iOS开发－三种倒计时的写法

iOS开发－三种倒计时的写法

1.通过NSThread的performSelectorInBackground；
2.通过定时器，属于比较简单的写法；
3.通过GCD中的dispatch_source；

先说第一种 1 .通过NSThread：

#import "ViewController.h"@interface ViewController (){    int _count;    UILabel *_label;}@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    _label=[[UILabel alloc]initWithFrame:CGRectMake(0, 0, KScreenWidth, 40)];    _label.backgroundColor=[UIColor greenColor];    _label.textAlignment=NSTextAlignmentCenter;    _label.font=[UIFont systemFontOfSize:30];    _label.text=@"60";    [self.view addSubview:_label];}- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {     //多线程读秒操作(可以加在button里控制)    [self performSelectorInBackground:@selector(thread) withObject:nil];}// 在异步线程中无法操作UI，如果想要操作UI必须回调主线程- (void)thread{    for(int i=59;i>=0;i--)    {        _count = i;        // 回调主线程        [self performSelectorOnMainThread:@selector(mainThread) withObject:nil waitUntilDone:YES];         //一秒一次        sleep(1);    }}// 此函数主线程执行- (void)mainThread{    _label.text=[NSString stringWithFormat:@"%d",_count];    if (_count==0) {           //这里操作倒计时结束后的事情           _label.text=@"重新发送";    }}@end

第二种 2 通过定时器：

#import "ViewController.h"@interface ViewController (){    UIButton *btn;    int timeDown; //60秒后重新获取验证码    NSTimer *timer;}@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.    btn=[UIButton buttonWithType:UIButtonTypeCustom];    btn.frame=CGRectMake(10, 200, 300, 50);    btn.backgroundColor=[UIColor cyanColor];    [btn setBackgroundImage:[UIImage imageNamed:@"bg_send_validate_code.png"] forState:UIControlStateNormal];    [btn setTitle:@"获取验证码" forState:UIControlStateNormal];    [btn addTarget:self action:@selector(btnAction) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:btn];}- (void)btnAction{    timeDown = 59;    [self handleTimer];    timer = [NSTimer scheduledTimerWithTimeInterval:(1.0) target:self        selector:@selector(handleTimer) userInfo:nil repeats:YES];}-(void)handleTimer{    if(timeDown>=0)    {        [btn setUserInteractionEnabled:NO];        [btn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];        int sec = ((timeDown%(24*3600))%3600)%60;        [btn setTitle:[NSString stringWithFormat:@"(%d)重发验证码",sec] forState:UIControlStateNormal];    }    else    {        [btn setUserInteractionEnabled:YES];        [btn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];        [btn setTitle:@"重发验证码" forState:UIControlStateNormal];        [timer invalidate];    }    timeDown = timeDown - 1;}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end

第三种 3 通过GCD中的dispatch_source：

#import "ViewController.h"@interface ViewController (){    UIButton *_getNumBtn;}@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    _getNumBtn=[UIButton buttonWithType:UIButtonTypeCustom];    _getNumBtn.frame=CGRectMake(10, 200, 300, 50);    [_getNumBtn setBackgroundImage:[UIImage imageNamed:@"bg_send_validate_code.png"] forState:UIControlStateNormal];    [_getNumBtn setTitle:@"获取验证码" forState:UIControlStateNormal];    [_getNumBtn addTarget:self action:@selector(getNumBtnAction) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:_getNumBtn];}- (void)getNumBtnAction{    __block NSInteger second = 60;    //全局队列    默认优先级    dispatch_queue_t quene = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    //定时器模式  事件源    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, quene);    //NSEC_PER_SEC是秒，＊1是每秒    dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), NSEC_PER_SEC * 1, 0);    //设置响应dispatch源事件的block，在dispatch源指定的队列上运行    dispatch_source_set_event_handler(timer, ^{        //回调主线程，在主线程中操作UI        dispatch_async(dispatch_get_main_queue(), ^{            if (second >= 0) {                [_getNumBtn setTitle:[NSString stringWithFormat:@"(%ld)重发验证码",second] forState:UIControlStateNormal];                second--;            }            else            {                //这句话必须写否则会出问题                dispatch_source_cancel(timer);                    [_getNumBtn setTitle:@"获取验证码" forState:UIControlStateNormal];            }        });    });    //启动源    dispatch_resume(timer);}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end