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PONullPointerException in ListView inside a LinearLayout
 

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  1. PONullPointerException in ListView inside a LinearLayout
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    <p>When I attempt to run this particular activity in my Android app, I get a NullPointerException at the line (appears as a single line in Eclipse) which I've marked with an arrow.</p> <p>This activity uses a linear layout, and features a ListView in one of the linear, I guess, 'segments'. I'm using the same ListView code in other activities that only have a ListView in the activity, so those classes extend ListActivity.</p> <p>In the code shown below, I'm just extending Activity as usual, since if I extend ListActivity here, I get an error stating that I must have a ListView whose attribute is 'android.R.id.list', which as you can see, there is.</p> <pre><code>@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_book_event); final ListView lv = (ListView) findViewById(android.R.id.list); lv.setAdapter(new ArrayAdapter&lt;String&gt;(this, android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.cities))); &lt;--- final Spinner s = (Spinner) findViewById(R.id.spinner); ArrayAdapter&lt;CharSequence&gt; aa = new ArrayAdapter&lt;CharSequence&gt;(this, R.array.noSeats, android.R.layout.simple_spinner_item); aa.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); s.setAdapter(aa); s.setOnItemSelectedListener(new OnItemSelectedListener() { @Override public void onItemSelected(AdapterView&lt;?&gt; arg0, View arg1, int arg2, long arg3) { noOfSeats = s.getSelectedItemPosition(); noOfSeats = noOfSeats + 1; } @Override public void onNothingSelected(AdapterView&lt;?&gt; arg0) { } }); } </code></pre> <p>What's the problem here? The other ListViews access the string array just fine, so how is this different?</p> <p>EDIT: Added stack trace</p> <pre><code>04-05 21:30:00.282: E/AndroidRuntime(12791): FATAL EXCEPTION: main 04-05 21:30:00.282: E/AndroidRuntime(12791): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.event_booker/com.example.event_booker.BookEvent}: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list' 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1659) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ActivityThread.access$1500(ActivityThread.java:121) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.os.Handler.dispatchMessage(Handler.java:99) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.os.Looper.loop(Looper.java:130) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ActivityThread.main(ActivityThread.java:3701) 04-05 21:30:00.282: E/AndroidRuntime(12791): at java.lang.reflect.Method.invokeNative(Native Method) 04-05 21:30:00.282: E/AndroidRuntime(12791): at java.lang.reflect.Method.invoke(Method.java:507) 04-05 21:30:00.282: E/AndroidRuntime(12791): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 04-05 21:30:00.282: E/AndroidRuntime(12791): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624) 04-05 21:30:00.282: E/AndroidRuntime(12791): at dalvik.system.NativeStart.main(Native Method) 04-05 21:30:00.282: E/AndroidRuntime(12791): Caused by: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list' 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ListActivity.onContentChanged(ListActivity.java:243) 04-05 21:30:00.282: E/AndroidRuntime(12791): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:230) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.Activity.setContentView(Activity.java:1657) 04-05 21:30:00.282: E/AndroidRuntime(12791): at com.example.event_booker.BookEvent.onCreate(BookEvent.java:22) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 04-05 21:30:00.282: E/AndroidRuntime(12791): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1623) 04-05 21:30:00.282: E/AndroidRuntime(12791): ... 11 more </code></pre>
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      1. PONullPointerException in ListView inside a LinearLayout
      1. USKarakuri
 

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