iOS多线程实现多图下载功能

// XMGAPP.h  #import <Foundation/Foundation.h>  @interface XMGAPP : NSObject  /** APP的名称 */ @property (nonatomic, strong) NSString *name; /** APP的图片的url地址 */ @property (nonatomic, strong) NSString *icon; /** APP的下载量 */ @property (nonatomic, strong) NSString *download;  +(instancetype)appWithDict:(NSDictionary *)dict; @end 

// XMGAPP.m  #import "XMGAPP.h"  @implementation XMGAPP  +(instancetype)appWithDict:(NSDictionary *)dict {   XMGAPP *appM = [[XMGAPP alloc]init];   //KVC   [appM setValuesForKeysWithDictionary:dict];      return appM; } @end 

// ViewController.m  #import "ViewController.h" #import "XMGAPP.h"  @interface ViewController () /** tableView的数据源 */ @property (nonatomic, strong) NSArray *apps; /** 内存缓存 */ @property (nonatomic, strong) NSMutableDictionary *images; /** 队列 */ @property (nonatomic, strong) NSOperationQueue *queue; /** 操作缓存 */ @property (nonatomic, strong) NSMutableDictionary *operations; @end  @implementation ViewController  #pragma mark ---------------------- #pragma mark lazy loading -(NSOperationQueue *)queue {   if (_queue == nil) {     _queue = [[NSOperationQueue alloc]init];     //设置最大并发数     _queue.maxConcurrentOperationCount = 5;   }   return _queue; } -(NSMutableDictionary *)images {   if (_images == nil) {     _images = [NSMutableDictionary dictionary];   }   return _images; } -(NSArray *)apps {   if (_apps == nil) {          //字典数组     NSArray *arrayM = [NSArray arrayWithContentsOfFile:[[NSBundle mainBundle]pathForResource:@"apps.plist" ofType:nil]];          //字典数组---->模型数组     NSMutableArray *arrM = [NSMutableArray array];     for (NSDictionary *dict in arrayM) {       [arrM addObject:[XMGAPP appWithDict:dict]];     }     _apps = arrM;   }   return _apps; }  -(NSMutableDictionary *)operations {   if (_operations == nil) {     _operations = [NSMutableDictionary dictionary];   }   return _operations; }  #pragma mark ---------------------- #pragma mark UITableViewDatasource -(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {   return 1; }  -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {   return self.apps.count; }  -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {   static NSString *ID = @"app";      //1.创建cell   UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];      //2.设置cell的数据   //2.1 拿到该行cell对应的数据   XMGAPP *appM = self.apps[indexPath.row];      //2.2 设置标题   cell.textLabel.text = appM.name;      //2.3 设置子标题   cell.detailTextLabel.text = appM.download;      //2.4 设置图标      //先去查看内存缓存中该图片时候已经存在,如果存在那么久直接拿来用,否则去检查磁盘缓存   //如果有磁盘缓存,那么保存一份到内存,设置图片,否则就直接下载   //1)没有下载过   //2)重新打开程序      UIImage *image = [self.images objectForKey:appM.icon];   if (image) {     cell.imageView.image = image;     NSLog(@"%zd处的图片使用了内存缓存中的图片",indexPath.row) ;   }else   {     //保存图片到沙盒缓存     NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];     //获得图片的名称,不能包含/     NSString *fileName = [appM.icon lastPathComponent];     //拼接图片的全路径     NSString *fullPath = [caches stringByAppendingPathComponent:fileName];               //检查磁盘缓存     NSData *imageData = [NSData dataWithContentsOfFile:fullPath];     //废除     imageData = nil;          if (imageData) {       UIImage *image = [UIImage imageWithData:imageData];       cell.imageView.image = image;              NSLog(@"%zd处的图片使用了磁盘缓存中的图片",indexPath.row) ;       //把图片保存到内存缓存       [self.images setObject:image forKey:appM.icon];        //      NSLog(@"%@",fullPath);     }else     {       //检查该图片时候正在下载,如果是那么久什么都捕捉,否则再添加下载任务       NSBlockOperation *download = [self.operations objectForKey:appM.icon];       if (download) {                }else       {                  //先清空cell原来的图片         cell.imageView.image = [UIImage imageNamed:@"Snip20160221_306"];                  download = [NSBlockOperation blockOperationWithBlock:^{           NSURL *url = [NSURL URLWithString:appM.icon];           NSData *imageData = [NSData dataWithContentsOfURL:url];           UIImage *image = [UIImage imageWithData:imageData];                       NSLog(@"%zd--下载---",indexPath.row);                      //容错处理           if (image == nil) {             [self.operations removeObjectForKey:appM.icon];             return ;           }           //演示网速慢的情况           //[NSThread sleepForTimeInterval:3.0];                    //把图片保存到内存缓存           [self.images setObject:image forKey:appM.icon];                      //NSLog(@"Download---%@",[NSThread currentThread]);           //线程间通信           [[NSOperationQueue mainQueue] addOperationWithBlock:^{                          //cell.imageView.image = image;             //刷新一行             [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationLeft];             //NSLog(@"UI---%@",[NSThread currentThread]);           }];                                 //写数据到沙盒           [imageData writeToFile:fullPath atomically:YES];                      //移除图片的下载操作           [self.operations removeObjectForKey:appM.icon];                    }];                  //添加操作到操作缓存中         [self.operations setObject:download forKey:appM.icon];                  //添加操作到队列中         [self.queue addOperation:download];       }            }   }      //3.返回cell   return cell; }  -(void)didReceiveMemoryWarning {   [self.images removeAllObjects];      //取消队列中所有的操作   [self.queue cancelAllOperations]; }  //1.UI很不流畅 --- > 开子线程下载图片 //2.图片重复下载 ---> 先把之前已经下载的图片保存起来(字典) //内存缓存--->磁盘缓存  //3.图片不会刷新--->刷新某行 //4.图片重复下载(图片下载需要时间,当图片还未完全下载之前,又要重新显示该图片) //5.数据错乱 ---设置占位图片  /*  Documents:会备份,不允许  Libray   Preferences:偏好设置 保存账号   caches:缓存文件  tmp:临时路径(随时会被删除)  */  @end