转载：//www.greatytc.com/p/ebed3bf3399a
经常会遇到这样的应用场景,例如在调用iOS系统分享功能前(UIActivityViewController),需要将所有的图片事先准备好,但是图片都在网络上.
这时,就需要先将图片都下载好后再进行调用.
可能是这个功能的实现太简单了,所以像SDWebImage,AFNetwork等都没有提供可以直接调用的API方法.
所以只好花了2秒钟自己写了一个方法;
#import"ImagesDownloadManager.h"#import"SDWebImageDownloader.h"@implementationImagesDownloadManager/**
批量下载图片
保持顺序;
全部下载完成后才进行回调;
回调结果中,下载正确和失败的状态保持与原先一致的顺序;
@return resultArray 中包含两类对象:UIImage , NSError
*/+(void)downloadImages:(NSArray<NSString*>*)imgsArray completion:(void(^)(NSArray*resultArray))completionBlock{SDWebImageDownloader*manager=[SDWebImageDownloader sharedDownloader];manager.downloadTimeout=20;__block NSMutableDictionary*resultDict=[NSMutableDictionary new];for(inti=0;i<imgsArray.count;i++){NSString*imgUrl=[imgsArray objectAtIndex:i];[manager downloadImageWithURL:[NSURL URLWithString:imgUrl]options:SDWebImageDownloaderUseNSURLCache|SDWebImageDownloaderScaleDownLargeImages progress:^(NSInteger receivedSize,NSInteger expectedSize,NSURL*_Nullable targetURL){}completed:^(UIImage*_Nullable image,NSData*_Nullable data,NSError*_Nullable error,BOOL finished){if(finished){if(error){//在对应的位置放一个error对象[resultDict setObject:error forKey:@(i)];}else{[resultDict setObject:image forKey:@(i)];}if(resultDict.count==imgsArray.count){//全部下载完成NSArray*resultArray=[ImagesDownloadManager createDownloadResultArray:resultDict count:imgsArray.count];if(completionBlock){completionBlock(resultArray);}}}}];}}+(NSArray*)createDownloadResultArray:(NSDictionary*)dict count:(NSInteger)count{NSMutableArray*resultArray=[NSMutableArray new];for(inti=0;i<count;i++){NSObject*obj=[dict objectForKey:@(i)];[resultArray addObject:obj];}returnresultArray;}@end
调用方法:
//下载图片[ImagesDownloadManager downloadImages:imgs completion:^(NSArray*resultArray){NSMutableArray*items=[NSMutableArray new];for(inti=0;i<resultArray.count;i++){NSObject*obj=[resultArray objectAtIndex:i];if([obj isKindOfClass:[UIImage class]]){//只取UIImage对象，其他类型忽略之[items addObject:obj];}}//调用系统自带的分享功能，把选中的图片们分享出去UIActivityViewController*activityVC=[[UIActivityViewController alloc]initWithActivityItems:items applicationActivities:nil];[selfpresentViewController:activityVC animated:YES completion:nil];}];
