List Views android exam

The ListView and Spinner views are useful for displaying long lists of items.

ListView View

The ListView view displays a list of items in a vertically scrolling list. To see how the ListView view works, add a new file to the res/layout folder and name it as listview.xml and populate it with the following element:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <ListView android:id="@+id/android:list"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent" />    
 
</LinearLayout>

Add a new class to the src/net.learn2develop.AndroidViews folder and name it as ListViewExample.java. Populate it as follows:

package net.learn2develop.AndroidViews;
 
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import android.app.ListActivity; 
 
public class ListViewExample extends ListActivity 
{
    String[] presidents = {
            "Dwight D. Eisenhower",
            "John F. Kennedy",
            "Lyndon B. Johnson",
            "Richard Nixon",
            "Gerald Ford",
            "Jimmy Carter",
            "Ronald Reagan",
            "George H. W. Bush",
            "Bill Clinton",
            "George W. Bush",
            "Barack Obama"
    };
 
    @Override  
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.listview);
 
        setListAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, presidents));
    }    
 
    public void onListItemClick(
    ListView parent, View v,
    int position, long id) 
    {   
        Toast.makeText(this, 
            "You have selected " + presidents[position], 
            Toast.LENGTH_SHORT).show();
    }  
}

Notice that the ListViewExample class extends the ListActivity class.
Modify the AndroidManifest.xml file to register the new activity:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="net.learn2develop.AndroidViews"
      android:versionCode="1"
      android:versionName="1.0.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
 
        <activity android:name=".ViewsActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
 
        <activity android:name=".ListViewExample"
                  android:label="@string/app_name" />
 
    </application>
</manifest>

Modify the ViewsActivity.java file as follows to start the ListViewExample activity:

package net.learn2develop.AndroidViews;
 
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
 
public class ViewsActivity extends Activity 
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
 
        startActivity(new Intent( this, ListViewExample.class));
 
    }
}

Press F11 to debug the application on the Android emulator. Figure 5 shows the ListView view in action. When an item is selected, a message will be displayed.

Figure 5: The ListView view in action