Android Views and ViewGroups

• A ViewGroup is a special view that can contain other views
• ViewGroup is the base class for layouts in Android, including LinearLayout, RelativeLayout, and FrameLayout
• ViewGroup defines the layout in which views (widgets) are set, arranged, or listed on the Android screen
• ViewGroups act as invisible containers for other Views and Layouts; a layout can contain another layout
• A View is the user interface for creating interactive UI components like TextView, ImageView, EditText, and RadioButton
• Views are responsible for event handling and drawing and are generally called Widgets
• A ViewGroup acts as a base class for layouts and layout parameters that hold other Views or ViewGroups
• ViewGroup defines layout properties, and are generally called layouts
• UI elements or widgets can be used in the Android framework in two ways:
  • Using UI elements in the XML file
  • Creating elements in the Kotlin file dynamically

Different Types of Views

• Android WebView is a browser for displaying web pages in an activity layout
• Android ListView is a ViewGroup for displaying scrollable lists of items in a single column
• Android GridView is a ViewGroup for displaying scrollable lists of items in a grid view of rows and columns
• Android RecyclerView is an advanced version of ListView with improved performance
• Android CardView is a new widget for displaying any sort of data with a rounded corner layout and a specific elevation
• Android TextView is used to display text to the user and can be optionally modified or edited
• Android Button is a user interface to perform an action when clicked or tapped
• Android RadioGroup, a Kotlin class, is used to create a container holding multiple RadioButtons
• Android ToggleButton is like a switch with two states: ON or OFF, represented by boolean values true and false
• Android CheckBox is a special kind of button with two states: checked or unchecked

ListView

• Android ListView is a ViewGroup that displays a list of items in multiple rows
• It contains an adapter that automatically inserts the items into the list
• The adapter fetches data from an array or database and inserts each item into the list
• Adapter pulls data from the strings.xml file, containing required strings in Kotlin or XML files

Android Adapter

• Adapter holds data fetched from an array and iterates through each item in a dataset
• It generates the respective views for each item of the list
• Adapters act as an intermediate between data sources and adapter views such as ListView and GridView

Different Types of Adapters

• ArrayAdapter accepts an Array or List as input, and list items can also be stored in the strings.xml file
• CursorAdapter always accepts an instance of a cursor
• SimpleAdapter accepts static data defined in resources like an array or database
• BaseAdapter has a generic implementation for all three adapter types, which can be used in views according to requirements

GridView

• GridView is a type of adapter view that displays data in a grid layout format
• The setAdapter() method sets data to the grid view adapter, setting data from a database or array list to grid view items

RecyclerView

• RecyclerView is an advanced ListView version with improved performance and the ability to reuse views
• RecyclerView reuses views when they go out of the screen or are not visible, which reduces power consumption and improves responsiveness
• onCreateViewHolder() sets the views to display the items
• onBindViewHolder() binds list items to widgets such as TextView and ImageView
• getItemCount() returns the number of items present in the list

CardView Attributes

• cardBackgroundColor sets the background color of the card
• cardElevation defines the card's elevation; its value should not be too large
• cardCornerRadius sets the radius around the corners of the card; a higher value results in more circular edges
• cardUseCompactPadding has true or false values; when set to true, the card sets padding for itself to improve the UI's appearance

TextView Attributes

• android:text sets the text of the TextView
• android:id gives a unique ID to the TextView
• android:cursorVisible makes the cursor visible or invisible; the default value is visible
• android:drawableBottom sets images or other graphic assets below the TextView
• android:drawableEnd sets images or other graphic assets at the end of the TextView
• android:drawableLeft sets images or other graphic assets to the left of the TextView
• android:drawablePadding sets padding to the drawable (images or other graphic assets) in the TextView
• android:autoLink automatically detects URLs or emails and shows them as clickable links
• android:autoText automatically corrects spelling errors in the TextView
• android:capitalize automatically capitalizes whatever the user types in the TextView
• android:drawableRight sets drawables to the right of the text
• android:drawableStart sets drawables to the start of the text
• android:drawableTop sets drawables to the top of the text
• android:ellipsize ellipsizes the text if it is longer than the TextView width
• android:ems sets the width of the TextView in ems
• android:gravity aligns the text vertically, horizontally , or both
• android:height sets the height of the TextView
• android:hint shows a hint when there is no text entered
• android:inputType sets the input type of the TextView, e.g., Number, Password, Phone
• android:lines sets the height of the TextView by the number of lines
• android:maxHeight sets the maximum height of the TextView
• android:minHeight sets the minimum height of the TextView
• android:maxLength sets the maximum character length of the TextView
• android:maxLines sets the maximum lines the Textview can have
• android:minLines sets the minimum lines the Textview can have
• android:maxWidth sets the maximum width the TextView can have
• android:minWidth sets the minimum width the TextView can have
• android:textAllCaps shows all text of the TextView in capital letters
• android:textColor sets color of text
• android:textSize sets font size of text
• android:textStyle sets style of text (bold, italic, bolditalic)
• android:typeface assigns typeface or front of the text (normal, sans, serif etc)
• android:width sets width