在运行时设置图像时不遵守UIImageView的contentmode

Question

I've got a UIImageView which is displayed fullscreen as a 'background'. Whenever I set a image in the viewdidload as it's default, it the contentMode works just fine.

However, when I do this:

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

    self.pickedPhotoImageView.contentMode = UIViewContentModeScaleAspectFit; // set desired contentMode here
    self.pickedPhotoImageView.clipsToBounds = YES;

    self.pickedPhoto = image;
    [self.pickedPhotoImageView setImage:image];
    [self dismissViewControllerAnimated:YES completion:nil];

}

All respect for the contentMode is lost and when taking a photo only a tiny bit of the photo is shown. How can a UIImageView lose respect of a property just like that?

Answer 1

Make sure the UIImageView has constraints set up properly. With Auto Layout, the size of each view is determined by the view's intrinsicContentSize (link) . This means when you reset the content of a subclass of UIView (wether it's the text in a UILabel or in this case, the image in UIImageView , auto layout will calculate the new size. If you don't have the proper constraints set up and set a content size larger than the current frame size, the frame will grow.

As to why this is happening even though you are setting the contentMode and clipsToBounds , contentMode seems to be done after the fact and will work with the constraints of height and width (either the height and width you give it, or the calculated height and width from the relative constraints on X and Y). clipsToBounds works in the same way, where it will clip anything outside of the frame's bounds after the layout has been calculated. In this case, the layout was calculated and deemed to be larger than the screen, and set the frame of the UIImageView accordingly which is why you only saw a tiny bit of the photo.

Hopefully that explanation helps!