iOS线程间通信

什么叫做线程间通信

在1个进程中，线程往往不是孤立存在的，多个线程之间需要经常进行通信

线程间通信的体现

1个线程传递数据给另1个线程
在1个线程中执行完特定任务后，转到另1个线程继续执行任务

线程间通信常用方法

1. NSThread ：一个线程传递数据给另一个线程

- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait;

- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait NS_AVAILABLE(10_5, 2_0);

//具体用法如下:
//点击屏幕开始执行下载方法
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self performSelectorInBackground:@selector(download) withObject:nil];
}

//下载图片
- (void)download
{    
    // 1.图片地址
    NSString *urlStr = @"http://d.jpg"; 
    NSURL *url = [NSURL URLWithString:urlStr]; 
    // 2.根据地址下载图片的二进制数据 
    NSData *data = [NSData dataWithContentsOfURL:url]; 
    // 3.设置图片
    UIImage *image = [UIImage imageWithData:data]; 
    // 4.回到主线程，刷新UI界面(为了线程安全)
    [self performSelectorOnMainThread:@selector(downloadFinished:) withObject:image waitUntilDone:NO]; 
   // [self performSelector:@selector(downloadFinished:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES]; 
    
}

- (void)downloadFinished:(UIImage *)image
{
    self.imageView.image = image; 
    NSLog(@"downloadFinished---%@", [NSThread currentThread]);
}

2. GCD ：一个线程传递数据给另一个线程

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event    
{  
 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        
        NSLog(@"donwload---%@", [NSThread currentThread]);
        
        // 1.子线程下载图片
        NSURL *url = [NSURL URLWithString:@"http://d.jpg"];
        
        NSData *data = [NSData dataWithContentsOfURL:url];
        
        UIImage *image = [UIImage imageWithData:data];
        
        // 2.回到主线程设置图片
        dispatch_async(dispatch_get_main_queue(), ^{
            
            NSLog(@"setting---%@ %@", [NSThread currentThread], image);
            
            [self.button setImage:image forState:UIControlStateNormal];
        });
    });
}

3. NSMachPort

NSPort有3个子类，NSSocketPort、NSMessagePort、NSMachPort，但在iOS下只有NSMachPort可用。

#define kMsg1 100
#define kMsg2 101
 
- (void)viewDidLoad {
    [super viewDidLoad]; 
    //1. 创建主线程的port
    // 子线程通过此端口发送消息给主线程
    NSPort *myPort = [NSMachPort port]; 
    //2. 设置port的代理回调对象
    myPort.delegate = self; 
    //3. 把port加入runloop，接收port消息
    [[NSRunLoop currentRunLoop] addPort:myPort forMode:NSDefaultRunLoopMode]; 
    //4. 启动次线程,并传入主线程的port
    MyWorkerClass *work = [[MyWorkerClass alloc] init];
    [NSThread detachNewThreadSelector:@selector(launchThreadWithPort:)
                             toTarget:work
                           withObject:myPort];
}

- (void)handlePortMessage:(NSMessagePort*)message{ 
    NSLog(@"接到子线程传递的消息！%@",message); 
    //1. 消息id
    NSUInteger msgId = [[message valueForKeyPath:@"msgid"] integerValue]; 
    //2. 当前主线程的port
    NSPort *localPort = [message valueForKeyPath:@"localPort"]; 
    //3. 接收到消息的port（来自其他线程）
    NSPort *remotePort = [message valueForKeyPath:@"remotePort"];
 
    if (msgId == kMsg1)
    {
        //向子线的port发送消息
        [remotePort sendBeforeDate:[NSDate date]
                             msgid:kMsg2
                        components:nil
                              from:localPort
                          reserved:0];
 
    }else if (msgId == kMsg2){
        NSLog(@"操作2....\n");
    }
}

//MyWorkerClass类

#import "MyWorkerClass.h"
 
@interface MyWorkerClass() <NSMachPortDelegate> {
    NSPort *remotePort;
    NSPort *myPort;
}
@end
 
#define kMsg1 100
#define kMsg2 101
 
@implementation MyWorkerClass
 
- (void)launchThreadWithPort:(NSPort *)port {
 
    @autoreleasepool {
        //1. 保存主线程传入的port
        remotePort = port;
        //2. 设置子线程名字
        [[NSThread currentThread] setName:@"MyWorkerClassThread"];
        //3. 开启runloop
        [[NSRunLoop currentRunLoop] run];
        //4. 创建自己port
        myPort = [NSPort port];
        //5.
        myPort.delegate = self;
        //6. 将自己的port添加到runloop
        //作用1、防止runloop执行完毕之后推出
        //作用2、接收主线程发送过来的port消息
        [[NSRunLoop currentRunLoop] addPort:myPort forMode:NSDefaultRunLoopMode];
        //7. 完成向主线程port发送消息
        [self sendPortMessage];
    }
}
 
/**
 *   完成向主线程发送port消息
 */
- (void)sendPortMessage {
 
    NSMutableArray *array  =[[NSMutableArray alloc]initWithArray:@[@"1",@"2"]];
    //发送消息到主线程，操作1
    [remotePort sendBeforeDate:[NSDate date]
                         msgid:kMsg1
                    components:array
                          from:myPort
                      reserved:0]; 
}
 
#pragma mark - NSPortDelegate
/**
 *  接收到主线程port消息
 */
- (void)handlePortMessage:(NSPortMessage *)message
{
    NSLog(@"接收到父线程的消息...\n"); 
}
 
@end

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