Android onConfigureChanges 是如何被调用的

此次分析基于Android 5.0.1源码

onConfigureChanges被调用的流程框架图：

源码分析

1.Android系统启动的时候会通过读取/init.rc文件启动zygote进程

service zygote /system/bin/app_process -Xzygote /system/bin --zygote
   socket zygote 666

2.zygote孵化出SystemServer进程，在frameworks\base\core\java\com\android\internal\os\ZygoteInit.java的main()中有如下代码段开启SystemServer进程

    public static void main(String argv[]) {
      ......

            // Disable tracing so that forked processes do not inherit stale tracing tags from
            // Zygote.
            Trace.setTracingEnabled(false);

            if (startSystemServer) {
                startSystemServer(abiList, socketName);
            }
            ......
    }

调用到ZygoteInit.java的startSystemServer()方法

private static boolean startSystemServer(String abiList, String socketName)
	......
 try {
            parsedArgs = new ZygoteConnection.Arguments(args);
            ZygoteConnection.applyDebuggerSystemProperty(parsedArgs);
            ZygoteConnection.applyInvokeWithSystemProperty(parsedArgs);

            /* Request to fork the system server process */
            pid = Zygote.forkSystemServe(
                    parsedArgs.uid, parsedArgs.gid,
                    parsedArgs.gids,
                    parsedArgs.debugFlags,
                    null,
                    parsedArgs.permittedCapabilities,
                    parsedArgs.effectiveCapabilities);
        } catch (IllegalArgumentException ex) {
            throw new RuntimeException(ex);
        }
		......
}

startSystemServer函数调用到 Zygote.forkSystemServer孵化出SystemService进程，根据startSystemServer参数socketName可以得知Zygote是根据socket监听创建进程请求，当我们点击桌面上的一个应用图标打开一个应用就是通过发送一个socket消息给zygote的socket服务端，zygote受到请求、解析然后fork出一个进程

3.在frameworks\base\services\java\com\android\server\SystemServer.java的main方法会为ServiceManager添加一些服务

    public static void main(String[] args) {
        new SystemServer().run();
    }

    private void run() {
        ......// Start services.
        try {
            startBootstrapServices();
            startCoreServices();
            startOtherServices();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        }  ......
        Looper.loop();
        throw new RuntimeException("Main thread loop unexpectedly exited");
    }

private void startOtherServices() {
	......
	Slog.i(TAG, "Window Manager");
	wm = WindowManagerService.main(context, inputManager,
                    mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,
                    !mFirstBoot, mOnlyCore);
	ServiceManager.addService(Context.WINDOW_SERVICE, wm);
	ServiceManager.addService(Context.INPUT_SERVICE, inputManager);
	mActivityManagerService.setWindowManager(wm);

	inputManager.setWindowManagerCallbacks(wm.getInputMonitor());
	inputManager.start();
	......
}

    public void start() {
        Slog.i(TAG, "Starting input manager");
        nativeStart(mPtr);

        // Add ourself to the Watchdog monitors.
        Watchdog.getInstance().addMonitor(this);

        registerPointerSpeedSettingObserver();
        registerShowTouchesSettingObserver();

        mContext.registerReceiver(new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                updatePointerSpeedFromSettings();
                updateShowTouchesFromSettings();
            }
        }, new IntentFilter(Intent.ACTION_USER_SWITCHED), null, mHandler);

        updatePointerSpeedFromSettings();
        updateShowTouchesFromSettings();
    }

创建了inputManager，inputManager类型为InputManagerService，并且调用了start()方法，接着调用一个jni方法nativeStart(mPtr)，看一下mPtr的定义

  // Pointer to native input manager service object.
    private final long mPtr;

注意注释// Pointer to native input manager service object，

指向了本地的input manager service对象，mPtr底层传上来的NativeInputManager对象的地址,底层通过调用这个对象的一些方法来回调java层的InputManagerSevice中的一些方法，比如notifyANR就调用到了InputManagerSevice的notifyANR。而mPtr是在InputManagerService的构造函数中通过调用nativeInit()获取的，也就是navtive中的input manager service和java层的input manager service是一起创建的，mPtr的初始化如下：

    public InputManagerService(Context context) {
        this.mContext = context;
        this.mHandler = new InputManagerHandler(DisplayThread.get().getLooper());

        mUseDevInputEventForAudioJack =
                context.getResources().getBoolean(R.bool.config_useDevInputEventForAudioJack);
        Slog.i(TAG, "Initializing input manager, mUseDevInputEventForAudioJack="
                + mUseDevInputEventForAudioJack);
        mPtr = nativeInit(this, mContext, mHandler.getLooper().getQueue());

