Question

http://www.youtube.com/watch?v=5al6qqRzzQg当我点击一下不止一次??? 我需要做什么

#import "FirstViewController.h"

@implementation FirstViewController

-(IBAction)start;{

    myticker = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(showActivity) userInfo:nil repeats:YES];
}
-(IBAction)stop;{ 

    [myticker invalidate];
}
-(IBAction)reset;{

    time.text = @"0";
}
-(void)showActivity;{ 

    int currentTime = [time.text intValue];
    int newTime = currentTime + 1;
    time.text = [NSString stringWithFormat:@"%d", newTime];
}


- (void)didReceiveMemoryWarning

Answer 1

将bool变量添加到类的标题中，如timerIsActive

-(IBAction)start;{
if (!timerIsActive) {
    myticker = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(showActivity) userInfo:nil repeats:YES];
  timerIsActive = YES;

}
}

-(IBAction)stop;{ 
    timerIsActive = NO;
    [myticker invalidate];
}

Answer 2

将启动和停止方法更改为：

-(IBAction)start;{

    [myticker invalidate];
    myticker = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(showActivity) userInfo:nil repeats:YES];
}

-(IBAction)stop;{ 

    [myticker invalidate];
    myticker = nil;
}

这将阻止它崩溃。另外，你应该添加：

-(void)dealloc
{
    [myticker invalidate];
}

为什么这个NSTimer会崩溃？

2 个答案: