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vertical layout little issue

I have a LinearLayout (vertical) and it should contain 3 elements in the following order: textview, listview and button. The listview could be really high so in order to keep all the 3 elements visible I put the 3 elements each one inside another layout. So my structure is like:
linear layout (vertical)
linear layout (horizontal)
textview
linear layout (vertial) *
listview
relative layout
button
In order to get it working I set a fixed height to the vertical linearlayout which only contains the listview (*) but I know it is a bad choice because on bigger devices there will be a lot of empty space. How can I fix it?
thanks

User percentage values for the LinearLayout(*), so they take up a percentage of the parent's height,
and for the rest, if you want them to take up remaining space, add attribute: android:layout_weight:1;

Implement your layout this way :
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="#+id/mTextView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:gravity="center"
android:padding="10dp"
android:text="Header Text" />
<ListView
android:id="#+id/mListView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_above="#+id/mButton"
android:layout_below="#+id/mTextView" >
</ListView>
<Button
android:id="#+id/mButton"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="Button1" />
</RelativeLayout>

// try this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp"
android:orientation="vertical">
<LinearLayout
android:layout_height="wrap_content"
android:layout_width="match_parent">
<TextView
android:id="#+id/textview"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="textview"/>
</LinearLayout>
<LinearLayout
android:layout_height="0dp"
android:layout_width="match_parent"
android:layout_marginTop="5dp"
android:layout_weight="1">
<ListView
android:layout_height="match_parent"
android:layout_width="match_parent"
android:cacheColorHint="#00000000"
android:divider="#null"
android:dividerHeight="0dp"
android:smoothScrollbar="true"
android:id="#+id/listview"/>
</LinearLayout>
<LinearLayout
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:layout_marginTop="5dp"
android:gravity="center">
<Button
android:id="#+id/button"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="button"/>
</LinearLayout>
</LinearLayout>

How to fill the screen with only one element?

I want to make an activity with 2 elements in the screen, one in the bottom, with a fixed size, and one on top of this which one must fill the screen.
How I can do that in a Layout?
Thank you

use layout_weight="1" for 1st element and put layout_height="0dp" and use linearlayout as the parent which contains the 2 elements.

Use below code:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >
<TextView
android:id="#+id/textView1"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center"
android:text="#string/hello_world" />
<TextView
android:id="#+id/textView2"
android:layout_width="match_parent"
android:layout_height="50dp"
android:gravity="center"
android:text="test" />
</LinearLayout>

Or you can do this,
<LinearLayout
android:id="#+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_alignParentTop="true"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_above="#+id/ll1"
>
</LinearLayout>
<LinearLayout
android:id="#+id/ll1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:orientation="horizontal"
>
</LinearLayout>

Add this to the first element:
android:layout_weight="0.8"
and for the second one
android:layout_weight="0.2"

You can use Relative Layout like...following example
<//you are second element
android:id="#+id/ui_radiogroup"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:clickable="false"
android:orientation="horizontal" >
<///you are second element>
<//you are First element
android:id="#+id/ui_pager"
android:layout_width="wrap_content"
android:layout_above="#id/ui_radiogroup"
android:layout_height="wrap_content"
android:scrollbars="horizontal" />
Other OPtion use Linear Layout assign android:layout_weight to each element depending upon your requirement

try this,
<?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="match_parent"
>
<TextView
android:id="#+id/footertext"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="center"
android:text="Footer" />
<TextView
android:id="#+id/centertext"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#id/footertext"
android:gravity="center"
android:text="center" />

Here is the complete trick :
Use a RelativeLayout to wrap your two items,
Put layout_alignParentBottom="true" on your bottom item
And layout_above="#+id/your_bottom_item_id" on your top item
Here is a complete working example that you can cpy/paste :
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:id="#+id/top_item"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_above="#+id/bottom_layout">
</LinearLayout>
<LinearLayout
android:id="#+id/bottom_item"
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="vertical"
android:layout_alignParentBottom="true">
</LinearLayout>
</RelativeLayout>

Simply use layout_weight="1" for first element and layout height should be match_parent.

