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

Question

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>

Answer 1

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>

Answer 2

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?

1. if your goal is to put the TextView in the horizontal center of the Layout/Screen you have to let the RelativeLayout know!

2. 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)

3. 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

4. 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>

Answer 3

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>

Answer 4

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.

Answer 5

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.

Answer 6

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.