我有一个Android游戏的开始。它有一个跟踪fps值的GameLoop（线程）类和一个GameView（surfaceview），用于实例化GameLoop对象并设置它运行等等。
现在我有一个单独的FpsText对象，它知道如何将自己绘制到屏幕上，但要更新我需要执行fpsText.setText(gameloop.getFps());
如果我在GameView课程中这样做，这不是问题，但我想尝试拥有一个FpsText对象，可以自行更新。我对线程没有任何其他经验，我认为它可能适得其反，但我尝试将fpsText gameloop引用作为参数传递。不出所料我每次运行应用程序时都会得到不同的不需要的结果，所以我想知道你认为处理这种情况的最佳方法是什么？
作为在fpsText中更新GameView的替代方法，我总是可以将gameloop类中的fps值公开，但我知道这是不好的做法！听起来不是很好的解决方案，或许还有更好的方法吗？
这里的参考是我的游戏循环，RedOrav建议的第二个变化是：
package biz.hireholly.engine;
import android.graphics.Canvas;
import android.util.Log;
import android.view.SurfaceHolder;
import biz.hireholly.gameplay.FpsText;
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 ArrayList<Double> fpsStore = new ArrayList<Double>(); //For the previous fps values
private long lastTimeFpsCalculated = System.currentTimeMillis(); //used in trackFps
FpsText fpsText;
public GameLoop(SurfaceHolder surfaceHolder, GameView gameview, FpsText fpsText) {
super();
this.surfaceHolder = surfaceHolder;
this.gameview = gameview;
this.fpsText = fpsText;
}
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(){
synchronized(fpsStore){
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){
for (Double fps : fpsStore){
lastFps += fps;
}
lastFps /= fpsStore.size();
synchronized(fpsText){ //update the Drawable FpsText object
fpsText.setText(String.valueOf((int)lastFps));
}
lastTimeFpsCalculated = System.currentTimeMillis();
//Log.d("trackFPS()", " fpsStore.size() = "+fpsStore.size()+"\t"+fpsStore.toString());
fpsStore.clear();
}
}
}
}
答案 0 :(得分：1)
你有什么不想要的结果？将fps变量公开并设置getfps（）与获取fps值完全相同，并且修改GameView中的fps值永远不会有任何意义。
我怀疑你在GameLoop中所做的是在几秒钟之间修改你的fps变量，即获得你的GameView可能也正在阅读的中间值。我建议仅每秒修改一次fps，并保持时间变量，以便进行计算。假设你开始时有0 fps。 GameLoop进行计算，一旦经过一秒钟，你已经收集了它处理的帧数和时间（1秒）。在此之前，无论GameLoop在做什么，GameView总是读取0。在那之后，假设你完成了60 fps，fps变量被修改，并且不受影响直到下一秒。因此，对于接下来的第二步，即使GameView对变量进行了更多的读取，它也总是会得到60。
// Inside GameLoop
private int fps; // Variable you're going to read
private int frameCount; // Keeps track or frames processed
private long lastUpdated;
while(running) {
if(System.currentTimeMillis() - lastUpdated > 1000) { // 1 second elapsed
fps = frameCount;
frameCount = 0;
}
frameCount++;
}
public int getFps() {
return fps;
}
另一种方法是将对fpsText的引用传递给GameLoop，GameLoop仅在每秒传递后修改它。这样，您的渲染线程只需要担心渲染，而GameLoop则需要关注每秒帧数。但请记住，您可能会遇到竞争条件（您在渲染方法中间的GameLoop中使用setText（）），您不必担心其他方式。在渲染时和修改它时将fpsText对象包含在同步括号中应该可以帮到你。
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