Android 7.1.2(Android N) BootaAimation–开机动画显示流程

@(izhoujinjian)
高清原文

Android系统底层基于Linux Kernel, 当Kernel启动过程会创建init进程, 该进程是uoyou用户空间的鼻祖, init进程会启动servicemanager(binder服务管家), Zygote进程(Java进程的鼻祖). Zygote进程会创建 system_server进程以及各种app进程。init是Linux系统中用户空间的第一个进程(pid=1), Kerner启动后会调用/system/core/init/Init.cpp的main()方法，会解析surfaceflinger.rc中的服务。开机动画是在什么时候启动的呢？通过查看源码，android开机动画是在启动SurfaceFlinger服务时启动的。
Android N的.rc文件跟之前的版本有一些改变，具体可参考：Android 7.0 init.rc的一点改变

/frameworks/native/services/surfaceflinger/surfaceflinger.rc

service surfaceflinger /system/bin/surfaceflingerclass coreuser systemgroup graphics drmrpconrestart restart zygotewritepid /dev/cpuset/system-background/tasks

surfaceflinger服务属于核心类(core class)，另外，当surfaceflinger重启时会触发zygote的重启。从surfaceflinger的 Android.mk文件可知，surfaceflinger服务启动的起点便是如下main_surfaceflinger的main()函数。

/frameworks/native/services/surfaceflinger/Android.mk

LOCAL_INIT_RC := surfaceflinger.rc......LOCAL_SRC_FILES := \   main_surfaceflinger.cpp......LOCAL_MODULE := surfaceflinger

/frameworks/native/services/surfaceflinger/main_surfaceflinger.cpp

int main(int, char**) {signal(SIGPIPE, SIG_IGN);// When SF is launched in its own process, limit the number of// binder threads to 4.ProcessState::self()->setThreadPoolMaxThreadCount(4);// start the thread poolsp ps(ProcessState::self());ps->startThreadPool();// instantiate surfaceflinger 实例化surfaceflingersp flinger = new SurfaceFlinger();setpriority(PRIO_PROCESS, 0, PRIORITY_URGENT_DISPLAY);set_sched_policy(0, SP_FOREGROUND);#ifdef ENABLE_CPUSETS// Put most SurfaceFlinger threads in the system-background cpuset// Keeps us from unnecessarily using big cores// Do this after the binder thread pool initset_cpuset_policy(0, SP_SYSTEM);#endif// initialize before clients can connect 初始化flinger->init();// publish surface flinger 发布surface flinger，注册到Service Managersp sm(defaultServiceManager());sm->addService(String16(SurfaceFlinger::getServiceName()), flinger, false);// publish GpuServicesp gpuservice = new GpuService();sm->addService(String16(GpuService::SERVICE_NAME), gpuservice, false);struct sched_param param = {0};param.sched_priority = 2;if (sched_setscheduler(0, SCHED_FIFO, ¶m) != 0) {    ALOGE("Couldn't set SCHED_FIFO");}// run surface flinger in this thread 运行在当前线程flinger->run();return 0;}

该方法的主要功能：

设定surfaceflinger进程的binder线程池个数上限为4，并启动binder线程池；
创建SurfaceFlinger对；
设置surfaceflinger进程为高优先级以及前台调度策略；
初始化SurfaceFlinger；
将”SurfaceFlinger”服务注册到Service Manager;
在当前主线程执行SurfaceFlinger的run方法；

实例化surfaceflinger，sp flinger = new SurfaceFlinger();

/frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp

SurfaceFlinger::SurfaceFlinger():   BnSurfaceComposer(),    mTransactionFlags(0),    mTransactionPending(false),    mAnimTransactionPending(false),    mLayersRemoved(false),    mRepaintEverything(0),    mRenderEngine(NULL),    mBootTime(systemTime()),    mBuiltinDisplays(),    mVisibleRegionsDirty(false),    mGeometryInvalid(false),    mAnimCompositionPending(false),    mDebugRegion(0),    mDebugDDMS(0),    mDebugDisableHWC(0),    mDebugDisableTransformHint(0),    mDebugInSwapBuffers(0),    mLastSwapBufferTime(0),    mDebugInTransaction(0),    mLastTransactionTime(0),    mBootFinished(false),    mForceFullDamage(false),    mPrimaryDispSync("PrimaryDispSync"),    mPrimaryHWVsyncEnabled(false),    mHWVsyncAvailable(false),    mHasColorMatrix(false),    mHasPoweredOff(false),    mFrameBuckets(),    mTotalTime(0),    mLastSwapTime(0)    {ALOGI("SurfaceFlinger is starting");// debugging stuff...char value[PROPERTY_VALUE_MAX];property_get("ro.bq.gpu_to_cpu_unsupported", value, "0");mGpuToCpuSupported = !atoi(value);property_get("debug.sf.showupdates", value, "0");mDebugRegion = atoi(value);property_get("debug.sf.ddms", value, "0");mDebugDDMS = atoi(value);if (mDebugDDMS) {    if (!startDdmConnection()) {        // start failed, and DDMS debugging not enabled        mDebugDDMS = 0;    }}ALOGI_IF(mDebugRegion, "showupdates enabled");ALOGI_IF(mDebugDDMS, "DDMS debugging enabled");property_get("debug.sf.disable_backpressure", value, "0");mPropagateBackpressure = !atoi(value);ALOGI_IF(!mPropagateBackpressure, "Disabling backpressure propagation");property_get("debug.sf.disable_hwc_vds", value, "0");mUseHwcVirtualDisplays = !atoi(value);ALOGI_IF(!mUseHwcVirtualDisplays, "Disabling HWC virtual displays");}

SurfaceFlinger继承于BnSurfaceComposer: public BnInterface ，class BnInterface : public INTERFACE, public BBinder，class BBinder : public IBinder，class IBinder : public virtual RefBase。
由于SurfaceFlinger继承于RefBase类，并重写了该类的onFirstRef()函数，我们知道，RefBase类的子类对象在第一次创建时，会自动调用onFirstRef()函数，因此在SurfaceFlinger对象构造完成时，将调用onFirstRef()函数。

<---SurfaceFlinger.cpp--->void SurfaceFlinger::onFirstRef(){mEventQueue.init(this);}

这里不对SurfaceFlinger的相关内容做详细介绍，本文的主要内容是介绍开机动画显示过程。

直接看SurfaceFlinger初始化 flinger->init();

<---SurfaceFlinger.cpp--->void SurfaceFlinger::init() {ALOGI(  "SurfaceFlinger's main thread ready to run. "        "Initializing graphics H/W...");{ // Autolock scope    Mutex::Autolock _l(mStateLock);    // initialize EGL for the default display    mEGLDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);    eglInitialize(mEGLDisplay, NULL, NULL);    // start the EventThread    sp vsyncSrc = new DispSyncSource(&mPrimaryDispSync,            vsyncPhaseOffsetNs, true, "app");    mEventThread = new EventThread(vsyncSrc, *this);    sp sfVsyncSrc = new DispSyncSource(&mPrimaryDispSync,            sfVsyncPhaseOffsetNs, true, "sf");    mSFEventThread = new EventThread(sfVsyncSrc, *this);    mEventQueue.setEventThread(mSFEventThread);    // set SFEventThread to SCHED_FIFO to minimize jitter    struct sched_param param = {0};    param.sched_priority = 2;    if (sched_setscheduler(mSFEventThread->getTid(), SCHED_FIFO, ¶m) != 0) {        ALOGE("Couldn't set SCHED_FIFO for SFEventThread");    }    // Get a RenderEngine for the given display / config (can't fail)    mRenderEngine = RenderEngine::create(mEGLDisplay,            HAL_PIXEL_FORMAT_RGBA_8888);}// Drop the state lock while we initialize the hardware composer. We drop// the lock because on creation, it will call back into SurfaceFlinger to// initialize the primary display.mHwc = new HWComposer(this);mHwc->setEventHandler(static_cast(this));Mutex::Autolock _l(mStateLock);// retrieve the EGL context that was selected/createdmEGLContext = mRenderEngine->getEGLContext();LOG_ALWAYS_FATAL_IF(mEGLContext == EGL_NO_CONTEXT,        "couldn't create EGLContext");// make the GLContext current so that we can create textures when creating// Layers (which may happens before we render something)getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);mEventControlThread = new EventControlThread(this);mEventControlThread->run("EventControl", PRIORITY_URGENT_DISPLAY);// initialize our drawing statemDrawingState = mCurrentState;// set initial conditions (e.g. unblank default device)initializeDisplays();mRenderEngine->primeCache();// start boot animationstartBootAnim();ALOGV("Done initializing");}

