1，概述

当configuration发生变化后，Activity方法onConfigurationChange会被调用，在此具体记录configuration更新在Framework中的调用过程，直至传入Activity；

2，源码

configuration包含一个应用对手机配置的感知，比如窗口大小、重力方向、手机模式等，可以查看具体成员，

ok，包含配置文件的容器是ConfigurationContainer类，主要成员如下：

    /*** Contains requested override configuration settings applied to this configuration container.*/private Configuration mRequestedOverrideConfiguration = new Configuration();/*** Contains the requested override configuration with parent and policy constraints applied.* This is the set of overrides that gets applied to the full and merged configurations.*/private Configuration mResolvedOverrideConfiguration = new Configuration();/** True if mRequestedOverrideConfiguration is not empty */private boolean mHasOverrideConfiguration;/*** Contains full configuration applied to this configuration container. Corresponds to full* parent's config with applied {@link #mResolvedOverrideConfiguration}.*/private Configuration mFullConfiguration = new Configuration();/*** Contains merged override configuration settings from the top of the hierarchy down to this* particular instance. It is different from {@link #mFullConfiguration} because it starts from* topmost container's override config instead of global config.*/private Configuration mMergedOverrideConfiguration = new Configuration();

mRequestedOverrideConfiguration是原始request，container简单将新配置用它保存；mResolvedOverrideConfiguration是特殊处理后的configuration，子类可以通过重写resolveOverrideConfiguration方法修改其中的配置，达到特殊化，父类只是简单将原始request保存到它，并未改写；

mFullConfiguration是实际更新后configuration的最终状态；

mMergedOverrideConfiguration是具备继承效应的configuration，即container改变configuration后，子类将继承此改变，以此类推；

具体，咱们看ConfigurationContainer.onConfiguration方法，

public void onConfigurationChanged(Configuration newParentConfig) {//临时configuration变量，保存更新之前的mResolvedOverrideConfigurationmResolvedTmpConfig.setTo(mResolvedOverrideConfiguration);//更新mResolvedOverrideConfiguration，可重写此方法增添特殊配置resolveOverrideConfiguration(newParentConfig);mFullConfiguration.setTo(newParentConfig);//根据差异更新最终状态:mFullConfigurationmFullConfiguration.updateFrom(mResolvedOverrideConfiguration);//合并此次修改，保存至mMergedOverrideConfigurationonMergedOverrideConfigurationChanged();if (!mResolvedTmpConfig.equals(mResolvedOverrideConfiguration)) {//进入此分支，代表特殊配置修改，通知监听者，// This depends on the assumption that change-listeners don't do// their own override resolution. This way, dependent hierarchies// can stay properly synced-up with a primary hierarchy's constraints.// Since the hierarchies will be merged, this whole thing will go away// before the assumption will be broken.// Inform listeners of the change.for (int i = mChangeListeners.size() - 1; i >= 0; --i) {mChangeListeners.get(i).onRequestedOverrideConfigurationChanged(mResolvedOverrideConfiguration);}}for (int i = mChangeListeners.size() - 1; i >= 0; --i) {//通知监听者，已经合并父配置修改mChangeListeners.get(i).onMergedOverrideConfigurationChanged(mMergedOverrideConfiguration);}for (int i = getChildCount() - 1; i >= 0; --i) {//传达configuration最终状态到子类final ConfigurationContainer child = getChildAt(i);child.onConfigurationChanged(mFullConfiguration);}}

查看onRequestedOverrideConfigurationChanged方法，当有配置request到达，调用onConfigurationChanged完成上一步；

public void onRequestedOverrideConfigurationChanged(Configuration overrideConfiguration) {// Pre-compute this here, so we don't need to go through the entire Configuration when// writing to proto (which has significant cost if we write a lot of empty configurations).mHasOverrideConfiguration = !Configuration.EMPTY.equals(overrideConfiguration);mRequestedOverrideConfiguration.setTo(overrideConfiguration);// Update full configuration of this container and all its children.final ConfigurationContainer parent = getParent();onConfigurationChanged(parent != null ? parent.getConfiguration() : Configuration.EMPTY);}

