UIPopoverPresentationController

- (void)buttonClick:(UIButton *)sender{
    self.buttonPopVC = [[PopoverViewController alloc] init];   //普通控制器 viewController
    self.buttonPopVC.modalPresentationStyle = UIModalPresentationPopover;
    self.buttonPopVC.popoverPresentationController.sourceView = _button;  //rect参数是以view的左上角为坐标原点（0，0）
    self.buttonPopVC.popoverPresentationController.sourceRect = _button.bounds; //指定箭头所指区域的矩形框范围（位置和尺寸），以view的左上角为坐标原点
    self.buttonPopVC.popoverPresentationController.permittedArrowDirections = UIPopoverArrowDirectionUp; //箭头方向
    self.buttonPopVC.popoverPresentationController.delegate = self;
    [self presentViewController:self.buttonPopVC animated:YES completion:nil];
}