iOS多图下载案例（三）

利用多线程进行优化

#import"ViewController.h"

#import"App.h"

@interfaceViewController()

@property(nonatomic,strong)NSArray*apps;

//内存缓存

@property(nonatomic,strong)NSMutableDictionary*imageDic;

@property(nonatomic,strong)NSOperationQueue*queue;

@property(nonatomic,strong)NSMutableDictionary*operation;

@end

@implementationViewController

- (NSMutableDictionary*)operation{

if(_operation==nil) {

_operation= [NSMutableDictionarydictionary];

}

return_operation;

}

- (NSOperationQueue*)queue{

if(_queue==nil) {

_queue= [[NSOperationQueuealloc]init];

//设置最大并发数

_queue.maxConcurrentOperationCount=5;

}

return_queue;

}

- (NSMutableDictionary*)imageDic{

if(_imageDic==nil) {

_imageDic= [NSMutableDictionarydictionary];

}

return_imageDic;

}

- (NSArray*)apps{

if(_apps==nil) {

NSArray*ary = [NSArrayarrayWithContentsOfFile:[[NSBundlemainBundle]pathForResource:@"apps"ofType:@"plist"]];

NSMutableArray*ary1 = [NSMutableArrayarray];

for(NSDictionary*dicinary) {

[ary1addObject:[AppappWithdic:dic]];

}

_apps= ary1;

}

return_apps;

}

- (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section{

returnself.apps.count;

}

- (NSInteger)numberOfSectionsInTableView:(UITableView*)tableView{

return1;

}

- (UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath{

staticNSString* ID =@"app";

UITableViewCell*cell =[tableViewdequeueReusableCellWithIdentifier:ID];

App*app =_apps[indexPath.row];

cell.textLabel.text= app.name;

cell.detailTextLabel.text=app.download;

//下载图片

//先查看图片在内存缓存中是否存在，如果存在，直接拿来用，但程序重新启动时，还要重新下载

//如果有磁盘缓存把磁盘缓存放到内存缓存，否则直接下载

//1.没有下载过

//2.下载过被销毁了

UIImage*imaged = [self.imageDicobjectForKey:app.icon];

if(imaged) {

cell.imageView.image=imaged;

NSLog(@"%ld---内存缓存",(long)indexPath.row);

}else{

NSString*Caches =NSSearchPathForDirectoriesInDomains(NSCachesDirectory,NSUserDomainMask,YES).lastObject;

NSString*filename = [app.iconlastPathComponent];

NSString* fullpath = [CachesstringByAppendingPathComponent:filename];

//检查磁盘缓存：

NSData*imageD = [NSDatadataWithContentsOfFile:fullpath];

if(imageD) {

UIImage*image = [UIImageimageWithData:imageD];

cell.imageView.image=image;

NSLog(@"%ld---磁盘缓存",(long)indexPath.row);

//把磁盘缓存放到内存缓存

[self.imageDicsetObject:imageforKey:app.icon];

}else{

//检查该操作是否在缓存中，如果是就什么也不做

NSBlockOperation*download = [self.operationobjectForKey:app.icon];

if(download) {

}else{

//先清空image,放个占位的图片

cell.imageView.image=[UIImageimageNamed:@"Snip20170530_1"];

download = [NSBlockOperationblockOperationWithBlock:^{

NSURL*url = [NSURLURLWithString:app.icon];

NSData*imageData = [NSDatadataWithContentsOfURL:url];

UIImage*image = [UIImageimageWithData:imageData];

//容错处理，防止url不正确，或者网络问题

if(image ==nil){

[self.operationremoveObjectForKey:app.icon];

return;

}

//演示网速慢的情况

[NSThreadsleepForTimeInterval:3.0];

NSLog(@"dowunload--%@",[NSThreadcurrentThread]);

//线程间通信

[[NSOperationQueuemainQueue]addOperationWithBlock:^{

//刷新某一行

[self.tableViewreloadRowsAtIndexPaths:@[indexPath]withRowAnimation:UITableViewRowAnimationLeft];

cell.imageView.image=image;

}];

//把图片保存在内存缓存里

[self.imageDicsetObject:imageforKey:app.icon];

[imageDatawriteToFile:fullpathatomically:YES];

NSLog(@"%ld",(long)indexPath.row);

//移除图片的下载缓存

[self.operationremoveObjectForKey:app.icon];

}];

//添加操作到操作缓存中

[self.operationsetObject:downloadforKey:app.icon];

//添加操作到队列

[self.queueaddOperation:download];

}

}

}

//打印沙盒路径

//NSLog(@"%@",NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES));

returncell;

}

//UI很不流畅-》开子线程下载

//图片重复下载-》缓存

//内存缓存-》磁盘缓存

//图片不会刷新：手动刷新，因为图片尺寸为0

//图片数据错乱

//图片重复下载：当图片还为完全下载之前，又要重新展示图片

//documents:手机连上itunes会备份，不允许把缓存数据放到这个路径。

//library:缓存路径：保存缓存数据偏好设置：保存一些账号信息

//tmp:临时路径，随时会被删除

@end

//如果出现内存警告

- (void)didReceiveMemoryWarning{

//不会影响图片显示

[self.imageDicremoveAllObjects];

//取消队列中所有操作

[self.queuecancelAllOperations];

}