为NSTimer添加暂停function

首先，这里是一些Xcode码表的工作代码。 我有两个button， Start和Stop 。 按下button时，它们的标题会改变。 现在我想添加一个暂停function。 我知道有很多关于这个的线索，但是（我不知道为什么），我无法得到它的工作。

那么在我的代码中实现这个function的最好方法是什么？

我已经尝试过使用暂停date，并从我的NSTimeInterval减去它，但得到负值…

非常感谢！

所以我这样做了：

 //use timer to update the ui only, store start date (NSDate) and time interval elapsed (NSTimeInterval) //this is called when the timer is not running, nor paused - a sort of 'first run' function -(void)onTimerStart { //zero the time elapsed time_passed = 0; //save the starting date start_date = [NSDate date]; //start a timer that will update the ui in the onTimer function timer = [NSTimer timerWithTimeInterval:1.0/10.0 target:self selector:@selector(onTimer) userInfo:nil repeats:YES]; } //called when the timer is running to pause it -(void)onPause { //calculate the time that passed ( += not = ) time_passed += [[NSDate date] timeIntervalSinceDate: start_date]; //stop the timer [timer invalidate]; //you can get rid of the start date now (using ARC ........) } //restarting the timer that was paused -(void)onUnpause { //get new start date start_date = [NSDate date]; //start the timer to update ui again timer = [NSTimer timerWithTimeInterval:1.0/10.0 target:self selector:@selector(onTimer) userInfo:nil repeats:YES]; } //use this function if you are stopping - not pausing! - the timer. -(void)onReset { //stop timer [timer invalidate]; //calculate the final time that passed //THE NEXT LINE IS PROBABLY WRONG AND HAS TO BE time_passed = 0; THEN IT WORKS time_passed += [[NSDate date] timeIntervalSinceDate: start_date]; //get rid of the start date now } //use this function to update UI - this is what gets called by the timer -(void)onTimer { //when timer ticks use ([[NSDate date] timeIntervalSinceDate: start_date] + time_passed) //to get the amount of time passed for display } #pragma mark - View lifecycle - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. [self onTimerStart]; } 

工作代码：

 #pragma mark - Timer - (void)timer { NSDate *currentDate = [NSDate date]; NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate]; NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"mm:ss.S"]; [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]]; NSString *timeString=[dateFormatter stringFromDate:timerDate]; timerLabel.text = timeString; } #pragma mark - Stopwatch - (IBAction)onStartPressed:(UIButton *)sender { if ([sender.titleLabel.text isEqualToString:@"Start"] && (![timer isValid]) && ([timerLabel.text isEqualToString:@"00:00.0"])) { startDate = [NSDate date]; timer = [NSTimer scheduledTimerWithTimeInterval:1.0/10.0 target:self selector:@selector(timer) userInfo:nil repeats:YES]; } } - (IBAction)onStopPressed:(UIButton *)sender { if ((![timer isValid]) && ([sender.titleLabel.text isEqualToString:@"Reset"])) { [timer invalidate]; timer = nil; timerLabel.text = @"00:00.0"; [sender setTitle:@"Stop" forState:UIControlStateNormal]; } if (([timer isValid]) && ([sender.titleLabel.text isEqualToString:@"Stop"])) { [timer invalidate]; timer = nil; [sender setTitle:@"Reset" forState:UIControlStateNormal]; } } 

Answer 1

NSTimer中没有内置暂停/恢复function，因此您必须按照以下方式执行某些操作：

 //THIS IS PSEUDOCODE //use timer to update the ui only, store start date (NSDate) and time interval elapsed (NSTimeInterval) //this is called when the timer is not running, nor paused - a sort of 'first run' function - onTimerStart: { //zero the time elapsed time_passed = 0; //save the starting date start_date = [NSDate date]; //start a timer that will update the ui in the onTimer function [timer start] } //called when the timer is running to pause it - onPause { //calculate the time that passed ( += not = ) time_passed += [[NSDate date] timeIntervalSinceDate: start_date]; //stop the timer [timer invalidate]; //you can get rid of the start date now } //restarting the timer that was paused - onUnpause { //get new start date start_date = [NSDate]; //start the timer to update ui again [timer start]; } //use this function if you are stopping - not pausing! - the timer. - onReset { //stop timer [timer invalidate]; //calculate the final time that passed time_passed += [[NSDate date] timeIntervalSinceDate: start_date]; //get rid of the start date now } //use this function to update UI - this is what gets called by the timer - onTimer { //when timer ticks use ([[NSDate date] timeIntervalSinceDate: start_date] + time_passed) //to get the amount of time passed for display }