java - ListView 不显示在屏幕上

Question

我最近开始在 Android 应用程序上使用 ListView，但我没有让它显示在屏幕上。

我看到了很多关于如何制作自定义 Adapter 的教程，并逐行进行了操作，但最终我无法使 ListView 显示在在我的屏幕上，我什至让一个 TextView 中的固定文本显示在 ListView 上，但它仍然没有显示。

这是我的实体代码的构造函数:

 public Classificacao(int colocacao, int time, int pontos) {
        this.colocacao = colocacao;
        this.time = time;
        this.pontos = pontos;
    }

这是我的自定义适配器，它扩展了“ArrayAdapter”

private Context context;
private ArrayList<Classificacao> classificacaoList;

ClassificacaoAdapter(Context context, ArrayList<Classificacao>         classificacaoList) {
    super(context, R.layout.layout_classificacao, classificacaoList);
    this.context = context;
    this.classificacaoList = classificacaoList;
}

@SuppressLint("SetTextI18n")
@Override
public View getView(int position, View convertView, ViewGroup parent) {

    LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    if(convertView == null){
        convertView = layoutInflater.inflate(R.layout.layout_classificacao, parent, false);
    }

    TextView colocacao = convertView.findViewById(R.id.texto1);
    colocacao.setText(Integer.toString(classificacaoList.get(position).getColocacao()));

    ImageView imagem = convertView.findViewById(R.id.imagem1);
    imagem.setImageResource(classificacaoList.get(position).getImagem());

    TextView nome = convertView.findViewById(R.id.texto2);
    nome.setText(classificacaoList.get(position).getTime());

    TextView pontos = convertView.findViewById(R.id.texto3);
    pontos.setText(Integer.toString(classificacaoList.get(position).getPontos()));

    return convertView;
}

这是具有 ListView 的布局“activity_atividade02”，以及我不会在此处显示的其他一些 TextView 。

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

这是布局“layout_classificacao”，将由适配器填充

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="20dp">

    <TextView
        android:id="@+id/texto1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="1"
        android:gravity="center"
        android:textColor="@android:color/black"
        android:textSize="30sp" />

    <ImageView
        android:id="@+id/imagem1"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_gravity="center"
        android:layout_weight="1"
        android:contentDescription="imagem do time"
        app:srcCompat="@drawable/flamengo" />

    <TextView
        android:id="@+id/texto2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="1"
        android:textColor="@color/colorPrimary"
        android:textSize="30sp" />

    <TextView
        android:id="@+id/texto3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="1"
        android:gravity="center"
        android:textColor="@android:color/black"
        android:textSize="30sp" />
</LinearLayout>

这是主类“Atividade02”一切开始

public class Atividade02 extends AppCompatActivity {

    ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_atividade02);

        listView = findViewById(R.id.listView);

        ArrayList<Classificacao> classificacaoArrayList = new ArrayList<>();

        classificacaoArrayList.add(new Classificacao(1, 2,46));
        classificacaoArrayList.add(new Classificacao(2, 1,42));
        classificacaoArrayList.add(new Classificacao(3,0,38));
        classificacaoArrayList.add(new Classificacao(4,3,35));
        classificacaoArrayList.add(new Classificacao(5,5,33));
        classificacaoArrayList.add(new Classificacao(6,4,33));

        ArrayAdapter classificacaoAdapter = new ClassificacaoAdapter(this, classificacaoArrayList);

        listView.setAdapter(classificacaoAdapter);

    }
}

继续，ListView 没有显示“ClassificacaoAdapter”，而我希望它能够显示。

Answer 1

确保适配器具有方法getItemcount()并且它返回classificacaoList.size()。它不应返回 0；