ConfigurationChanged流程梳理(屏幕旋转、语言及字体切换)

关键字：Configuration，屏幕旋转，语言切换，字体切换， 源码

前段时间做了关于系统字体切换的功能，其中涉及到较多ConfigurationChanged的流程。屏幕旋转、mcc、系统语言切换等均是通过该流程来实现的。
网上少有这方面的描述，故将该部分总结提炼出来做个小结。
以下以屏幕旋转为例。关于屏幕旋转对于Activity的生命周期的影响也在以下可以体现。

ConfigurationChange Flow

讲太多也不如一个图来得实在，下图也是整个ConfigurationChange通用流程的概括，该流程是基于Android 5.1 和6.0画出，kk版本应该也是差不多的

流程跟踪

下面是对屏幕旋转的事件跟踪，尽量干货.
注：有序列表标号代表对应上图中的时序节点

1.屏幕旋转事件上传

G-Sensor将旋转事件由底层上传到FW处理，改变Configuration中orientation的值并将事件继续上传：
Configuration中对屏幕方向的定义：

    /**     * Overall orientation of the screen.  May be one of     * {@link #ORIENTATION_LANDSCAPE}, {@link #ORIENTATION_PORTRAIT}.     */    public int orientation;

调用ActivityManagerNative.getDefault().updatePersistentConfiguration(newConfig);将事件上传

2.ActivityManagerNative中使用远程代理通过Binder调用AMS的同名方法updatePersistentConfiguration

（远程代理这块不作深入了解）

   public void updatePersistentConfiguration(Configuration values) throws RemoteException    {        Parcel data = Parcel.obtain();        Parcel reply = Parcel.obtain();        data.writeInterfaceToken(IActivityManager.descriptor);        values.writeToParcel(data, 0);        mRemote.transact(UPDATE_PERSISTENT_CONFIGURATION_TRANSACTION, data, reply, 0);        reply.readException();        data.recycle();        reply.recycle();    }

然后在AMS中，遍历每一个最近运行的程序，同步顺序执行以下方法

    /**     * 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     */boolean updateConfigurationLocked(Configuration values, ActivityRecord starting, boolean persistent, boolean initLocale) {    ...    mSystemThread.applyConfigurationToResources(configCopy);    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) {         }    }    ...}

3.通过代理对每个进程上传事件

得到远程服务对象在ActivityManagerService在本地的代理，最终调用了AMS的updateConfiguration()来更新系统Configuration。
其中scheduleConfigurationChanged()实际是通过Binder远程调用(该过程同步)ActivityThread中的同名方法//咳咳：

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();}public void scheduleConfigurationChanged(Configuration config) {    updatePendingConfiguration(config);    sendMessage(H.CONFIGURATION_CHANGED, config);}

4.每个进程进行事件响应

将该进程下执行对应CONFIGURATION_CHANGED处理：

final void handleConfigurationChanged(Configuration config, CompatibilityInfo compat) {    ...    mResourcesManager.applyConfigurationToResourcesLocked(config, compat);             ...    configDiff = mConfiguration.diff(config);    mConfiguration.updateFrom(config);    config = applyCompatConfiguration(mCurDefaultDisplayDpi);    ArrayList<ComponentCallbacks2> callbacks = collectComponentCallbacks(false, config);    freeTextLayoutCachesIfNeeded(configDiff);    if (callbacks != null) {        final int N = callbacks.size();        for (int i=0; i<N; i++) {            performConfigurationChanged(callbacks.get(i), config);        }    }}

5.更新资源

Reload New Resources: 将Config应用到Resource的一系列操作。

public final boolean applyConfigurationToResourcesLocked(Configuration config,        CompatibilityInfo compat) {    ... //对Configuration的比较以及更新到Resource          Resources.updateSystemConfiguration(config, defaultDisplayMetrics, compat);    ApplicationPackageManager.configurationChanged();//清空Icon和String缓存    Configuration tmpConfig = null;    for (int i=mActiveResources.size()-1; i>=0; i--) {        ResourcesKey key = mActiveResources.keyAt(i);        Resources r = mActiveResources.valueAt(i).get();        if (r != null) {            ...//更新Resource的Config        } else {            //Slog.i(TAG, "Removing old resources " + v.getKey());            mActiveResources.removeAt(i);        }    }    return changes != 0;}

