Question

我正在尝试为我的ListView创建自定义视图，但尝试打开它时应用程序崩溃了。我阅读了很多页面，但没有找到解决方案。请帮帮我！

这是我的自定义适配器：

public class AdaptadorCatalogo extends BaseAdapter {
  protected Activity activity;
  protected ArrayList<LineaCatalogo> items;

  public AdaptadorCatalogo(Activity activity, ArrayList<LineaCatalogo> items) {
    this.activity = activity;
    this.items = items;
  }

  @Override
  public int getCount() {
    return items.size();
  }

  @Override
  public Object getItem(int position) {
    return items.get(position);
  }

  @Override
  public long getItemId(int position){
     return 0;
  }

  @Override
  public View getView(int position, View contentView, ViewGroup parent) {
    View vi=contentView;

    if(contentView == null) {
      LayoutInflater inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
      vi = inflater.inflate(R.layout.listitem_catalogo, null);
    }

    LineaCatalogo item = items.get(position);

    TextView primeraLinea = (TextView) vi.findViewById(R.id.lblPrimeraLinea);
    primeraLinea.setText(item.getPrimeraLinea());

    TextView segundaLinea = (TextView) vi.findViewById(R.id.lblSegundaLinea);
    segundaLinea.setText(item.getSegundaLinea());

    TextView magnitud = (TextView) vi.findViewById(R.id.lblMagnitud);
    magnitud.setText(item.getMagnitud());

    return vi;
  }
}

这是我的xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".listaSismos" >

 <RelativeLayout
     android:id="@+id/general"
     style="@style/AppCentral"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:paddingLeft="50dp" >

        <TextView
        android:id="@+id/titulo_catalogo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="@string/esperando_info" />

        <ListView
            android:id="@+id/listaDatos"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_marginBottom="50dp"
            android:layout_marginTop="50dp"
            android:layout_marginLeft="30dp" />


    </RelativeLayout> 
</RelativeLayout>

这是我的活动：

public class listaSismos extends Activity {

    private TextView tituloCatalogo;
    private ListView listaDatos;
    private String opcion;
    private String codigoUsuario;
    private String latitud;
    private String longitud;
    private String idioma;
    private int difHoraria;
    private ArrayList<LineaCatalogo> Catalogo;

    @Override
    public void onCreate(Bundle savedInstanceState){

        super.onCreate(savedInstanceState);
        setContentView(R.layout.lista_sismos);

        tituloCatalogo = (TextView)findViewById(R.id.titulo_catalogo);
        listaDatos = (ListView)findViewById(R.id.listaDatos);
        Bundle bundle = getIntent().getExtras();
        opcion = bundle.getString("lista");
        codigoUsuario = bundle.getString("codigoUsuario");
        latitud = bundle.getString("latitud");
        longitud = bundle.getString("longitud");
        idioma = getResources().getConfiguration().locale.toString();
        TimeZone defaultTZ = TimeZone.getDefault();
        difHoraria =  defaultTZ.getRawOffset() / 1000;

        ListarCatalogo conexion = new ListarCatalogo();
        conexion.execute();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    private class ListarCatalogo extends AsyncTask<String,Integer,Boolean> {

        private int contador;

        protected Boolean doInBackground(String... params) {

            boolean resul = true;

            HttpClient httpClient = new DefaultHttpClient();

            HttpGet del = 
                    new HttpGet(my_app_server_url);

            del.setHeader("content-type", "application/json");

            try
            {
                HttpResponse resp = httpClient.execute(del);
                String respStr = EntityUtils.toString(resp.getEntity());

                JSONArray respJSON = new JSONArray(respStr);

                ArrayList<LineaCatalogo> Catalogo = new ArrayList<LineaCatalogo>();
                contador = respJSON.length();

                for(int cont=0; cont<contador; cont++)
                {

                    JSONObject obj = respJSON.getJSONObject(cont);

                    String tituloS = obj.getString("P");
                    String subtituloS = obj.getString("S");
                    String magnitudS = obj.getString("M");

                    Catalogo.add(new LineaCatalogo(tituloS, subtituloS, magnitudS));

                }

            }
            catch(Exception ex)
            {
                resul = false;
            }

            return resul;
        }

        protected void onPostExecute(Boolean result) {

            tituloCatalogo.setText(R.string.titulo_catalogo);
            if (result)
            {

                //Rellenamos la lista con los resultados
                AdaptadorCatalogo adaptador = new AdaptadorCatalogo(listaSismos.this, Catalogo);

                listaDatos.setAdapter(adaptador);

                tituloCatalogo.setText("OK");
            } else {
                tituloCatalogo.setText(R.string.no_datos);
            }
        }
    }

}

如果我评论“listaDatos.setAdapter（adaptador）;”这一行，该应用程序运行正常。如果没有，我得到这个LogCat：

12-06 09:34:32.443: W/dalvikvm(903): threadid=1: thread exiting with uncaught exception (group=0x41465700)
12-06 09:34:32.559: E/AndroidRuntime(903): FATAL EXCEPTION: main
12-06 09:34:32.559: E/AndroidRuntime(903): java.lang.NullPointerException
12-06 09:34:32.559: E/AndroidRuntime(903):  at com.tapsistemas.avcanquake.AdaptadorCatalogo.getCount(AdaptadorCatalogo.java:23)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.widget.ListView.setAdapter(ListView.java:463)
12-06 09:34:32.559: E/AndroidRuntime(903):  at com.tapsistemas.avcanquake.listaSismos$ListarCatalogo.onPostExecute(listaSismos.java:124)
12-06 09:34:32.559: E/AndroidRuntime(903):  at com.tapsistemas.avcanquake.listaSismos$ListarCatalogo.onPostExecute(listaSismos.java:1)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.os.AsyncTask.finish(AsyncTask.java:631)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.os.AsyncTask.access$600(AsyncTask.java:177)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.os.Looper.loop(Looper.java:137)
12-06 09:34:32.559: E/AndroidRuntime(903):  at android.app.ActivityThread.main(ActivityThread.java:5103)
12-06 09:34:32.559: E/AndroidRuntime(903):  at java.lang.reflect.Method.invokeNative(Native Method)
12-06 09:34:32.559: E/AndroidRuntime(903):  at java.lang.reflect.Method.invoke(Method.java:525)
12-06 09:34:32.559: E/AndroidRuntime(903):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
12-06 09:34:32.559: E/AndroidRuntime(903):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-06 09:34:32.559: E/AndroidRuntime(903):  at dalvik.system.NativeStart.main(Native Method)

我仍在工作一周寻找解决方案，但我无法做到。请帮我。我的英语很差，对不起，我是加那利群岛的西班牙人。

Answer 1

声明并初始化为

private ArrayList<LineaCatalogo> Catalogo= new ArrayList<LineaCatalogo>();
@Override
public void onCreate(Bundle savedInstanceState){

删除

 ArrayList<LineaCatalogo> Catalogo = new ArrayList<LineaCatalogo>(); 
 // becomes local to doInbackground as it is declared and initialized there.

doInbackground中的

。

在您的情况下，Catalogo为空。

Answer 2

您使用

重新定义列表

ArrayList<LineaCatalogo> Catalogo = new ArrayList<LineaCatalogo>();

在doInBacground中

仅使用

Catalogo = new ArrayList<LineaCatalogo>();

Android：自定义ListView适配器的java.lang.nullPointerException

2 个答案: