一、简介
1.NSOperation的作用
配合使用NSOperation和NSOperationQueue也能实现多线程编程
2.NSOperation和NSOperationQueue实现多线程的具体步骤
先将需要执行的操作封装到一个NSOperation对象中
然后将NSOperation对象添加到NSOperationQueue中
系统会自动将NSOperationQueue中的NSOperation取出来
将取出的NSOperation封装的操作放到一条新线程中执行
2.NSOperation的子类
NSOperation是个抽象类，并不具备封装操作的能力，必须使用它的子类.
使用NSOperation子类的方式有3种
NSInvocationOperation
NSBlockOperation
自定义子类继承NSOperation，实现内部相应的方法
二、NSInvocationOperation
默认情况下，调用了start方法后并不会开一条新线程去执行操作，而是在当前线程同步执行操作
只有将NSOperation放到一个NSOperationQueue中，才会异步执行操作
- (void)invocationOperation
{
NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(run) object:nil];
[op start];
}
- (void)run
{
NSLog(@"------%@", [NSThread currentThread]);
}
三、NSBlockOperation
只要NSBlockOperation封装的操作数 >1，就会异步执行操作
NSBlockOperation *op = [NSBlockOperation blockOperationWithBlock:^{
// 在主线程
NSLog(@"下载1------%@", [NSThread currentThread]);
}];
// 添加额外的任务(在子线程执行)
[op addExecutionBlock:^{
NSLog(@"下载2------%@", [NSThread currentThread]);
}];
[op addExecutionBlock:^{
NSLog(@"下载3------%@", [NSThread currentThread]);
}];
[op addExecutionBlock:^{
NSLog(@"下载4------%@", [NSThread currentThread]);
}];
[op start];
四、NSOperationQueue
1.NSOperationQueue的作用
如果将NSOperation添加到NSOperationQueue（操作队列）中，系统会自动异步执行NSOperation中的操作
2.添加操作到NSOperationQueue中
(1)-(void)addOperation:(NSOperation*)op;
// 创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
// 创建操作（任务）
// 创建NSInvocationOperation
NSInvocationOperation *op1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download1) object:nil];
NSInvocationOperation *op2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download2) object:nil];
// 创建NSBlockOperation
NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"download3 --- %@", [NSThread currentThread]);
}];
[op3 addExecutionBlock:^{
NSLog(@"download4 --- %@", [NSThread currentThread]);
}];
[op3 addExecutionBlock:^{
NSLog(@"download5 --- %@", [NSThread currentThread]);
}];
NSBlockOperation *op4 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"download6 --- %@", [NSThread currentThread]);
}];
// 创建XMGOperation
XMGOperation *op5 = [[XMGOperation alloc] init];
// 添加任务到队列中
[queue addOperation:op1]; // [op1 start]
[queue addOperation:op2]; // [op2 start]
[queue addOperation:op3]; // [op3 start]
[queue addOperation:op4]; // [op4 start]
[queue addOperation:op5]; // [op5 start]
(2)-(void)addOperationWithBlock:(void(^)(void))block;
// 创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
// 创建操作
// NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
// NSLog(@"download1 --- %@", [NSThread currentThread]);
// }];
// 添加操作到队列中
// [queue addOperation:op1];
[queue addOperationWithBlock:^{
NSLog(@"download1 --- %@", [NSThread currentThread]);
}];
[queue addOperationWithBlock:^{
NSLog(@"download2 --- %@", [NSThread currentThread]);
}];
3.最大并发数
// 创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
// 设置最大并发操作数
// queue.maxConcurrentOperationCount = 2;
queue.maxConcurrentOperationCount = 1; // 就变成了串行队列
// 添加操作
[queue addOperationWithBlock:^{
NSLog(@"download1 --- %@", [NSThread currentThread]);
[NSThread sleepForTimeInterval:0.01];
}];
[queue addOperationWithBlock:^{
NSLog(@"download2 --- %@", [NSThread currentThread]);
[NSThread sleepForTimeInterval:0.01];
}];
[queue addOperationWithBlock:^{
NSLog(@"download3 --- %@", [NSThread currentThread]);
[NSThread sleepForTimeInterval:0.01];
}];
4.队列的取消、暂停和恢复
// 创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
self.queue = queue;
// if (self.queue.isSuspended) {
// // 恢复队列，继续执行
// self.queue.suspended = NO;
// } else {
// // 暂停（挂起）队列，暂停执行
// self.queue.suspended = YES;
// }
[self.queue cancelAllOperations];
5.NSOperation之间可以设置依赖来保证执行顺序
比如一定要让操作A执行完后，才能执行操作B，可以这么写
