为了创建游戏循环，我跟着this excellent tutorial。但是我认为显示FPS的下一个教程有点不确定，所以我试着单独进行。我对我所做的trackFps()方法充满信心;在计算帧之间的时间差之后调用它，每次运行时测量预测的FPS，将那些预测的FPS值存储在ArrayList中，然后每秒一次将这些预测的FPS加起来并除以添加到的值的数量。获得平均FPS。
当我使用调试器运行它时，它运行正常，但是当我通过它时，我得到以下异常：
FATAL EXCEPTION: Thread-11
java.lang.IndexOutOfBoundsException: Invalid index 26, size is 6
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
at java.util.ArrayList.get(ArrayList.java:311)
at biz.hireholly.engine.GameLoop.trackFps(GameLoop.java:120)
at biz.hireholly.engine.GameLoop.run(GameLoop.java:73)
这是非常明确的解释，发生在这一行fps += fpsStore.get(fpsTrackCount-1);上。但我看不出fpsTrackCount变量如何高达26，它应该只与ArrayList fpsStore中存储的变量数一样高。
有人会查看我的GameLoop课程，特别是底部的trackFps()方法吗？我会提供整件事。它评论很多，但它并不多，对你们中的一些人应该非常熟悉。
GameLoop（包含用于计算底部FPS的trackFps()方法）：
package biz.hireholly.engine;
import android.graphics.Canvas;
import android.view.SurfaceHolder;
import java.util.ArrayList;
/**
* The GameLoop is a thread that will ensure updating and drawing is done at set intervals.
* The thread will sleep when it has updated/rendered quicker than needed to reach the desired fps.
* The loop is designed to skip drawing if the update/draw cycle is taking to long, up to a MAX_FRAME_SKIPS.
* The Canvas object is created and managed to some extent in the game loop,
* this is so that we can prevent multiple objects trying to draw to it simultaneously.
* Note that the gameloop has a reference to the gameview and vice versa.
*/
public class GameLoop extends Thread {
private static final String TAG = GameLoop.class.getSimpleName();
//desired frames per second
private final static int MAX_FPS = 30;
//maximum number of drawn frames to be skipped if drawing took too long last cycle
private final static int MAX_FRAME_SKIPS = 5;
//ideal time taken to update & draw
private final static int CYCLE_PERIOD = 1000 / MAX_FPS;
private SurfaceHolder surfaceHolder;
//the gameview actually handles inputs and draws to the surface
private GameView gameview;
private boolean running;
private long beginTime = 0; // time when cycle began
private long timeDifference = 0; // time it took for the cycle to execute
private int sleepTime = 0; // milliseconds to sleep (<0 if drawing behind schedule)
private int framesSkipped = 0; // number of render frames skipped
private double lastFps = 0; //The last FPS tracked, the number displayed onscreen
private int fpsTrackCount = 1; // number we'll divide the fpsSTore by to get average
private ArrayList<Double> fpsStore = new ArrayList<Double>(); //For the previous fps values
private long lastTimeFpsCalculated = System.currentTimeMillis(); //used in trackFps
public GameLoop(SurfaceHolder holder, GameView gameview) {
super();
this.surfaceHolder = holder;
this.gameview = gameview;
}
public void setRunning(boolean running) {
this.running = running;
}
@Override
public void run(){
Canvas c;
while (running) {
c = null;
//try locking canvas, so only we can edit pixels on surface
try{
c = this.surfaceHolder.lockCanvas();
//sync so nothing else can modify while were using it
synchronized (surfaceHolder){
beginTime = System.currentTimeMillis();
framesSkipped = 0; //reset frame skips
this.gameview.update();
this.gameview.draw(c);
//calculate how long cycle took
timeDifference = System.currentTimeMillis() - beginTime;
//good time to trackFps?
