负荷文档目录保存图像

Question

我已经使用给here的代码来保存和载入图像

，当我在一个视图控制器一起使用它，它工作正常，但是当我使用saveImage方法在一个视图控制器并尝试加载图像中的图像返回空白另一个视图控制器...

鉴于控制器A我用下面的保存图像

- (void)saveImage: (UIImage*)image 
{ 
    NSLog(@"saveimage called"); 

    if (image != nil) 
    { 
     NSLog(@"Image not null"); 
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, 
                  NSUserDomainMask, YES); 
     NSString *documentsDirectory = [paths objectAtIndex:0]; 
     NSString* path = [documentsDirectory stringByAppendingPathComponent: 
          @"test.png" ]; 
     NSData* data = UIImagePNGRepresentation(image); 
     [data writeToFile:path atomically:YES]; 
     QrImageView.image = nil; 
    } 
} 

而且在视图控制器说B I很装载图片使用..

- (UIImage*)loadImage 
{ 
    NSError *error; 

    NSFileManager *fileMgr = [NSFileManager defaultManager]; 

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, 
                 NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString* path = [documentsDirectory stringByAppendingPathComponent: 
         @"test.png" ]; 
    UIImage* image = [UIImage imageWithContentsOfFile:path]; 

    // Write out the contents of home directory to console 
    NSLog(@"Documents directory: %@", [fileMgr contentsOfDirectoryAtPath:documentsDirectory error:&error]); 

    return image; 
} 

我也得在控制台中的文件的内容，但我不明白为什么图像是空白

2013-07-06 14:13:19.750 YouBank[500:c07] Documents directory: (
    "test.png" 
) 

任何想法，我做错了什么......

EDIT: 

在viewDidload方法的视图控制器B中，我执行以下操作：

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view from its nib. 

    ImageView.image=[self loadImage]; 
    ImageName.text = @"Cash Withdrawal"; 
} 

Answer 1

问题是你只是在viewDidLoad上用UIImage更新你的UIImageView。从文件系统获得更新后（最好在后台线程中），您需要添加更新。因此，这将是这个样子：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0),^{ 
    UIImage *loadedImage = [self loadImage]; 
    dispatch_async(dispatch_get_main_queue(),^{ 
     ImageView.image = loadedImage; 
    }); 
}); 

我也建议使用的名字开始与实例名称小写字符，所以你应该重新命名的ImageView - imageWithContentsOfFile后> ImageView的

Answer 2

试试这个

//Document Directory 
    #define kAppDirectoryPath NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) 


    #pragma mark - File Functions - Document/Cache Directory Functions 
    -(void)createDocumentDirectory:(NSString*)pStrDirectoryName 
    { 
     NSString *dataPath = [self getDocumentDirectoryPath:pStrDirectoryName]; 

     if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath]) 
      [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:NULL]; 
    } 

    -(NSString*)getDocumentDirectoryPath:(NSString*)pStrPathName 
    { 
     NSString *strPath = @""; 
     if(pStrPathName) 
      strPath = [[kAppDirectoryPath objectAtIndex:0] stringByAppendingPathComponent:pStrPathName]; 

     return strPath; 
    } 

当你写的照片

 [self createDocumentDirectory:@"MyPhotos"]; 
     NSString *pngPath = [NSHomeDirectory() stringByAppendingPathComponent:strImageName]; 
     [UIImagePNGRepresentation(imgBg.image) writeToFile:pngPath atomically:YES]; 

当你得到的文件
编辑

NSError *error = nil; 
    NSArray *dirContents = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:[FunctionManager getDocumentDirectoryPath:@"MyPhotos"] error:&error]; 
    if (!error) { 
      NSPredicate *predicate = [NSPredicate predicateWithFormat:@"self ENDSWITH '.png'"]; 
     NSArray *imagesOnly = [dirContents filteredArrayUsingPredicate:predicate]; 
      for (int i=0;i<[imagesOnly count]; i++) { 
       [arrSaveImage addObject:[imagesOnly objectAtIndex:i]]; //arrSaveImage is Array of image that fetch one by one image and stored in the array 
      } 
} 


    NSString *strPath=[self getDocumentDirectoryPath:@"MyPhotos"]; // "MyPhotos" is Your Directory name 
    strPath=[NSString stringWithFormat:@"%@/%@",strPath,[arrSaveImage objectAtIndex:i]]; //You can set your image name instead of [arrSaveImage objectAtIndex:i] 
    imgBackScroll.image=[UIImage imageWithData:[NSData dataWithContentsOfFile:strPath]]; 

它可以帮助你。