点击之间的 iOS 计时

Question

我试图在敲击之间保持节奏。但是，我随机获得巨大的值(value)，我不确定为什么。

@implementation GameScene
{
   CFTimeInterval previousFrameTime;
   SKLabelNode* myLabel;
}

-(void)didMoveToView:(SKView *)view {
   previousTimeFrame = 0.0f;
   myLabel = [SKLabelNode labelNodeWithFontNamed:@"Chalkduster"];

   myLabel.text = @" ";
   myLabel.fontSize = 12;
   myLabel.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
[self addChild:myLabel];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    myLabel.text = [NSSTring stringWithFormat: @"%f", previousFrameTime];
}

//Called every frame
-(void)update:(CFTimeInterval)currentTime {
    //get the time between frames
    previousFrameTime = CACurrentMediaTime() - previousFrameTime;
}

输出:0.653230.935271.653265866.42930 <-- ????2.524425.231565888.21345 <-- ??????

是什么导致了这些随机跳跃？

Answer 1

这条线对我来说似乎坏了:

previousFrameTime = CACurrentMediaTime() - previousFrameTime;

让我们看看如果您每秒都点击一次，这将如何工作:

1.) previousFrameTime = 1000 - 0; (1000)
2.) previousFrameTime = 1001 - 1000; (1)
3.) previousFrameTime = 1002 - 1; (1001)
4.) previousFrameTime = 1003 - 1001; (2)