trackFps();
//calculate potential sleep time
sleepTime = (int)(CYCLE_PERIOD - timeDifference);
//sleep for remaining cycle
if (sleepTime >0){
try{
Thread.sleep(sleepTime); //saves battery! :)
} catch (InterruptedException e){}
}
//if sleepTime negative then we're running behind
while (sleepTime < 0 && framesSkipped < MAX_FRAME_SKIPS){
//update without rendering to catch up
this.gameview.update();
//skip as many frame renders as needed to get back into
//positive sleepTime and continue as normal
sleepTime += CYCLE_PERIOD;
framesSkipped++;
}
}
} finally{
//finally executes regardless of exception,
//so surface is not left in an inconsistent state
if (c != null){
surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
/* Calculates the average fps every second */
private void trackFps(){
long currentTime = System.currentTimeMillis();
if(timeDifference != 0){
fpsStore.add((double)(1000 / timeDifference));
}
//If a second has past since last time average was calculated,
// it's time to calculate a new average fps to display
if ((currentTime - 1000) > lastTimeFpsCalculated){
int fps = 0;
int toDivideBy = fpsTrackCount;
while ((fpsStore != null) && (fpsTrackCount > 0 )){
fps += fpsStore.get(fpsTrackCount-1);
fpsTrackCount--;
}
lastFps = fps / toDivideBy;
lastTimeFpsCalculated = System.currentTimeMillis();
fpsTrackCount = 1;
fpsStore.clear();
}
else{
fpsTrackCount++;
}
}
/* So That it can be drawn in the gameview */
public String getFps() {
return String.valueOf(lastFps);
}
}
答案 0 :(得分：2)
好吧，让我们先来看看......
java.lang.IndexOutOfBoundsException: Invalid index 26, size is 6
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
at java.util.ArrayList.get(ArrayList.java:311)
at biz.hireholly.engine.GameLoop.trackFps(GameLoop.java:120)
所以在trackFPS的某个地方，get（）是荒谬的超出界限......
private void trackFps()
{
long currentTime = System.currentTimeMillis();
if(timeDifference != 0)
{
fpsStore.add((double)(1000 / timeDifference));
}
//If a second has past since last time average was calculated,
// it's time to calculate a new average fps to display
if ((currentTime - 1000) > lastTimeFpsCalculated)
{
int fps = 0;
int toDivideBy = fpsTrackCount;
while ((fpsStore != null || !fpsStore.isEmpty()) && (fpsTrackCount > 0 ) && (fpsTrackCount < fpsStore.getCount()))
{
//synchronized(this) {
fps += fpsStore.get(fpsTrackCount-1);
fpsStore.remove(fpsTrackCount-1); //otherwise we'll get stuck because of getCount condition
fpsTrackCount--;
//}
}
lastFps = fps / toDivideBy;
lastTimeFpsCalculated = System.currentTimeMillis();
//fpsTrackCount = 1;
//fpsStore.clear();
Log.d("trackFPS()", "fpsTrackCount = "+fpsTrackCount+"\tfpsStore.size() = "+fpsStore.size()+"\t"+fpsStore.toString());
}
else
fpsTrackCount++;
}
给它一个旋转。如果效果不好，请尝试取消注释sync'd块。
至于你的另一个问题，关于TextDrawable，我看了你的GameView ......
这是我在SurfaceChanged（）
中所做的事情 fps = new TextDrawable();
fps.setText("HELLO");
现在，你为什么不把它移到SurfaceCreated（）？也许你会得到很多surfaceChanged（）回调，但由于你没有Logcat调用，所以不知道它？ :)它是唯一从我能看到的TextDrawable实例化的地方。
答案 1 :(得分：1)
您还可以在Android Play商店中使用应用来测量FPS。最近发布的一款非常好的应用是GameBench。它不仅可以捕获FPS，还可以捕获屏幕截图，这样您就可以了解FPS下降时的情况。它还提供CPU使用率，在某些设备中也提供GPU使用率。我相信你会发现它很有用。
链接是this
答案 2 :(得分：-4)
我认为这段代码应该适合你
cputhrottle=(int) System.currentTimeMillis();
cputhrottle = (int)System.currentTimeMillis() - cputhrottle;cputhrottle=33-cputhrottle;
每秒30帧对你有用