Develop Reference

Why doesn't gravity work when applied to Relative Layout?

I already understand that if I use layout_gravity="center_horizontal" on the text view, then the text will be center. But I don't want to use that because I want to have as little code as possible and the best way to do that is by applying gravity="center_horizontal" to my relative layout. I am also asking this question because I am concerned about even using gravity or layout_gravity with relative layouts at all. As when doing my research I came upon this answer.
Notice the part that says:
Don't use gravity/layout_gravity with a RelativeLayout. Use them for Views in LinearLayouts and FrameLayouts.
Even though it seems pretty apparent to me from the relative layout Android Documentation, which clearly lists gravity as a valid attribute, that Google intended these attributes to be used with relative layouts.
If that quote is correct, how do I center views in relative layouts?
Also, here is my code:
Notice the title is not centered horizontally
<?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:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:gravity="center_horizontal"
tools:context="com.something">
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textAlignment="center"
android:text="#string/app_title"
android:layout_marginBottom="#dimen/main_spacing"
android:textSize="24sp" />
<AutoCompleteTextView
android:id="#+id/enterContact"
android:text="Enter Contact"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAlignment="center"
android:layout_below="#+id/title"
android:layout_marginBottom="#dimen/main_spacing" />
</RelativeLayout>

This is a supplemental answer to Gravity and layout_gravity on Android.
View gravity and layout_gravity inside a Relative Layout
My original statement that gravity and layout_gravity should not be used in the subviews of a RelativeLayout was partly wrong. The gravity actually works fine. However, layout_gravity has no effect. This can be seen in the example below. The light green and light blue are TextViews. The other two background colors are RelativeLayouts.
As you can see, gravity works, but layout_gravity doesn't work.
Relative Layout with gravity
My original answer about gravity and layout_gravity dealt with these attributes being applied to the Views within a ViewGroup (specifically a LinearLayout), not to the ViewGroup itself. However, it is possible to set gravity and layout_gravity on a RelativeLayout. The layout_gravity would affect how the RelativeLayout is positioned within its own parent, so I will not deal with that here. How gravity affects the subviews, though, is shown in the image below.
I resized the widths of all the subviews so that what is happening is more clear. Note that the way RelativeLayout handles gravity is to take all the subviews as a group and move them around the layout. This means that whichever view is widest will determine how everything else is positioned. So gravity in a Relative layout is probably only useful if all the subviews have the same width.
Linear Layout with gravity
When you add gravity to a LinearLayout, it does arrange the subviews as one would expect. For example, one could "save code" by setting the gravity of LinearLayout to center_horizontally. That way there is no need individually set the layout_gravity of each subview. See the various options in the image below.
Note that when a view uses layout_gravity, it overrides the LinearLayout's gravity. (This can be seen in the title for the two layouts in the left image. The LinearLayout gravity was set to left and right, but the title TextView's layout_gravity was set to center_horizontally.)
Final notes
When positioning views within a RelativeLayout, the general way to do it is adding things like the following to each view:
layout_alignParentTop
layout_centerVertical
layout_below
layout_toRightOf
If one wants to set all the views at once, a LinearLayout would likely be better (or perhaps using a Style).
So to sum up,
The layout_gravity does not work for subviews in a RelativeLayout.
The gravity of a RelativeLayout does work, but not as one might expect.
Supplemental XML
XML for image "View gravity and layout_gravity inside a Relative Layout":
<?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" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="#e3e2ad" >
<TextView
android:id="#+id/tvTop1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:textSize="24sp"
android:text="Views' gravity=" />
<!-- examples of gravity -->
<TextView
android:id="#+id/tvTop2"
android:layout_below="#id/tvTop1"
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="left"
android:text="left" />
<TextView
android:id="#+id/tvTop3"
android:layout_below="#id/tvTop2"
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center_horizontal"
android:text="center_horizontal" />
<TextView
android:id="#+id/tvTop4"
android:layout_below="#id/tvTop3"
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="right"
android:text="right" />
<TextView
android:id="#+id/tvTop5"
android:layout_below="#id/tvTop4"
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center"
android:text="center" />
</RelativeLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="#d6c6cd" >
<TextView
android:id="#+id/tvBottom1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:textSize="24sp"
android:text="Views' layout_gravity=" />
<!-- examples of layout_gravity -->
<TextView
android:id="#+id/tvBottom2"
android:layout_below="#id/tvBottom1"
android:layout_width="200dp"
android:layout_height="40dp"
android:layout_gravity="left"
android:background="#bcf5b1"
android:text="left" />
<TextView
android:id="#+id/tvBottom3"
android:layout_below="#id/tvBottom2"
android:layout_width="200dp"
android:layout_height="40dp"
android:layout_gravity="center_horizontal"
android:background="#aacaff"
android:text="center_horizontal" />
<TextView
android:id="#+id/tvBottom4"
android:layout_below="#id/tvBottom3"
android:layout_width="200dp"
android:layout_height="40dp"
android:layout_gravity="right"
android:background="#bcf5b1"
android:text="right" />
<TextView
android:id="#+id/tvBottom5"
android:layout_below="#id/tvBottom4"
android:layout_width="200dp"
android:layout_height="40dp"
android:layout_gravity="center"
android:background="#aacaff"
android:text="center" />
</RelativeLayout>
</LinearLayout>
XML for image "Relative Layout with gravity":
<?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" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center_horizontal"
android:background="#e3e2ad" >
<TextView
android:id="#+id/tvTop1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="24sp"
android:text="Views' gravity=" />
<!-- examples of gravity -->
<TextView
android:id="#+id/tvTop2"
android:layout_below="#id/tvTop1"
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="left"
android:text="left" />
<TextView
android:id="#+id/tvTop3"
android:layout_below="#id/tvTop2"
android:layout_width="300dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center_horizontal"
android:text="center_horizontal" />
<TextView
android:id="#+id/tvTop4"
android:layout_below="#id/tvTop3"
android:layout_width="100dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="right"
android:text="right" />
<TextView
android:id="#+id/tvTop5"
android:layout_below="#id/tvTop4"
android:layout_width="150dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center"
android:text="center" />
</RelativeLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center"
android:background="#d6c6cd" >
<TextView
android:id="#+id/tvBottom1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="24sp"
android:text="Views' gravity=" />
<!-- examples of layout_gravity -->
<TextView
android:id="#+id/tvBottom2"
android:layout_below="#id/tvBottom1"
android:layout_width="200dp"
android:layout_height="40dp"
android:gravity="left"
android:background="#bcf5b1"
android:text="left" />
<TextView
android:id="#+id/tvBottom3"
android:layout_below="#id/tvBottom2"
android:layout_width="300dp"
android:layout_height="40dp"
android:gravity="center_horizontal"
android:background="#aacaff"
android:text="center_horizontal" />
<TextView
android:id="#+id/tvBottom4"
android:layout_below="#id/tvBottom3"
android:layout_width="100dp"
android:layout_height="40dp"
android:gravity="right"
android:background="#bcf5b1"
android:text="right" />
<TextView
android:id="#+id/tvBottom5"
android:layout_below="#id/tvBottom4"
android:layout_width="150dp"
android:layout_height="40dp"
android:gravity="center"
android:background="#aacaff"
android:text="center" />
</RelativeLayout>
</LinearLayout>
XML for image "Linear Layout with gravity":
<?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" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center_horizontal"
android:background="#e3e2ad"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:textSize="24sp"
android:text="View's gravity=" />
<TextView
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="left"
android:text="left" />
<TextView
android:layout_width="300dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center_horizontal"
android:text="center_horizontal" />
<TextView
android:layout_width="100dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="right"
android:text="right" />
<TextView
android:layout_width="150dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center"
android:text="center" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center"
android:background="#d6c6cd"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:textSize="24sp"
android:text="View's gravity=" />
<TextView
android:layout_width="200dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="left"
android:text="left" />
<TextView
android:layout_width="300dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center_horizontal"
android:text="center_horizontal" />
<TextView
android:layout_width="100dp"
android:layout_height="40dp"
android:background="#bcf5b1"
android:gravity="right"
android:text="right" />
<TextView
android:layout_width="150dp"
android:layout_height="40dp"
android:background="#aacaff"
android:gravity="center"
android:text="center" />
</LinearLayout>
</LinearLayout>

Testing your layout, for me it's working (the TextView is centered correctly).
However, you could also remove android:gravity="center_horizontal" from the RelativeLayout and add android:layout_centerHorizontal="true" in the TextView.