7.8.更新资源Res

在Resource中更新资源，在重新加载时就会使用新的资源

public void updateConfiguration(Configuration config, DisplayMetrics metrics, CompatibilityInfo compat) {    synchronized (mAccessLock) {        ...         //更新Resource指向        //{@kth add 20151127 start        //像字体大小切换、语言切换等都会在此处开始更新资源的指向        //kth add 20151127 end@}        ...        //清空drawable资源        clearDrawableCachesLocked(mDrawableCache, configChanges);        clearDrawableCachesLocked(mColorDrawableCache, configChanges);        mAnimatorCache.onConfigurationChange(configChanges);        mStateListAnimatorCache.onConfigurationChange(configChanges);        mColorStateListCache.clear();        flushLayoutCache();    }    ...}

10.回调反馈

当Configuration的操作执行完后，实现了ComponentCallbacks2接口的组件如Activity、Services、Application等将会执行回调onConfigurationChanged()方法(接口回调)，从而实现正在运行的app中所有组件对Config的更新响应。针对屏幕旋转更新前台显示，其他Configuration如字体、语言等需要通知所有。
该方法针对同一进程下Activity的状态进行甄别，将符合条件的Act放入list以方便后面操作.。

private static 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;    ...    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 (shouldChangeConfig) {        cb.onConfigurationChanged(config);        if (activity != null) {            ...            activity.mCurrentConfig = new Configuration(config);        }    }}

Activity、Service、Application、Provider同样实现了ComponentCallbacks接口，从而实现四大组件全部更新状态和资源

   ArrayList<ComponentCallbacks2> collectComponentCallbacks(boolean allActivities, Configuration newConfig) {        ArrayList<ComponentCallbacks2> callbacks= new ArrayList<ComponentCallbacks2>();         synchronized (mResourcesManager) {            final int NAPP = mAllApplications.size();// Application            for (int i=0; i<NAPP; i++) {                callbacks.add(mAllApplications.get(i));            }            final int NACT = mActivities.size();// Activity            for (int i=0; i<NACT; i++) {                ActivityClientRecord ar = mActivities.valueAt(i);                Activity a = ar.activity;                if (a != null) {                    Configuration thisConfig = applyConfigCompatMainThread(                            mCurDefaultDisplayDpi, newConfig,                            ar.packageInfo.getCompatibilityInfo());                    if (!ar.activity.mFinished && (allActivities || !ar.paused)) {                        // If the activity is currently resumed, its configuration                        // needs to change right now.                        callbacks.add(a);                    } else if (thisConfig != null) {                        // Otherwise, we will tell it about the change                        // the next time it is resumed or shown.  Note that                        // the activity manager may, before then, decide the                        // activity needs to be destroyed to handle its new                        // configuration.                        if (DEBUG_CONFIGURATION) {                            Slog.v(TAG, "Setting activity " + ar.activityInfo.name + " newConfig=" + thisConfig);                        }                        ar.newConfig = thisConfig;                    }                }            }            final int NSVC = mServices.size();// Service            for (int i=0; i<NSVC; i++) {                callbacks.add(mServices.valueAt(i));            }        }        synchronized (mProviderMap) {            final int NPRV = mLocalProviders.size();// Provider            for (int i=0; i<NPRV; i++) {                callbacks.add(mLocalProviders.valueAt(i).mLocalProvider);            }        }        return callbacks;    }

11.四大组件事件响应

如果在manifest.xml中配置了configChnages属性则表示由app自己来处理configuration change，就会回调Activity等组件的onConfigurationChanged方法。否则就重启当前这个activity（这个重启步骤位于当activity回到前台时执行onDestroy->onStart->onResume），而重启之前，旧的resources已经被清空, 那么就会装载新的资源。对于未启动的应用则会在启动时加载新的资源。参考如下：

(引自Activity.java)

   /**     * 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.     */

顺道贴下ConfigurationChanged时Act的生命周期以便理解：

01-02 18:01:44.039 11305 11305 E MainActivity: onPause01-02 18:01:44.040 11305 11305 E MainActivity: onSaveInstanceState01-02 18:01:44.040 11305 11305 E MainActivity: onStop01-02 18:01:44.040 11305 11305 E MainActivity: onDestroy01-02 18:01:44.063 11305 11305 E MainActivity: onStart01-02 18:01:44.064 11305 11305 E MainActivity: onRestoreInstanceState01-02 18:01:44.064 11305 11305 E MainActivity: onResume

小结

以上就是Configuration时间的流程梳理,好记性不如烂笔头。主要是流程时序图麻烦，从自己知道到写下来中间也来回经历好些个小时翻源码。
记录以供需要的人参考。

Fucking The Source Code
附上参考过的csdn链接
七号大蒜
android源码分析(一) - 语言切换机制
谢捧场
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