Android 切换系统语言源码分析

以前了解Android的多语言实现很简单，可以在不同的语言环境下使用不同的资源，就做好相应的语言适配就好，但是一直没有实际使用过。 最近公司的项目要用到多国语言切换，并且还是和手机上系统设置里面的语言切换功能一样，于是就上网查了下资料。一般都是在应用类实现多国语言切换，这个是很简单。而我想切换整个系统的语言。由于谷歌没有把系统设置里面的接口给开放出来，所以就只好去查看它的源码了~

• android语言切换是在：

packages/apps/Settings/com/android/settings/LocalePicker.java

的updateLocale()函数中调用，源码如下：

/** * Requests the system to update the system locale. Note that the system looks halted for a while during the Locale migration, so the caller need to take care of it. */        public static void updateLocale(Locale locale) {            try {                IActivityManager am = ActivityManagerNative.getDefault();                Configuration config = am.getConfiguration();                  config.locale = locale;                  // indicate this isn't some passing default - the user wants this remembered               config.userSetLocale = true;                  am.updateConfiguration(config);                // Trigger the dirty bit for the Settings Provider.               BackupManager.dataChanged("com.android.providers.settings");            } catch (RemoteException e) {                // Intentionally left blank           }        }  

• 从注释可以看出, 只要本地local改变就会调用该函数. 查看ActivityManagerNative的getDefault()可以看到, 该函数返回的是远程服务对象ActivityManagerServices.java在本地的一个代理. 最终调用的是ActivityManagerService.java中的updateConfiguration()函数.

public void updateConfiguration(Configuration values) {            enforceCallingPermission(android.Manifest.permission.CHANGE_CONFIGURATION,                    "updateConfiguration()");              synchronized(this) {                if (values == null && mWindowManager != null) {                    // sentinel: fetch the current configuration from the window manager                   values = mWindowManager.computeNewConfiguration();                }                  if (mWindowManager != null) {                    mProcessList.applyDisplaySize(mWindowManager);                }                  final long origId = Binder.clearCallingIdentity();                if (values != null) {                    Settings.System.clearConfiguration(values);                }                updateConfigurationLocked(values, null, false, false);                Binder.restoreCallingIdentity(origId);            }        }  

• 该函数, 首先进行的是权限的校验. 然后调用updateConfigurationLocked()函数.

/** * Do either or both things: (1) change the current configuration, and (2) * make sure the given activity is running with the (now) current * configuration. Returns true if the activity has been left running, or * false if <var>starting</var> is being destroyed to match the new * configuration. * @param persistent TODO */        public boolean updateConfigurationLocked(Configuration values,                ActivityRecord starting, boolean persistent, boolean initLocale) {            int changes = 0;              boolean kept = true;              if (values != null) {                Configuration newConfig = new Configuration(mConfiguration);                changes = newConfig.updateFrom(values);                if (changes != 0) {                    if (DEBUG_SWITCH || DEBUG_CONFIGURATION) {                        Slog.i(TAG, "Updating configuration to: " + values);                    }                      EventLog.writeEvent(EventLogTags.CONFIGURATION_CHANGED, changes);                      if (values.locale != null && !initLocale) {                        saveLocaleLocked(values.locale,                                          !values.locale.equals(mConfiguration.locale),                                         values.userSetLocale, values.simSetLocale);                    }                        mConfigurationSeq++;                    if (mConfigurationSeq <= 0) {                        mConfigurationSeq = 1;                    }                    newConfig.seq = mConfigurationSeq;                    mConfiguration = newConfig;                    Slog.i(TAG, "Config changed: " + newConfig);                      final Configuration configCopy = new Configuration(mConfiguration);                      AttributeCache ac = AttributeCache.instance();                    if (ac != null) {                        ac.updateConfiguration(configCopy);                    }                      // Make sure all resources in our process are updated                   // right now, so that anyone who is going to retrieve                   // resource values after we return will be sure to get                   // the new ones. This is especially important during                   // boot, where the first config change needs to guarantee                   // all resources have that config before following boot                   // code is executed.                   mSystemThread.applyConfigurationToResources(configCopy);                      if (persistent && Settings.System.hasInterestingConfigurationChanges(changes)) {                        Message msg = mHandler.obtainMessage(UPDATE_CONFIGURATION_MSG);                        msg.obj = new Configuration(configCopy);                        mHandler.sendMessage(msg);                    }                      for (int i=mLruProcesses.size()-1; i>=0; i--) {                        ProcessRecord app = mLruProcesses.get(i);                        try {                            if (app.thread != null) {                                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Sending to proc "                                        + app.processName + " new config " + mConfiguration);                                app.thread.scheduleConfigurationChanged(configCopy);                            }                        } catch (Exception e) {                        }                    }                    Intent intent = new Intent(Intent.ACTION_CONFIGURATION_CHANGED);                    intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY                            | Intent.FLAG_RECEIVER_REPLACE_PENDING);                    broadcastIntentLocked(null, null, intent, null, null, 0, null, null,                            null, false, false, MY_PID, Process.SYSTEM_UID);                    if ((changes&ActivityInfo.CONFIG_LOCALE) != 0) {                        broadcastIntentLocked(null, null,                                new Intent(Intent.ACTION_LOCALE_CHANGED),                                null, null, 0, null, null,                                null, false, false, MY_PID, Process.SYSTEM_UID);                    }                  }            }              if (changes != 0 && starting == null) {                // If the configuration changed, and the caller is not already               // in the process of starting an activity, then find the top               // activity to check if its configuration needs to change.               starting = mMainStack.topRunningActivityLocked(null);            }              if (starting != null) {                kept = mMainStack.ensureActivityConfigurationLocked(starting, changes);                // And we need to make sure at this point that all other activities               // are made visible with the correct configuration.               mMainStack.ensureActivitiesVisibleLocked(starting, changes);            }              if (values != null && mWindowManager != null) {                mWindowManager.setNewConfiguration(mConfiguration);            }              return kept;        }  

• 整个语言切换就在这个函数中完成. 咋一看似乎没感觉到该函数做了哪些事情. 我们首先来看注释: Do either or both things: (1) change the current configuration, and (2)

  make sure the given activity is running with the (now) current. configuration大概意思是: 这个函数做了两件事情. (1). 改变当前的configuration. 意思就是让改变的configuration更新到当前configuration. (2) 确保所有正在运行的activity都能更新改变后的configuration.(这点是关键.) . 我们按照这个思路看看android是如何更新configuration. 查看代码 , 首先看到 这个函数首先判断values是否为空, 这里values肯定不为空的, 然后changes = newConfig.updateFrom(values); 我们看看updateFrom做了什么操作。

/**        * Copy the fields from delta into this Configuration object, keeping        * track of which ones have changed.  Any undefined fields in        * <var>delta</var> are ignored and not copied in to the current        * Configuration.        * @return Returns a bit mask of the changed fields, as per        * {@link #diff}.        */        public int updateFrom(Configuration delta) {            int changed = 0;            ...            if (delta.locale != null   && (locale == null || !locale.equals(delta.locale))) {                changed |= ActivityInfo.CONFIG_LOCALE;                locale = delta.locale != null   ? (Locale) delta.locale.clone() : null;                textLayoutDirection = LocaleUtil.getLayoutDirectionFromLocale(locale);            }            if (delta.userSetLocale && (!userSetLocale || ((changed & ActivityInfo.CONFIG_LOCALE) != 0)))            {                userSetLocale = true;                changed |= ActivityInfo.CONFIG_LOCALE;            }            ...            return changed;        }  

• 因为语言改变了, 那么 (!locale.equals(delta.locale)) 是true. changed 大于0, 然后return changed. 回到ActivityManagerService.java的updateConfigurationLocked函数, 因为changed不为0 , 所以走if这个流程. 继续看代码。

        for (int i=mLruProcesses.size()-1; i>=0; i--) {                        ProcessRecord app = mLruProcesses.get(i);                        try {                            if (app.thread != null) {                                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Sending to proc "                                        + app.processName + " new config " + mConfiguration);                                app.thread.scheduleConfigurationChanged(configCopy);                            }                        } catch (Exception e) {                        }                    }  

