ここに私が取り組んでいるコードがあります:
UIButton *mainButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
[mainButton setImage:[UIImage imageNamed:@"CircleShape.png"] forState:UIControlStateNormal];
mainButton.center = CGPointMake(self.view.frame.size.width/2.0f, self.view.frame.size.height/2.0f);
[self.view addSubview:mainButton];
UIView *subView = [[UIView alloc] initWithFrame:CGRectMake(0, 100, 200, 100)];
[subView setBackgroundColor:[UIColor purpleColor]];
[mainButton addSubview:subView];
UIButton *secondButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
[secondButton setImage:[UIImage imageNamed:@"CircleShape.png"] forState:UIControlStateNormal];
secondButton.center = CGPointMake(subView.frame.size.width/2.0f, subView.frame.size.height/2.0f);
[subView addSubview:secondButton];
mainButton はクリックできるのに、secondButton はクリックできないのはなぜですか?