Android7.1在SurfaceFlinger实时显示帧率

1.在frameworks/native/services/surfaceflinger/SurfaceFlinger.h
class SurfaceFlinger : public BnSurfaceComposer, private IBinder::DeathRecipient,private HWComposer::EventHandler{
  void debugShowFPS(); //add
  mat4 mPreviousColorMatrix;
};

2.在frameworks/native/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
oid SurfaceFlinger::debugShowFPS(){
/*
  uint32_t flipCount = getDefaultDisplayDevice()->getPageFlipCount();
  flipCount: SurfaceFlinger合成帧次数,即向屏幕提交多少帧数据.
  在t1 时刻获取 mPageFlipCount 的数值 v1，在在 t2时刻获取 mPageFlipCount 的数值 v2，FPS 的计算公式：
  FPS = (v2 - v1) / (t2 - t1);
*/
  static int mFrameCount; //就是flipCount的值,static全局变量
  static int mLastFrameCount = 0;
  static nsecs_t mLastFpsTime = 0;
  static float mFps = 0;
  char value[16];

  mFrameCount++;
  nsecs_t now = systemTime();
  nsecs_t diff = now - mLastFpsTime;
  ALOGE(“xxx———> %s(), %d, startTime = %tu",__FUNCTION__,__LINE__,mLastFpsTime/(1000*1000));//ms
  ALOGE(“xxx———> %s(), %d, endTime = %tu",__FUNCTION__,__LINE__,now/(1000*1000));//ms
  ALOGE(“xxx———> %s(), %d, diff = %tu",__FUNCTION__,__LINE__,diff/(1000*1000));//ms
  ALOGE(“xxx———> %s(), %d, mFrameCount = %d",__FUNCTION__,__LINE__,mFrameCount);//
  //if(diff > ms2ns(250)) {//250ms显示一次
  if(diff > ms2ns(1000)) {//1s显示一次
     ALOGE("zgj------> %s(), %d, mCount ================ %d",__FUNCTION__,__LINE__,mFrameCount - mLastFrameCount);//mCount:SurfaceFlinger1s合成的帧率
     mFps = ((mFrameCount - mLastFrameCount) * float(s2ns(1))) / diff;
     mLastFpsTime = now;
     mLastFrameCount = mFrameCount;

     property_get("debug.showfps.flags", value, "0");
     if (value[0] == '1') {
      ALOGE(“xxx———> %s(), %d, fps ======================>  %.2f",__FUNCTION__,__LINE__,mFps);
     }
   }
}

3.编译
# mm
注意：此时需要拷贝system/lib64/libsurfaceflinger.so,然后push到设备的/system/lib64下，重启或杀死surfaceflinger即可.
4.启动打印
# adb shell setprop debug.showfps.flags 1