When I insert a listview in a fragment in my application, it doesn't show up after I populate it with items. In fact, the application crashes due to a NullPointerException. Can anybody help me? Here is the detail activity from which I show the fragments. package com.example.sample; import android.content.Intent; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentTransaction; import android.support.v4.app.NavUtils; import android.widget.ArrayAdapter; import android.widget.ListView; import com.actionbarsherlock.app.ActionBar; import com.actionbarsherlock.app.ActionBar.Tab; import com.actionbarsherlock.app.SherlockFragmentActivity; import com.actionbarsherlock.view.MenuItem; /** * An activity representing a single Course detail screen. This activity is only * used on handset devices. On tablet-size devices, item details are presented * side-by-side with a list of items in a {@link CourseListActivity}. * <p> * This activity is mostly just a 'shell' activity containing nothing more than * a {@link CourseDetailFragment}. */ public class CourseDetailActivity extends SherlockFragmentActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_course_detail); // Show the Up button in the action bar. ActionBar actionBar = getSupportActionBar(); actionBar.setDisplayHomeAsUpEnabled(true); actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); // initiating both tabs and set text to it. ActionBar.Tab assignTab = actionBar.newTab().setText("Assignments"); ActionBar.Tab schedTab = actionBar.newTab().setText("Schedule"); ActionBar.Tab contactTab = actionBar.newTab().setText("Contact"); // Create three fragments to display content Fragment assignFragment = new Assignments(); Fragment schedFragment = new Schedule(); Fragment contactFragment = new Contact(); assignTab.setTabListener(new MyTabsListener(assignFragment)); schedTab.setTabListener(new MyTabsListener(schedFragment)); contactTab.setTabListener(new MyTabsListener(contactFragment)); actionBar.addTab(assignTab); actionBar.addTab(schedTab); actionBar.addTab(contactTab); ListView listView = (ListView) findViewById(R.id.assignlist); String[] values = new String[] { "Android", "iPhone", "WindowsMobile", "Blackberry", "WebOS", "Ubuntu", "Windows7", "Max OS X", "Linux", "OS/2" }; // First paramenter - Context // Second parameter - Layout for the row // Third parameter - ID of the TextView to which the data is written // Forth - the Array of data ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, android.R.id.text1, values); // Assign adapter to ListView listView.setAdapter(adapter); } @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case android.R.id.home: // This ID represents the Home or Up button. In the case of this // activity, the Up button is shown. Use NavUtils to allow users // to navigate up one level in the application structure. For // more details, see the Navigation pattern on Android Design: // // http://developer.android.com/design/patterns/navigation.html#up-vs-back // NavUtils.navigateUpTo(this, new Intent(this, CourseListActivity.class)); return true; } return super.onOptionsItemSelected(item); } class MyTabsListener implements ActionBar.TabListener { public Fragment fragment; public Fragment fragment2; public MyTabsListener(Fragment fragment) { this.fragment = fragment; } @Override public void onTabReselected(Tab tab, FragmentTransaction ft) { } @Override public void onTabSelected(Tab tab, FragmentTransaction ft) { ft.replace(R.id.main_across, fragment); } @Override public void onTabUnselected(Tab tab, FragmentTransaction ft) { ft.remove(fragment); } } } The fragment that I am currently trying to get working is called the Assignments fragment. As you can see in the CourseDetailActvity, I populate smaple items in the listview to see if it the listview shows up. The fragment gets inflated properly, but when I try to add items to the listview, the application crashes! Here is the logcat. 11-17 11:54:28.037: E/AndroidRuntime(282): FATAL EXCEPTION: main 11-17 11:54:28.037: E/AndroidRuntime(282): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sample/com.example.sample.CourseDetailActivity}: java.lang.NullPointerException 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.os.Handler.dispatchMessage(Handler.java:99) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.os.Looper.loop(Looper.java:123) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.ActivityThread.main(ActivityThread.java:4627) 11-17 11:54:28.037: E/AndroidRuntime(282): at java.lang.reflect.Method.invokeNative(Native Method) 11-17 11:54:28.037: E/AndroidRuntime(282): at java.lang.reflect.Method.invoke(Method.java:521) 11-17 11:54:28.037: E/AndroidRuntime(282): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 11-17 11:54:28.037: E/AndroidRuntime(282): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 11-17 11:54:28.037: E/AndroidRuntime(282): at dalvik.system.NativeStart.main(Native Method) 11-17 11:54:28.037: E/AndroidRuntime(282): Caused by: java.lang.NullPointerException 11-17 11:54:28.037: E/AndroidRuntime(282): at com.example.sample.CourseDetailActivity.onCreate(CourseDetailActivity.java:66) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 11-17 11:54:28.037: E/AndroidRuntime(282): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 11-17 11:54:28.037: E/AndroidRuntime(282): ... 11 more