Android Relative Layout

Relative layout as its name suggest that in this type of layout we can specify the position of child views relative to each other. This position either can be related to its parent or other views in the layout.

Relative layout is very powerful layout because it can remove some unnecessary nesting of layouts and will keep your hierarchy in a flat manner that will improve performance of our application.It can help to replace some nesting of linear layouts.Nesting of layouts decrease performance of our application and make hierarchy complex.

Here are some important attributes of android relative layout -

	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.

Below are some more important attributes -

	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".

Below is an example of relative layout -

<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>

In above example we have created a relative layout with three child and one nested linear layout and we have arranged them relative to each other like linear layout is below to edit text. Here we can also remove linear layout and can arrange button to below edit text and second button to below of button.It will remove the use of linear layout.You should try it yourself.

Below is an output screen of this layout -