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).
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.
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.
