Set width of Button in Android

Question

How can I set a fixed width for an Android button? Everytime I try to set a fixed width it fills the current parent (the RelativeView). Here is my XML:

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout android:id="@+id/relativelayout" android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android">

    <EditText android:layout_height="wrap_content" android:editable="false" android:layout_width="fill_parent" android:id="@+id/output"></EditText>

    <Button android:layout_height="wrap_content" android:id="@+id/Button01" android:layout_below="@id/output" android:text="7" android:layout_width="wrap_content"></Button>
    <Button android:layout_below="@id/output" android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/Button02" android:layout_toRightOf="@+id/Button01" android:text="8"></Button>
    <Button android:layout_below="@id/output" android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/Button03" android:layout_toRightOf="@+id/Button02" android:text="9"></Button>
</RelativeLayout>

How would I give it a FIXED width?
UPDATE
Say I have several buttons that I want the same size as each other and 1/3 of the entire view (Portrait), then I want a button with double the width. Then a button with double the height. How could I accomplish this other that manually sizing them?

Answer 1

To accomplish what you want, you can use a LinearLayout with a weightsum. For example, you can put a WeightSum of 9. If you put the weight of three button inside to 1 each. They will take 1/3 of the place, and you can put 2 for another object. This object will be twice as big as the other.

http://developer.android.com/reference/android/widget/LinearLayout.html#setWeightSum(float)

Edit: I would like to add that for this to work correctly, you have to set the width or height to 0px (depending on if it's an horizontal or a vertical layout).