开源 Objective-C IOS 应用开发（二十）多线程处理

#import <UIKit/UIKit.h>

@class CustomViewController;

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) CustomViewController *viewController;

@end

#import "AppDelegate.h"
#import "CustomViewController.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // 创建主窗口
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    
    // 创建自定义视图控制器
    self.viewController = [[CustomViewController alloc] init];
    
    // 设置根视图控制器
    self.window.rootViewController = self.viewController;
    
    // 设置窗口背景色并显示
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    
    return YES;
}

@end

#import <UIKit/UIKit.h>

@interface CustomViewController : UIViewController

// 线程控制相关属性
@property (nonatomic, strong) NSThread *backgroundThread;
@property (nonatomic, assign) BOOL shouldKeepRunning;
@property (nonatomic, strong) dispatch_queue_t serialQueue;
@property (nonatomic, strong) dispatch_queue_t concurrentQueue;

// UI 组件
@property (nonatomic, strong) UILabel *statusLabel;
@property (nonatomic, strong) UIButton *startButton;
@property (nonatomic, strong) UIButton *stopButton;
@property (nonatomic, strong) UIButton *dispatchButton;
@property (nonatomic, strong) UITextView *logTextView;
@property (nonatomic, strong) UIActivityIndicatorView *activityIndicator;

// 线程控制方法
- (void)startBackgroundThread;
- (void)stopBackgroundThread;
- (void)performTaskOnMainThread;
- (void)performTaskOnGlobalQueue;
- (void)performTaskOnSerialQueue;
- (void)updateUIWithText:(NSString *)text;

@end

#import "CustomViewController.h"

@interface CustomViewController ()

@property (nonatomic, strong) NSMutableString *logContent;

@end

@implementation CustomViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self setupUI];
    [self setupQueues];
    self.logContent = [NSMutableString string];
}

- (void)setupUI {
    self.view.backgroundColor = [UIColor systemBackgroundColor];
    
    // 状态标签
    self.statusLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 60, self.view.bounds.size.width - 40, 30)];
    self.statusLabel.text = @"线程状态: 就绪";
    self.statusLabel.textAlignment = NSTextAlignmentCenter;
    self.statusLabel.font = [UIFont boldSystemFontOfSize:16];
    [self.view addSubview:self.statusLabel];
    
    // 开始按钮
    self.startButton = [UIButton buttonWithType:UIButtonTypeSystem];
    self.startButton.frame = CGRectMake(20, 110, 80, 40);
    [self.startButton setTitle:@"开始线程" forState:UIControlStateNormal];
    [self.startButton addTarget:self action:@selector(startBackgroundThread) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.startButton];
    
    // 停止按钮
    self.stopButton = [UIButton buttonWithType:UIButtonTypeSystem];
    self.stopButton.frame = CGRectMake(120, 110, 80, 40);
    [self.stopButton setTitle:@"停止线程" forState:UIControlStateNormal];
    [self.stopButton addTarget:self action:@selector(stopBackgroundThread) forControlEvents:UIControlEventTouchUpInside];
    self.stopButton.enabled = NO;
    [self.view addSubview:self.stopButton];
    
    // GCD 任务按钮
    self.dispatchButton = [UIButton buttonWithType:UIButtonTypeSystem];
    self.dispatchButton.frame = CGRectMake(220, 110, 120, 40);
    [self.dispatchButton setTitle:@"执行GCD任务" forState:UIControlStateNormal];
    [self.dispatchButton addTarget:self action:@selector(performGCDTasks) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.dispatchButton];
    
    // 活动指示器
    self.activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleMedium];
    self.activityIndicator.frame = CGRectMake(self.view.bounds.size.width - 60, 115, 30, 30);
    [self.view addSubview:self.activityIndicator];
    
    // 日志文本框
    self.logTextView = [[UITextView alloc] initWithFrame:CGRectMake(20, 170, self.view.bounds.size.width - 40, 300)];
    self.logTextView.editable = NO;
    self.logTextView.font = [UIFont systemFontOfSize:12];
    self.logTextView.backgroundColor = [UIColor secondarySystemBackgroundColor];
    self.logTextView.text = @"线程日志:\n";
    [self.view addSubview:self.logTextView];
}