该函数首先是初始化Android的图形显示系统，启动SurfaceFlinger事件线程，这些内容只有了解了Android的显示原理及SurfaceFlinger服务之后才能理解，这里不做介绍。当显示系统初始化完毕后，调用startBootAnim()函数来显示开机动画。

<---SurfaceFlinger.cpp--->void SurfaceFlinger::startBootAnim() {// start boot animationproperty_set("service.bootanim.exit", "0");property_set("ctl.start", "bootanim");}

启动开机动画进程也是通过Android属性系统来实现的，具体启动过程可以查看Android 系统属性SystemProperty实现方式。在Android系统启动脚本bootanim .rc中配置了开机动画服务进程。
/frameworks/base/cmds/bootanimation/bootanim.rc

service bootanim /system/bin/bootanimationclass coreuser graphicsgroup graphics audiodisabledoneshotwritepid /dev/stune/top-app/tasks

property_set("ctl.start", "bootanim");就是启动bootanim进程来显示开机动画，该进程对应的源码位于

/frameworks/base/cmds/bootanimation/bootanimation_main.cpp

int main(){setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_DISPLAY);char value[PROPERTY_VALUE_MAX];property_get("debug.sf.nobootanimation", value, "0");int noBootAnimation = atoi(value);ALOGI_IF(noBootAnimation,  "boot animation disabled");if (!noBootAnimation) {    sp proc(ProcessState::self());    ProcessState::self()->startThreadPool();    // create the boot animation object    sp boot = new BootAnimation();    IPCThreadState::self()->joinThreadPool();}return 0;}

该函数构造了一个BootAnimation对象，同时创建了Binder线程池，并将bootanim进程的主线程注册到Binder线程池中，用于接收客户进程的Binder通信请求。

/frameworks/base/cmds/bootanimation/BootAnimation.cpp

BootAnimation::BootAnimation() : Thread(false), mClockEnabled(true), mTimeIsAccurate(false),    mTimeFormat12Hour(false), mTimeCheckThread(NULL) {mSession = new SurfaceComposerClient();// If the system has already booted, the animation is not being used for a boot.mSystemBoot = !property_get_bool(BOOT_COMPLETED_PROP_NAME, 0);}

在构造BootAnimation对象时，实例化SurfaceComposerClient对象，用于请求SurfaceFlinger显示开关机动画。由于BootAnimation类继承于RefBase，同时重写了onFirstRef()函数，因此在构造BootAnimation对象时，会调用该函数。

void BootAnimation::onFirstRef() {status_t err = mSession->linkToComposerDeath(this);ALOGE_IF(err, "linkToComposerDeath failed (%s) ", strerror(-err));if (err == NO_ERROR) {    run("BootAnimation", PRIORITY_DISPLAY);}}

该函数首先为SurfaceComposerClient对象注册Binder死亡通知,然后调用BootAnimation的run方法,由于BootAnimation同时继承于Thread类,前面介绍SurfaceFlinger时已经介绍到,当某个类继承于Thread类时,当调用该类的run函数时,函数首先会执行readyToRun()函数来完成线程执行前的一些工作,然后线程反复执行threadLoop()函数,在BootAnimation类中,同样重新了这两个方法。

