多线程是为了解决主线程被阻塞,并提高效率的一种方式.
首先我们要学习多线程编程就要看看它有哪几种方式:
- NSThread
- NSOperation
- Grand Centeral Dispatch
我们看看NSThread的创建方式::
NSThread *thread = [[NSThread alloc]initWithTarget:self selector:@selector(btnSum:) object:nil]; //通过iniit 创建NSThread 需要手动开启线程 [thread start]; [thread cancel]; //第二种开启并自动执行 btnSum 是自己写的一个方法 [NSThread detachNewThreadSelector:@selector(btnSum:) toTarget:self withObject:nil];
- (void)btnSum:(UIButton *)sender {
long sum = 0;
for (long i = 0; i < 10; i ++) {
sum += i;
NSLog(@"number %ld current Thred : %@ %@",sum,[NSThread currentThread],[NSOperationQueue currentQueue]);
}
}
使用NSThread 或直接从 NSObject 的类方法 performSelectorInBackground:withObject: 来创建一个线程。如果你选择thread来实现多线程，那么 NSThread 就是官方推荐优先选用的方式
NSOperation
/**
NSOperationQueue线程队列
*/
// 1.NSInvocationOperation操作
NSInvocationOperation *iOP =[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(btnSum:) object:nil];
//Operation是不能执行的,需要队列进行调用
[[NSOperationQueue mainQueue] addOperation:iOP];
//2.NSBlockOperation
NSBlockOperation *bOP = [[NSBlockOperation alloc]init];
//以代码块的方式添加操作
[bOP addExecutionBlock:^{
[self btnSum:nil];
}];
//添加到线程队列
[self.operationQueue addOperation:bOP];
为了创建一个简单的NSOperation对象,直接重写了getter方法
- (NSOperationQueue *)operationQueue{
if (!_operationQueue ) {
_operationQueue = [[NSOperationQueue alloc]init];
[_operationQueue setName:@"queue"];
}
return _operationQueue;
}
//NSBlockOperation 创建方式,可以用便利构造器,直接添加block
NSBlockOperation *bOP = [NSBlockOperation blockOperationWithBlock:^{
for (int i = 0; i < 100; i ++) {
NSLog(@"%d,当前线程:::%@",i,[NSThread currentThread]);
}
}];
NSBlockOperation *aOP = [NSBlockOperation blockOperationWithBlock:^{
for (int i = 0; i < 100; i ++) {
NSLog(@"%d,当前线程:::%@",i,[NSThread currentThread]);
}
}];
NSBlockOperation *cOP = [NSBlockOperation blockOperationWithBlock:^{
for (int i = 0; i < 100; i ++) {
NSLog(@"%d,当前线程333333333:::%@",i,[NSThread currentThread]);
}
}];
//添加到主队列
[[NSOperationQueue mainQueue] addOperation:bOP];
[[NSOperationQueue mainQueue] addOperation:cOP];
//自定义队列
self.operation = [[NSOperationQueue alloc]init];
//设置最大并发数
self.operation.maxConcurrentOperationCount = 1;//在同一连续时刻只执行一个操作
// self.operation.maxConcurrentOperationCount = 4;
[self performSelectorInBackground:@selector(printNumber:) withObject:@"NSObject"];
[self.operation addOperation:aOP];
[self.operation addOperation:cOP];
GCD
/**
GCD 中央派发机制 Grand Central Dispatch
基于函数,使用分发队列FIFO
*/
//1.主线程队列::等同于[NSOperationQueue mainQueue]
//2.全局线程队列 后台队列 并行
//3.自定义线程队列 DISPATCH_QUEUE_SERIAL 串行
// DISPATCH_QUEUE_CONCURRENT 并行
/*
//创建自定义队列,默认为串行(故加了个优先级的东东::DISPATCH_QUEUE_PRIORITY_DEFAULT)
dispatch_queue_t myQueue = dispatch_queue_create("com.liulei.www.myQueue",DISPATCH_QUEUE_PRIORITY_DEFAULT);
//串行队列
// dispatch_async(队列, 执行block) 异步
// dispatch_sync(队列, 执行block)同步
dispatch_async(myQueue, ^{
[self printNumber:@"GCD"];
[self printNumber:@"GCD1"];
});
dispatch_async(myQueue, ^{
[self printNumber:@"GCD2"];
});
*/
/*
//并行队列
dispatch_queue_t conQueue = dispatch_queue_create("conQueue", DISPATCH_QUEUE_CONCURRENT);
//一个bolck中串行
dispatch_async(conQueue, ^{
//顺序执行
[self printNumber:@"G1"];
[self printNumber:@"G2"];
[self printNumber:@"G3"];
});
//并行执行
dispatch_async(conQueue, ^{
[self printNumber:@"G4"];
});
dispatch_async(conQueue, ^{
[self printNumber:@"G5"];
});
*/
//dispatch_after ..//延时操作
既然说道多线程的开发，难免会在多线程之间进行通讯；
利用NSObject的一些类方法，可以轻松搞定。(NSObject内置方法来创建线程)
在应用程序主线程中做事情：
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array
在指定线程中做事情：
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array
在当前线程中做事情：
//Invokes a method of the receiver on the current thread using the default mode after a delay.
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay
performSelector:withObject:afterDelay:inModes:
取消发送给当前线程的某个消息
cancelPreviousPerformRequestsWithTarget:
cancelPreviousPerformRequestsWithTarget:selector:object:
如在我们在某个线程中下载数据，下载完成之后要通知主线程中更新界面等等，可以使用如下接口：-
[self performSelectorOnMainThread:@selector(updateUI) withObject:nil waitUntilDone:NO];
比如下载完成后,通知主线程(ui线程),以便app再做其他工作