计时器---倒计时功能的实现

问题的实现描述：首先设置倒计时的时间，通过UIDatePicker来制定倒计时的时长，点击“确定”按钮，跳转到倒计时页面，同时将UIDatePicker定义的时间传到新push的页面的上方label位置，点击“开始”按钮，开始倒计时，这期间可以点击“暂停/继续”按钮
来控制倒计时时间的停止和继续，同时，倒计时开始后，也可重置倒计时时间pop到UIDatePicker页面，重新设置倒计时的时间。倒计时结束时，弹出提示框。

效果图：













代码如下：

JSQViewController.m文件

#import "JSQViewController.h"

#import "PushViewController.h"

#define kW self.view.frame.size.width

#define kH self.view.frame.size.height

@interface
JSQViewController ()

@property (nonatomic,weak)
UIDatePicker * picker;

@end

@implementation JSQViewController

- (void)viewDidLoad {

[super
viewDidLoad];

self.title=@"计时器";

//加载视图

[self
_loadViews];

}

#pragma mark - 加载视图
- (void) _loadViews
{

//添加picker
高度：216

UIDatePicker * picker=[[UIDatePicker
alloc]initWithFrame:CGRectMake(0,
64, 0,
0)];

//NSLog(@"%f_ _ _ _ _ _ _ _ _%f",picker.frame.origin.y,picker.frame.size.height);

picker.backgroundColor=[UIColor
colorWithRed:0.1
green:0.1
blue:0.1
alpha:0.1];

picker.datePickerMode=UIDatePickerModeCountDownTimer;

_picker=picker;
[self.view
addSubview:picker];
//添加到子视图

UIButton * button=[[UIButton
alloc]initWithFrame:CGRectMake((367-100)/2,
64+216+50,
100, 100)];

[button setTitle:@"确定"
forState:UIControlStateNormal];

[button setTitleColor:[UIColor
redColor] forState:UIControlStateNormal];

button.layer.cornerRadius=50;

button.showsTouchWhenHighlighted=YES;

button.backgroundColor=[UIColor
colorWithRed:0.1
green:0.1
blue:0.1
alpha:0.2];

[button addTarget:self
action:@selector(pushVC)
forControlEvents:UIControlEventTouchUpInside];
[self.view
addSubview:button];

}

#pragma mark - pushVC
- (void) pushVC
{

//NSLog(@"%f",_picker.countDownDuration);

PushViewController * pushVC=[[PushViewController
alloc]init];

pushVC.timeCount=_picker.countDownDuration;

[self.navigationController
pushViewController:pushVC animated:YES];
}

- (void)setDate:(NSDate *)date animated:(BOOL)animated;
{

NSDate * temDate=[[NSDate
alloc]initWithTimeIntervalSinceNow:2];
date=temDate;

NSLog(@"%@",_picker.minimumDate);
}

@end

PushViewController.m文件

#import "PushViewController.h"

#define kW self.view.frame.size.width

#define kH self.view.frame.size.height

@interface
PushViewController ()

{

NSTimer * _timer;
//定时器
}

@property (nonatomic,weak)
UILabel * label;

@property (nonatomic,weak)
UIButton * button;

@end

@implementation PushViewController

- (void)viewDidLoad {

[super
viewDidLoad];

NSLog(@"%.0f",self.timeCount);

[self
pushView];

}

- (void) pushView
{

//上方子视图

UIView * view=[[UIView
alloc]initWithFrame:CGRectMake(0,
65,
kW, 216)];

view.backgroundColor=[UIColor
whiteColor];

//倒计时Label

UILabel * label=[[UILabel
alloc]initWithFrame:CGRectMake(0,
0, kW,
216)];

//label.backgroundColor=[UIColor redColor];

label.textAlignment=NSTextAlignmentCenter;

NSString * str=[NSString
stringWithFormat:@"%02d:%02d:%02d",(int)(self.timeCount)/3600%24,(int)(self.timeCount)/60%60,(int)(self.timeCount)%60];
label.text=str;

[label setFont:[UIFont
fontWithName:nil
size:80]];

self.label=label;
[view
addSubview:label];

[self.view
addSubview:view];
//添加到主视图

//NSLog(@"%@",picker.minimumDate);

//添加下方视图模块

UIView * btmView=[[UIView
alloc]initWithFrame:CGRectMake(0,
65+216,
kW, kH-49-45-216)];
btmView.backgroundColor=[UIColor
whiteColor];

UIView * xView=[[UIView
alloc]initWithFrame:CGRectMake(0,
0, kW,
kH-49-45-216)];

xView.backgroundColor=[UIColor
colorWithRed:0.1
green:0.1
blue:0.1
alpha:0.1];

//添加提示Label

UILabel * tsLabel=[[UILabel
alloc]initWithFrame:CGRectMake(0,
2, kW,
48)];
tsLabel.backgroundColor=[UIColor
whiteColor];