static const char OEM_BOOTANIMATION_FILE[] = "/oem/media/bootanimation.zip";static const char SYSTEM_BOOTANIMATION_FILE[] = "/system/media/bootanimation.zip";static const char SYSTEM_ENCRYPTED_BOOTANIMATION_FILE[] = "/system/media/bootanimation-encrypted.zip";status_t BootAnimation::readyToRun() {mAssets.addDefaultAssets();sp dtoken(SurfaceComposerClient::getBuiltInDisplay(        ISurfaceComposer::eDisplayIdMain));DisplayInfo dinfo;status_t status = SurfaceComposerClient::getDisplayInfo(dtoken, &dinfo);if (status)    return -1;// create the native surfacesp control = session()->createSurface(String8("BootAnimation"),        dinfo.w, dinfo.h, PIXEL_FORMAT_RGB_565);SurfaceComposerClient::openGlobalTransaction();control->setLayer(0x40000000);SurfaceComposerClient::closeGlobalTransaction();sp s = control->getSurface();// initialize opengl and eglconst EGLint attribs[] = {        EGL_RED_SIZE,   8,        EGL_GREEN_SIZE, 8,        EGL_BLUE_SIZE,  8,        EGL_DEPTH_SIZE, 0,        EGL_NONE};EGLint w, h;EGLint numConfigs;EGLConfig config;EGLSurface surface;EGLContext context;EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);eglInitialize(display, 0, 0);eglChooseConfig(display, attribs, &config, 1, &numConfigs);surface = eglCreateWindowSurface(display, config, s.get(), NULL);context = eglCreateContext(display, config, NULL, NULL);eglQuerySurface(display, surface, EGL_WIDTH, &w);eglQuerySurface(display, surface, EGL_HEIGHT, &h);if (eglMakeCurrent(display, surface, surface, context) == EGL_FALSE)    return NO_INIT;mDisplay = display;mContext = context;mSurface = surface;mWidth = w;mHeight = h;mFlingerSurfaceControl = control;mFlingerSurface = s;// If the device has encryption turned on or is in process// of being encrypted we show the encrypted boot animation.char decrypt[PROPERTY_VALUE_MAX];property_get("vold.decrypt", decrypt, "");bool encryptedAnimation = atoi(decrypt) != 0 || !strcmp("trigger_restart_min_framework", decrypt);if (encryptedAnimation && (access(SYSTEM_ENCRYPTED_BOOTANIMATION_FILE, R_OK) == 0)) {    mZipFileName = SYSTEM_ENCRYPTED_BOOTANIMATION_FILE;}else if (access(OEM_BOOTANIMATION_FILE, R_OK) == 0) {    mZipFileName = OEM_BOOTANIMATION_FILE;}else if (access(SYSTEM_BOOTANIMATION_FILE, R_OK) == 0) {    mZipFileName = SYSTEM_BOOTANIMATION_FILE;}return NO_ERROR;}

在该函数里创建SurfaceControl对象,通过SurfaceControl对象得到Surface对象,并初始化好OpenGL，同时判断动画文件是否存在，如果不存在，则设置标志位mAndroidAnimation为true，表示显示Android滚动字样。当初始化完这些必需资源后，线程进入循环执行体threadLoop()。

bool BootAnimation::threadLoop(){bool r;// We have no bootanimation file, so we use the stock android logo// animation.如果mAndroidAnimation为true，表示动画文件不存在，则显示Android滚动字样  if (mZipFileName.isEmpty()) {    r = android();} else {//显示动画      r = movie();}//资源回收  eglMakeCurrent(mDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);eglDestroyContext(mDisplay, mContext);eglDestroySurface(mDisplay, mSurface);mFlingerSurface.clear();mFlingerSurfaceControl.clear();eglTerminate(mDisplay);IPCThreadState::self()->stopProcess();return r;}

开机画面主要是由一个zip格式的压缩包bootanimation.zip组成，压缩包里面包含数张png格式的图片，还有一个desc.txt的文本文档，开机时按desc.txt里面的指令，屏幕上会按文件名称顺序连续的播放一张张的图片，就像播放原始的胶带影片一样，形成动画。desc.txt是一个保存形式为ANSI格式的文件，用于设置这个动画像素（大小），帧数，闪烁次数，文件夹名称等。内容如下（bootanimation.zip基于Google pixel手机Android 7.1.2）：

