一、缓存图片
//1.首先创建在沙盒中创建一个文件夹用于保存图片
NSFileManager *fileManager = [[NSFileManager alloc] init];
NSString *pathDocuments = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *createPath = [NSString stringWithFormat:@"%@/Image", pathDocuments];
// 判断文件夹是否存在，如果不存在，则创建
if (![[NSFileManager defaultManager] fileExistsAtPath:createPath]) {
[fileManager createDirectoryAtPath:createPath withIntermediateDirectories:YES attributes:nil error:nil];
} else {
NSLog(@"FileDir is exists.");
}
for (int i = 0; i < viewsArray.count; i++) {
UIImageView * imageV = [[UIImageView alloc]initWithFrame:CGRectMake(screenWidth * i, 0, screenWidth, self.homePageview.height)];
[imageV sd_setImageWithURL:[viewsArray objectAtIndex:i]placeholderImage:[UIImage imageNamed:@"Moren6p.png"]];
UITapGestureRecognizer * tap =[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapAction:)];
[imageV addGestureRecognizer:tap];
imageV.userInteractionEnabled = YES;
[self.homePageview addSubview:imageV];
UIImage * image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[viewsArray objectAtIndex:i]]];
//2.缓存我所需要的图片
NSString *path_sandox = NSHomeDirectory();
//创建路径
NSString *CachePath = [NSString stringWithFormat:@"/Documents/Image/HomeScroll%d.png",i];
//设置一个图片的存储路径
NSString *imagePath = [path_sandox stringByAppendingString:CachePath];
//把图片直接保存到指定的路径（同时应该把图片的路径imagePath存起来，下次就可以直接用来取）
[UIImagePNGRepresentation(image) writeToFile:imagePath atomically:YES];
}
二、读取图片
//1.首先获取沙盒路径
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSFileManager *fileManage = [NSFileManager defaultManager];
NSString *CacheDocuments = [documentsDirectory stringByAppendingPathComponent:@"/Image”];//我把图片缓存到沙盒中的Document下得Image文件夹中
NSArray *CacheScrollImage = [fileManage subpathsOfDirectoryAtPath:CacheDocuments error:nil];//这个是获取Image文件夹下所有文件的文件名数组
//2.离线加载沙盒中缓存的图片
for (int i =0; i<CacheScrollImage.count; i++) {
NSString * CacheImage = [NSString stringWithFormat:@"Image/HomeScroll%d.png",i];
NSString *myDirectory = [documentsDirectory stringByAppendingPathComponent:CacheImage];
NSData *data = [fileManage contentsAtPath:myDirectory];
UIImage * image = [UIImage imageWithData:data];
}