- (void)setupQueues {
    // 创建串行队列
    self.serialQueue = dispatch_queue_create("com.example.serialQueue", DISPATCH_QUEUE_SERIAL);
    
    // 创建并发队列
    self.concurrentQueue = dispatch_queue_create("com.example.concurrentQueue", DISPATCH_QUEUE_CONCURRENT);
}

#pragma mark - 线程控制方法

- (void)startBackgroundThread {
    if (self.backgroundThread && !self.backgroundThread.isFinished) {
        [self updateLog:@"后台线程已在运行"];
        return;
    }
    
    self.shouldKeepRunning = YES;
    self.backgroundThread = [[NSThread alloc] initWithTarget:self selector:@selector(backgroundThreadMain) object:nil];
    [self.backgroundThread start];
    
    self.startButton.enabled = NO;
    self.stopButton.enabled = YES;
    [self.activityIndicator startAnimating];
    
    [self updateLog:@"后台线程已启动"];
    self.statusLabel.text = @"线程状态: 运行中";
}

- (void)stopBackgroundThread {
    self.shouldKeepRunning = NO;
    
    // 给线程一些时间来清理和退出
    [self performSelector:@selector(forceStopThread) onThread:self.backgroundThread withObject:nil waitUntilDone:NO];
    
    [self updateLog:@"正在停止后台线程..."];
}

- (void)forceStopThread {
    // 在线程内部执行清理操作
    [self updateLog:@"后台线程正在清理..."];
    
    // 回到主线程更新UI
    [self performSelectorOnMainThread:@selector(threadStopped) withObject:nil waitUntilDone:NO];
}

- (void)threadStopped {
    self.startButton.enabled = YES;
    self.stopButton.enabled = NO;
    [self.activityIndicator stopAnimating];
    
    [self updateLog:@"后台线程已停止"];
    self.statusLabel.text = @"线程状态: 已停止";
}

- (void)backgroundThreadMain {
    @autoreleasepool {
        NSThread *currentThread = [NSThread currentThread];
        [self updateLog:[NSString stringWithFormat:@"后台线程开始: %@", currentThread]];
        
        int taskCount = 0;
        while (self.shouldKeepRunning && taskCount < 10) {
            @autoreleasepool {
                taskCount++;
                
                // 模拟后台任务
                [NSThread sleepForTimeInterval:2.0];
                
                // 更新UI必须在主线程
                [self performSelectorOnMainThread:@selector(updateTaskProgress:) withObject:@(taskCount) waitUntilDone:NO];
                
                if (!self.shouldKeepRunning) {
                    break;
                }
            }
        }
        
        [self updateLog:@"后台线程自然结束"];
        [self performSelectorOnMainThread:@selector(threadStopped) withObject:nil waitUntilDone:NO];
    }
}

- (void)updateTaskProgress:(NSNumber *)progress {
    self.statusLabel.text = [NSString stringWithFormat:@"任务进度: %d/10", progress.intValue];
    [self updateLog:[NSString stringWithFormat:@"完成任务 %d", progress.intValue]];
}

- (void)performGCDTasks {
    [self updateLog:@"开始执行GCD任务序列"];
    
    // 在串行队列上执行任务
    dispatch_async(self.serialQueue, ^{
        [self updateLog:@"串行队列任务1开始"];
        [NSThread sleepForTimeInterval:1.0];
        [self updateLog:@"串行队列任务1完成"];
    });
    
    dispatch_async(self.serialQueue, ^{
        [self updateLog:@"串行队列任务2开始"];
        [NSThread sleepForTimeInterval:1.0];
        [self updateLog:@"串行队列任务2完成"];
    });
    
    // 在并发队列上执行任务
    for (int i = 0; i < 3; i++) {
        dispatch_async(self.concurrentQueue, ^{
            [self updateLog:[NSString stringWithFormat:@"并发队列任务%d开始", i+1]];
            [NSThread sleepForTimeInterval:1.5];
            [self updateLog:[NSString stringWithFormat:@"并发队列任务%d完成", i+1]];
        });
    }
    