1440 240 60c 1 0 part0 #FFFFFF -1c 0 0 part1 #FFFFFF -1c 1 0 part2 #FFFFFF -1

1440 240 60 ---这里的1440 代表图片的像素（大小）宽度，240 代表图片的像素（大小）高度，60 代表帧数；

c 1 0 part0 ---这里的c代表标志符，1代表循环次数为1次，0代表阶段间隔时间为0，part0代表对应的文件夹名，为第一阶段动画图片目录；

c 0 0 part1---这里的c代表标志符，0代表本阶段无限循环，0代表阶段间隔时间为0，part1代表对应的文件夹名，为第二阶段动画图片目录；

c 1 0 part2---这里的c代表标志符，1代表本阶段无限循环，0代表阶段间隔时间为0，part2代表对应的文件夹名，为第三阶段动画图片目录；

bootanimation.gif

bootanimation.zip && bootanimation.gif

bool BootAnimation::movie(){//加载动画文件Animation* animation = loadAnimation(mZipFileName);if (animation == NULL)    return false;bool anyPartHasClock = false;for (size_t i=0; i < animation->parts.size(); i++) {    if(validClock(animation->parts[i])) {        anyPartHasClock = true;        break;    }}if (!anyPartHasClock) {    mClockEnabled = false;}// Check if npot textures are supportedmUseNpotTextures = false;String8 gl_extensions;const char* exts = reinterpret_cast(glGetString(GL_EXTENSIONS));if (!exts) {    glGetError();} else {    gl_extensions.setTo(exts);    if ((gl_extensions.find("GL_ARB_texture_non_power_of_two") != -1) ||        (gl_extensions.find("GL_OES_texture_npot") != -1)) {        mUseNpotTextures = true;    }}// Blend required to draw time on top of animation frames.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);glShadeModel(GL_FLAT);glDisable(GL_DITHER);glDisable(GL_SCISSOR_TEST);glDisable(GL_BLEND);glBindTexture(GL_TEXTURE_2D, 0);glEnable(GL_TEXTURE_2D);glTexEnvx(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);bool clockFontInitialized = false;if (mClockEnabled) {    clockFontInitialized =        (initFont(&animation->clockFont, CLOCK_FONT_ASSET) == NO_ERROR);    mClockEnabled = clockFontInitialized;}if (mClockEnabled && !updateIsTimeAccurate()) {    mTimeCheckThread = new TimeCheckThread(this);    mTimeCheckThread->run("BootAnimation::TimeCheckThread", PRIORITY_NORMAL);}//播放动画playAnimation(*animation);if (mTimeCheckThread != NULL) {    mTimeCheckThread->requestExit();    mTimeCheckThread = NULL;}releaseAnimation(animation);if (clockFontInitialized) {    glDeleteTextures(1, &animation->clockFont.texture.name);}return false;}

进入loadAnimation()函数。

BootAnimation::Animation* BootAnimation::loadAnimation(const String8& fn){if (mLoadedFiles.indexOf(fn) >= 0) {    ALOGE("File \"%s\" is already loaded. Cyclic ref is not allowed",        fn.string());    return NULL;}ZipFileRO *zip = ZipFileRO::open(fn);if (zip == NULL) {    ALOGE("Failed to open animation zip \"%s\": %s",        fn.string(), strerror(errno));    return NULL;}Animation *animation =  new Animation;animation->fileName = fn;animation->zip = zip;animation->clockFont.map = nullptr;mLoadedFiles.add(animation->fileName);parseAnimationDesc(*animation);if (!preloadZip(*animation)) {    return NULL;}mLoadedFiles.remove(fn);return animation;}bool BootAnimation::parseAnimationDesc(Animation& animation){String8 desString;//打开zip压缩文件中的desc.txt文件if (!readFile(animation.zip, "desc.txt", desString)) {    return false;}char const* s = desString.string();//解析desc.txt文件内容  // Parse the description filefor (;;) {//从字符串s中查找是否有字符串"\n"，如果有，返回s中"\n"起始位置的指针，如果没有，返回null。      const char* endl = strstr(s, "\n");    if (endl == NULL) break;    String8 line(s, endl - s);    //取得文件一行内容    const char* l = line.string();    int fps = 0;    int width = 0;    int height = 0;    int count = 0;    int pause = 0;    char path[ANIM_ENTRY_NAME_MAX];    char color[7] = "000000"; // default to black if unspecified    char clockPos1[TEXT_POS_LEN_MAX + 1] = "";    char clockPos2[TEXT_POS_LEN_MAX + 1] = "";    char pathType;    //从文件第一行中读取宽度，高度，帧数      if (sscanf(l, "%d %d %d", &width, &height, &fps) == 3) {        // ALOGD("> w=%d, h=%d, fps=%d", width, height, fps);        animation.width = width;        animation.height = height;        animation.fps = fps;    } else if (sscanf(l, " %c %d %d %s #%6s %16s %16s",                      &pathType, &count, &pause, path, color, clockPos1, clockPos2) >= 4) {        //ALOGD("> type=%c, count=%d, pause=%d, path=%s, color=%s, clockPos1=%s, clockPos2=%s",        //    pathType, count, pause, path, color, clockPos1, clockPos2);        //    一个part描述一个动画文件夹内容          Animation::Part part;        part.playUntilComplete = pathType == 'c';        part.count = count;        part.pause = pause;        part.path = path;        part.audioData = NULL;        part.animation = NULL;        if (!parseColor(color, part.backgroundColor)) {            ALOGE("> invalid color '#%s'", color);            part.backgroundColor[0] = 0.0f;            part.backgroundColor[1] = 0.0f;            part.backgroundColor[2] = 0.0f;        }        parsePosition(clockPos1, clockPos2, &part.clockPosX, &part.clockPosY);        animation.parts.add(part);    }    else if (strcmp(l, "$SYSTEM") == 0) {        // ALOGD("> SYSTEM");        Animation::Part part;        part.playUntilComplete = false;        part.count = 1;        part.pause = 0;        part.audioData = NULL;        part.animation = loadAnimation(String8(SYSTEM_BOOTANIMATION_FILE));        if (part.animation != NULL)            animation.parts.add(part);    }    s = ++endl;}return true;

