why marginBottom not working?

Answer 1

In some case you have lots of attributs or you just missed that you included earlier :

android:layout_margin="xdp"

You can't use it with specific layout margination

Answer 2

I had a <View> inside a <RelativeLayout> and the marginBottom on that view did not work. I found out that my chain of layout_below was broken, so therefore it makes sense that the layout did not know from which view the margin should be calculated.

If you chain it properly using layout_below or the other positioning tools, you do not need to worry about wrap_content or match_parent like others are suggesting. Example:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <View
        android:id="@+id/separator"
        android:layout_width="match_parent"
        android:layout_height="1px"
        android:layout_marginBottom="11dp" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/separator">

        ...

Answer 3

Maybe you can set android:paddingBottom="" of <RelativeLayout> to get the same effect.

Answer 4

It is realy just a bug of the <RelativeLayout>, so you could try to wrap the RelativeLayout inside of a <LinearLayout> and set the margin there.

Answer 5

Make sure the layout_height of your root container is set to match_parent instead of wrap_content.

Answer 6

It works if you use android:layout_marginBottom with android:layout_alignParentBottom="true".

For example :

android:layout_alignParentBottom="true"
android:layout_marginBottom="50dp">