iOS开发多线程篇—基础知识 NSOperation

//  DYFViewController.m
//  624-03-NSOperation
//
//  Created by dyf on 14-6-24.
//  Copyright (c) 2014年 ___FULLUSERNAME___. All rights reserved.
//

#import "DYFViewController.h"

@interface DYFViewController ()

@end

@implementation DYFViewController

- (void)viewDidLoad
{
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  
  
  [self testOperationQueue];
}

- (void)testOperationListen {
  NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"下载图片1111111%@", [NSThread currentThread]);
    // 下载图片
  }];
  operation3.completionBlock = ^{
    // 下载完图片后想做的时期
  };
  // 2.创建队列
  NSOperationQueue *queue = [[NSOperationQueue alloc] init];

  [queue addOperation:operation3];

}

- (void)testOperationQueue {
  // 1.封装操作
  NSInvocationOperation *operation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
  NSInvocationOperation *operation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(run) object:nil];
  
  NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"1111111%@", [NSThread currentThread]);
  }];
  
  [operation3 addExecutionBlock:^{
    NSLog(@"222222%@", [NSThread currentThread]);
  }];
  [operation3 addExecutionBlock:^{
    NSLog(@"33333%@", [NSThread currentThread]);
  }];
  // 2.创建队列
  NSOperationQueue *queue = [[NSOperationQueue alloc] init];
  // 5以内，2~3为宜
  queue.maxConcurrentOperationCount = 2;
#warning 面试题
  // 设置操作依赖(一定要在添加到队列中前设置)
  [operation2 addDependency:operation1]; // 执行顺序取决于依赖，先执行完operation1再执行operation2
// 注意：不能相互依赖，循环操作
  
  // 3.添加操作到队列中（自动执行操作，自动开启线程）
  [queue addOperation:operation1];
  [queue addOperation:operation2];
  [queue addOperation:operation3];
  
  // 取消所有线程
  //[queue cancelAllOperations];
  
  // 暂停队列
  //[queue setSuspended:YES];
  
  // 设置操作优先级
  //operation1.queuePriority = NSOperationQueuePriorityVeryHigh;
  
  
}

- (void)testNSBlockOperation {
  // 1.创建操作对象，封装要执行的任务
  NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
    for (int i = 0; i < 11; i++) {
      NSLog(@"1111111%@", [NSThread currentThread]);
    }
  }];
  // 任务数在2各以上，就会开线程
  [operation addExecutionBlock:^{
    for (int i = 0; i < 11; i++) {
      NSLog(@"222222%@", [NSThread currentThread]);
    }
  }];
  [operation addExecutionBlock:^{
    for (int i = 0; i < 11; i++) {
      NSLog(@"33333%@", [NSThread currentThread]);
    }
  }];

  // 2.执行操作
  [operation start];
}

- (void)testNSInvocationOperation {
  // 1.创建操作对象，封装要执行的任务
  NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
  // 2.执行操作(默认情况下，若操作没有放到队列queue中，都是同步执行)
  [operation start];
}

- (void)download
{
  for (int i = 0; i < 11; i++) {
    NSLog(@"download-----%@", [NSThread currentThread]);
  }
}

- (void)run
{
  for (int i = 0; i < 11; i++) {
    NSLog(@"run------%@", [NSThread currentThread]);
  }
}

@end

----自定义NSOperation---

//
//  DYFDownloadOperation.h
//  624-05-自定义Operation
//
//  Created by dyf on 14-6-24.
//  Copyright (c) 2014年 dyf. All rights reserved.
//

#import <Foundation/Foundation.h>

@class DYFDownloadOperation;
@protocol DYFDownloadOperationDelegate <NSObject>

@optional
- (void)downloadOperation:(DYFDownloadOperation *)operation didFinishedDownload:(UIImage *)image;

@end

@interface DYFDownloadOperation : NSOperation

@property (nonatomic, copy) NSString *url;
@property (nonatomic, strong) NSIndexPath *indexPath;

@property (nonatomic, weak) id<DYFDownloadOperationDelegate> delegate;

@end

//
//  DYFDownloadOperation.m
//  624-05-自定义Operation
//
//  Created by dyf on 14-6-24.
//  Copyright (c) 2014年 dyf. All rights reserved.
//

#import "DYFDownloadOperation.h"

@implementation DYFDownloadOperation
/**
 *  在main方法中实现具体操作
 */
- (void)main
{
  @autoreleasepool {
    if (self.isCancelled) return;
    NSURL *imaUrl = [NSURL URLWithString:self.url];
    if (self.isCancelled) return;
    // 下面这行很耗时
    NSData *data = [NSData dataWithContentsOfURL:imaUrl];
    if (self.isCancelled) return;
    UIImage *image = [UIImage imageWithData:data];
    if (self.isCancelled) return;
    
    // 返回主线程显示图片
    // 通过代理
    if ([self.delegate respondsToSelector:@selector(downloadOperation:didFinishedDownload:)]) {
      [self.delegate downloadOperation:self didFinishedDownload:image];
    }
  }
}