• 首先看到的是mLurProcesses 是ArrayList类型. LRU : Least Recently Used保存所有运行过的进程. ProcessRecord进程类, 一个apk文件运行时会对应一个进程. app.thread. 此处的thread代表的是ApplicationThreadNative.java类型. 然后调用其scheduleConfigurationChanged(); 查看该函数。

    public final void scheduleConfigurationChanged(Configuration config)                throws RemoteException {            Parcel data = Parcel.obtain();           data.writeInterfaceToken(IApplicationThread.descriptor);           config.writeToParcel(data, 0);           mRemote.transact(SCHEDULE_CONFIGURATION_CHANGED_TRANSACTION, data, null,                   IBinder.FLAG_ONEWAY);            data.recycle();       }  

• 又是通过binder调用, 所以 , binder在android中是一个很重要的概念. 此处远程调用的是ActivityThread.java中的私有内部内ApplicationThread。

    private class ApplicationThread extends ApplicationThreadNative {            private static final String HEAP_COLUMN = "%13s %8s %8s %8s %8s %8s %8s";            private static final String ONE_COUNT_COLUMN = "%21s %8d";            private static final String TWO_COUNT_COLUMNS = "%21s %8d %21s %8d";            private static final String TWO_COUNT_COLUMNS_DB = "%21s %8d %21s %8d";            private static final String DB_INFO_FORMAT = " %8s %8s %14s %14s %s";                ...            public void scheduleConfigurationChanged(Configuration config) {                updatePendingConfiguration(config);                queueOrSendMessage(H.CONFIGURATION_CHANGED, config);            }            ...    }  

• 而ApplicationThread中的handler的CONFIGURATION_CHANGED是调用handleConfigurationChanged()。

    final void handleConfigurationChanged(Configuration config, CompatibilityInfo compat) {             ArrayList<ComponentCallbacks2> callbacks = null;          ...         ...           applyConfigurationToResourcesLocked(config, compat);             ...             callbacks = collectComponentCallbacksLocked(false, config);           ...             if (callbacks != null) {               final int N = callbacks.size();               for (int i=0; i<N; i++) {                   performConfigurationChanged(callbacks.get(i), config);               }           }  

• 这个函数首先是调用applyConfigurationToResourcesLocked(). 看函数名大概可以猜想到: 将configuration应用到resources.这里configuration改变的是local 本地语言. 那而resources资源包含语言包吗？

    final boolean applyConfigurationToResourcesLocked(Configuration config,                CompatibilityInfo compat) {              int changes = mResConfiguration.updateFrom(config);            DisplayMetrics dm = getDisplayMetricsLocked(null, true);                if (compat != null && (mResCompatibilityInfo == null ||                    !mResCompatibilityInfo.equals(compat))) {                mResCompatibilityInfo = compat;                changes |= ActivityInfo.CONFIG_SCREEN_LAYOUT                        | ActivityInfo.CONFIG_SCREEN_SIZE                        | ActivityInfo.CONFIG_SMALLEST_SCREEN_SIZE;            }              ...              Resources.updateSystemConfiguration(config, dm, compat);              ...              Iterator<WeakReference<Resources>> it =                mActiveResources.values().iterator();            while (it.hasNext()) {                WeakReference<Resources> v = it.next();                Resources r = v.get();                if (r != null) {                    if (DEBUG_CONFIGURATION) Slog.v(TAG, "Changing resources "                            + r + " config to: " + config);                    r.updateConfiguration(config, dm, compat);                    //Slog.i(TAG, "Updated app resources " + v.getKey()                    //        + " " + r + ": " + r.getConfiguration());                } else {                    //Slog.i(TAG, "Removing old resources " + v.getKey());                    it.remove();                }            }              return changes != 0;        }  

