写项目的时候需要一个计时器来做短信验证码的倒计时，场景需求是按钮点击后开始读秒，按钮不可用，当读秒结束按钮可用，在读秒期间切换控制器，或者将应用切换到后台在切换回读秒页面依旧在继续读秒。
代码如下：
一个继承NSObject的单例类
.h文件
#import
@interface CaptchaTimerManager : NSObject
@property (nonatomic, assign)__block int timeout;
+ (id)sharedTimerManager;
- (void)countDown;
@end
.m文件
#import "CaptchaTimerManager.h"
@implementation CaptchaTimerManager
+ (id)sharedTimerManager{
static CaptchaTimerManager *manager = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
if (manager == nil) {
manager = [[self alloc]init];
}
});
return manager;
}
- (void)countDown{
if (_timeout > 0) {
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
dispatch_source_set_event_handler(_timer, ^{
if(_timeout<=0){ //倒计时结束，关闭
dispatch_source_cancel(_timer);
}else{
_timeout--;
}
});
dispatch_resume(_timer);
}
}
@end
在实际需要计时器的控制器中具体实现细节如下
#import "ViewController.h"
#import "CaptchaTimerManager.h"
@interface ViewController ()
@property (strong, nonatomic)UIButton *button;
@property (nonatomic, assign) __block int timeout;
@end
@implementation ViewController
//页面出现前取出计时器单例的时间进行判断是否还在倒计时
- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
CaptchaTimerManager *manager = [CaptchaTimerManager sharedTimerManager];
int temp = manager.timeout;
if (temp > 0) {
_timeout= temp; //倒计时时间
[self timerCountDown];
}
}
//页面消失前记录倒计时时间到单例里
- (void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
if (self.timeout > 0) {
CaptchaTimerManager *manager = [CaptchaTimerManager sharedTimerManager];
if (manager.timeout == 0) {
manager.timeout = _timeout;
[manager countDown];
}
_timeout = 0;//置为0，释放controller
}
}
//按钮点击事件
- (IBAction)touch1:(id)sender {
_timeout = 60; //倒计时时间
[self timerCountDown];
}
//控制器里的计时器
- (void)timerCountDown{
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
dispatch_source_set_event_handler(_timer, ^{
if(_timeout<=0){ //倒计时结束，关闭
dispatch_source_cancel(_timer);
dispatch_async(dispatch_get_main_queue(), ^{
//这里写倒计时结束button的处理
});
}else{
dispatch_async(dispatch_get_main_queue(), ^{
//这里写倒计时期间button的处理（重设button的tiitle、用户交互等）
});
_timeout--;
}
});
dispatch_resume(_timer);
}
- (void)viewDidLoad {
[super viewDidLoad];
// button初始化处理.
}
@end