iOS---倒计时

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方法1：使用NSTimer来实现

主要使用的是NSTimer的scheduledTimerWithTimeInterval方法来每1秒执行一次timeFireMethod函数，timeFireMethod进行倒计时的一些操作，完成时把timer给invalidate掉就ok了，代码如下：

[cpp] view plaincopyprint?
 secondsCountDown = 60;//60秒倒计时  
 countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeFireMethod) userInfo:nil repeats:YES];  
-(void)timeFireMethod{  
    secondsCountDown--;  
    if(secondsCountDown==0){  
      [countDownTimer invalidate];  
    }  
}  

方法2：使用GCD来实现

代码如下：

[cpp] view plaincopyprint?
  __block int timeout=300; //倒计时时间  
  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_release(_timer);  
          dispatch_async(dispatch_get_main_queue(), ^{  
//设置界面的按钮显示 根据自己需求设置  
              。。。。。。。。  
          });  
      }else{  
          int minutes = timeout / 60;  
          int seconds = timeout % 60;  
          NSString *strTime = [NSString stringWithFormat:@"%d分%.2d秒后重新获取验证码",minutes, seconds];  
          dispatch_async(dispatch_get_main_queue(), ^{  
              //设置界面的按钮显示 根据自己需求设置  
。。。。。。。。  
          });  
          timeout--;  
            
      }  
  });  
  dispatch_resume(_timer);  

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

使用 GCD 实现倒计时效果

效果如下：

使用 GCD 实现倒计时效果0

ViewController.h

1 #import <UIKit/UIKit.h>2 3 @interface ViewController : UIViewController4 @property (assign, nonatomic) NSInteger surplusSecond;5 6 @property (strong, nonatomic) IBOutlet UILabel *lblMessage;7 @property (strong, nonatomic) IBOutlet UIButton *btnSendCAPTCHA;8 9 @end

ViewController.m

 1 #import "ViewController.h" 2  3 @interface ViewController () 4 - (void)layoutUI; 5 - (void)countDown; 6 @end 7  8 @implementation ViewController 9 #define kSurplusSecond 510 11 - (void)viewDidLoad {12     [super viewDidLoad];13     14     [self layoutUI];15 }16 17 - (void)didReceiveMemoryWarning {18     [super didReceiveMemoryWarning];19     // Dispose of any resources that can be recreated.20 }21 22 - (void)layoutUI {23     _surplusSecond = kSurplusSecond; //剩余秒数；这里指验证码发送完，间隔多少秒才能再次点击「验证」按钮进行发送验证码24     25     _btnSendCAPTCHA.tintColor = [UIColor darkGrayColor];26     _btnSendCAPTCHA.layer.masksToBounds = YES;27     _btnSendCAPTCHA.layer.cornerRadius = 10.0;28     _btnSendCAPTCHA.layer.borderColor = [UIColor grayColor].CGColor;29     _btnSendCAPTCHA.layer.borderWidth = 1.0;30 }31 32 /**33  *  倒计时34  */35 - (void)countDown {36     //全局并发队列37     dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);38     //主队列；属于串行队列39     dispatch_queue_t mainQueue = dispatch_get_main_queue();40     41     //定时循环执行事件42     //dispatch_source_set_timer 方法值得一提的是最后一个参数（leeway），他告诉系统我们需要计时器触发的精准程度。所有的计时器都不会保证100%精准，这个参数用来告诉系统你希望系统保证精准的努力程度。如果你希望一个计时器每5秒触发一次，并且越准越好，那么你传递0为参数。另外，如果是一个周期性任务，比如检查email，那么你会希望每10分钟检查一次，但是不用那么精准。所以你可以传入60，告诉系统60秒的误差是可接受的。他的意义在于降低资源消耗。43     dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, globalQueue);44     dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1.0 * NSEC_PER_SEC, 0.0 * NSEC_PER_SEC);45     dispatch_source_set_event_handler(timer, ^{ //计时器事件处理器46         NSLog(@"Event Handler");47         if (_surplusSecond <= 0) {48             dispatch_source_cancel(timer); //取消定时循环计时器；使得句柄被调用，即事件被执行49             dispatch_async(mainQueue, ^{50                 _btnSendCAPTCHA.enabled = YES;51                 [_btnSendCAPTCHA setTitle:@"验证" forState:UIControlStateNormal];52                 53                 _lblMessage.text = @"使用 GCD 实现倒计时效果";54                 _surplusSecond = kSurplusSecond;55             });56         } else {57             _surplusSecond--;58             dispatch_async(mainQueue, ^{59                 NSString *btnInfo = [NSString stringWithFormat:@"%ld秒", (long)(_surplusSecond + 1)];60                 _btnSendCAPTCHA.enabled = NO;61                 [_btnSendCAPTCHA setTitle:btnInfo forState:UIControlStateDisabled];62             });63         }64     });65     dispatch_source_set_cancel_handler(timer, ^{ //计时器取消处理器；调用 dispatch_source_cancel 时执行66         NSLog(@"Cancel Handler");67     });68     dispatch_resume(timer);  //恢复定时循环计时器；Dispatch Source 创建完后默认状态是挂起的，需要主动恢复，否则事件不会被传递，也不会被执行69 }70 71 - (IBAction)sendCAPTCHA:(id)sender {72     _lblMessage.text = [NSString stringWithFormat:@"验证码发送成功，%d秒后可重新发送", kSurplusSecond];73     74     [self countDown];75 }76 77 @end

