iOS学习笔记——多线程（简单售票系统）

进程是系统资源管理的最小单位。线程是程序执行的最小单位。多线程是一个进程里包含多个线程。一个进程数据会加载到一个内存区间中，其中的线程共享相同的内存空间。各个进程的地址是独立的，只有进程能刷新UI、更新数据。线程需要手动开启。

建立一个简单售票系统，连接线程的运行。首先创建一个单视图工程，在.h文件中代码：

@interface LinViewController : UIViewController{    //声明剩余票数、卖出票数成员名    int _leftTickets;    int _soldTickets;    //声明线程成员名    NSThread * _firstThread;    NSThread * _secondThread;    NSThread * _thridThread;    //声明线程锁    NSCondition * _ticketsCondition;}//创建标签栏的对象，用来显示剩余票数、卖出票数、当前线程名@property (retain, nonatomic) UILabel * leftLabel;@property (retain, nonatomic) UILabel * soldLabel;@property (retain, nonatomic) UILabel * currentThreadLabel;@end

在.m文件中的代码：

#import "LinViewController.h"//预编译变量，设置票的总数量#define MaxTickets 100@implementation LinViewController//释放创建的对象- (void)dealloc{    [_leftLabel release];    [_soldLabel release];    [_currentThreadLabel release];    [super dealloc];}- (void)viewDidLoad{    [super viewDidLoad];    //加载辅助的标签栏，只显示内容    [self addLabel:nil];        //设置标签栏对象的位置    self.leftLabel = [[UILabel alloc]initWithFrame:CGRectMake(150, 90, 100, 30)];    self.soldLabel = [[UILabel alloc]initWithFrame:CGRectMake(150, 170, 100, 30)];    self.currentThreadLabel = [[UILabel alloc]initWithFrame:CGRectMake(150, 250, 100, 30)];    //设置标签栏对象的背景颜色    self.leftLabel.backgroundColor = [UIColor lightGrayColor];    self.soldLabel.backgroundColor = [UIColor lightGrayColor];    self.currentThreadLabel.backgroundColor = [UIColor lightGrayColor];    //把标签栏添加到当前的视图中    [self.view addSubview:self.leftLabel];    [self.view addSubview:self.soldLabel];    [self.view addSubview:self.currentThreadLabel];        //初始化成员并赋值    _leftTickets = MaxTickets;    _soldTickets = 0;    _ticketsCondition = [[NSCondition alloc]init];        //创建按钮对象    UIButton * pButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];    //设置按钮的位置    [pButton setFrame:CGRectMake(80, 340, 180, 40)];    //为按钮添加标题    [pButton setTitle:@"开始卖票" forState:UIControlStateNormal];    //设置按钮的方法，响应方式    [pButton addTarget:self action:@selector(threadStart:) forControlEvents:UIControlEventTouchUpInside];    //把按钮添加到当前视图中    [self.view addSubview:pButton];}#pragma mark-------增加辅助标签栏- (void)addLabel:(id)sender{    //初始化标签栏对象对设置位置    UILabel * pLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, 20, 300, 40)];    UILabel * pLabel1 = [[UILabel alloc]initWithFrame:CGRectMake(10, 80, 120, 50)];    UILabel * pLabel2 = [[UILabel alloc]initWithFrame:CGRectMake(10, 160, 120, 50)];    UILabel * pLabel3 = [[UILabel alloc]initWithFrame:CGRectMake(10, 240, 120, 50)];    //设置标签栏的内容文本    pLabel.text = @"模拟火车票销售---多线程";    pLabel1.text = @"剩余票数";    pLabel2.text = @"售出票数";    pLabel3.text = @"当前进程";    //设置标签栏的背景颜色    pLabel.backgroundColor = [UIColor clearColor];    pLabel1.backgroundColor = [UIColor clearColor];    pLabel2.backgroundColor = [UIColor clearColor];    pLabel3.backgroundColor = [UIColor clearColor];    //设置标签栏的文本居中    pLabel.textAlignment = NSTextAlignmentCenter;    pLabel1.textAlignment = NSTextAlignmentCenter;    pLabel2.textAlignment = NSTextAlignmentCenter;    pLabel3.textAlignment = NSTextAlignmentCenter;    //把标签栏对象添加到视图中    [self.view addSubview:pLabel];    [self.view addSubview:pLabel1];    [self.view addSubview:pLabel2];    [self.view addSubview:pLabel3];    //释放创建的对象    [pLabel release];    [pLabel1 release];    [pLabel2 release];    [pLabel3 release];}#pragma mark-------开始卖票，线程开始运行- (void)threadStart:(id)sender{    //初始化子线程，设置子线程的方法    _firstThread = [[NSThread alloc]initWithTarget:self selector:@selector(sellTickets:) object:nil];    //设置子线程的名字    [_firstThread setName:@"thread-1"];    //⭐️手动开启子线程，必须添加，系统不能自主进行    [_firstThread start];        _secondThread = [[NSThread alloc]initWithTarget:self selector:@selector(sellTickets:) object:nil];    [_secondThread setName:@"thread-2"];    [_secondThread start];        _thridThread = [[NSThread alloc]initWithTarget:self selector:@selector(sellTickets:) object:nil];    [_thridThread setName:@"thread-3"];    [_thridThread start];}//卖票的方法- (void)sellTickets:(id)sender{    while (YES)    {        //⭐️锁定线程，防止同一子线程多次运行，必须有        [_ticketsCondition lock];        //判断票是否卖完        if (_leftTickets > 0)        {            //设置线程停止0.1秒            [NSThread sleepForTimeInterval:0.1];            //卖票的算法            _leftTickets--;            _soldTickets = MaxTickets - _leftTickets;        }        else if (_leftTickets == 0)        {            NSLog(@"票已经卖完！");            break;        }        //子线程调用主线程更新视图，只有进程能更新视图        [self performSelectorOnMainThread:@selector(updateMyView:) withObject:[[NSThread currentThread]name] waitUntilDone:YES];        //输出剩余票数、售出票数、当前线程，可以省略        NSLog(@"剩余票数:%i售出票数:%i当前线程%@",_leftTickets,_soldTickets,[[NSThread currentThread]name]);        //线程解锁        [_ticketsCondition unlock];    }}#pragma mark-------更新界面，进程可以，线程不可以- (void)updateMyView:(id)sender{    //设置标签栏的显示内容    self.leftLabel.text = [NSString stringWithFormat:@"%i",_leftTickets];    self.soldLabel.text = [NSString stringWithFormat:@"%i",_soldTickets];    self.currentThreadLabel.text = (NSString *)sender;    //判断是否卖完，若卖完则弹出警告框    if (_leftTickets == 0)    {        UIAlertView * pAlertView = [[UIAlertView alloc]initWithTitle:@"温馨提示" message:@"票已经全部售出！" delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];        [pAlertView show];        [pAlertView release];    }    }- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];}@end