ios - NSTimer 迭代 4

Question

我有一个计时器，我想每秒迭代一次，但计数器每次迭代 4，我不知道为什么。它打印:4,4,8,8,12,12,16,16,20

timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerFunction:) userInfo: nil repeats:YES];

-(void)timerFunction:(NSTimer *)timer {
    NSLog(@"%d", timerCounter);
    timerCounter += 1;
    NSLog(@"%d", timerCounter);
    if(timerCounter >= 20){
        [self kestrelAlert];
        timerCounter = 0;
        [[self cancelButton] setHidden:YES];
    }


}

Answer 1

看来您在分配之前调用了 2 次

if (timer == nil) {
 timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerFunction:) userInfo: nil repeats:YES];
}
else {
    // active
}

你还打印两次

NSLog(@"%d", timerCounter); // 1
timerCounter += 1;
NSLog(@"%d", timerCounter); // 2