iphone - 显示 UIImageView 的问题

Question

我尝试使用 [self.view addSubview:imageView]; 显示 UIImageView 但什么也没有发生。 imageView 不为空。我使用以下代码从图像库分配图像；

-(void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSString *mediaType = [info
                           objectForKey:UIImagePickerControllerMediaType];
    [self dismissModalViewControllerAnimated:YES];
    if ([mediaType isEqualToString:(NSString *)kUTTypeImage]) {
        UIImage *image = [info 
                          objectForKey:UIImagePickerControllerOriginalImage];

        [imageView setImage:image];
        if (newMedia)
            UIImageWriteToSavedPhotosAlbum(image, 
                                           self,
                                           @selector(image:finishedSavingWithError:contextInfo:),
                                           nil);
    }
}

为什么不起作用？

imageView创建如下；

UIImageView *imageView;
@property (nonatomic, retain) IBOutlet UIImageView *imageView;
@synthesize imageView;

Answer 1

声明和合成属性imageView不会创建UIImageView的实例。因此，以下行中的 imageView 为 nil:

[imageView setImage:image];

在使用UIImageView之前，您必须先创建一个实例。例如:

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    //...
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];

    self.imageView = [[UIImageView alloc] initWithFrame:(CGRectMake(100, 100, 100, 100)];
    self.imageView.image = image;
    [self.view addSubview:self.imageView];

    //...
}

或者，如果您正在使用 Interface Builder，您可能忘记链接到 imageView。