ios 從網絡下載圖片，保存，並用imageview從保存中顯示

-(UIImage *) getImageFromURL:(NSString *)fileURL {
    NSLog(@"執行圖片下載函數");
    UIImage * result;
    
    NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
    result = [UIImage imageWithData:data];
    
    return result;
}


-(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    if ([[extension lowercaseString] isEqualToString:@"png"]) {
        [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
    } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
        [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
    } else {
        //ALog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
        NSLog(@"文件后綴不認識");
    }
}


-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];
    
    return result;
}

 NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSLog(@"保存路徑:%@",documentsDirectoryPath);
    //Get Image From URL
    UIImage * imageFromURL = [self getImageFromURL:@"http://file.duteba.com/phone/2009/04/5/ftGxL8kcUL.jpg"];
    
    //Save Image to Directory
    [self saveImage:imageFromURL withFileName:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];
    
    //Load Image From Directory
    UIImage * imageFromWeb = [self loadImage:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];
    [img setImage:imageFromWeb];
    
    //取得目錄下所有文件名
    NSArray *file = [[[NSFileManager alloc] init] subpathsAtPath:documentsDirectoryPath];
    //NSLog(@"%d",[file count]);
    NSLog(@"%@",file);
    
    //如何獲取下載的文件的完整路徑?

把已經下載的jpg用imageview顯示

 NSString *documentsDirectory2 = [path2 objectAtIndex:0]; //path數組里貌似只有一個元素
    //字符串拼接得到文件完整路徑
    NSString *filestr = @"/MyImage.jpg";
    NSString *newstr = [documentsDirectory2 stringByAppendingString:filestr];
    NSLog(@"完整路徑是:%@",newstr);
    
    NSData *dd = [NSData dataWithContentsOfFile:newstr];
    [img222 setImage:[UIImage imageWithData:dd]];