I've always had problems with RelativeLayouts and TextViews too. I think that this is due to the fact that TextView calculates its size dynamically and this prevents it to work well with layout's gravity. That's just one my supposition.
The solution I generally adopt is to configure a textview horizontal size with match_parent. It might be a suboptimal solution, but should work. In case you need a Fixed size textView you can put a fixed size dimension and should work too, it gives problems only with wrap_content.
<?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:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:gravity="center_horizontal"
tools:context="com.something">
<TextView
android:id="#+id/title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textAlignment="center"
android:text="#string/app_title"
android:layout_marginBottom="#dimen/main_spacing"
android:textSize="24sp" />
</RelativeLayout>
Edit:
as suggested by #Valentino S., adding
android:layout_centerHorizontal="true"
with wrap_content should work too. The reason is in my head still the same: size of textView is calculated later.

As the documentation says:
android:gravity
Specifies how an object should position its content, on both the X and
Y axes, within its own bounds.
...
center_horizontal
Place object in the horizontal center of its container, not changing
its size.
So the android:gravity="center_horizontal" will center horizontal-ing the RelativeLayout to its parent. Not making its content center horizontal.
Remember that android:layout_gravity is used for the view itself relative to the parent or layout.
Please be aware that the behaviour of Layout can differ slightly for each API Level. And be noted, that we can't 100% sure that the visual result in Layout Editor is correct. Always test your layout in real devices.

try this:
<?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:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:background="#000000"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin">
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginBottom="10dp"
android:background="#ffffffff"
android:text="TITLE"
android:textAlignment="center"
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textSize="24sp" />
<AutoCompleteTextView
android:id="#+id/enterContact"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/title"
android:layout_marginBottom="10dp"
android:background="#ffffffff"
android:text="Enter Contact"
android:textAlignment="center" />
</RelativeLayout>

TlDr: android:gravity Works with RelativeLayout , you can skip to the bottom if you don't want to read the explanation
EDIT this is a giant wall of text, please bear with me
This is what I imagine you want to achieve:
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textAlignment="center"
android:text="#string/app_title"
android:layout_marginBottom="#dimen/main_spacing"
android:textSize="24sp"
android:layout_centerHorizontal="true"/> <!-- LAYOUT PARAMS WORK!!!-->
Why does this work, while android:gravity (apparently) doesn't?
if your goal is to put the TextView in the horizontal center of the Layout/Screen you have to let the RelativeLayout know!
this is achieved through something called LayoutParams - these are data structures defined by each View which are used by the View's parent (in this case the RelativeLayout)
so let's say your TextView has the following LayoutParams :
android:layout_centerHorizontal="true"
you will get something like this:
When the RelativeLayout is distributing its child views around the screen, along the way there is a callback method being run - onLayout(...) - which is part of a more complex method sequence that will determine the position of each child View inside the RelativeLayout, this is achieved in part by accessing the LayoutParams in each child View, in this case that line in your TextView
This is why we say LayoutParams are passed on to the parent like in the link you mentioned before
WARNING: Endless Confusion Source!
View positioning inside Layouts / ViewGroups is done through LayoutParams the onLayout calls
It so happens that some layouts like FrameLayout have a LayoutParam called android:layout_gravity which causes great confusion with the android:gravity property that each view can define, which is NOT the same and not even a LayoutParam
android:gravity is used by any View (like a TextView for example) to place its content inside.
Example: let's say that you change your TextView to be very high, and you want the text at the bottom of the TextView, instead of at the top
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="95dp" <------------ very high!
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textAlignment="center"
android:text="#string/app_title"
android:layout_marginBottom="#dimen/main_spacing"
android:textSize="24sp"
android:layout_centerHorizontal="true" <----- LayoutParams for RelativeLayout
/>
TextView is CENTERED in the RelativeLayout but text is at the TOP of the "box"
Let's use android:gravity to manage the text position INSIDE THE TextView
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="95dp"
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textAlignment="center"
android:text="#string/app_title"
android:layout_marginBottom="#dimen/main_spacing"
android:textSize="24sp"
android:layout_centerHorizontal="true"
android:gravity="bottom" <---**NOT LayoutParams**, NOT passed to RLayout
/>
Result: As expected only the inside of the View changed
TLDR
Now if you want to ignore everything above and still use android:gravity with RelativeLayout, RelativeLayout is also a Viewso it has the android:gravity property, but you have to remove other properties or LayoutParams which will override the behaviour defined by the android:gravity property look at android:gravity at work with 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:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:gravity="bottom"> <!-- NOT LAYOUT PARAMS -->
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="95dp"
android:textAppearance="#style/TextAppearance.AppCompat.Title"
android:textAlignment="center"
android:text="#string/app_title"
android:layout_marginBottom="#dimen/main_spacing"
android:textSize="24sp"
android:layout_centerHorizontal="true"
/>
<AutoCompleteTextView
android:id="#+id/enterContact"
android:text="Enter Contact"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAlignment="center"
android:layout_below="#+id/title"
android:layout_marginBottom="#dimen/main_spacing" />
</RelativeLayout>

