Android ListView with Adapter

What is ListView?

ListView is a view group that displays a list of scrollable items.
ListView is used to show a vertical list of scrollable items, which has data populated using an Adpater.
The simplest adapter to use in ListView is called an ArrayAdapter.
The main purpose of an ArrayAdapter is to convert an ArrayList of objects into View items loaded into the ListView container.

In the above diagram, The Adapter (which means ArrayAdapter) fits in between an Data source (ArrayList) and the Adapter View (List View).

The ArrayAdapter configures two aspects:
1. Which array is used as the data source for the list?
2. How to convert any given item in the array into a corresponding View object?

Adapter

Adapter manages the data model.
It extends the BaseAdapter class.
It adopts the data model to the individual entries in the widget.

ListView with ArrayAdapter

ArrayAdapter class handles a list or array of Java objects as input.
The user can add new elements with the add() method.
This class allows to remove all elements in its underlying data structure with the clear() method call.
ArrayAdapter creates a view for each array item by calling toString() method and place the contents in a TextView.

Syntax:
ArrayAdapter adapter = new ArrayAdapter<String>(this,R.layout.ListView,StringArray);

Parameters of the above constructor

this – It is the application content.
R.layout – It is a layout defined in an XML file and have TextView for each string in the array.
StringArray – It is an array of strings, populated in the text view.

ListView Attributes

Attributes	Description
android:id	It is the ID of layout for identifying uniquely.
android:entries	It specifies the reference to an array resource that will populate the ListView.
android:divider	It is drawable or color to draw between list items.
android:dividerHeight	It specifies the height of the divider.
android:footerDividersEnabled	Its default value id true. If it sets to false, the ListView will not draw the divider before each footer view.
android:headerDividersEnabled	Its default value is true. If it sets to false, the ListView will not draw the divider after each header view.

Example : ListView Control with ArrayAdapter

XML file for ListView Control

<ListView
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
android:id = "@+id/listView"
android:layout_alignParentLeft = "true"
android:layout_alignParentStart = "true" />

File Name: MainActivity.java

public class MainActivity extends AppCompatActivity
{
     ListView lvObj;
     String [] city={"Pune","Gwalior","Patna","Nasik","Kashmir",""};
     @Override
     protected void onCreate(Bundle savedInstanceState)
     {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);   //XML file name activity_main.xml
          lvObj = (ListView)findViewById(R.id.listView);
          ArrayAdapter<String>arrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,city);
          lvObj.setAdapter(arrayAdapter);
          lvObj.setOnItemClickListener(new AdapterView.OnItemClickListener()
          {
               @Override
               public void onItemClick (AdapterView<?> parent, View view, intposition, long id)
               {
                    String item = (String)lvObj.getItemAtPosition(position);
                    Toast toast = Toast.makeText(getApplicationContext(),"Your selected city ="+item,Toast.LENGTH_LONG);
                    toast.setGravity(Gravity.CENTER,30,150);
                    toast.show();
               }
          });
     }
}

Output:

In the above example, the getItemAtPosition() provides the text of selected item from the ListView control.