Layouts

Prasanna Kumar K R

Layout

• Layout defines the structure for a user interface in your app, such as in an activity.
• All elements in the layout are built using a hierarchy of View and ViewGroup objects.
• A View usually draws something the user can see and interact with. View objects are usually called "widgets"
• ViewGroup is an invisible container that defines the layout structure for View and other ViewGroup objectsL
• Layouts

Declare a Layout

• Declare a layout in two ways:
• Declare UI elements in XML.
• Android provides a straightforward XML vocabulary that corresponds to the View classes and subclasses, such as those for widgets and layouts.
• Instantiate layout elements at runtime.
• app can create View and ViewGroup objects (and manipulate their properties) programmatically.

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Load the XML Resource

Layout Parameters

• XML layout attributes named layout_something

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layout_width and layout_height

• wrap_content tells your view to size itself to the dimensions required by its content.
• match_parent tells your view to become as big as its parent view group will allow.

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LinearLayout

• It is a view group that aligns all children in either vertically or horizontally.
• 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:orientation
• It is specifies the direction of arrangement and you will use "horizontal" for a row, "vertical" for a column.
• The default is horizontal.

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Linear Layout

<LinearLayout

android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" >

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</LinearLayout>

Relative Layout

• Enables you to specify the location of child objects relative to each other or to the parent
• android:gravity
• It 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.

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<RelativeLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:paddingLeft="16dp" android:paddingRight="16dp" >

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</RelativeLayout>

Table Layout

• Android TableLayout going to be arranged groups of views into rows and columns.

<TableLayout

android:layout_width="fill_parent" android:layout_height="fill_parent">

<TableRow android:layout_width="fill_parent" android:layout_height="fill_parent"> <TextView android:text="Time" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_column="1" /> <TextClock android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/textClock" android:layout_column="2" />

</TableRow>

<TableRow> <TextView android:text="First Name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_column="1" /> <EditText android:width="200px" android:layout_width="wrap_content" android:layout_height="wrap_content" />

</TableRow>

</TableLayout>

List View

• It is a view which groups several items and display them in vertical scrollable list.
• An adapter actually bridges between UI components and the data source that fill data into UI Component

GridView

• It shows items in two-dimensional scrolling grid (rows & columns) and the grid items are not necessarily predetermined but they automatically inserted to the layout using a ListAdapter