RelativeLayout content can not be seen

Like the following layout shows, when the items in list are too much, more than one screen.
I can not see the following LinearLayout content when I drag down.
How to solve this problem?
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="#+id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
<LinearLayout
android:id="#+id/linearLayout1"
android:layout_width="wrap_content"
android:layout_height="100dp"
android:layout_below="#+id/list"
android:layout_centerHorizontal="true"
android:orientation="horizontal" >
<TextView
android:id="#+id/UserIDStatic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/UserID" />
.
.
.
</LinearLayout>
</RelativeLayout>
Thanks in advance!

change to this
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="#+id/list"
android:layout_width="match_parent"
android:layout_height="100dp" > <!-- use a definate dimension here -->
</ListView>
<LinearLayout
android:id="#+id/linearLayout1"
android:layout_width="wrap_content"
android:layout_height="100dp"
android:layout_below="#+id/list"
android:layout_centerHorizontal="true"
android:orientation="horizontal" >
<TextView
android:id="#+id/UserIDStatic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/UserID" />
.
.
.
</LinearLayout>
</RelativeLayout>
or else put both ListView and LinearLayout in ScrollView
or as bellow comment
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:weightSum="1"
android:orientatio="verticle" >
<ListView
android:id="#+id/list"
android:layout_weight="0.5"
android:layout_width="match_parent"
android:layout_height="0dp" >
</ListView>
<LinearLayout
android:id="#+id/linearLayout1"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="0.5"
android:orientation="horizontal" >
<TextView
android:id="#+id/UserIDStatic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/UserID" />
.
.
.
</LinearLayout>
</LinearLayout>

There are two options comes in picture.
Instead of Relative layout Use Vertical Linear layout with appropriate wieght to listview and inner linear layout (eg. 0.7 and 0.3)
Use same Relative layout as above with inner LinearLayout to alignparentbottom = true
and listview above="#innerLinearLayout" linearlayout.
This might solve your problem.
Using specific height for listview might cause different look in UI for different sized screens.

How to place Relative layout at bottom of screen(or linear layout).?

I have following in xml
I wanna put the second linear layout at the bottom of the screen.
How will i do?
I have set the property of second Relative layout to bottom but still not showing at bottom..
**
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_height="fill_parent"
android:layout_width="fill_parent">
<RelativeLayout android:id="#+id/RelativeLayout01"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</RelativeLayout>
<RelativeLayout android:id="#+id/RelativeLayout02"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</RelativeLayout>
<RelativeLayout android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:layout_gravity="bottom">
</RelativeLayout>
</LinearLayout>
**
Thanx in advance

I was searching for this a while too. My just found solution is to use the property:
android:layout_alignParentBottom="true"
instead of your existing android:layout_gravity="bottom"
This unfortunately with my layout only works when having an additional RelativeLayout as root layout and the rest added to it. Maybe this is not always the case, but with having a LinearLayout (even when told to use fill_parent) it only used the height all added elements needed and put my footer at the bottom of those.
I came to this solution, looking at this related question: How do I achieve the following result using RelativeLayout?
EDIT here because format in answer comment got lost:
Do you mean you can't re-write it or that it didn't work?
I had a vertical LinearLayout too and my new xml structure looks (without the layout size params etc.) sth. like this:
<RelativeLayout>
<RelativeLayout
android:id="#+id/RelativeLayout01">
</RelativeLayout>
<RelativeLayout
android:id="#+id/RelativeLayout02"
android:layout_below="#+id/RelativeLayout01">
</RelativeLayout>
<RelativeLayout
android:layout_below="#+id/RelativeLayout02"
android:layout_alignParentBottom="true">
</RelativeLayout>
</RelativeLayout>

The Layout you want at the bottom should have:
android:gravity = "bottom"
and its parent should have:
android:layout_height="fill_parent"

<Linearlayout android:layout_height="fill_parent"
android:orinationtation="vertical"
android:layout_width="fill_parent">
<RelativeLayout android:layout_height="0dp"
android:layout_width="fill_parent"
android:weight="1">
</RelativeLayout>
<RelativeLayout
android:layout_height="0dp"
android:layout_width="fill_parent"
android:weight="1"
>
</RelativeLayout>
</Linearlayout >

You should put a View before your last layout with weight 1, and it will put it to bottom. Like this:
<View android:id="#+id/emptySpace"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1"
/>

Try using:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffb3e5fc"
android:id="#+id/linearLayout1">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="bottom">
<Button
android:id="#+id/button1"
android:text="Left"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_toLeftOf="#+id/centerPoint" />
<TextView
android:id="#+id/centerPoint"
android:text=""
android:layout_width="1dip"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true" />
<Button
android:id="#+id/button2"
android:text="Right"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_toRightOf="#+id/centerPoint" />
</RelativeLayout>
</LinearLayout>
It produces something that looks like this

For my it's work.
<RelativeLayout
android:id="#+id/InnerRelativeLayout"
android:layout_width="match_parent"
android:layout_height="40dp"
android:background="#fff"
android:gravity="bottom"
app:layout_anchor="#+id/fab_inout"
app:layout_anchorGravity="bottom|center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="dsfsdfasdf df" />
</RelativeLayout>

How do I align views at the bottom of the screen?

