Everything seems alright, except that you don't have a top level layout.
Maybe there's something wrong in your code.
How do you set those images for the buttons? Do you alter their sizes in any way?
Are the images all the same size?
I just have these 2 components in the dialog. Should I have a top level layout compulsarily?
No I do not alter their sizes.
Yes. All are of the same image size.

Not sure what you mean.
Do you want them to be horizontally centered relatively to the top labels?
Yes. Horizontally center aligned.

Thanks
Arjun