharedPreferences(String name, int mode) {
134         return mBase.getSharedPreferences(name, mode);
135     }
...

so where does it pass the Context instance to the Service

The Context instance must implements the method

than I found the implementation in ApplicationContext which extends the Context

android_opensource/frameworks/base/core/java/android/app/ApplicationContext.java

...
@Override
303     public SharedPreferences getSharedPreferences(String name, int mode) {
304         SharedPreferencesImpl sp;
305         File f = makeFilename(getPreferencesDir(), name + ".xml");
306         synchronized (sSharedPrefs) {
307             sp = sSharedPrefs.get(f);
308             if (sp != null && !sp.hasFileChanged()) {
309                 //Log.i(TAG, "Returning existing prefs " + name + ": " + sp);
310                 return sp;
311             }
312         }
313
314         FileInputStream str = null;
315         File backup = makeBackupFile(f);
316         if (backup.exists()) {
317             f.delete();
318             backup.renameTo(f);
319         }
320
321         // Debugging
322         if (f.exists() && !f.canRead()) {
323             Log.w(TAG, "Attempt to read preferences file " + f + " without permission");
324         }
325
326         Map map = null;
327         if (f.exists() && f.canRead()) {
328             try {
329                 str = new FileInputStream(f);
330                 map = XmlUtils.readMapXml(str);
331                 str.close();
332             } catch (org.xmlpull.v1.XmlPullParserException e) {
333                 Log.w(TAG, "getSharedPreferences", e);
334             } catch (FileNotFoundException e) {
335                 Log.w(TAG, "getSharedPreferences", e);
336             } catch (IOException e) {
337                 Log.w(TAG, "getSharedPreferences", e);
338             }
339         }
340
341         synchronized (sSharedPrefs) {
342             if (sp != null) {
343                 //Log.i(TAG, "Updating existing prefs " + name + " " + sp + ": " + map);
344                 sp.replace(map);
345             } else {
346                 sp = sSharedPrefs.get(f);
347                 if (sp == null) {
348                     sp = new SharedPreferencesImpl(f, mode, map);
349                     sSharedPrefs.put(f, sp);
350                 }
351             }
352             return sp;
353         }
354     }
...

but I still did't found where it pass the ApplicationContext in

after few minutes search I found another class ActivityThread

It had a method handleCreateService which should be called when create a Service

android_opensource/frameworks/base/core/java/android/app/ActivityThread.java

...
2436     private final void handleCreateService(CreateServiceData data) {
2437         // If we are getting ready to gc after going to the background, well
2438         // we are back active so skip it.
2439         unscheduleGcIdler();
2440
2441         PackageInfo packageInfo = getPackageInfoNoCheck(
2442                 data.info.applicationInfo);
2443         Service service = null;
2444         try {
2445             java.lang.ClassLoader cl = packageInfo.getClassLoader();
2446             service = (Service) cl.loadClass(data.info.name).newInstance();
2447         } catch (Exception e) {
2448             if (!mInstrumentation.onException(service, e)) {
2449                 throw new RuntimeException(
2450                     "Unable to instantiate service " + data.info.name
2451                     + ": " + e.toString(), e);
2452             }
2453         }
2454
2455         try {
2456             if (localLOGV) Log.v(TAG, "Creating service " + data.info.name);
2457
2458             ApplicationContext context = new ApplicationContext();
2459             context.init(packageInfo, null, this);
2460
2461             Application app = packageInfo.makeApplication();
2462             context.setOuterContext(service);
2463             service.attach(context, this, data.info.name, data.token, app,
2464                     ActivityManagerNative.getDefault());
2465             service.onCreate();
2466             mServices.put(data.token, service);
2467             try {
2468                 ActivityManagerNative.getDefault().serviceDoneExecuting(data.token);
2469             } catch (RemoteException e) {
2470                 // nothing to do.
2471             }
2472         } catch (Exception e) {
2473             if (!mInstrumentation.onException(service, e)) {
2474                 throw new RuntimeException(
2475                     "Unable to create service " + data.info.name
2476                     + ": " + e.toString(), e);
2477             }
2478         }
2479     }
...

In the method it call the service's method attch and pass a ApplicationContext as parameter

then The service's attch method would pass the context throght the attachBaseContext(context) method
android_opensource/frameworks/base/core/java/android/app/Service.java

...
356     public final void attach(
357             Context context,
358             ActivityThread thread, String className, IBinder token,
359             Application application, Object activityManager) {
360         attachBaseContext(context);
361         mThread = thread;           // NOTE:  unused - remove?
362         mClassName = className;
363         mToken = token;
364         mApplication = application;
365         mActivityManager = (IActivityManager)activityManager;
366     }
...

android_opensource/frameworks/base/core/java/android/content/ContextWrapper.java

...
50     /**
51      * Set the base context for this ContextWrapper.  All calls will then be
52      * delegated to the base context.  Throws
53      * IllegalStateException if a base context has already been set.
54      *
55      * @param base The new base context for this wrapper.
56      */
57     protected void attachBaseContext(Context base) {
58         if (mBase != null) {
59             throw new IllegalStateException("Base context already set");
60         }
61         mBase = base;
62     }
...

so the service get the Context instance which implement the getSharedPreferences(String name, int mode) method

the original url http://hi.baidu.com/ksoftware/blog/item/de17bbd6806b202507088bd8.html