Android测量每秒帧数Frames Per Second (FPS)的方法

package net.obviam.droidz;import java.text.DecimalFormat;import android.graphics.Canvas;import android.util.Log;import android.view.SurfaceHolder;/** * @author impaler * * The Main thread which contains the game loop. The thread must have access to * the surface view and holder to trigger events every game tick. */public class MainThread extends Thread { private static final String TAG = MainThread.class.getSimpleName(); // desired fps private final static int MAX_FPS = 50; // maximum number of frames to be skipped private final static int MAX_FRAME_SKIPS = 5; // the frame period private final static int FRAME_PERIOD = 1000 / MAX_FPS; // Stuff for stats */ private DecimalFormat df = new DecimalFormat("0.##"); // 2 dp // we'll be reading the stats every second private final static int STAT_INTERVAL = 1000; //ms // the average will be calculated by storing // the last n FPSs private final static int FPS_HISTORY_NR = 10; // last time the status was stored private long lastStatusStore = 0; // the status time counter private long statusIntervalTimer = 0l; // number of frames skipped since the game started private long totalFramesSkipped   = 0l; // number of frames skipped in a store cycle (1 sec) private long framesSkippedPerStatCycle = 0l; // number of rendered frames in an interval private int frameCountPerStatCycle = 0; private long totalFrameCount = 0l; // the last FPS values private double fpsStore[]; // the number of times the stat has been read private long statsCount = 0; // the average FPS since the game started private double averageFps = 0.0; // Surface holder that can access the physical surface private SurfaceHolder surfaceHolder; // The actual view that handles inputs // and draws to the surface private MainGamePanel gamePanel; // flag to hold game state private boolean running; public void setRunning(boolean running) {  this.running = running; } public MainThread(SurfaceHolder surfaceHolder, MainGamePanel gamePanel) {  super();  this.surfaceHolder = surfaceHolder;  this.gamePanel = gamePanel; } @Override public void run() {  Canvas canvas;  Log.d(TAG, "Starting game loop");  // initialise timing elements for stat gathering  initTimingElements();  long beginTime;  // the time when the cycle begun  long timeDiff;  // the time it took for the cycle to execute  int sleepTime;  // ms to sleep (<0 if we're behind)  int framesSkipped; // number of frames being skipped   sleepTime = 0;  while (running) {   canvas = null;   // try locking the canvas for exclusive pixel editing   // in the surface   try {    canvas = this.surfaceHolder.lockCanvas();    synchronized (surfaceHolder) {     beginTime = System.currentTimeMillis();     framesSkipped = 0; // resetting the frames skipped     // update game state     this.gamePanel.update();     // render state to the screen     // draws the canvas on the panel     this.gamePanel.render(canvas);     // calculate how long did the cycle take     timeDiff = System.currentTimeMillis() - beginTime;     // calculate sleep time     sleepTime = (int)(FRAME_PERIOD - timeDiff);     if (sleepTime > 0) {      // if sleepTime > 0 we're OK      try {       // send the thread to sleep for a short period       // very useful for battery saving       Thread.sleep(sleepTime);      } catch (InterruptedException e) {}     }     while (sleepTime < 0 && framesSkipped < MAX_FRAME_SKIPS) {      // we need to catch up      this.gamePanel.update(); // update without rendering      sleepTime += FRAME_PERIOD; // add frame period to check if in next frame      framesSkipped++;     }     if (framesSkipped > 0) {      Log.d(TAG, "Skipped:" + framesSkipped);     }     // for statistics     framesSkippedPerStatCycle += framesSkipped;     // calling the routine to store the gathered statistics     storeStats();    }   } finally {    // in case of an exception the surface is not left in    // an inconsistent state    if (canvas != null) {     surfaceHolder.unlockCanvasAndPost(canvas);    }   } // end finally  } } /**  * The statistics - it is called every cycle, it checks if time since last  * store is greater than the statistics gathering period (1 sec) and if so  * it calculates the FPS for the last period and stores it.  *  * It tracks the number of frames per period. The number of frames since  * the start of the period are summed up and the calculation takes part  * only if the next period and the frame count is reset to 0.  */ private void storeStats() {  frameCountPerStatCycle++;  totalFrameCount++;  // check the actual time  statusIntervalTimer += (System.currentTimeMillis() - statusIntervalTimer);  if (statusIntervalTimer >= lastStatusStore + STAT_INTERVAL) {   // calculate the actual frames pers status check interval   double actualFps = (double)(frameCountPerStatCycle / (STAT_INTERVAL / 1000));   //stores the latest fps in the array   fpsStore[(int) statsCount % FPS_HISTORY_NR] = actualFps;   // increase the number of times statistics was calculated   statsCount++;   double totalFps = 0.0;   // sum up the stored fps values   for (int i = 0; i < FPS_HISTORY_NR; i++) {    totalFps += fpsStore[i];   }   // obtain the average   if (statsCount < FPS_HISTORY_NR) {    // in case of the first 10 triggers    averageFps = totalFps / statsCount;   } else {    averageFps = totalFps / FPS_HISTORY_NR;   }   // saving the number of total frames skipped   totalFramesSkipped += framesSkippedPerStatCycle;   // resetting the counters after a status record (1 sec)   framesSkippedPerStatCycle = 0;   statusIntervalTimer = 0;   frameCountPerStatCycle = 0;   statusIntervalTimer = System.currentTimeMillis();   lastStatusStore = statusIntervalTimer;//   Log.d(TAG, "Average FPS:" + df.format(averageFps));   gamePanel.setAvgFps("FPS: " + df.format(averageFps));  } } private void initTimingElements() {  // initialise timing elements  fpsStore = new double[FPS_HISTORY_NR];  for (int i = 0; i < FPS_HISTORY_NR; i++) {   fpsStore[i] = 0.0;  }  Log.d(TAG + ".initTimingElements()", "Timing elements for stats initialised"); }}