        LocalServices.addService(InputManagerInternal.class, new LocalService());
    }

nativeInit底层实现如下:

static jlong nativeInit(JNIEnv* env, jclass clazz,
        jobject serviceObj, jobject contextObj, jobject messageQueueObj) {
    sp messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);
    if (messageQueue == NULL) {
        jniThrowRuntimeException(env, "MessageQueue is not initialized.");
        return 0;
    }

    NativeInputManager* im = new NativeInputManager(contextObj, serviceObj,
            messageQueue->getLooper());
    im->incStrong(0);
    return reinterpret_cast(im);
}

这个函数创建了NativeInputManager对方，并且将地址返回给了mPtr，这个NativeInputManager就是回调java层的对象.

nativeStart()的实现在文件

frameworks\base\services\core\jni\com_android_server_input_InputManagerService.cpp 中

static void nativeStart(JNIEnv* env, jclass clazz, jlong ptr) {
    NativeInputManager* im = reinterpret_cast(ptr);

    status_t result = im->getInputManager()->start();
    if (result) {
        jniThrowRuntimeException(env, "Input manager could not be started.");
    }
}

这个函数返回的im对象,

然后start方法实现如下：

status_t InputManager::start() {
    status_t result = mDispatcherThread->run("InputDispatcher", PRIORITY_URGENT_DISPLAY);
    if (result) {
        ALOGE("Could not start InputDispatcher thread due to error %d.", result);
        return result;
    }

    result = mReaderThread->run("InputReader", PRIORITY_URGENT_DISPLAY);
    if (result) {
        ALOGE("Could not start InputReader thread due to error %d.", result);

        mDispatcherThread->requestExit();
        return result;
    }

    return OK;
}

所以跟了这么久最终启动的时候会启动InputDispatcherThread和InputReaderThread两个线程

InputDispatcherThread和InputReaderThread是在InputManager构造方法中创建的

InputManager::InputManager(
        const sp& reader,
        const sp& dispatcher) :
        mReader(reader),
        mDispatcher(dispatcher) {
        initialize();
}

void InputManager::initialize() {
    mReaderThread = new InputReaderThread(mReader);
    mDispatcherThread = new InputDispatcherThread(mDispatcher);
}

mReaderThread是InputReaderThread线程，mDispatcherThread是InputDispatcherThread线程

mReaderThread持有一个InputReader对象

mDispatcherThread持有一个InputDispatcher对象

mReaderThread在轮询设备信息的时候，会回调到InputReader的loopOnce()方法，进而调用到InputDispatcher的方法

void InputReader::loopOnce() {
	......
    // Flush queued events out to the listener.
    // This must happen outside of the lock because the listener could potentially call
    // back into the InputReader's methods, such as getScanCodeState, or become blocked
    // on another thread similarly waiting to acquire the InputReader lock thereby
    // resulting in a deadlock.  This situation is actually quite plausible because the
    // listener is actually the input dispatcher, which calls into the window manager,
    // which occasionally calls into the input reader.
    mQueuedListener->flush();
}

flush()的实现

void QueuedInputListener::flush() {
    size_t count = mArgsQueue.size();
    for (size_t i = 0; i < count; i++) {
        NotifyArgs* args = mArgsQueue[i];
        args->notify(mInnerListener);
        delete args;
    }
    mArgsQueue.clear();
}

呵呵，这个mInnerListener就是InputDispatcher对象，也就inputReader是接收到消息后就通知InputDispatcher
查看以下NotifyArgs的notify实现

void NotifyKeyArgs::notify(const sp& listener) const {
    listener->notifyKey(this);
}

void NotifySwitchArgs::notify(const sp& listener) const {
    listener->notifySwitch(this);
}

void NotifyMotionArgs::notify(const sp& listener) const {
    listener->notifyMotion(this);
}

void NotifyDeviceResetArgs::notify(const sp& listener) const {
    listener->notifyDeviceReset(this);
}

void NotifyConfigurationChangedArgs::notify(const sp& listener) const {
    listener->notifyConfigurationChanged(this);
}

呀，这么多实现呀，会调用哪个呀，其实在收到消息loopOnce被调用的时候，会根据消息类型构造不同的NotifyArgs对象入队，如果是配置发生改变就构造NotifyConfigurationChangedArgs对象入队，调用然后扫描这个队列挨个对象执行notify，有点像观察者模式的变形。

几经波折就是为了告诉你消息的走向为InputReaderThread->InputReader->InputDispatcher  不同的消息回掉InputDispatcher 的不同方法。下面介绍一下这两个线程

InputReaderThread：一个独立的循环线程，不断的轮询设备相关设备节点是否有新的事情发生

/* Reads raw events from the event hub and processes them, endlessly. */
class InputReaderThread : public Thread {
public:
    InputReaderThread(const sp& reader);
    virtual ~InputReaderThread();

private:
    sp mReader;

    virtual bool threadLoop();
};

注意它上面的注视/* Reads raw events from the event hub and processes them, endlessly. */  无止境的读取原始设备信息然后处理之

InputDispatcherThread：与InputReaderThread协同工作，以保证事件正确的派发和处理

/* Enqueues and dispatches input events, endlessly. */
class InputDispatcherThread : public Thread {
public:
    explicit InputDispatcherThread(const sp& dispatcher);
    ~InputDispatcherThread();

private:
    virtual bool threadLoop();

    sp mDispatcher;
};

注意它上面的注视 /* Enqueues and dispatches input events, endlessly. */无止境的分发输入消息

InputDispatcherThread能源源不断的获知系统设备中实时发生的时间，而且它还可以向InputReader注册监听多种事件

notifyConfigurationChanged()
notifyInputChannelBroken()
notifyANR()
......

notifyConfigurationChanged()就是我们要分析的，我们已经分析到notifyConfigurationChanged()被调用的过程

void InputDispatcher::notifyConfigurationChanged(const NotifyConfigurationChangedArgs* args) {
#if DEBUG_INBOUND_EVENT_DETAILS
    ALOGD("notifyConfigurationChanged - eventTime=%lld", args->eventTime);
#endif

    bool needWake;
    { // acquire lock
        AutoMutex _l(mLock);

        ConfigurationChangedEntry* newEntry = new ConfigurationChangedEntry(args->eventTime);
        needWake = enqueueInboundEventLocked(newEntry);
    } // release lock

    if (needWake) {
        mLooper->wake();
    }
}

notifyConfigurationChanged中，构造一个消息实体入队了，当队列有消息入队时thredLoop就会执行，具体thredLoop怎么被调用的还不知道

bool InputDispatcherThread::threadLoop() {
    mDispatcher->dispatchOnce();
    return true;
}

void InputDispatcher::dispatchOnce() {
        ......
        // Run a dispatch loop if there are no pending commands.
        // The dispatch loop might enqueue commands to run afterwards.
        if (!haveCommandsLocked()) {
            dispatchOnceInnerLocked(&nextWakeupTime);
        }

        // Run all pending commands if there are any.
        // If any commands were run then force the next poll to wake up immediately.
        if (runCommandsLockedInterruptible()) {
            nextWakeupTime = LONG_LONG_MIN;
        }
    } // release lock
	......
}

进而调用到dispatchOnceInnerLocked()

void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime)
{
    ......
    switch (mPendingEvent->type) {
    case EventEntry::TYPE_CONFIGURATION_CHANGED: {
        ConfigurationChangedEntry* typedEntry =
                static_cast(mPendingEvent);
        done = dispatchConfigurationChangedLocked(currentTime, typedEntry);
        dropReason = DROP_REASON_NOT_DROPPED; // configuration changes are never dropped
        break;
    }
    ......
}

如果获取到的消息是TYPE_CONFIGURATION_CHANGED则调用dispatchConfigurationChangedLocked

bool InputDispatcher::dispatchConfigurationChangedLocked(
        nsecs_t currentTime, ConfigurationChangedEntry* entry) {
#if DEBUG_OUTBOUND_EVENT_DETAILS
    ALOGD("dispatchConfigurationChanged - eventTime=%lld", entry->eventTime);
#endif

    // Reset key repeating in case a keyboard device was added or removed or something.
    resetKeyRepeatLocked();

    // Enqueue a command to run outside the lock to tell the policy that the configuration changed.
    CommandEntry* commandEntry = postCommandLocked(
            & InputDispatcher::doNotifyConfigurationChangedInterruptible);
    commandEntry->eventTime = entry->eventTime;
    return true;
}

void InputDispatcher::doNotifyConfigurationChangedInterruptible(
        CommandEntry* commandEntry) {
    mLock.unlock();

    mPolicy->notifyConfigurationChanged(commandEntry->eventTime);

    mLock.lock();
}

mPolicy->notifyConfigurationChanged(commandEntry->eventTime)会回调到InputManagerService.java的notifyConfigurationChanged

