Develop Reference

Android: Correctly position buttons inside layout

I have a following layout :
<LinearLayout //container, should adjust height based on CONTENT view height
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:baselineAligned="false"
android:clickable="false"
android:padding="20dp">
<RelativeLayout //this is the CONTENT view height
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="5">....</RelativeLayout>
...
<RelativeLayout //this is the button layout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="2">
<Button android:layout_width="40sp" android:layout_height="40sp"/>
<Button android:layout_width="40sp" android:layout_height="40sp"/>
</RelativeLayout>
</LinearLayout>
I want the height of the container (LinearLayout) to be adjusted to contain all the views in the RelativeLayout (shown on the left, let's call it CONTAINER).
Then, there are two buttons in the RelativeLayout (shown on the right). I need to align them on top and bottom borders of RelativeLayot, correspondingly. What's really important, is that the height of the buttons' container should be the same (should correspond) to the height of the CONTAINER.
The problem is, if I try to use android:layout_alignParentBottom="true" and android:layout_alignParentTop="true" attributes for the buttons, they will stretch the container height, and it will take the whole screen height.
So, what magic should I use to do the trick? :)

Try to align your right relative layout top and bottom to the left one.
Try something like this:
<RelativeLayout //container, should adjust height based on CONTENT view height
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:baselineAligned="false"
android:clickable="false"
android:padding="20dp">
<RelativeLayout //this is the CONTENT view height
android:id="#+id/contentRL"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="5"
android:layout_alignParentLeft="true">....</RelativeLayout>
...
<RelativeLayout //this is the button layout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="2"
android:layout_alignTop="#id/contentRL"
android:layout_alignBottom="#id/contentRL"
android:layout_alignParentRight="true">
<Button android:layout_width="40sp"
android:layout_height="40sp"
android:layout_alignParentTop="true"/>
<Button android:layout_width="40sp"
android:layout_height="40sp"
android:layout_alignParentBottom="true"/>
</RelativeLayout>

Use this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:baselineAligned="false"
android:clickable="false"
android:padding="20dp">
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="5"></RelativeLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="2">
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"/>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"/>
</RelativeLayout>
</LinearLayout>

Ok, based on a hint provided by Damien R. above I successfully accomplished the task by doing following:
Use RelativeLayout as a root with paramters layout_width="wrap_content", layout_height="wrap_content"
Use LinearLayout as a "wrapper" around container RelativeLayouts. This is because I need to lay out these containers using layout_weight attribute.
RelativeLayout layout_height should be fill_parent. No need to use android:layout_alignBottom="#id/..." and android:layout_alignBottom="#id/..." in the RelativeLayout attributes. This will only work if RelativeLayout is a child View of another RelativeLayout, and that's not the case, because I need to use LinearLayout's weight
The code is:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:baselineAligned="false"
android:clickable="false"
android:padding="10dp">
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#drawable/ticketbackground"
android:id="#+id/ticket_layout"
>
<RelativeLayout
android:id="#+id/contentRL"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="5"
android:layout_alignParentLeft="true">
</RelativeLayout>
<!--second column-->
<RelativeLayout
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3">
...
</RelativeLayout>
<!--third column with buttons-->
<RelativeLayout
android:id="#+id/sdfsdf"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="2">
<Button...
android:layout_alignParentTop="true" />
<Button...
android:layout_alignParentBottom="true" />
</RelativeLayout>
</LinearLayout>
</RelativeLayout>

Button spanning 2 fragments (xml layout)

Can't figure out how to set this up in XML...
Trying to get a button to lay over 2 fragments that sit behind it.
What I want:
What I have:
My code:
<?xml version="1.0" encoding="utf-8"?>
<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="horizontal"
tools:context=".VulgarActivity"
>
<Button
android:id="#+id/luckBtn"
android:layout_gravity="bottom"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/feel_lucky"
android:textColor="#ffffff"
/>
<fragment
android:name="com.wizardknight.visionaryvulgarity.FirstWord"
android:id="#+id/firstWord"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent"
/>
<fragment
android:name="com.wizardknight.visionaryvulgarity.LastWord"
android:id="#+id/lastWord"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent"
/>
</LinearLayout>

You can do this with a RelativeLayout:
<?xml version="1.0" encoding="utf-8"?>
<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"
android:orientation="horizontal" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent" >
<fragment
android:id="#+id/firstWord"
android:name="com.wizardknight.visionaryvulgarity.FirstWord"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" />
<fragment
android:id="#+id/lastWord"
android:name="com.wizardknight.visionaryvulgarity.LastWord"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" />
</LinearLayout>
<Button
android:id="#+id/luckBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_gravity="bottom"
android:text="#string/feel_lucky"
android:textColor="#ffffff" />
</RelativeLayout>
Explanation:
The difference between RelativeLayout and LinearLayout is simple. LinearLayouts order their child views, like the name already says, linearly. That means, that the child will order themselves, depending on the orientation of the LinearLayout, vertically or horizontally to each other. The child view of a RelativeLayout on the other hand order themselves relative to the parent view or to other views. In this layout I just changed the parent layout to RelativeLayout and wrapped your fragments in a LinearLayout, so it they can use the layout_weight attribute. Then I set this to the button:
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
This aligns the button to the bottom and centers them horizontally. Now, since it does this relative to the top level layout, it overlaps the fragment. 

Android some of the view elements not visible

I am creating a layout as below but the checkbox element is not visible on the scren where am i goign wrong ?
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<SeekBar android:id="#+id/seek"
android:layout_width="300dip"
android:layout_height="wrap_content"
android:progress="50"/>
...and a few more elements here.
</LinearLayout>
<CheckBox android:id="#+id/CheckBox"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="somestring" />
</LinearLayout>

The LinearLayout before the CheckBox has its height set to MATCH_PARENT(and it fills all the parent's height) and the parent LinearLayout of both has the orientation set to vertical so the CheckBox is pushed out of the screen.
Set the height of the LinearLayout containing the SeekBar to WRAP_CONTENT for example.

You need to set your inner Linear Layout's height and width to wrap content.
Try this.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<SeekBar
android:id="#+id/seek"
android:layout_width="300dip"
android:layout_height="wrap_content"
android:progress="50" />
</LinearLayout>
<CheckBox
android:id="#+id/CheckBox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="somestring" />
</LinearLayout>

Try This :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:weightSum="10" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="9"
android:orientation="horizontal" >
<SeekBar
android:id="#+id/seek"
android:layout_width="300dip"
android:layout_height="wrap_content"
android:progress="50" />
</LinearLayout>
<CheckBox
android:id="#+id/CheckBox"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="somestring" />
</LinearLayout>

In your layout chose one element that you want to be flexible in size, say height wise. Then make its height="0dp" and weight="1". Make heights of rest of elements: height="wrap_content".
Also you may have given discreet size of some dp to your other elements, and hence their total height runs out of available screen space OR there are too many elements that they go beyond your screen height. In this case, wrap your layout in a ScrollView.

change your LinerLayout definition it cannot be android:layout_height="match_parent"
<LinearLayout android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="0px"
android:layout_weight="1">
if you set match_parent for linearlayout it consumes all content so wrap_content is better.
But if you set it as I wrote checkbox will be at bottom page a linearlayout will consumes remaing part of screen.

RelativeLayout - CenterInParent and marginTop

I has the following XML:
<RelativeLayout android:id="#+id/cover_box"
android:layout_width="wrap_content" android:layout_height="wrap_content">
<ImageView android:id="#+id/cover"
android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageView android:id="#+id/download" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:src="#drawable/mark_download"
android:layout_centerInParent="true" android:layout_marginTop="90px" />
</RelativeLayout>
But it's look's like the marginTop is being ignored.

If you want the 2nd image to be 90dp under the center of the screen, you could replace it with a FrameLayout where you can control the padding to move your image downwards.
<FrameLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:paddingTop="90dp">
<ImageView android:id="#+id/download"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/mark_download"/>
</FrameLayout>

When you use center in parent the view is put directly in the center. The margin top will only come into play if an object is within 90px of the top of your view. Thus pushing the centered view down to keep at least 90px of space on top of it. So it isn't being ignored but it is not having the effect that you think it should have.

I want the progressbar to shown under android:layout_centerInParent="true" so i have added a dummy TextView and set it to centerInParent .Then i put my progressbar under it. Now you can increase its distance from center in two ways . First by increasing marginTop in TextView and second increasing TextView height.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/widget"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/splash" >
<FrameLayout
android:id="#+id/splash_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<TextView
android:id="#+id/txt1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true" />
<com.s3.tdd.interfaces.CircularProgressBar
android:id="#+id/circularprogressbar2"
style="#style/Widget.ProgressBar.Holo.CircularProgressBar"
android:layout_width="110dip"
android:layout_height="110dip"
android:layout_below="#+id/txt1"
android:layout_centerHorizontal="true" />
</RelativeLayout>

You can put your imageview inside of other ViewGroup (LinearLayout of RelativeLayout layout), leaving the margin of imageview, and doing android:centerInParent="true" for the ViewGroup:
<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">
<LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:centerInParent="true">
<ImageView android:id="#+id/download" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="#drawable/mark_download" android:layout_marginTop="90px" />
</LinearLayout>
</RelativeLayout>

You can make a dummy view and center it to parent. Now align your view relative to dummy view using layout:alignComponent and give the marginTop. Now in the code move it according to the width of your view to center it.

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.