Main.storyboard

 1 <?xml version="1.0" encoding="UTF-8" standalone="no"?> 2 <document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="7706" systemVersion="14E46" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" initialViewController="vXZ-lx-hvc"> 3     <dependencies> 4         <deployment identifier="iOS"/> 5         <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="7703"/> 6     </dependencies> 7     <scenes> 8         <!--View Controller--> 9         <scene sceneID="ufC-wZ-h7g">10             <objects>11                 <viewController id="vXZ-lx-hvc" customClass="ViewController" sceneMemberID="viewController">12                     <layoutGuides>13                         <viewControllerLayoutGuide type="top" id="jyV-Pf-zRb"/>14                         <viewControllerLayoutGuide type="bottom" id="2fi-mo-0CV"/>15                     </layoutGuides>16                     <view key="view" contentMode="scaleToFill" id="kh9-bI-dsS">17                         <rect key="frame" x="0.0" y="0.0" width="600" height="600"/>18                         <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>19                         <subviews>20                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="使用 GCD 实现倒计时效果" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="1Kh-pV-cfz">21                                 <rect key="frame" x="200" y="289.5" width="200" height="20.5"/>22                                 <fontDescription key="fontDescription" type="system" pointSize="17"/>23                                 <color key="textColor" cocoaTouchSystemColor="darkTextColor"/>24                                 <nil key="highlightedColor"/>25                             </label>26                             <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="rFe-Xb-ZSc">27                                 <rect key="frame" x="240" y="510" width="120" height="50"/>28                                 <constraints>29                                     <constraint firstAttribute="width" constant="120" id="gVH-aT-gen"/>30                                     <constraint firstAttribute="height" constant="50" id="jJP-Vc-fpy"/>31                                 </constraints>32                                 <state key="normal" title="验证">33                                     <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>34                                 </state>35                                 <connections>36                                     <action selector="sendCAPTCHA:" destination="vXZ-lx-hvc" eventType="touchUpInside" id="I6T-s9-9H6"/>37                                 </connections>38                             </button>39                         </subviews>40                         <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>41                         <constraints>42                             <constraint firstAttribute="centerX" secondItem="rFe-Xb-ZSc" secondAttribute="centerX" id="CoE-CP-eDN"/>43                             <constraint firstAttribute="centerY" secondItem="1Kh-pV-cfz" secondAttribute="centerY" id="bX4-jS-0xm"/>44                             <constraint firstAttribute="centerX" secondItem="1Kh-pV-cfz" secondAttribute="centerX" id="mKH-Zw-Utb"/>45                             <constraint firstItem="2fi-mo-0CV" firstAttribute="top" secondItem="rFe-Xb-ZSc" secondAttribute="bottom" constant="40" id="y3Q-IA-qIO"/>46                         </constraints>47                     </view>48                     <connections>49                         <outlet property="btnSendCAPTCHA" destination="rFe-Xb-ZSc" id="UFG-TS-ImX"/>50                         <outlet property="lblMessage" destination="1Kh-pV-cfz" id="gzx-3T-euc"/>51                     </connections>52                 </viewController>53                 <placeholder placeholderIdentifier="IBFirstResponder" id="x5A-6p-PRh" sceneMemberID="firstResponder"/>54             </objects>55         </scene>56     </scenes>57 </document>

输出结果：

1 2015-08-31 14:40:02.083 KMCountDown[5102:103949] Event Handler2 2015-08-31 14:40:03.087 KMCountDown[5102:103949] Event Handler3 2015-08-31 14:40:04.084 KMCountDown[5102:103949] Event Handler4 2015-08-31 14:40:05.086 KMCountDown[5102:103971] Event Handler5 2015-08-31 14:40:06.085 KMCountDown[5102:103949] Event Handler6 2015-08-31 14:40:07.085 KMCountDown[5102:103949] Event Handler7 2015-08-31 14:40:07.085 KMCountDown[5102:103949] Cancel Handler

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