iOS 8如何防止Spritekit帧速率下降

在我创建的一个游戏中，我创建了一个游戏模式，玩家有30秒的时间来击中尽可能多的目标。我在-（void）update:（CFTimeInterval）currentTime方法中添加了一个30秒的倒计时计时器。当开始倒计时时，帧速率显著下降，并且每当对象与目标碰撞时，都会使用99%的cpu。计时器未运行时不会发生这种情况。是否有其他方法添加倒计时计时器？如果没有，我如何减少cpu使用并保持帧速率不变？我使用的是Xcode 6.1，代码如下。这也是iOS 8的一个问题。在iOS 7.1上运行良好

-(void)update:(CFTimeInterval)currentTime {
/* Called before each frame is rendered */
//reset counter if starting
int highscoret = [[NSUserDefaults standardUserDefaults] integerForKey: @"highScoret"];    
if (startGamePlay){
startTime = currentTime;
startGamePlay = NO;
}
countDown.text = [NSString stringWithFormat:@"Start!"];

int countDownInt = 30.0 -(int)(currentTime-startTime);
if(countDownInt>0){ //if counting down to 0 show counter
countDown.text = [NSString stringWithFormat:@"%i", countDownInt];
}else if(countDownInt==0) { //if not show message, dismiss, whatever you need to do.
countDown.text=@"Time's Up!";

self.highScoret.text = [NSString stringWithFormat:@"%d Baskets",highscoret];
SKScene *endGameScene = [[GameOverT alloc] initWithSize:self.size];
SKTransition *reveal = [SKTransition fadeWithDuration:0.5];
[self.view presentScene:endGameScene transition:reveal];
[self saveScore2];

if (self.points > highscoret) {
    self.highScoret.text = [NSString stringWithFormat:@"%d Points",highscoret];
    [self saveScore];
    self.points = 0;
    self.scoreLabel.text = [NSString stringWithFormat:@"%d Points",_points];
}

else {
    self.points = 0;
    self.scoreLabel.text = [NSString stringWithFormat:@"%d Points",_points];
    self.highScoret.text = [NSString stringWithFormat:@"%d Points",highscoret];
}


}
}

这是其他相关代码

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
/* Called when a touch begins */
for (UITouch *touch in touches) {
CGPoint location = [touch locationInNode:self];
if (CGRectContainsPoint(countDown.frame, location)){
    startGamePlay = YES;
    self.baskett = 0;
    [self reset];
}
}

UITouch * touch = [touches anyObject];
CGPoint location = [touch locationInNode:self];

SKSpriteNode * object = [SKSpriteNode spriteNodeWithImageNamed:@"object.png"];
object.position = self.object2.position;

object.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:ball.size.width/2];
object.physicsBody.dynamic = YES;
object.physicsBody.categoryBitMask = objectCategory;
object.physicsBody.contactTestBitMask = targetCategory;
object.physicsBody.collisionBitMask = 0;
object.physicsBody.usesPreciseCollisionDetection = YES;
CGPoint offset = rwSub(location, object.position);

if (offset.y <= 0) return;

[self addChild:object];

CGPoint direction = rwNormalize(offset);

CGPoint shootAmount = rwMult(direction, 1000);

CGPoint realDest = rwAdd(shootAmount, object.position);

float velocity = 200/1.0;
float realMoveDuration = self.size.width / velocity;
SKAction * actionMove = [SKAction moveTo:realDest duration:realMoveDuration];
SKAction * actionMoveDone = [SKAction removeFromParent];
[object runAction:[SKAction sequence:@[actionMove, actionMoveDone]]];
}

-(void)object:(SKSpriteNode *) object didCollideWithTarget:(SKSpriteNode *) target {
[object removeFromParent];

[[self scene] runAction:[SKAction playSoundFileNamed:@"effect2.wav" waitForCompletion:NO]];
self.points++;
self.scoreLabel.text = [NSString stringWithFormat:@"%d Points",_points];

if (self.points == 3) {
[self obstacle];
}

}

-（void）touchesbeated:（NSSet*）toucheevent:（UIEvent*）event{
/*当触摸开始时调用*/
用于（UITouch*触摸屏）{
CGPoint位置=[触摸位置Innode:self]；
if（CGRectContainsPoint（countDown.frame，location））{
startGamePlay=是；
self.baskett=0；
[自复位]；
}
}
UITouch*touch=[触摸任何对象]；
CGPoint位置=[触摸位置Innode:self]；
SKSpriteNode*对象=[SKSpriteNode SPRITENODEWITHIMAGENAME:@“object.png”]；
object.position=self.object2.position；
object.physicsBody=[SKPhysicsBody-withcircleofradius:ball.size.width/2]；
object.physicsBody.dynamic=是；
object.physicsBody.categoryBitMask=objectCategory；
object.physicsBody.contactTestBitMask=targetCategory；
object.physicsBody.collisionBitMask=0；
object.physicsBody.usesprecisecollisondetection=YES；
CGPoint offset=rwSub（位置，object.position）；
如果在更新函数中使用（offset.y计时器是个坏主意，那么像这样使用带有waitForDuration的skaction可能会解决您的问题

SKAction *updateTime= [SKAction sequence:@[
                                                ///fire function after one second
                                               [SKAction waitForDuration:1.0f],
                                               [SKAction performSelector:@selector(callFunction)
                                                                onTarget:self]

                                               ]];
     //where 30 is number of time you want’s to call your function
    [self runAction:[SKAction repeatAction:updateTime count:30] ];




-(void) callFunction
{

   //what ever you want to do
}

使用仪器来找出到底是什么消耗了CPU时间，否则这只是猜测，可能需要比学习使用仪器花费的时间更长的时间才能弄清楚。这会更好！是否有任何方法可以使计时器可见？创建一个变量来保存计时器执行的时间数（NSinteger t=100）同时创建一个SKLabelNode，将其赋值为t，并每次减少t值一-（void）callFunction excuteI已经尝试过类似的操作，但是LabelNodes显示在彼此的顶部。我尝试创建可以删除和添加新LabelNodes的SKActions，但是效果不好，所以我决定不使用它。感谢您的帮助！为什么创建serval synodes只需在callFunction中创建一个更新其skiable.text属性