NullPointerException с ListView и ArrayAdapter

Question

Когда я выбираю свой btnPlaylist в моей main.java, я получаю код ошибки в botton. Я не знаю, что я делаю неправильно. Он говорит, что мне нужно иметь ListView с R.id.list. Я предполагаю, что это касается моего playlist_item_row.xml, но я попробовал это и продолжаю очищать свой проект.

public class PlayListActivity extends ListActivity { 
ListView listView; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.playlist); 

    listView = (ListView)findViewById(R.id.listView); 
    //double check that it's list_item 

    String[] songs = this.getResources().getStringArray(R.array.TrackNames); 

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.playlist_item_row,R.id.song_title,songs); 

    listView.setAdapter(adapter); 
} 

} это XML для PlayListActivity.java называется playlist.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
android:orientation="vertical"> 

<ListView 
    android:id="@+id/listView" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:divider="#242424" 
    android:dividerHeight="1dp" 
    android:listSelector="@drawable/list_selector" /> 

Этот XML-я держит свои ценности ресурсы XML в разрешении> значения> 'track_array.xml '

 <resources> 
    <string-array name="TrackNames"> 
     <item>100 - Welcome to London</item> 
     <item>102 - Trafalgarsquare</item> 
</string-array> 
</resources> 

playlist_item_row.xml

<TextView 
    android:id="@+id/song_title" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="Large Text" 
    android:textAppearance="?android:attr/textAppearanceLarge" 
    android:padding="10dp" /> 

main.java

private MediaPlayer mp; 
private MediaPlayer nextMp; 
private TextView tvTime; 
private long currentTime; 
private long duration; 
private boolean isPlaying; 

private boolean mCompatMode = true; 
private MediaPlayer mNextPlayer; 
private OnCompletionListener mCompletion; 

private ImageButton btnPlay; 
private ImageButton btnPlaylist; 
private SeekBar songProgressBar; 
private TextView songTitleLabel; 
//private Handler mHandler = new Handler(); // Handler to update UI timer, progress bar etc,. 
//private SongsManager songManager; 
private Utilities utils; 
private String[] fileList; 
//private int seekForwardTime = 5000; // 5000 milliseconds 
//private int seekBackwardTime = 5000; // 5000 milliseconds 
//private int currentSongIndex = 0; 



@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.player); 

    // All player buttons 
    btnPlay = (ImageButton) findViewById(R.id.btnPlay); 
    btnNext = (ImageButton) findViewById(R.id.btnNext); 
    btnBack = (ImageButton) findViewById(R.id.btnBack); 
    btnPlaylist = (ImageButton) findViewById(R.id.btnPlaylist); 
    songProgressBar = (SeekBar) findViewById(R.id.songProgressBar); 
    songTitleLabel = (TextView) findViewById(R.id.songTitle); 
    // PlayListActivity(): 

    fillAssetList(); 
    Toast.makeText(getApplicationContext(), "fill asset list", Toast.LENGTH_LONG).show(); 

    if (savedInstanceState != null) { 
     duration = savedInstanceState.getLong("duration"); 
     currentTime = savedInstanceState.getLong("currentTime"); 
     isPlaying = savedInstanceState.getBoolean("isPlaying"); 

     if (isPlaying) { 
      pauseMusic(null); 
     } 

    } 

    btnPlaylist.setOnClickListener(new View.OnClickListener() { 

     //@Override 
     public void onClick(View arg0) { 
      Intent i = new Intent(getApplicationContext(), PlayListActivity.class); 
      startActivityForResult(i, 100); 
     } 
    }); 



} 

main_layout.xml

<!-- Playlist button --> 
    <ImageButton 
     android:id="@+id/btnPlaylist" 
     android:layout_width="wrap_content" 
     android:layout_height="fill_parent" 
     android:src="@drawable/btn_playlist" 
     android:background="@null"/> 
</LinearLayout> 

ошибка

03-08 06:16:14.149 25914-25914/com.macmac.tourplayer W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41854e90) 
03-08 06:16:14.159 25914-25914/com.macmac.tourplayer E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.macmac.tourplayer, PID: 25914 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.macmac.tourplayer/com.macmac.tourplayer.PlayListActivity}: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list' 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2205) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2255) 
      at android.app.ActivityThread.access$800(ActivityThread.java:142) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1203) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:136) 
      at android.app.ActivityThread.main(ActivityThread.java:5118) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:606) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list' 
      at android.app.ListActivity.onContentChanged(ListActivity.java:243) 
      at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:322) 
      at android.app.Activity.setContentView(Activity.java:1973) 
      at com.macmac.tourplayer.PlayListActivity.onCreate(PlayListActivity.java:16) 
      at android.app.Activity.performCreate(Activity.java:5275) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2255) 
            at android.app.ActivityThread.access$800(ActivityThread.java:142) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1203) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:136) 
            at android.app.ActivityThread.main(ActivityThread.java:5118) 
            at java.lang.reflect.Method.invokeNative(Native Method) 

Answer 1

ОК, я понял. Мне пришлось продлить Activity, а не ListActivity. Я не понимаю, почему, но это сработало.

Answer 2

Изменить идентификатор ListView в playlist.xml

android:id="@android:id/list" 

Answer 3

Проверено ссылка на ListView. setAdapter принимает ListAdapter вместо ArrayAdapter. setAdapter(ListAdapter adapter)