• Resources.updateSystemConfiguration()清除一部分系统资源, 并且将config更新到Resources, 而Resources包含了一个AssetManager对象, 该对象的核心实现是在AssetManager.cpp中完成的. 然后循环清空mActivityResources资源. 再回到handleConfigurationChanged()函数, 执行完updateSystemConfiguration后, 会循环该进程的所有activity:

if (callbacks != null) {

        final int N = callbacks.size();          for (int i=0; i<N; i++) {              performConfigurationChanged(callbacks.get(i), config);          }      }

再来看performConfigurationChanged的实现:

private final void performConfigurationChanged(                ComponentCallbacks2 cb, Configuration config) {            // Only for Activity objects, check that they actually call up to their           // superclass implementation. ComponentCallbacks2 is an interface, so           // we check the runtime type and act accordingly.           Activity activity = (cb instanceof Activity) ? (Activity) cb : null;            if (activity != null) {                activity.mCalled = false;            }              boolean shouldChangeConfig = false;            if ((activity == null) || (activity.mCurrentConfig == null)) {                shouldChangeConfig = true;            } else {                  // If the new config is the same as the config this Activity               // is already running with then don't bother calling               // onConfigurationChanged               int diff = activity.mCurrentConfig.diff(config);                if (diff != 0) {                    // If this activity doesn't handle any of the config changes                   // then don't bother calling onConfigurationChanged as we're                   // going to destroy it.                   if ((~activity.mActivityInfo.getRealConfigChanged() & diff) == 0) {                        shouldChangeConfig = true;                    }                }            }              if (DEBUG_CONFIGURATION) Slog.v(TAG, "Config callback " + cb                    + ": shouldChangeConfig=" + shouldChangeConfig);            if (shouldChangeConfig) {                cb.onConfigurationChanged(config);                  if (activity != null) {                    if (!activity.mCalled) {                        throw new SuperNotCalledException(                                "Activity " + activity.getLocalClassName() +                            " did not call through to super.onConfigurationChanged()");                    }                    activity.mConfigChangeFlags = 0;                    activity.mCurrentConfig = new Configuration(config);                }            }        }  

• 该函数判断configuration是否改变, 如果改变那么shouldChangeConfig为true. 然后调用activity的onConfigurationChange(config);

/**       * Called by the system when the device configuration changes while your       * activity is running.  Note that this will <em>only</em> be called if       * you have selected configurations you would like to handle with the       * {@link android.R.attr#configChanges} attribute in your manifest. If       * any configuration change occurs that is not selected to be reported       * by that attribute, then instead of reporting it the system will stop       * and restart the activity (to have it launched with the new       * configuration).       *        * <p>At the time that this function has been called, your Resources       * object will have been updated to return resource values matching the       * new configuration.       *        * @param newConfig The new device configuration.       */       public void onConfigurationChanged(Configuration newConfig) {           mCalled = true;             mFragments.dispatchConfigurationChanged(newConfig);             if (mWindow != null) {               // Pass the configuration changed event to the window               mWindow.onConfigurationChanged(newConfig);           }             if (mActionBar != null) {               // Do this last; the action bar will need to access               // view changes from above.               mActionBar.onConfigurationChanged(newConfig);           }       }  

• 查看注释, 大概意思是: 如果你的activity运行 , 设备信息有改变(即configuration改变)时由系统调用. 如果你在manifest.xml中配置了configChnages属性则表示有你自己来处理configuration change. 否则就重启当前这个activity. 而重启之前, 旧的resources已经被清空, 那么就会装载新的资源, 整个过程就完成了语言切换后 , 能够让所有app使用新的语言。
• 上面这些就是对Android 系统里面的语言切换进行了源码分析，就先分析到这里；有些东西我也不是很看懂，能力有限~
• 明天我们再来分析怎么来实现Android 系统语言切换的功能。 Android 切换系统语言功能实现 ！
• O(∩_∩)O~ 打哈欠了睡觉了~