OC popoverPresentationController

vc.m

@interface ViewController ()<UIPopoverPresentationControllerDelegate>

- (void)rightBtnAction:(UIBarButtonItem *)barBtn {
    PopVC *vc = [[PopVC alloc] init];
    vc.modalPresentationStyle = UIModalPresentationPopover;
    //设置依附的按钮
    vc.popoverPresentationController.barButtonItem = barBtn;
    //可以指示小箭头颜色
    vc.popoverPresentationController.backgroundColor = [UIColor systemRedColor];
    //content尺寸
    vc.preferredContentSize = CGSizeMake(30, 40);
    //方向
    vc.popoverPresentationController.permittedArrowDirections = UIPopoverArrowDirectionAny;
    vc.popoverPresentationController.delegate = self;
    [self presentViewController:vc animated:YES completion:nil];
}

#pragma mark - UIPopoverPresentationControllerDelegate

- (UIModalPresentationStyle)adaptivePresentationStyleForPresentationController:(UIPresentationController *)controller {
    return UIModalPresentationNone;
}

popvc.m

//重置本控制器的大小
- (CGSize)preferredContentSize {
    if (nil != self.popoverPresentationController) {
        CGSize tmpSize;
        tmpSize.height = self.view.frame.size.height;
        //该view显示的宽度，设置了1000也不会超过屏幕宽度
        tmpSize.width = 200;
        CGSize size = [_tvList sizeThatFits:tmpSize];
        return size;
    } 

    return [super preferredContentSize];
}