UIAlertController应用
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"保存" message:@"是否保存图片？" preferredStyle:UIAlertControllerStyleActionSheet];
UIAlertAction *action = [UIAlertAction actionWithTitle:@"保存" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
[self saveImage];
}];
UIAlertAction *action2 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
}];
[alertController addAction:action];
[alertController addAction:action2];
[self presentViewController:alertController animated:YES completion:nil];
