iOS多线程实现多图下载功能

本文实例为大家分享了iOS多线程实现多图下载功能的具体代码，供大家参考，具体内容如下

一.模型文件代码如下

// 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

控制器.m代码如下:

// 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 

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