Android 切換系統語言源碼分析

以前了解Android的多語言實現很簡單，可以在不同的語言環境下使用不同的資源，就做好相應的語言適配就好，但是一直沒有實際使用過。 最近公司的項目要用到多國語言切換，並且還是和手機上系統設置裡面的語言切換功能一樣，於是就上網查了下資料。一般都是在應用類實現多國語言切換，這個是很簡單。而我想切換整個系統的語言。由於谷歌沒有把系統設置裡面的接口給開放出來，所以就只好去查看它的源碼了~

android語言切換是在：

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

的updateLocale()函數中調用，源碼如下：

/** * 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 
        }  
    }

從注釋可以看出, 只要本地local改變就會調用該函數. 查看ActivityManagerNative的getDefault()可以看到, 該函數返回的是遠程服務對象ActivityManagerServices.java在本地的一個代理. 最終調用的是ActivityManagerService.java中的updateConfiguration()函數.

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);  
        }  
    }

該函數, 首先進行的是權限的校驗. 然後調用updateConfigurationLocked()函數.

/** * 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;  
    }

整個語言切換就在這個函數中完成. 咋一看似乎沒感覺到該函數做了哪些事情. 我們首先來看注釋: 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: 這個函數做了兩件事情. (1). 改變當前的configuration. 意思就是讓改變的configuration更新到當前configuration. (2) 確保所有正在運行的activity都能更新改變後的configuration.(這點是關鍵.) . 我們按照這個思路看看android是如何更新configuration. 查看代碼 , 首先看到 這個函數首先判斷values是否為空, 這裡values肯定不為空的, 然後changes = newConfig.updateFrom(values); 我們看看updateFrom做了什麼操作。

/** 
     * 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;  
    }

因為語言改變了, 那麼 (!locale.equals(delta.locale)) 是true. changed 大於0, 然後return changed. 回到ActivityManagerService.java的updateConfigurationLocked函數, 因為changed不為0 , 所以走if這個流程. 繼續看代碼。

        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類型. LRU : Least Recently Used保存所有運行過的進程. ProcessRecord進程類, 一個apk文件運行時會對應一個進程. app.thread. 此處的thread代表的是ApplicationThreadNative.java類型. 然後調用其scheduleConfigurationChanged(); 查看該函數。

    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(); 
    }

又是通過binder調用, 所以 , binder在android中是一個很重要的概念. 此處遠程調用的是ActivityThread.java中的私有內部內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是調用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);  
           }  
       }

這個函數首先是調用applyConfigurationToResourcesLocked(). 看函數名大概可以猜想到: 將configuration應用到resources.這裡configuration改變的是local 本地語言. 那而resources資源包含語言包嗎？

    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()清除一部分系統資源, 並且將config更新到Resources, 而Resources包含了一個AssetManager對象, 該對象的核心實現是在AssetManager.cpp中完成的. 然後循環清空mActivityResources資源. 再回到handleConfigurationChanged()函數, 執行完updateSystemConfiguration後, 會循環該進程的所有activity:

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

再來看performConfigurationChanged的實現:

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);  
            }  
        }  
    }

該函數判斷configuration是否改變, 如果改變那麼shouldChangeConfig為true. 然後調用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);  
       }  
   }

查看注釋, 大概意思是: 如果你的activity運行 , 設備信息有改變(即configuration改變)時由系統調用. 如果你在manifest.xml中配置了configChnages屬性則表示有你自己來處理configuration change. 否則就重啟當前這個activity. 而重啟之前, 舊的resources已經被清空, 那麼就會裝載新的資源, 整個過程就完成了語言切換後 , 能夠讓所有app使用新的語言。

上面這些就是對Android 系統裡面的語言切換進行了源碼分析，就先分析到這裡；有些東西我也不是很看懂，能力有限~