SLComposeServiceViewController preview view doesn't show up

问题

I want to use SLComposeServiceViewController inside my app as a UI for composing and posting a message to my backend.

However, if I override loadPreviewView and return a view as stated in the documentation, that view doesn't show up.

This is my code:

@interface ComposeViewController : SLComposeServiceViewController
@end


@implementation ComposeViewController
- (UIView *)loadPreviewView {
    UIView *v = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
    v.backgroundColor = [UIColor redColor];
    return v;
}
@end

This is how it looks:

Why is my red view not showing up?

来源：https://stackoverflow.com/questions/37542359/slcomposeserviceviewcontroller-preview-view-doesnt-show-up