iOS 多线程
一、多线程的理解
1.多线程可以使多个线程并行的工作以完成多项任务，以提高系统的效率。线程是在同一时间需要完成多项任务的时候被实现的。
2.在刷新tableView，Block回调这都必须回到主线程。
二、多线程的种类
1.NSThread
2.NSOperation和NSOperationQueue
3.GCD（Grand Central Dispatch）
三、多线程的操作
1.NSThread
//NSTread 线程手动启动1
- (IBAction)clickNSTreadBtnAction:(UIButton *)sender {
NSThread *thread = [[NSThread alloc]initWithTarget:self selector:@selector(addWithStr:) object:@"dsbhdbj"];
[thread start];
}
//NSTread 线程手动启动2
- (IBAction)clickNSTreadBtnAction2:(UIButton *)sender {
[NSThread detachNewThreadSelector:@selector(addWithStr:) toTarget:self withObject:@"张亮真帅"];
}
//求和
-(void)addWithStr:(NSString *)str{
NSLog(@"%@", str);
int sum = 0;
for (int i = 0; i < 900000000; i++) {
sum += i;
NSLog(@"%d",sum);
}
}
2.NSOperation和NSOperationQueue
//NSOperation的子类：NSInvocationOperation和NSBlockOperation
//注意：当NSOperation的子类关联执行方法或者block语法块，单一使用的只是执行了关联的方法或者block语法块，并没有开子线程，如果需要开子线程执行，需要和NSOperationQueue联合使用
//方法一 NSInvocationOperationn
- (IBAction)clickOperationBtnAction:(UIButton *)sender {
NSInvocationOperation *operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(addWithStr:) object:@"sdjd"];
//执行
[operation start];
}
//方法二 NSBlockOperation
- (IBAction)clickBlockOperationBtnAction:(UIButton *)sender {
NSBlockOperation *blockOperation = [NSBlockOperation blockOperationWithBlock:^{
[self addWithStr:nil];
}];
//执行
[blockOperation start];
}
//OperationQueue
- (IBAction)clickOperationQueueBtnAction:(UIButton *)sender {
//创建Operation 对象
NSInvocationOperation *operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(operation1) object:nil];
//创建Operation 对象
NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"我是2");
}];
//创建OperationQueue对象 1和2 是并发执行的 无序
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
//最大并发数
queue.maxConcurrentOperationCount = 1;
//依赖关系 2先执行 1后执行
[operation1 addDependency:operation2];
//添加OperationQueue对象，（Operation 不需要手动开启）
[queue addOperation:operation2];
[queue addOperation:operation1];
}
-(void)operation1{
NSLog(@"我是1");
}
3.GCD（Grand Central Dispatch）
1.GCD主队列
- (IBAction)clickGCDBtnAction:(UIButton *)sender {
//主队列（串行) 按顺序执行
//获取主队列
dispatch_queue_t mainQueue = dispatch_get_main_queue();
//执行任务 第一个参数：队列 第二个参数：任务
dispatch_async(mainQueue, ^{
NSLog(@"我是第一个");
});
dispatch_async(mainQueue, ^{
NSLog(@"我是第二个");
});
dispatch_async(mainQueue, ^{
for (int i = 0; i < 10; i++) {
NSLog(@"%d",++i);
}
});
dispatch_async(mainQueue, ^{
NSLog(@"我是第四个");
});
dispatch_async(mainQueue, ^{
NSLog(@"我是第五个");
});
}
2.GCD自定义队列
- (IBAction)clickGCDBtnAction:(UIButton *)sender {
//自定义队列（串行的、并发的）
//第一个参数： 队列名 第二个参数：属性（默认DISPATH_QUEUE_SERIAL(NULL)代表串行 DISPATCH_QUEUE_CONCURRENT代表并发）
//获取主队列
dispatch_queue_t queue1 = dispatch_queue_create("queue1", DISPATCH_QUEUE_CONCURRENT);
//给队列添加任务
dispatch_async(queue1, ^{
NSLog(@"queue1-1");
});
dispatch_async(queue1, ^{
NSLog(@"queue1-2");
});
dispatch_async(queue1, ^{
NSLog(@"queue1-3");
});
dispatch_async(queue1, ^{
NSLog(@"queue1-4");
});
}
3.GCD全局队列
- (IBAction)clickGCDBtnAction:(UIButton *)sender {
//全局队列（并发的）
//获取主队列
//第一个参数：（优先级别） 第二个参数：标志
dispatch_queue_t global = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
dispatch_queue_t global2 = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0);
dispatch_async(global2, ^{
NSLog(@"global2-1");
});
dispatch_async(global2, ^{
NSLog(@"global2-2");
});
dispatch_async(global2, ^{
NSLog(@"global2-3");
});
dispatch_async(global2, ^{
NSLog(@"global2-4");
});
dispatch_async(global, ^{
NSLog(@"global-1");
});
dispatch_async(global, ^{
NSLog(@"global-2");
});
dispatch_async(global, ^{
NSLog(@"global-3");
});
dispatch_async(global, ^{
NSLog(@"global-4");
});
}
四、GCD官方文档
https://developer.apple.com/library/ios/documentation/Performance/Reference/GCD_libdispatch_Ref/index.html#//apple_ref/doc/uid/TP40008079