    // 在主队列执行UI更新
    dispatch_async(dispatch_get_main_queue(), ^{
        [self updateLog:@"主队列UI更新任务"];
        self.statusLabel.textColor = [UIColor systemBlueColor];
    });
    
    // 组任务示例
    dispatch_group_t group = dispatch_group_create();
    
    for (int i = 0; i < 2; i++) {
        dispatch_group_async(group, self.concurrentQueue, ^{
            [self updateLog:[NSString stringWithFormat:@"组任务%d执行中", i+1]];
            [NSThread sleepForTimeInterval:1.0];
        });
    }
    
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        [self updateLog:@"所有组任务已完成"];
        self.statusLabel.textColor = [UIColor systemGreenColor];
    });
}

#pragma mark - 工具方法

- (void)updateLog:(NSString *)message {
    // 确保UI更新在主线程执行
    if (![NSThread isMainThread]) {
        [self performSelectorOnMainThread:@selector(updateLog:) withObject:message waitUntilDone:NO];
        return;
    }
    
    NSString *timestamp = [self currentTimestamp];
    NSString *logMessage = [NSString stringWithFormat:@"[%@] %@\n", timestamp, message];
    
    [self.logContent appendString:logMessage];
    self.logTextView.text = self.logContent;
    
    // 自动滚动到底部
    if (self.logContent.length > 0) {
        NSRange bottom = NSMakeRange(self.logContent.length - 1, 1);
        [self.logTextView scrollRangeToVisible:bottom];
    }
}

- (NSString *)currentTimestamp {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"HH:mm:ss.SSS"];
    return [formatter stringFromDate:[NSDate date]];
}

- (void)dealloc {
    self.shouldKeepRunning = NO;
}

@end

info.plist中去掉manifest选项

三、源码分析

1. AppDelegate 类

application:didFinishLaunchingWithOptions: 方法

objective-c

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// 创建主窗口 - 应用程序的根窗口
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

// 创建自定义视图控制器 - 应用程序的主界面
self.viewController = [[CustomViewController alloc] init];

// 设置根视图控制器 - 建立窗口与控制器的关系
self.window.rootViewController = self.viewController;

    // 设置窗口背景色并显示 - 使窗口可见并准备好接收事件
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

return YES;
}

功能：应用程序启动入口点，负责初始化主窗口和根视图控制器。

2. CustomViewController 类

viewDidLoad 方法

objective-c

- (void)viewDidLoad {
[super viewDidLoad];

    [self setupUI];        // 初始化用户界面组件
    [self setupQueues];    // 创建GCD队列
    self.logContent = [NSMutableString string]; // 初始化日志内容存储
}

功能：视图控制器加载完成后的初始化工作。

setupUI 方法

objective-c

- (void)setupUI {
// 设置视图背景色
self.view.backgroundColor = [UIColor systemBackgroundColor];

    // 创建状态标签 - 显示线程运行状态
    self.statusLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 60, self.view.bounds.size.width - 40, 30)];
    self.statusLabel.text = @"线程状态: 就绪";
    self.statusLabel.textAlignment = NSTextAlignmentCenter;
    self.statusLabel.font = [UIFont boldSystemFontOfSize:16];

    // 创建开始按钮 - 启动后台线程
    self.startButton = [UIButton buttonWithType:UIButtonTypeSystem];
    self.startButton.frame = CGRectMake(20, 110, 80, 40);
    [self.startButton setTitle:@"开始线程" forState:UIControlStateNormal];
    [self.startButton addTarget:self action:@selector(startBackgroundThread) forControlEvents:UIControlEventTouchUpInside];

    // 创建停止按钮 - 停止后台线程（初始禁用）
    self.stopButton = [UIButton buttonWithType:UIButtonTypeSystem];
    self.stopButton.frame = CGRectMake(120, 110, 80, 40);
    [self.stopButton setTitle:@"停止线程" forState:UIControlStateNormal];
    [self.stopButton addTarget:self action:@selector(stopBackgroundThread) forControlEvents:UIControlEventTouchUpInside];
    self.stopButton.enabled = NO;