Simple Android Layout Resize

I'm attempting to resize buttons on rotate to expand proportionately. Right now, they are a fix length, but I'm unsure of an alternative method to get the buttons to resize (setting the weight doesn't seem to help). I want the buttons to essentially fill the length of the screen both vertically and horizontally. Please let me know if you need more information.
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:layout_gravity="center_vertical" >
<Button
android:id="#+id/mainCommentBtn"
android:layout_width="119dp"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:layout_weight="1"
android:text="#string/commentBtn" />
<Button
android:id="#+id/mainProfileBtn"
android:layout_width="119dp"
android:layout_height="wrap_content"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:layout_weight="1"
android:layout_centerInParent="true"
android:text="#string/profileBtn" />
<Button
android:id="#+id/mainDetailBtn"
android:layout_width="119dp"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:layout_weight="1"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:text="#string/shareBtn" />
</LinearLayout>

Replace your resource with this. Copy the edited changes
Notice how there width is 0dp because they are using weight.
Using Weight:
1. In order to use weight you need to set the weightSum in the parent.
2. Make sure the width or height is set to 0 according to how you are using weight.
(for instance since we are going with horizontal orientation we want to use "0dp" width. This allows weight to control the width of the object.
3. Lastly make sure the weight of all the objects add up to the weightSum.
<?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="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_marginTop="5dp"
android:orientation="horizontal"
android:weightSum="3" >
<Button
android:id="#+id/mainCommentBtn"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_weight="1"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:text="#string/commentBtn" />
<Button
android:id="#+id/mainProfileBtn"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_weight="1"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:text="#string/profileBtn" />
<Button
android:id="#+id/mainDetailBtn"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_weight="1"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:text="#string/shareBtn" />
</LinearLayout>

You need to specify an orientation for the LinearLayout.
I guess you want to use android:orientation="horizontal".
Then, in order to make android:weight work, you'd need to specify the width of every button as 0px by using android:layout_width="0px" for every button.

<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:text="Button" />
These xml properties size the button to fill the screen both vertically and horizontally.

You can create the layout with the help of layout weight so that it will automatically fill the screen in landscape mode also as below:
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="3" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 1"
android:layout_weight="1" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 2"
android:layout_weight="1" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 3"
android:layout_weight="1" />
</LinearLayout>

Aligning views with views outside the RelativeLayout

I am designing a table using RelativeLayout in Android and add entries programmically. The result pleases me so far:
The layout code is
<RelativeLayout
android:id="#+id/table_relativelayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:id="#+id/column1_header"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="#string/column1_header"
style="?android:attr/listSeparatorTextViewStyle"
android:layout_weight="1.0"
/>
<TextView
android:id="#+id/column2_header"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_alignBaseline="#id/column1_header"
android:text="#string/column1_header"
android:textSize="14sp"
android:textStyle="bold"
android:textAllCaps="true"
android:textColor="#color/textColor"
/>
<TextView
android:id="#+id/column3_header"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignBaseline="#id/column1_header"
android:text="#string/column3_header"
android:textSize="14sp"
android:textAllCaps="true"
android:textStyle="bold"
android:paddingRight="8dip"
/>
<TextView
android:id="#+id/example_column1_entry"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#id/column1_header"
android:text=""
android:paddingLeft="8dip"
android:visibility="gone"
/>
<TextView
android:id="#+id/example_column2_entry"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#id/column2_header"
android:text=""
android:visibility="gone"
/>
<TextView
android:id="#+id/example_column3_entry"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#id/column3_header"
android:paddingRight="8dip"
android:text=""
android:visibility="gone"
/>
</RelativeLayout>
However, as more entries are added, scrolling becomes necessary. So I wrap the whole thing in a ScrollView (as per this answer)
<ScrollView
android:id="#+id/table_scrollview"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:scrollbars="vertical"
android:fillViewport="true"
>
...
</ScrollView>
This of course has the result that the header row is hidden if I scroll down. I'd much rather have it outside the ScrollView but then I don't know how to align the entries with the header. Any ideas?

