适配iPad的操作表sheet

在

UIAlertController *alert = [UIAlertController

alertControllerWithTitle:@"上传文件"

message:@"请选择"

preferredStyle:UIAlertControllerStyleActionSheet];之后插入下面这段代码，就可以完成适配。

UIPopoverPresentationController *popover =

        alert.popoverPresentationController;

    // UIButton *button = (UIButton *)sender;

    if (popover) {

      popover.sourceRect =

          CGRectMake(self.view.center.x, self.view.frame.size.height, , );

      popover.sourceView = self.view;

      popover.permittedArrowDirections = UIPopoverArrowDirectionDown;

    }

最后，推出

[self presentViewController:alert animated:YES completion:nil];

成功。