[operationB addDependency:operationA];
注意：不能相互依赖
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"download1----%@", [NSThread currentThread]);
}];
NSBlockOperation *op2 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"download2----%@", [NSThread currentThread]);
}];
NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"download3----%@", [NSThread currentThread]);
}];
NSBlockOperation *op4 = [NSBlockOperation blockOperationWithBlock:^{
for (NSInteger i = 0; i<10; i++) {
NSLog(@"download4----%@", [NSThread currentThread]);
}
}];
NSBlockOperation *op5 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"download5----%@", [NSThread currentThread]);
}];
op5.completionBlock = ^{
NSLog(@"op5执行完毕---%@", [NSThread currentThread]);
};
// 设置依赖
[op3 addDependency:op1];
[op3 addDependency:op2];
[op3 addDependency:op4];
[queue addOperation:op1];
[queue addOperation:op2];
[queue addOperation:op3];
[queue addOperation:op4];
[queue addOperation:op5];
五、线程间的通信
[[[NSOperationQueue alloc] init] addOperationWithBlock:^{
// 图片的网络路径
NSURL *url = [NSURL URLWithString:@"http://img.pconline.com.cn/images/photoblog/9/9/8/1/9981681/200910/11/1255259355826.jpg"];
// 加载图片
NSData *data = [NSData dataWithContentsOfURL:url];
// 生成图片
UIImage *image = [UIImage imageWithData:data];
// 回到主线程
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
self.imageView.image = image;
}];
}];
六、多线程下载图片
#import "ViewController.h"
#import "XMGApp.h"
@interface ViewController ()
/** 所有数据 */
@property (nonatomic, strong) NSArray *apps;
/** 内存缓存的图片 */
@property (nonatomic, strong) NSMutableDictionary *images;
/** 队列对象 */
@property (nonatomic, strong) NSOperationQueue *queue;
@end
@implementation ViewController
- (NSOperationQueue *)queue
{
if (!_queue) {
_queue = [[NSOperationQueue alloc] init];
_queue.maxConcurrentOperationCount = 3;
}
return _queue;
}
- (NSMutableDictionary *)images
{
if (!_images) {
_images = [NSMutableDictionary dictionary];
}
return _images;
}
- (NSArray *)apps
{
if (!_apps) {
NSArray *dictArray = [NSArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"apps.plist" ofType:nil]];
NSMutableArray *appArray = [NSMutableArray array];
for (NSDictionary *dict in dictArray) {
[appArray addObject:[XMGApp appWithDict:dict]];
}
_apps = appArray;
}
return _apps;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
#pragma mark - 数据源方法
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.apps.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *ID = @"app";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
XMGApp *app = self.apps[indexPath.row];
cell.textLabel.text = app.name;
cell.detailTextLabel.text = app.download;
// 先从内存缓存中取出图片
UIImage *image = self.images[app.icon];
if (image) { // 内存中有图片
cell.imageView.image = image;
} else { // 内存中没有图片
// 获得Library/Caches文件夹
NSString *cachesPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
// 获得文件名
NSString *filename = [app.icon lastPathComponent];
// 计算出文件的全路径
NSString *file = [cachesPath stringByAppendingPathComponent:filename];
// 加载沙盒的文件数据
NSData *data = [NSData dataWithContentsOfFile:file];
if (data) { // 直接利用沙盒中图片
UIImage *image = [UIImage imageWithData:data];
cell.imageView.image = image;
// 存到字典中
self.images[app.icon] = image;
} else { // 下载图片
[self.queue addOperationWithBlock:^{
// 下载图片
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:app.icon]];
UIImage *image = [UIImage imageWithData:data];
[NSThread sleepForTimeInterval:1.0];
// 回到主线程显示图片
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
cell.imageView.image = image;
}];
// 存到字典中
self.images[app.icon] = image;
// 将图片文件数据写入沙盒中
[data writeToFile:file atomically:YES];
}];
}
}
return cell;
}
@end