Try with something like this:
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="#+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_alignParentTop="true">
<TextView
android:id="#+id/column1_header"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="#string/column1_header"
style="?android:attr/listSeparatorTextViewStyle"
android:layout_weight="1.0"
/>
<TextView
android:id="#+id/column2_header"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_alignBaseline="#id/column1_header"
android:text="#string/column1_header"
android:textSize="14sp"
android:textStyle="bold"
android:textAllCaps="true"
android:textColor="#color/textColor"
/>
<TextView
android:id="#+id/column3_header"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignBaseline="#id/column1_header"
android:text="#string/column3_header"
android:textSize="14sp"
android:textAllCaps="true"
android:textStyle="bold"
android:paddingRight="8dip"
/>
</LinearLayout>
<ScrollView
android:layout_below="#id/header"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="#+id/scroll_view_container"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<rows>
</LinearLayout>
</ScrollView>
<RelativeLayout>

you don't want to do this with xml.
Because you simply can't reference views inside of an relativeLayout
from the outside and vice versa, to align things.
I had to deal with exactly your issue, as I implemented a in size selfadjusting tableView. The trick is to add all your textViews for one row into a ViewGroup (LinearLayout e.g, because easy to use with addView) and calculate the width of every row header in forehand. Than set the size of the viewGroups programmaticaly.
That's the key. This way, you can easily change your row header later and keep beeing flexible. Moreover you are not limited to a fixed size of columns.
calculate the width of the header
set the size of the (e.g) LinearLayouts for every row
add all TextViews to the LinearLayouts
This should hopefully help you. Answers to all the upcoming question for calculation sizes etc, should you find yourself on stackoverflow.
Greets, Steve.

OK, I found a solution: I'll have the three header TextViews outside of the ScrollView, as suggested by several commenters, and three additional "header" TextViews with the same parameters plus android:visibility="invisible" inside the ScrollViews. Those invisible TextViews will be used to align the visible entries.
Thanks for your answers!

Android layout - Two views next to each other, equal width, use full screen-width

I have a problem with a layout in android. I want that two views should have the equal width, and they should almost use the full width of the screen. Each view should contain a centered label.
It should look like this when it's done:
Here is what I have so far:
<?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">
<View
android:id="#+id/view1"
android:layout_width="10dp"
android:layout_height="90dp"
android:layout_alignParentTop="true"
android:layout_marginTop="10dp"
android:layout_marginLeft="10dp" />
<View
android:id="#+id/view2"
android:layout_width="10dp"
android:layout_height="90dp"
android:layout_alignParentTop="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp" />
</RelativeLayout>
I just have placeholder values for the width right now.
Thanks.

You have to use android:layout_weight attribute in xml so try below code hope it will resolve your problem :-
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:text="Register"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:padding="10dip"
android:layout_margin="5dp"
android:layout_weight="1" />
<Button
android:text="Not this time"
android:id="#+id/cancel"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:padding="10dip"
android:layout_margin="5dp"
android:layout_weight="1" />
</LinearLayout>
To create a linear layout in which each child uses the same amount of
space on the screen, set the android:layout_height of each view to
"0dp" (for a vertical layout) or the android:layout_width of each view
to "0dp" (for a horizontal layout). Then set the android:layout_weight
of each view to "1"
For more info you need to read Linear layout.