Here's my layout code;
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:text="#string/welcome"
android:id="#+id/TextView"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</TextView>
<LinearLayout android:id="#+id/LinearLayout"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="bottom">
<EditText android:id="#+id/EditText"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</EditText>
<Button android:text="#string/label_submit_button"
android:id="#+id/Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
</LinearLayout>
</LinearLayout>
What this looks like is on the left and what I want it to look like is on the right.
The obvious answer is to set the TextView to fill_parent on height, but this causes no room to be left for the button or entry field.
Essentially the issue is that I want the submit button and the text entry to be a fixed height at the bottom and the text view to fill the rest of the space. Similarly, in the horizontal linear layout I want the submit button to wrap its content and for the text entry to fill the rest of the space.
If the first item in a linear layout is told to fill_parent it does exactly that, leaving no room for other items. How do I get an item which is first in a linear layout to fill all space apart from the minimum required by the rest of the items in the layout?
Relative layouts were indeed the answer:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:text="#string/welcome"
android:id="#+id/TextView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true">
</TextView>
<RelativeLayout
android:id="#+id/InnerRelativeLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true" >
<Button
android:text="#string/label_submit_button"
android:id="#+id/Button"
android:layout_alignParentRight="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
<EditText
android:id="#+id/EditText"
android:layout_width="fill_parent"
android:layout_toLeftOf="#id/Button"
android:layout_height="wrap_content">
</EditText>
</RelativeLayout>
</RelativeLayout>

The modern way to do this is to have a ConstraintLayout and constrain the bottom of the view to the bottom of the ConstraintLayout with app:layout_constraintBottom_toBottomOf="parent"
The example below creates a FloatingActionButton that will be aligned to the end and the bottom of the screen.
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_height="match_parent"
android:layout_width="match_parent">
<android.support.design.widget.FloatingActionButton
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
</android.support.constraint.ConstraintLayout>
For reference, I will keep my old answer.
Before the introduction of ConstraintLayout the answer was a relative layout.
If you have a relative layout that fills the whole screen you should be able to use android:layout_alignParentBottom to move the button to the bottom of the screen.
If your views at the bottom are not shown in a relative layout then maybe the layout above it takes all the space. In this case you can put the view, that should be at the bottom, first in your layout file and position the rest of the layout above the views with android:layout_above. This enables the bottom view to take as much space as it needs, and the rest of the layout can fill all the rest of the screen.

In a ScrollView this doesn't work, as the RelativeLayout would then overlap whatever is in the ScrollView at the bottom of the page.
I fixed it using a dynamically stretching FrameLayout :
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:fillViewport="true">
<LinearLayout
android:id="#+id/LinearLayout01"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical">
<!-- content goes here -->
<!-- stretching frame layout, using layout_weight -->
<FrameLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
</FrameLayout>
<!-- content fixated to the bottom of the screen -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<!-- your bottom content -->
</LinearLayout>
</LinearLayout>
</ScrollView>

You can keep your initial linear layout by nesting the relative layout within the linear layout:
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:text="welcome"
android:id="#+id/TextView"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</TextView>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button android:text="submit"
android:id="#+id/Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true">
</Button>
<EditText android:id="#+id/EditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_toLeftOf="#id/Button"
android:layout_alignParentBottom="true">
</EditText>
</RelativeLayout>
</LinearLayout>

The answer above (by Janusz) is quite correct, but I personnally don't feel 100% confortable with RelativeLayouts, so I prefer to introduce a 'filler', empty TextView, like this:
<!-- filler -->
<TextView android:layout_height="0dip"
android:layout_width="fill_parent"
android:layout_weight="1" />
before the element that should be at the bottom of the screen.

You can do this with a LinearLayout or a ScrollView, too. Sometimes it is easier to implement than a RelativeLayout. The only thing you need to do is to add the following view before the Views you want to align to the bottom of the screen:
<View
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="1" />
This creates an empty view, filling the empty space and pushing the next views to the bottom of the screen.