    // 创建GCD任务按钮 - 执行GCD演示任务
    self.dispatchButton = [UIButton buttonWithType:UIButtonTypeSystem];
    self.dispatchButton.frame = CGRectMake(220, 110, 120, 40);
    [self.dispatchButton setTitle:@"执行GCD任务" forState:UIControlStateNormal];
    [self.dispatchButton addTarget:self action:@selector(performGCDTasks) forControlEvents:UIControlEventTouchUpInside];

    // 创建活动指示器 - 显示线程运行状态
    self.activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleMedium];
    self.activityIndicator.frame = CGRectMake(self.view.bounds.size.width - 60, 115, 30, 30);

    // 创建日志文本框 - 显示线程执行日志
    self.logTextView = [[UITextView alloc] initWithFrame:CGRectMake(20, 170, self.view.bounds.size.width - 40, 300)];
    self.logTextView.editable = NO;
    self.logTextView.font = [UIFont systemFontOfSize:12];
    self.logTextView.backgroundColor = [UIColor secondarySystemBackgroundColor];
    self.logTextView.text = @"线程日志:\n";
}

功能：创建和配置所有UI组件，包括标签、按钮、活动指示器和日志显示区域。

setupQueues 方法

objective-c

- (void)setupQueues {
// 创建串行队列 - 任务按顺序执行
self.serialQueue = dispatch_queue_create("com.example.serialQueue", DISPATCH_QUEUE_SERIAL);

// 创建并发队列 - 任务可以并行执行
self.concurrentQueue = dispatch_queue_create("com.example.concurrentQueue", DISPATCH_QUEUE_CONCURRENT);
}

功能：初始化GCD队列，为后续的多线程任务做准备。

3. 线程控制核心方法

startBackgroundThread 方法

objective-c

- (void)startBackgroundThread {
    // 检查线程是否已在运行
    if (self.backgroundThread && !self.backgroundThread.isFinished) {
        [self updateLog:@"后台线程已在运行"];
        return;
    }

// 设置线程运行标志
self.shouldKeepRunning = YES;

    // 创建并启动新线程，执行backgroundThreadMain方法
    self.backgroundThread = [[NSThread alloc] initWithTarget:self selector:@selector(backgroundThreadMain) object:nil];
    [self.backgroundThread start];

    // 更新UI状态
    self.startButton.enabled = NO;
    self.stopButton.enabled = YES;
    [self.activityIndicator startAnimating];

[self updateLog:@"后台线程已启动"];
self.statusLabel.text = @"线程状态: 运行中";
}

功能：启动新的后台线程，更新UI状态，设置线程运行标志。

backgroundThreadMain 方法

objective-c

- (void)backgroundThreadMain {
    @autoreleasepool { // 创建自动释放池，管理内存
        // 获取当前线程信息并记录日志
        NSThread *currentThread = [NSThread currentThread];
        [self updateLog:[NSString stringWithFormat:@"后台线程开始: %@", currentThread]];

        int taskCount = 0;
        // 主循环：检查运行标志并执行任务
        while (self.shouldKeepRunning && taskCount < 10) {
            @autoreleasepool { // 内层自动释放池，每次循环释放资源
                taskCount++;

// 模拟耗时任务 - 线程休眠2秒
[NSThread sleepForTimeInterval:2.0];

// 在主线程更新任务进度
[self performSelectorOnMainThread:@selector(updateTaskProgress:) withObject:@(taskCount) waitUntilDone:NO];

                // 检查是否应该停止
                if (!self.shouldKeepRunning) {
                    break;
                }
            }
        }

        // 线程自然结束处理
        [self updateLog:@"后台线程自然结束"];
        [self performSelectorOnMainThread:@selector(threadStopped) withObject:nil waitUntilDone:NO];
    }
}

功能：后台线程的主循环，执行模拟任务，通过主线程更新UI。

stopBackgroundThread 方法

objective-c

- (void)stopBackgroundThread {
// 设置停止标志
self.shouldKeepRunning = NO;

// 在线程内部执行清理操作（不等待完成）
[self performSelector:@selector(forceStopThread) onThread:self.backgroundThread withObject:nil waitUntilDone:NO];