    // Native callback.
    private void notifyConfigurationChanged(long whenNanos) {
        mWindowManagerCallbacks.notifyConfigurationChanged();
    }

如上源码里面已经注释了这是native的回调

mWindowManagerCallbacks是什么，回到SystemService的main中有这么一句话

            wm = WindowManagerService.main(context, inputManager,
                    mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,
                    !mFirstBoot, mOnlyCore);
            ServiceManager.addService(Context.WINDOW_SERVICE, wm);
            ServiceManager.addService(Context.INPUT_SERVICE, inputManager);

            mActivityManagerService.setWindowManager(wm);

            inputManager.setWindowManagerCallbacks(wm.getInputMonitor());
            inputManager.start();

mWindowManagerCallbacks是WindowManagerService中的一个InputMonitor成员,所以又进一步调用到了InputMonitor的notifyConfigurationChanged方法

    public void notifyConfigurationChanged() {
        mService.sendNewConfiguration();

        synchronized (mInputDevicesReadyMonitor) {
            if (!mInputDevicesReady) {
                mInputDevicesReady = true;
                mInputDevicesReadyMonitor.notifyAll();
            }
        }
    }

mService为WindowManagerService，sendNewConfiguration实现

    void sendNewConfiguration() {
        try {
            mActivityManager.updateConfiguration(null);
        } catch (RemoteException e) {
        }
    }

mActivityManager为ActivityManagerService，并调用到它的updateConfiguration

    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);
        }
    }

   boolean updateConfigurationLocked(Configuration values,
            ActivityRecord starting, boolean persistent, boolean initLocale)
                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) {
                    }
                }
	}

app.thread.scheduleConfigurationChanged(configCopy);这是一个binder远程调用，会调用到ActivityThread的scheduleConfigurationChanged，这就总算调用到我们的应用程序了

大家跟着标红的函数放下走

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

发了一个CONFIGURATION_CHANGED，处理过程在handle中

                case CONFIGURATION_CHANGED:
                    Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "configChanged");
                    mCurDefaultDisplayDpi = ((Configuration)msg.obj).densityDpi;
                    handleConfigurationChanged((Configuration)msg.obj, null);
                    Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                    break;

    final void handleConfigurationChanged(Configuration config, CompatibilityInfo compat) {
	......
        ArrayList callbacks = collectComponentCallbacks(false, config);
        if (callbacks != null) {
            final int N = callbacks.size();
            for (int i=0; i

对每个callback执行performConfigurationChanged方法

ArrayList callbacks = collectComponentCallbacks(false, config);

callbacks 是本进程所有的application、activity、service、contentprovider的集合，看它的实现就知道了

    ArrayList collectComponentCallbacks(
            boolean allActivities, Configuration newConfig) {
        ArrayList callbacks
                = new ArrayList();

        synchronized (mResourcesManager) {
            final int NAPP = mAllApplications.size();
            for (int i=0; i                    if (!ar.activity.mFinished && (allActivities || !ar.paused)) {
                   
                        callbacks.add(a);
                    } else if (thisConfig != null) {
         .
                        if (DEBUG_CONFIGURATION) {
                            Slog.v(TAG, "Setting activity "
                                    + ar.activityInfo.name + " newConfig=" + thisConfig);
                        }
                        ar.newConfig = thisConfig;
                    }
                }
            }
            final int NSVC = mServices.size();
            for (int i=0; i

因为application、activity、service、contentprovider都实现了ComponentCallbacks2接口。

根据条件可知

          if (!ar.activity.mFinished && (allActivities || !ar.paused)) {
                        callbacks.add(a);
                    } 

只有没有finish()掉的和没有paused掉的Acitivity才会被加到callbacks当中。

    private static void performConfigurationChanged(ComponentCallbacks2 cb, Configuration config) {
      ......

        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);
            }
        }
    }

cb是从callbacks集合中取出来的，cb.onConfigurationChanged(config);总算看到onConfigurationChanged方法被调用到了，这个cb就是activity、application、service、contentProvider中的一个。当然在callbacks里面的activity不一定都会毁掉onConfigurationChanged,还要根据一些activity的配置项去决定是否回调onConfigurationChanged

这就是整个onConfigureChange回凋流程。

其实不仅仅是onConfigureChange遵循这个流程，像按键消息、触摸消息也是这么一个流程