从 NSDate 获得百分之一秒的差异

Question

我想得到两次触摸之间的百分之一秒的时间差

float starttime;
float endtime;

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    starttime = [[NSDate date] timeIntervalSince1970];

}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{

      endtime = [[NSDate date] timeIntervalSince1970];

      NSLog(@"starttime %f endtime %f",starttime,endtime);

      float diff = endtime - starttime;


}

1. 问题是我发现 endtime 和 starttime 都是一样的，无论我触摸多久，但如果我删除 timeIntervalSince1970 ，它不是

2. 有什么方法可以得到这种差异

Answer 1

我最好用

double startTime = CACurrentMediaTime();

这是相对计时的推荐方式

double starttime;
double endtime;

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    startTime = CACurrentMediaTime();
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{

    endtime = CACurrentMediaTime();
    NSLog(@"starttime %f endtime %f",starttime,endtime);
    double diff = endtime - starttime;
    NSLog(@"Diff - %f", diff);
}