Android Relative Layout

Android RelativeLayout enables you to specify how child views are positioned relative to each other. The position of each view can be specified as relative to sibling elements or relative to the parent.

Relative Layout

RelativeLayout Attributes

Following are the important attributes specific to RelativeLayout −

Sr.No.	Attribute & Description
1	android:id This is the ID which uniquely identifies the layout.
2	android:gravity This specifies how an object should position its content, on both the X and Y axes. Possible values are top, bottom, left, right, center, center_vertical, center_horizontal etc.
3	android:ignoreGravity This indicates what view should not be affected by gravity.

Sr.No.

Attribute & Description

android:id

This is the ID which uniquely identifies the layout.

android:gravity

This specifies how an object should position its content, on both the X and Y axes. Possible values are top, bottom, left, right, center, center_vertical, center_horizontal etc.

android:ignoreGravity

This indicates what view should not be affected by gravity.

Using RelativeLayout, you can align two elements by right border, or make one below another, centered in the screen, centered left, and so on. By default, all child views are drawn at the top-left of the layout, so you must define the position of each view using the various layout properties available from RelativeLayout.LayoutParams and few of the important attributes are given below −

Sr.No.	Attribute & Description
1	android:layout_above Positions the bottom edge of this view above the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name"
2	android:layout_alignBottom Makes the bottom edge of this view match the bottom edge of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
3	android:layout_alignLeft Makes the left edge of this view match the left edge of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
4	android:layout_alignParentBottom If true, makes the bottom edge of this view match the bottom edge of the parent. Must be a boolean value, either "true" or "false".
5	android:layout_alignParentEnd If true, makes the end edge of this view match the end edge of the parent. Must be a boolean value, either "true" or "false".
6	android:layout_alignParentLeft If true, makes the left edge of this view match the left edge of the parent. Must be a boolean value, either "true" or "false".
7	android:layout_alignParentRight If true, makes the right edge of this view match the right edge of the parent. Must be a boolean value, either "true" or "false".
8	android:layout_alignParentStart If true, makes the start edge of this view match the start edge of the parent. Must be a boolean value, either "true" or "false".
9	android:layout_alignParentTop If true, makes the top edge of this view match the top edge of the parent. Must be a boolean value, either "true" or "false".
10	android:layout_alignRight Makes the right edge of this view match the right edge of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
11	android:layout_alignStart Makes the start edge of this view match the start edge of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
12	android:layout_alignTop Makes the top edge of this view match the top edge of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
13	android:layout_below Positions the top edge of this view below the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
14	android:layout_centerHorizontal If true, centers this child horizontally within its parent. Must be a boolean value, either "true" or "false".
15	android:layout_centerInParent If true, centers this child horizontally and vertically within its parent. Must be a boolean value, either "true" or "false".
16	android:layout_centerVertical If true, centers this child vertically within its parent. Must be a boolean value, either "true" or "false".
17	android:layout_toEndOf Positions the start edge of this view to the end of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
18	android:layout_toLeftOf Positions the right edge of this view to the left of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
19	android:layout_toRightOf Positions the left edge of this view to the right of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".
20	android:layout_toStartOf Positions the end edge of this view to the start of the given anchor view ID and must be a reference to another resource, in the form "@[+][package:]type:name".

Example

This example will take you through simple steps to show how to create your own Android application using Relative Layout. Follow the following steps to modify the Android application we created in Hello World Example chapter −

Step	Description
1	You will use Android Studio IDE to create an Android application and name it as demo under a package com.example.demo as explained in the Hello World Example chapter.
2	Modify the default content of res/layout/activity_main.xml file to include few widgets in Relative layout.
3	Define required constants in res/values/strings.xml file
4	Run the application to launch Android emulator and verify the result of the changes done in the application.

Following is the content of the modified main activity file src/com.example.demo/MainActivity.java. This file can include each of the fundamental lifecycle methods.

package com.example.demo;

import android.os.Bundle;
import android.app.Activity;

public class MainActivity extends Activity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
   }
   
}

Following will be the content of res/layout/activity_main.xml file −

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:paddingLeft="16dp"
   android:paddingRight="16dp" >
   
   <EditText
      android:id="@+id/name"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:hint="@string/reminder" />
      
   <LinearLayout
      android:orientation="vertical"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:layout_alignParentStart="true"
      android:layout_below="@+id/name">
      
      <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="New Button"
         android:id="@+id/button" />
      
      <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="New Button"
         android:id="@+id/button2" />
      
   </LinearLayout>

</RelativeLayout>

Following will be the content of res/values/strings.xml to define two new constants −

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <string name="action_settings">Settings</string>
   <string name="reminder">Enter your name</string>
</resources>

Let's try to run our modified Hello World! application we just modified. I assume you had created your AVD while doing environment setup. To run the app from Android Studio, open one of your project's activity files and click Run Eclipse Run Icon icon from the toolbar. Android Studio installs the app on your AVD and starts it and if everything is fine with your setup and application, it will display following Emulator window −

android_user_interface_layouts.htm

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