进入下一步，Activity如何感知到配置的改变？这是一个binder过程，先从Activity生命周期说起；

配置改变后通过binder调用IApplicationThread.scheduleTransaction方法，

public void schedule() throws RemoteException {mClient.scheduleTransaction(this);}

然后配置改变消息会进入应用进程，经过ActivityThread.H发送消息，执行Transaction，进入TransactionExecutor.executeCallbacks方法，

这个ClientTransactionItem.execute方法如下，

 @Overridepublic void execute(ClientTransactionHandler client, IBinder token,PendingTransactionActions pendingActions) {// TODO(lifecycler): detect if PIP or multi-window mode changed and report it here.Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityConfigChanged");client.handleActivityConfigurationChanged(token, mConfiguration, INVALID_DISPLAY);Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);}

最终调用到performActivityConfigurationChanged方法，执行如下分支，回调Activity.onConfiguration方法，完成应用进程回调；

if (shouldReportChange) {activity.mCalled = false;activity.onConfigurationChanged(configToReport);if (!activity.mCalled) {throw new SuperNotCalledException("Activity " + activity.getLocalClassName() +" did not call through to super.onConfigurationChanged()");}}

那么系统进程如何传送配置信息到应用进程？这个还得从配置改变说起；

ConfigurationContainer是一个抽象类，直接子类是WindowContainer

WindowContainer是应用Window容器，所有顶层WindowContainer的容器是RootWindowContainer类，当configuration更新后，wms会调用setDisplayOverrideConfigurationIfNeed方法，然后通过ConfigurationContainer前文介绍的方法依次通知children配置update信息；

void setNewDisplayOverrideConfiguration(Configuration overrideConfig,@NonNull DisplayContent dc) {if (dc.mWaitingForConfig) {dc.mWaitingForConfig = false;mLastFinishedFreezeSource = "new-config";}mRoot.setDisplayOverrideConfigurationIfNeeded(overrideConfig, dc);}

于是乎，通过children调用至ActivityStack.onConfiguration，它继承WindowContainer，

该方法末尾，调用resize方法，再调用ensureVisibleActivitiesConfiguration方法;

void ensureVisibleActivitiesConfiguration(ActivityRecord start, boolean preserveWindow) {mEnsureVisibleActivitiesConfigHelper.process(start, preserveWindow);}

process方法内，会更新配置，然后更新焦距中的Activity

 final PooledFunction f = PooledLambda.obtainFunction(EnsureVisibleActivitiesConfigHelper::processActivity, this,PooledLambda.__(ActivityRecord.class));forAllActivities(f, start, true /*includeBoundary*/, true /*traverseTopToBottom*/);f.recycle();if (mUpdateConfig) {// Ensure the resumed state of the focus activity if we updated the configuration of// any activity.mRootWindowContainer.resumeFocusedStacksTopActivities();}

进一步查看processActivity方法，

boolean processActivity(ActivityRecord r) {mUpdateConfig |= r.ensureActivityConfiguration(0 /*globalChanges*/, mPreserveWindow);mBehindFullscreen |= r.occludesParent();return mBehindFullscreen;}

跟进ensureActivityConfiguration，在ActivityRecord.ensureActivityConfiguration方法中，有如下代码，

if (changes == 0 && !forceNewConfig) {if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG_CONFIGURATION,"Configuration no differences in " + this);// There are no significant differences, so we won't relaunch but should still deliver// the new configuration to the client process.if (displayChanged) {scheduleActivityMovedToDisplay(newDisplayId, newMergedOverrideConfig);} else {scheduleConfigurationChanged(newMergedOverrideConfig);}return true;}

displayChanged未改变的前提下，走scheduleConfigurationChange，通知应用进程，

private void scheduleConfigurationChanged(Configuration config) {if (!attachedToProcess()) {if (DEBUG_CONFIGURATION) Slog.w(TAG,"Can't report activity configuration update - client not running"+ ", activityRecord=" + this);return;}try {if (DEBUG_CONFIGURATION) Slog.v(TAG, "Sending new config to " + this + ", config: "+ config);mAtmService.getLifecycleManager().scheduleTransaction(app.getThread(), appToken,ActivityConfigurationChangeItem.obtain(config));} catch (RemoteException e) {// If process died, whatever.}}

至此，应用进程可以根据新配置更新布局等信息。

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【android】configuration

1，概述

2，源码

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