1. Use ConstraintLayout in your root Layout
And set app:layout_constraintBottom_toBottomOf="parent" to let the Layout on the bottom of the screen:
<LinearLayout
android:id="#+id/LinearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintBottom_toBottomOf="parent">
</LinearLayout>
2. Use FrameLayout in your root Layout
Just set android:layout_gravity="bottom" in your layout
<LinearLayout
android:id="#+id/LinearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:orientation="horizontal">
</LinearLayout>
3. Use LinearLayout in your root Layout (android:orientation="vertical")
(1) Set a layout android:layout_weight="1" on the top of the your Layout
<TextView
android:id="#+id/TextView"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:text="welcome" />
(2) Set the child LinearLayout for android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="bottom"
The main attribute is ndroid:gravity="bottom", let the child View on the bottom of Layout.
<LinearLayout
android:id="#+id/LinearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="bottom"
android:orientation="horizontal">
</LinearLayout>
4. Use RelativeLayout in the root Layout
And set android:layout_alignParentBottom="true" to let the Layout on the bottom of the screen
<LinearLayout
android:id="#+id/LinearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:orientation="horizontal">
</LinearLayout>
Output

This also works.
<LinearLayout
android:id="#+id/linearLayout4"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_below="#+id/linearLayout3"
android:layout_centerHorizontal="true"
android:orientation="horizontal"
android:gravity="bottom"
android:layout_alignParentBottom="true"
android:layout_marginTop="20dp"
>
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
/>
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
/>
</LinearLayout>

Following up on Timores's elegant solution, I have found that the following creates a vertical fill in a vertical LinearLayout and a horizontal fill in a horizontal LinearLayout:
<Space
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1" />

You don't even need to nest the second relative layout inside the first one. Simply use the android:layout_alignParentBottom="true" in the Button and EditText.

If you don't wish to make many changes, then you could just put:
android:layout_weight="1"
for the TextView having ID as #+id/TextView i.e
<TextView android:text="#string/welcome"
android:id="#+id/TextView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1">
</TextView>

Creating both header and footer, here is an example:
Layout XML
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#color/backgroundcolor"
tools:context=".MainActivity">
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="40dp"
android:background="#FF0000">
</RelativeLayout>
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="40dp"
android:layout_alignParentBottom="true"
android:background="#FFFF00">
</RelativeLayout>
</RelativeLayout>
Screenshot

For a case like this, always use RelativeLayouts. A LinearLayout is not intended for such a usage.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/db1_root"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<!-- Place your layout here -->
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_gravity="bottom"
android:orientation="horizontal"
android:paddingLeft="20dp"
android:paddingRight="20dp" >
<Button
android:id="#+id/setup_macroSavebtn"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Save" />
<Button
android:id="#+id/setup_macroCancelbtn"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Cancel" />
</LinearLayout>
</RelativeLayout>

Use the below code. Align the button to buttom. It's working.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<Button
android:id="#+id/btn_back"
android:layout_width="100dp"
android:layout_height="80dp"
android:text="Back" />
<TextView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.97"
android:gravity="center"
android:text="Payment Page" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Submit"/>
</LinearLayout>
</LinearLayout>

Use android:layout_alignParentBottom="true" in your <RelativeLayout>.
This will definitely help.

In case you have a hierarchy like this:
<ScrollView>
|-- <RelativeLayout>
|-- <LinearLayout>
First, apply android:fillViewport="true" to the ScrollView and then apply android:layout_alignParentBottom="true" to the LinearLayout.
This worked for me perfectly.
<ScrollView
android:layout_height="match_parent"
android:layout_width="match_parent"
android:scrollbars="none"
android:fillViewport="true">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:id="#+id/linearLayoutHorizontal"
android:layout_alignParentBottom="true">
</LinearLayout>
</RelativeLayout>
</ScrollView>

You can just give your top child view (the TextView #+id/TextView) an attribute:
android:layout_weight="1".
This will force all other elements below it to the bottom.

This can be done with a linear layout too.
Just provide Height = 0dp and weight = 1 to the layout above and the one you want in the bottom. Just write height = wrap content and no weight.
It provides wrap content for the layout (the one that contains your edit text and button) and then the one that has weight occupies the rest of the layout.
I discovered this by accident.

I used the solution Janusz posted, but I added padding to the last View since the top part of my layout was a ScrollView.
The ScrollView will be partly hidden as it grows with content. Using android:paddingBottom on the last View helps show all the content in the ScrollView.