Android系统默认使用的关屏效果是fade，要激活旧CRT效果，需要修改以下文件，关闭fade效果。

frameworks/base/core/res/res/values/config.xml

- true

+ false

为啥如此修改就可以激活旧CRT效果，让我们跟踪下代码，先贴上相关代码：

frameworks\base\services\java\com\android\server\PowerManagerService.java

475 mAnimationSetting = 0;

476 if (windowScale > 0.5f) {

477 mAnimationSetting |= ANIM_SETTING_OFF;

478 }

2284 public void run() {

2285 if (mAnimateScreenLights) {

2286 synchronized (mLocks) {

2287 long now = SystemClock.uptimeMillis();

2288 boolean more = mScreenBrightness.stepLocked();

2289 if (more) {

2290 mScreenOffHandler.postAtTime(this, now+(1000/60));

2291 }

2292 }

2293 } else {

2294 synchronized (mLocks) {

2295 // we're turning off

2296 final boolean animate = animating && targetValue == Power.BRIGHTNESS_OFF;

2297 if (animate) {

2298 // It's pretty scary to hold mLocks for this long, and we should

2299 // redesign this, but it works for now.

2300 nativeStartSurfaceFlingerAnimation(

2301 mScreenOffReason == WindowManagerPolicy.OFF_BECAUSE_OF_PROX_SENSOR

2302 0 : mAnimationSetting);

2303 }

2304 mScreenBrightness.jumpToTargetLocked();

2305 }

2306 }

2307 }

2308 }

frameworks/base/services/jni/com_android_server_PowerManagerService.cpp

131 static void android_server_PowerManagerService_nativeStartSurfaceFlingerAnimation(JNIEnv* env,

132 jobject obj, jint mode) {

133 sp s(ComposerService::getComposerService());

134 s->turnElectronBeamOff(mode);

135 }

frameworks/base/services/surfaceflinger/SurfaceFlinger.cpp

2385 status_t SurfaceFlinger::turnElectronBeamOff(int32_t mode)

2386 {

2387 class MessageTurnElectronBeamOff : public MessageBase {

2388 SurfaceFlinger* flinger;

2389 int32_t mode;

2390 status_t result;

2391 public:

2392 MessageTurnElectronBeamOff(SurfaceFlinger* flinger, int32_t mode)

2393 : flinger(flinger), mode(mode), result(PERMISSION_DENIED) {

2394 }

2395 status_t getResult() const {

2396 return result;

2397 }

2398 virtual bool handler() {

2399 Mutex::Autolock _l(flinger->mStateLock);

2400 result = flinger->turnElectronBeamOffImplLocked(mode);

2401 return true;

2402 }

2403 };

2404

2405 sp msg = new MessageTurnElectronBeamOff(this, mode);

2406 status_t res = postMessageSync(msg);

2407 if (res == NO_ERROR) {

2408 res = static_cast( msg.get() )->getResult();

2409

2410 // work-around: when the power-manager calls us we activate the

2411 // animation. eventually, the "on" animation will be called