}

进入playAnimation()、releaseAnimation()数。

 bool BootAnimation::playAnimation(const Animation& animation){//读取动画个数  const size_t pcount = animation.parts.size();nsecs_t frameDuration = s2ns(1) / animation.fps;const int animationX = (mWidth - animation.width) / 2;const int animationY = (mHeight - animation.height) / 2;//遍历zip压缩包中的所有文件  for (size_t i=0 ; i 0) {                glBindTexture(GL_TEXTURE_2D, frame.tid);            } else {                if (part.count != 1) {                    glGenTextures(1, &frame.tid);                    glBindTexture(GL_TEXTURE_2D, frame.tid);                    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);                    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);                }                int w, h;                initTexture(frame.map, &w, &h);            }            const int xc = animationX + frame.trimX;            const int yc = animationY + frame.trimY;            Region clearReg(Rect(mWidth, mHeight));            clearReg.subtractSelf(Rect(xc, yc, xc+frame.trimWidth, yc+frame.trimHeight));            if (!clearReg.isEmpty()) {                Region::const_iterator head(clearReg.begin());                Region::const_iterator tail(clearReg.end());                glEnable(GL_SCISSOR_TEST);                while (head != tail) {                    const Rect& r2(*head++);                    glScissor(r2.left, mHeight - r2.bottom, r2.width(), r2.height());                    glClear(GL_COLOR_BUFFER_BIT);                }                glDisable(GL_SCISSOR_TEST);            }            // specify the y center as ceiling((mHeight - frame.trimHeight) / 2)            // which is equivalent to mHeight - (yc + frame.trimHeight)            glDrawTexiOES(xc, mHeight - (yc + frame.trimHeight),                          0, frame.trimWidth, frame.trimHeight);            if (mClockEnabled && mTimeIsAccurate && validClock(part)) {                drawClock(animation.clockFont, part.clockPosX, part.clockPosY);            }            eglSwapBuffers(mDisplay, mSurface);            nsecs_t now = systemTime();            nsecs_t delay = frameDuration - (now - lastFrame);            //ALOGD("%lld, %lld", ns2ms(now - lastFrame), ns2ms(delay));            lastFrame = now;            if (delay > 0) {                struct timespec spec;                spec.tv_sec  = (now + delay) / 1000000000;                spec.tv_nsec = (now + delay) % 1000000000;                int err;                do {                    err = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &spec, NULL);                } while (err<0 && errno == EINTR);            }            checkExit();        }        usleep(part.pause * ns2us(frameDuration));        // For infinite parts, we've now played them at least once, so perhaps exit        if(exitPending() && !part.count)            break;    }}// Free textures created for looping parts now that the animation is done.for (const Animation::Part& part : animation.parts) {    if (part.count != 1) {        const size_t fcount = part.frames.size();        for (size_t j = 0; j < fcount; j++) {            const Animation::Frame& frame(part.frames[j]);            glDeleteTextures(1, &frame.tid);        }    }}// we've finally played everything we're going to playaudioplay::setPlaying(false);audioplay::destroy();return true;}void BootAnimation::releaseAnimation(Animation* animation) const{for (Vector::iterator it = animation->parts.begin(),     e = animation->parts.end(); it != e; ++it) {    if (it->animation)        releaseAnimation(it->animation);}if (animation->zip)    delete animation->zip;delete animation;}

参考文档：

Android 7.0 init.rc的一点改变
Android 开机动画显示源码分析

Android 7.1.2(Android N) BootaAimation–开机动画显示流程