It will be easier with LinearLayout, set the layout to match_parent with horizontal orientation.
After that, set layout_width to 0px and layout_weight=1 in both of your view.
See this for good explanation :
Layout buttons so each divides up the space equally

You have to use layout_weight attribute for this.
<Button
android:text="Register"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:padding="10dip"
android:layout_margin="5dp"
android:layout_weight="1" />
<Button
android:text="Not this time"
android:id="#+id/cancel"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:padding="10dip"
android:layout_margin="5dp"
android:layout_weight="1" />
</LinearLayout>

Adding ScrollView to RelativeLayout changes position of wigdets

The following is the XML of my layout. It explicitly states that the title, time and description TextViews should be under the image of the alarm. However, as the screen shot shows, the TextViews have moved into the ImageView. Why does this happen and how can I fix this? The problem only started happening when I added the scrollview.
XML
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView
android:id="#+id/img_alarm"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/alarm"
android:layout_centerInParent="true"
android:contentDescription="#string/content_description_layout_alarm"/>
<TextView
android:id="#+id/lbl_alarm_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20dip"
android:textStyle="bold"
android:layout_centerHorizontal="true"
android:layout_below="#+id/img_alarm"
android:layout_alignLeft="#+id/img_alarm"
android:text="#string/empty"
/>
<TextView
android:id="#+id/lbl_alarm_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20dip"
android:textStyle="bold"
android:layout_centerHorizontal="true"
android:layout_below="#+id/img_alarm"
android:layout_alignRight="#+id/img_alarm"
android:text="#string/empty"
/>
<TextView
android:id="#+id/lbl_alarm_description"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_below="#+id/lbl_alarm_title"
android:layout_alignLeft="#+id/lbl_alarm_title"
android:layout_alignRight="#+id/lbl_alarm_time"
android:maxLines="1"
android:ellipsize="marquee"
android:text="#string/empty"
/>
<Button
android:id="#+id/btn_stop"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/lbl_alarm_description"
android:layout_centerHorizontal="true"
android:layout_marginTop="5dip"
android:paddingLeft="20dip"
android:paddingRight="20dip"
android:text="#string/stop_layout_alarm"
android:gravity="center" />
</RelativeLayout>
</ScrollView>
Image

Cute app :)
hmm... not sure why it's doing it, looks like you have the right code, without busting out eclipse. but i've also had some weird bugs with relativelayout that i didn't understand and didn't have time to debug.
i do know of an alternative way you can accomplish what you're looking for -
have a scrollview that encases a linearlayout instead of a relative layout. Do these things:
For the linearlayout, you can set orientation = vertical so that it's still a top down order.
For the part where you need two textviews where one is aligned to the right and the other is aligned to the right, you need another inner linearlayout with its orientation=horizontal. then have one element align parent left, and the other align parent right. add a weightSum=1 attribute to this linearlayout and have each of the two textviews layout_width=0.5 so that each is half the width of the screen
Apply a weightSum=1 attribute to your outer most linearlayout, and see each element inside so that it's layout_weight sum adds up to 1. layout_weight will allow an element to take up that much % of real estate on the screen. like if you set your imageView to have android:layout_weight=0.8 then it'll take up 80% of the screen... since mathematically, (layout_weight/weightSum) = (.08/1) = 80%
try to use that mechanism instead, and if should work :) if it's confusing i can give code
example
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="1">
<ImageView
android:id="#+id/img_alarm"
android:layout_width="match_parent"
android:layout_height="0dip"
android:src="#drawable/alarm"
android:layout_weight="0.7"
android:contentDescription="#string/content_description_layout_alarm"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="0.1">
<TextView
android:id="#+id/lbl_alarm_title"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dip"
android:textStyle="bold"
android:text="#string/empty"
/>
<TextView
android:id="#+id/lbl_alarm_time"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textSize="20dip"
android:textStyle="bold"
android:text="#string/empty"
/>
</LinearLayout>
<TextView
android:id="#+id/lbl_alarm_description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_weight="0.1"
android:maxLines="1"
android:ellipsize="marquee"
android:text="#string/empty"
/>
<Button
android:id="#+id/btn_stop"
android:layout_weight="0.1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="5dip"
android:paddingLeft="20dip"
android:paddingRight="20dip"
android:text="#string/stop_layout_alarm"
android:gravity="center" />
</LinearLayout>
</ScrollView>
i hope this deserves at least an upvote for the effort :D