[tsLabel setFont:[UIFont
fontWithName:nil
size:20]];

tsLabel.textAlignment=NSTextAlignmentCenter;

tsLabel.text=@"计时结束时，启用234 Do Do Do... >";
[xView
addSubview:tsLabel];

//开始/重置
按钮

UIButton * kqButton=[[UIButton
alloc]initWithFrame:CGRectMake((kW-200)/3,
50+50,
100, 100)];
kqButton.backgroundColor=[UIColor
whiteColor];

kqButton.layer.cornerRadius=50;

[kqButton setTitle:@"开始"
forState:UIControlStateNormal];

[kqButton setTitleColor:[UIColor
redColor] forState:UIControlStateNormal];

[kqButton setTitle:@"重置"
forState:UIControlStateSelected];

[kqButton setTitleColor:[UIColor
grayColor] forState:UIControlStateSelected];

[kqButton addTarget:self
action:@selector(startRenew:)
forControlEvents:UIControlEventTouchUpInside];

self.button=kqButton;
[xView
addSubview:kqButton];

//暂停/继续
按钮

UIButton *zkButton=[[UIButton
alloc]initWithFrame:CGRectMake((kW-200)/3*2+100,
100, 100,
100)];
zkButton.backgroundColor=[UIColor
whiteColor];

zkButton.layer.cornerRadius=50;

[zkButton setTitle:@"暂停"
forState:UIControlStateNormal];

[zkButton setTitleColor:[UIColor
redColor] forState:UIControlStateNormal];

[zkButton setTitle:@"继续"
forState:UIControlStateSelected];

[zkButton setTitleColor:[UIColor
greenColor] forState:UIControlStateSelected];

[zkButton addTarget:self
action:@selector(stopContinue:)
forControlEvents:UIControlEventTouchUpInside];
[xView
addSubview:zkButton];

[btmView
addSubview:xView];

[self.view
addSubview: btmView];
//添加到主视图
}

#pragma mark - 开始重置按钮点击事件
- (void) startRenew: (UIButton *) button
{
button.selected=!button.selected;

if(_timer==nil)
{

//每隔0.01秒刷新一次页面

_timer=[NSTimer
scheduledTimerWithTimeInterval:0.1
target:self
selector:@selector(runAction)
userInfo:nil
repeats:YES];

[[NSRunLoop
currentRunLoop] addTimer:_timer
forMode:NSRunLoopCommonModes];

NSLog(@"开始倒计时.....");
}

else
{
[_timer
invalidate]; //定时器失效
[self
_popView];
}

}

- (void) _popView
{

[self.navigationController
popViewControllerAnimated:YES];
}

- (void) runAction
{

_timeCount--;

if (_timeCount==0)
{
[_timer
invalidate];//让定时器失效

UIAlertView * alert=[[UIAlertView
alloc]initWithTitle:@"提示"
message:@"滴滴滴滴滴...时间到！"
delegate:nil
cancelButtonTitle:@"确定"
otherButtonTitles:nil,
nil];

[alert
show];
}

NSString * str=[NSString
stringWithFormat:@"%02d:%02d:%02d",(int)(self.timeCount)/3600%24,(int)(self.timeCount)/60%60,(int)(self.timeCount)%60];

_label.text=str;

}

#pragma mark - 暂停继续按钮点击事件
- (void) stopContinue:(UIButton *) button
{

if([self.label.text
isEqualToString:@"00:00:00"] || !self.button.selected)
{

return;
}
button.selected=!button.selected;

if (!button.selected)
{

//每隔0.01秒刷新一次页面

_timer=[NSTimer
scheduledTimerWithTimeInterval:0.1
target:self
selector:@selector(runAction)
userInfo:nil
repeats:YES];

[[NSRunLoop
currentRunLoop] addTimer:_timer
forMode:NSRunLoopCommonModes];

NSLog(@"继续.....");
}

else
{
[_timer
invalidate];//让定时器失效

NSLog(@"暂停中.....");
}

}

@end

PushViewController.h文件

#import <UIKit/UIKit.h>

@interface PushViewController :
UIViewController

@property (nonatomic,assign)
float timeCount;

@end 在该文件中提供了一个接口，当push页面时，可以将picker的值传过来

需要注意的是：picker的大小是固定的（高度216），所以自定义picker时，只需考虑它的起始位置即可.还有一个就是秒表和计时器有啥区别，秒表是正着走，从零开始，你要它停它停，你要它走它走；而计时器是你事先给它定好一段时间，它开始倒计时，等到00:00:00时就停下。。。(其实我以前傻傻分不清楚哪个是哪个来着)
PS：最近在学多线程，不要问我多线程是啥，我已经绕里面出不来了，什么同步异步，串行并行，还有主线程和子线程！完全搞晕中~
快被自己蠢哭了！我只知道，刷新UI要在主线程，不要太笨啊！