Why adapter is used in android

Java adapter classes provide the default implementation of listener interfaces. If you inherit the adapter class, you will not be forced to provide the implementation of all the methods of listener interfaces. So it saves code. The adapter classes are found in java. An adapter class provides the default implementation of all methods in an event listener interface. Adapter classes are very useful when you want to process only few of the events that are handled by a particular event listener interface.

It holds the data and send the data to an Adapter view then view can takes the data from the adapter view and shows the data on different views like as ListView, GridView, Spinner etc.

Android provides several subclasses of Adapter that are useful for retrieving different kinds of data and building views for an AdapterView i. ListView or GridView. Abstract class: is a restricted class that cannot be used to create objects to access it, it must be inherited from another class.

Abstract method: can only be used in an abstract class, and it does not have a body. The body is provided by the subclass inherited from.

The event listener interfaces that contain more than one method have a corresponding event adapter class that implements the interface and defines each method in the interface with an empty method body. For example, the adapter class for the WindowListener interface is WindowAdapter. They are used to provide the implementation of Listener interfaces. The advantage of the adapter class is that it saves code.

Tkinter Module. Network Programming with Python. Learn Web Scraping. More in Python Python Compiler. Java Core Java Tutorial. Java Type Conversion Examples. Java Wrapper Class. Java 8. Java More in Java Java Compiler. Computer Sci. Computer Architecture. Computer Network. Database DBMS. Learn SQL. Practice SQL. More Tutorials Game Development. GO Language. GIT Guide. Linux Guide. Spring Framework. Learn C Language. Core Java. Computer Science. To fill data in a list or a grid we need to implement Adapter.

Adapters acts like a bridge between UI component and data source. Here data source is the source from where we get the data and UI components are list or grid items in which we want to display that data. Whenever we need a customized list in a ListView or customized grids in a GridView we create our own adapter and extend base adapter in that. Base Adapter can be extended to create a custom Adapter for displaying a custom list item.

ArrayAdapter is also an implementation of BaseAdapter. In above code snippet we see the overrided functions of BaseAdapter which are used to set the data in a list, grid or a spinner. These functions are described in BaseAdapter tutorial with example. Whenever we have a list of single items which is backed by an Array, we can use ArrayAdapter.

For instance, list of phone contacts, countries or names. The above function are described in ArrayAdapter tutorial with example. ArrayAdapter is also an implementation of BaseAdapter, so if we want more customization then we can create a custom adapter and extend ArrayAdapter in that. These functions are described in Custom ArrayAdapter tutorial with example. In Android we can specify the data backing to a list as an ArrayList of Maps i.

Each entry in a ArrayList is corresponding to one row of a list. The Map contains the data for each row. Here we also specify an XML file custom list items file that defines the views which is used to display the row, and a mapping from keys in the Map to specific views.