Mise en page d'onglet verticale Android

Question

Je continue d'obtenir cette erreur en cours d'exécution mais pas d'erreurs de compilation? voici le logcat et le code pour main.

05-25 12:29:25.543: W/dalvikvm(384): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 
05-25 12:29:25.582: E/AndroidRuntime(384): FATAL EXCEPTION: main 
05-25 12:29:25.582: E/AndroidRuntime(384): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.tablayout/com.example.tablayout.TablayoutActivity}: java.lang.NullPointerException 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.os.Handler.dispatchMessage(Handler.java:99) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.os.Looper.loop(Looper.java:123) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.ActivityThread.main(ActivityThread.java:4627) 
05-25 12:29:25.582: E/AndroidRuntime(384): at java.lang.reflect.Method.invokeNative(Native Method) 
05-25 12:29:25.582: E/AndroidRuntime(384): at java.lang.reflect.Method.invoke(Method.java:521) 
05-25 12:29:25.582: E/AndroidRuntime(384): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
05-25 12:29:25.582: E/AndroidRuntime(384): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
05-25 12:29:25.582: E/AndroidRuntime(384): at dalvik.system.NativeStart.main(Native Method) 
05-25 12:29:25.582: E/AndroidRuntime(384): Caused by: java.lang.NullPointerException 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.Activity.setContentView(Activity.java:1647) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.TabActivity.ensureTabHost(TabActivity.java:114) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.TabActivity.getTabHost(TabActivity.java:136) 
05-25 12:29:25.582: E/AndroidRuntime(384): at com.example.tablayout.TablayoutActivity.<init>(TablayoutActivity.java:15) 
05-25 12:29:25.582: E/AndroidRuntime(384): at java.lang.Class.newInstanceImpl(Native Method) 
05-25 12:29:25.582: E/AndroidRuntime(384): at java.lang.Class.newInstance(Class.java:1429) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
05-25 12:29:25.582: E/AndroidRuntime(384): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 
05-25 12:29:25.582: E/AndroidRuntime(384): ... 11 more 






    <?xml version="1.0" encoding="utf-8"?> 
    <TabHost xmlns:android="http://schemas.android.com/apk/res/android" 
     android:id="@android:id/tabhost" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent"> 
    <LinearLayout android:orientation="horizontal" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:baselineAligned="false"> 
    <FrameLayout android:layout_width="0dip" 
     android:layout_height="fill_parent" 
     android:layout_weight="0.2"> 
    <TabWidget android:id="@android:id/tabs" 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:visibility="invisible"/> 
     <LinearLayout android:layout_width="fill_parent" 
      android:layout_height="fill_parent" 
      android:orientation="vertical"> 
      <Button android:layout_height="0dip" 
       android:layout_width="fill_parent" 
       android:layout_weight="1.0" 
      android:background="@drawable/icon_photos_tab"    
       android:id="@+id/artist_id" 
       android:onClick="tabHandler"/> 
      <Button android:layout_height="0dip" 
       android:layout_width="fill_parent" 
       android:layout_weight="1.0" 
      android:background="@drawable/icon_videos_tab" 
       android:id="@+id/album_id" 
       android:onClick="tabHandler"/> 
      <Button android:layout_height="0dip" 
       android:layout_width="fill_parent" 
       android:layout_weight="1.0" 
      android:background="@drawable/icon_songs_tab" 
       android:id="@+id/song_id" 
       android:onClick="tabHandler"/> 
    </LinearLayout> 
    </FrameLayout>  
    <FrameLayout 
    android:id="@android:id/tabcontent" 
    android:layout_width="0dip" 
    android:layout_height="fill_parent" 
    android:layout_weight="0.8"/> 
    </LinearLayout> 
    </TabHost> 

Voici le fichier main.java, de cette façon vous pouvez voir comment c'était une variable globale et où je l'ai retiré. Aussi ajouté les boutons globalement au lieu de localement à cet endroit.

import android.app.TabActivity; 
    import android.content.Intent; 
    import android.os.Bundle; 
    import android.view.View; 
    import android.widget.Button; 
    import android.widget.TabHost; 
    import android.widget.TabHost.TabSpec; 

    public class TablayoutActivity extends TabActivity { 
    /** Called when the activity is first created. */ 

Button artistButton, songButton, videosButton; 
TabHost tabHost = getTabHost(); 

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

    //TabHost tabHost = getTabHost(); 

    // Tab for Photos 
    TabSpec photospec = tabHost.newTabSpec("Photos"); 
    // setting Title and Icon for the Tab 
    photospec.setIndicator("Photos", getResources().getDrawable(R.drawable.icon_photos_tab)); 
    Intent photosIntent = new Intent(this, PhotosActivity.class); 
    photospec.setContent(photosIntent); 

    // Tab for Songs 
    TabSpec songspec = tabHost.newTabSpec("Songs"); 
    songspec.setIndicator("Songs", getResources().getDrawable(R.drawable.icon_songs_tab)); 
    Intent songsIntent = new Intent(this, SongsActivity.class); 
    songspec.setContent(songsIntent); 

    // Tab for Videos 
    TabSpec videospec = tabHost.newTabSpec("Videos"); 
    videospec.setIndicator("Videos",   getResources().getDrawable(R.drawable.icon_videos_tab)); 
    Intent videosIntent = new Intent(this, VideosActivity.class); 
    videospec.setContent(videosIntent); 

    // Adding all TabSpec to TabHost 
    tabHost.addTab(photospec); // Adding photos tab 
    tabHost.addTab(songspec); // Adding songs tab 
    tabHost.addTab(videospec); // Adding videos tab 




    } 

    public void tabHandler(View target){ 
    artistButton.setSelected(false); 
    videosButton.setSelected(false); 
    songButton.setSelected(false); 
    if(target.getId() == R.id.artist_id){ 
     tabHost.setCurrentTab(0); 
     artistButton.setSelected(true); 
    } else if(target.getId() == R.id.album_id){ 
     tabHost.setCurrentTab(1); 
     videosButton.setSelected(true); 
    } else if(target.getId() == R.id.song_id){ 
     tabHost.setCurrentTab(2); 
     songButton.setSelected(true); 
    } 
    }; 

    } 

Answer 1

Vous essayez probablement d'appeler getTabHost() quelque part dans votre constructeur ou à mettre un champ de votre classe. Vous devez l'appeler à partir de onCreate() puisque getTabHost() descend profondément essaie d'obtenir la fenêtre courante, qui n'est pas encore créée au moment du constructeur.

Tout le temps après onCreate() a été appelé ira bien.