如何为Android中的所有屏幕尺寸提供相同的按钮大小？

I am new to android and I am designing a screen with two buttons(cancel & Next )in android and the button size should be same.It is normally working 3 inches screen in portrait but when i rotate the mobile to Landscape the size is not same as in portrait.I have used android:weight also and i did not find any changes .could some one help me out of this...thanks in advance.I am new to android and I am designing a screen