[self updateLog:@"正在停止后台线程..."];
}

功能：请求停止后台线程，设置停止标志并在目标线程执行清理。

forceStopThread 和 threadStopped 方法

objective-c

- (void)forceStopThread {
// 在线程内部执行清理操作
[self updateLog:@"后台线程正在清理..."];

// 回到主线程更新UI
[self performSelectorOnMainThread:@selector(threadStopped) withObject:nil waitUntilDone:NO];
}

- (void)threadStopped {
    // 更新UI状态
    self.startButton.enabled = YES;
    self.stopButton.enabled = NO;
    [self.activityIndicator stopAnimating];

[self updateLog:@"后台线程已停止"];
self.statusLabel.text = @"线程状态: 已停止";
}

功能：线程停止的清理工作和UI状态更新。

4. GCD任务演示方法

performGCDTasks 方法

objective-c

- (void)performGCDTasks {
[self updateLog:@"开始执行GCD任务序列"];

    // 串行队列演示 - 任务按顺序执行
    dispatch_async(self.serialQueue, ^{
        [self updateLog:@"串行队列任务1开始"];
        [NSThread sleepForTimeInterval:1.0]; // 模拟任务执行
        [self updateLog:@"串行队列任务1完成"];
    });

    dispatch_async(self.serialQueue, ^{
        [self updateLog:@"串行队列任务2开始"];
        [NSThread sleepForTimeInterval:1.0];
        [self updateLog:@"串行队列任务2完成"];
    });

    // 并发队列演示 - 任务并行执行
    for (int i = 0; i < 3; i++) {
        dispatch_async(self.concurrentQueue, ^{
            [self updateLog:[NSString stringWithFormat:@"并发队列任务%d开始", i+1]];
            [NSThread sleepForTimeInterval:1.5];
            [self updateLog:[NSString stringWithFormat:@"并发队列任务%d完成", i+1]];
        });
    }

    // 主队列UI更新 - 确保UI操作在主线程
    dispatch_async(dispatch_get_main_queue(), ^{
        [self updateLog:@"主队列UI更新任务"];
        self.statusLabel.textColor = [UIColor systemBlueColor];
    });

// 任务组演示 - 等待多个任务完成
dispatch_group_t group = dispatch_group_create();

    for (int i = 0; i < 2; i++) {
        dispatch_group_async(group, self.concurrentQueue, ^{
            [self updateLog:[NSString stringWithFormat:@"组任务%d执行中", i+1]];
            [NSThread sleepForTimeInterval:1.0];
        });
    }

    // 组任务完成通知
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        [self updateLog:@"所有组任务已完成"];
        self.statusLabel.textColor = [UIColor systemGreenColor];
    });
}

功能：演示GCD的各种使用场景，包括串行队列、并发队列、主队列和任务组。

5. 工具方法

updateLog: 方法

objective-c

- (void)updateLog:(NSString *)message {
    // 确保在主线程执行UI更新
    if (![NSThread isMainThread]) {
        [self performSelectorOnMainThread:@selector(updateLog:) withObject:message waitUntilDone:NO];
        return;
    }

    // 添加时间戳并格式化日志消息
    NSString *timestamp = [self currentTimestamp];
    NSString *logMessage = [NSString stringWithFormat:@"[%@] %@\n", timestamp, message];

    // 更新日志内容
    [self.logContent appendString:logMessage];
    self.logTextView.text = self.logContent;

    // 自动滚动到底部
    if (self.logContent.length > 0) {
        NSRange bottom = NSMakeRange(self.logContent.length - 1, 1);
        [self.logTextView scrollRangeToVisible:bottom];
    }
}

功能：线程安全的日志更新，确保UI操作在主线程执行。

currentTimestamp 方法

objective-c

- (NSString *)currentTimestamp {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"HH:mm:ss.SSS"]; // 格式化时间戳
    return [formatter stringFromDate:[NSDate date]];
}

功能：生成带毫秒的当前时间戳，用于日志记录。

6. 内存管理

dealloc 方法

objective-c

- (void)dealloc {
self.shouldKeepRunning = NO; // 确保线程停止
}

功能：对象销毁时确保后台线程停止，防止内存泄漏。