@end

具体利用MVC模式创建的文件老生常谈，只来一个Controller.m文件供参考，数据存储存在问题，可以改用SDWebImage框架处理

//
//  DYFTableViewController.m
//  624-05-自定义Operation
//
//  Created by dyf on 14-6-24.
//  Copyright (c) 2014年 ___FULLUSERNAME___. All rights reserved.
//

#import "DYFTableViewController.h"
#import "DYFAppModel.h"
#import "DYFDownloadOperation.h"

#warning Dictionary基础知识不太理解，字典的赋值回去看看笔记
@interface DYFTableViewController ()<DYFDownloadOperationDelegate>

@property (nonatomic, strong) NSArray *apps;
@property (nonatomic, strong) NSOperationQueue *queue;

/**
 *  key:url   value:operation对象
 */
@property (nonatomic, strong) NSMutableDictionary *oprations;
/**
 *  key:url   value:image对象
 */
@property (nonatomic, strong) NSMutableDictionary *images;

@end

@implementation DYFTableViewController

#pragma mark - 4个懒加载
- (NSArray *)apps
{
  if (!_apps) {
    NSString *path = [[NSBundle mainBundle] pathForResource:@"apps" ofType:@"plist"];
    NSArray *arrayApps = [NSArray arrayWithContentsOfFile:path];
    
    NSMutableArray *arrayM = [NSMutableArray arrayWithCapacity:arrayApps.count];
    for (NSDictionary *dict in arrayApps) {
      DYFAppModel *appM = [DYFAppModel appWithDict:dict];
      [arrayM addObject:appM];
    }
    _apps = arrayM;
  }
  return _apps;
}
- (NSOperationQueue *)queue
{
  if (!_queue) {
    _queue = [[NSOperationQueue alloc] init];
    // 设置最大并发线程数，最多同时下载3张图片
    _queue.maxConcurrentOperationCount = 3;
  }
  return _queue;
}
- (NSMutableDictionary *)oprations
{
  if (!_oprations) {
    _oprations = [[NSMutableDictionary alloc] init];
  }
  return _oprations;
}
- (NSMutableDictionary *)images
{
  if (!_images) {
    _images = [NSMutableDictionary dictionary];
  }
  return _images;
}

- (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
{
  // 1.创建cell
  static NSString *identifier = @"apps";
  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
  if (!cell) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:identifier];
  }
  // 2.设置cell的数据
  DYFAppModel *app = self.apps[indexPath.row];
  cell.textLabel.text = app.name;
  cell.detailTextLabel.text = app.download;
  
  // 重点是如何从网络下载图片传入cell上面
  // 每个url对应一个DYFDownloadOperation对象
  // 每个url对应一个image对象
  UIImage *image = self.images[app.icon];
  if (image) {
    // 若缓存中存在图片
    cell.imageView.image = image;
  }else
  {
    // 若缓存中不存在图片，则图片要从网上下载
    // 设置下载前系统刷出的图片
    cell.imageView.image = [UIImage imageNamed:@"身份证小"];
    
    // 基础差，下面这行不太理解
    DYFDownloadOperation *operation = self.oprations[app.icon];
    if (operation) {
      // 若正在下载，则不执行其它操作
    }else
    {
      // 若没在下载，则创建开始下载的子线程
      DYFDownloadOperation *operation = [[DYFDownloadOperation alloc] init];
      operation.url = app.icon;
      operation.indexPath = indexPath;
      operation.delegate = self;
      // 添加任务进队列，异步下载
      [self.queue addOperation:operation];
      // 基础差，下面这行不太理解
      self.oprations[app.icon] = operation;
    }
  }
  
  // 3.返回cell
  return cell;
}

#pragma mark - DYFDownloadOperationDelegate
- (void)downloadOperation:(DYFDownloadOperation *)operation didFinishedDownload:(UIImage *)image
{
  // 1.删除执行完毕的下载操作
  [self.oprations removeObjectForKey:operation.url];
  // 若图片下载好
  if (image) {
    // 2.将下载好的图片存入缓存
    self.images[operation.url] = image;
    // 3.刷新这一行cell的数据
    [self.tableView reloadRowsAtIndexPaths:@[operation.indexPath] withRowAnimation:UITableViewRowAnimationNone];
    // 4.将图片存入沙盒
    
    // 4.1图片先转换为2进制数据
    NSData *data = UIImagePNGRepresentation(image);
    // 4.2设置沙盒路径
    NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:[self.apps[operation.indexPath.row] icon]];
    NSLog(@"%@", path);
    // 4.3保存data到path中
    [data writeToFile:path atomically:YES];
  }
}

// 开始拖拽时候暂停队列
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
  [self.queue setSuspended:YES];
}
// 停止拖拽的时候重启队列
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
  [self.queue setSuspended:NO];
}

@end