ios多图下载，优化cell

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{static NSString *ID &＃61; &＃64;"app";//1.创建cellUITableViewCell *cell &＃61; [tableView dequeueReusableCellWithIdentifier:ID];//2.设置cell数据//2.1拿到该行cell对应的数据JKYApp *appM &＃61; self.apps[indexPath.row];cell.textLabel.text &＃61; appM.name;cell.detailTextLabel.text &＃61; appM.download;//设置图标
UIImage *image &＃61; [self.imageDic objectForKey:appM.icon];if (image) {cell.imageView.image &＃61; image;}else{NSURL *url &＃61; [NSURL URLWithString:appM.icon];NSData *imageData &＃61; [NSData dataWithContentsOfURL:url];UIImage *image &＃61; [UIImage imageWithData:imageData];cell.imageView.image &＃61; image;//将图片保存到内存缓存
[self.imageDic setObject:image forKey:appM.icon];}//3.返回cellreturn cell;
}

/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 &＃61; [self.images objectForKey:appM.icon];if (image) {cell.imageView.image &＃61; image;NSLog(&＃64;"%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 &＃61; [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];//获得图片的名称,不能包含/NSString *fileName &＃61; [appM.icon lastPathComponent];//拼接图片的全路径NSString *fullPath &＃61; [caches stringByAppendingPathComponent:fileName];//检查磁盘缓存NSData *imageData &＃61; [NSData dataWithContentsOfFile:fullPath];//废除imageData &＃61; nil;if (imageData) {UIImage *image &＃61; [UIImage imageWithData:imageData];cell.imageView.image &＃61; image;NSLog(&＃64;"%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(&＃64;"%&＃64;",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 &＃61; [self.operations objectForKey:appM.icon];if (download) {}else{//先清空cell原来的图片cell.imageView.image &＃61; [UIImage imageNamed:&＃64;"Snip20160221_306"];download &＃61; [NSBlockOperation blockOperationWithBlock:^{NSURL *url &＃61; [NSURL URLWithString:appM.icon];NSData *imageData &＃61; [NSData dataWithContentsOfURL:url];UIImage *image &＃61; [UIImage imageWithData:imageData];NSLog(&＃64;"%zd--下载---",indexPath.row);//容错处理if (image &＃61;&＃61; 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(&＃64;"Download---%&＃64;",[NSThread currentThread]);//线程间通信[[NSOperationQueue mainQueue] addOperationWithBlock:^{//cell.imageView.image &＃61; image;//刷新一行
[self.tableView reloadRowsAtIndexPaths:&＃64;[indexPath] withRowAnimation:UITableViewRowAnimationLeft];//NSLog(&＃64;"UI---%&＃64;",[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cellreturn cell;

-(void)didReceiveMemoryWarning
{[self.images removeAllObjects];//取消队列中所有的操作
[self.queue cancelAllOperations];
}