Question

我尝试将ListView与BaseAdapter一起使用。我在这一行上有一个 java.lang.NullPointerException ：

    titolo.setText(getResources().getString(R.string.nome_cognome_utente, p.nome));

我做错了什么？

这是我的主要活动：

public class ListaUtenti extends Activity {

private ListView listView;
private ListAdapter adapter;
private List<Persona> persona = new LinkedList<Persona>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_lista_utenti);

    listView = (ListView)findViewById(R.id.listaUtenti);

    adapter = new BaseAdapter() {

        @Override
        public int getCount() {
            return persona.size();
        }
        @Override
        public Persona getItem(int position) {
            return persona.get(position);
        }

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

        @Override
        public View getView(int position, View view, ViewGroup viewGroup) {
            if(view == null){
                view = getLayoutInflater().inflate(R.layout.list_item_persona, null);
            }
            final TextView titolo = (TextView)findViewById(R.id.firstLine);
            final TextView descrizione = (TextView)findViewById(R.id.secondLine);

            final Persona p = getItem(position);

            titolo.setText(getResources().getString(R.string.nome_cognome_utente, p.nome));
            descrizione.setText(getResources().getString(R.string.descrizione, p.cognome));
            return view;
        }
    };
    listView.setAdapter(adapter);
}

@Override
protected void onStart(){
    super.onStart();
    persona.clear();
    persona.add(new Persona("nome1","cognome1"));
    persona.add(new Persona("nome2","cognome2"));
    persona.add(new Persona("nome3","cognome3"));
    listView.setAdapter(adapter);
}
}

这是xml文件activity_lista_utenti中的ListView：

<ListView
    android:id="@+id/listaUtenti"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    tools:listitem="@android:layout/simple_list_item_1" />

这是xml文件list_item_persona：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white">

<ImageView
    android:id="@+id/icon"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_margin="5dp"
    android:src="@drawable/ic_contact_picture"
    android:contentDescription="@string/immagine_profilo" />

<TextView
    android:id="@+id/firstLine"
    android:layout_width="fill_parent"
    android:background="@color/yellow2"
    android:layout_height="30dp"
    android:layout_alignParentTop="true"
    android:layout_marginTop="5dp"
    android:layout_toRightOf="@id/icon"
    android:layout_toEndOf="@id/icon"
    android:ellipsize="marquee"
    android:singleLine="true"
    android:gravity="center_vertical"
    android:textSize="20sp" />

<TextView
    android:id="@+id/secondLine"
    android:layout_width="fill_parent"
    android:background="@color/yellow"
    android:layout_height="20dp"
    android:layout_alignParentTop="true"
    android:layout_marginTop="35dp"
    android:layout_toRightOf="@id/icon"
    android:layout_toEndOf="@id/icon"
    android:ellipsize="marquee"
    android:singleLine="true"
    android:gravity="center_vertical"
    android:textSize="15sp" />

</RelativeLayout>

Answer 1

从view的findViewById获取textview，即。变化

 final TextView titolo = (TextView)findViewById(R.id.firstLine);
 final TextView descrizione = (TextView)findViewById(R.id.secondLine);

到

 final TextView titolo = (TextView)view.findViewById(R.id.firstLine);
 final TextView descrizione = (TextView)view.findViewById(R.id.secondLine);

因为它们是list_item_persona视图的一部分。

带有ListView和BaseAdapter的java.lang.NullPointerException

1 个答案: