ListView 不显示项目的问题，而一切似乎都很好

Question

我基本上得到了解决这个问题的抑郁症，因为在我看来一切都很好。所以基本上我正在制作一个 ArrayAdapter 来让我的 ListView 显示来自我创建的另一个布局的项目。一切正常，但由于某种原因，它没有显示项目。请帮忙。 这是我的 MainActivity 类：

public class MainActivity extends AppCompatActivity {

private static final String TAG = "MainActivity";
public SQLiteDatabase database;


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

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

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

    Intent intent = new Intent(this, CreateActivity.class);

    database = getBaseContext().openOrCreateDatabase("database.db", MODE_PRIVATE, null);

    database.execSQL("CREATE TABLE IF NOT EXISTS connections(name TEXT, hostname TEXT, username TEXT, password TEXT, domain TEXT, localdir TEXT, remotedir TEXT, retry INTEGER, timeout INTEGER, port INTEGER);");
    Log.d(TAG, "onCreate: SQL WORKED");

    View.OnClickListener fabListener = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(intent);
        }
    };

    fab.setOnClickListener(fabListener);

    ConnectionsAdapter adapter = new ConnectionsAdapter(this, R.layout.list_connections, getConnections());

    listView.setAdapter(adapter);
}

private List<Connections> getConnections() {
    List<Connections> connections = new ArrayList<>();

    Cursor query = database.rawQuery("SELECT * FROM connections;", null);

    if(query.moveToFirst()) {

    }

    return connections;
}

这是我的 ConnectionsAdapter 类：

public class ConnectionsAdapter extends ArrayAdapter<Connections> {

private int resourceLayout;
private Context mContext;
private List<Connections> connectionsList;

public ConnectionsAdapter(@NonNull Context context, int resource, @NonNull List<Connections> objects) {
    super(context, resource, objects);
    this.resourceLayout = resource;
    this.mContext = context;
    this.connectionsList = objects;
}

public View getView(int position, View convertView, ViewGroup parent) {

    View view = convertView;

    View.OnClickListener buttonListener = new View.OnClickListener() {
        @Override
        public void onClick(View view) {

        }
    };

    if(view == null) {
        LayoutInflater inflater;
        inflater = LayoutInflater.from(mContext);
        view = inflater.inflate(resourceLayout, null);
    }

    if(view != null) {
        TextView status = (TextView) view.findViewById(R.id.status);
        TextView name = (TextView) view.findViewById(R.id.name);
        TextView size = (TextView) view.findViewById(R.id.size);
        ImageView imageView = (ImageView) view.findViewById(R.id.imageView);
        Button button = (Button) view.findViewById(R.id.details);

        status.setText(Color.GREEN + "ONLINE");
        name.setText("FIRST ONE");
        imageView.setImageDrawable(view.getResources().getDrawable(R.drawable.hard_drive_icon));
        size.setText("232/465 GB");

        button.setOnClickListener(buttonListener);
    }

    return view;
}

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

@Nullable
@Override
public Connections getItem(int position) {
    return super.getItem(position);
}

}

这是我的 MainActivity.xml：

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/black">

<ListView
    android:id="@+id/connectionsList"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<com.google.android.material.floatingactionbutton.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"

    android:layout_height="wrap_content"
    android:contentDescription="@string/click_this_to_add_new_connection"
    android:src="@drawable/fab_icon"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.954"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.976"
    tools:ignore="SpeakableTextPresentCheck,RedundantDescriptionCheck" /></androidx.constraintlayout.widget.ConstraintLayout>

这是我的 list_connections.xml（用于 listview 适配器的布局）：

<androidx.appcompat.widget.LinearLayoutCompat xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000000">

<TextView
    android:id="@+id/status"
    android:layout_width="60dp"
    android:layout_height="100dp"
    android:gravity="center_horizontal|center_vertical"
    android:textColor="#FFFFFF"
    android:textStyle="bold"
    tools:text="Offline" />

<ImageView
    android:id="@+id/imageView"
    android:layout_width="80dp"
    android:layout_height="100dp"
    android:contentDescription="@string/just_an_icon_for_decoration"
    app:srcCompat="@drawable/hard_drive_icon" />

<TextView
    android:id="@+id/name"
    android:layout_width="90dp"
    android:layout_height="wrap_content"
    android:textAlignment="center"
    android:textColor="#FFFFFF"
    android:textStyle="bold"
    tools:text="Name" />

<TextView
    android:id="@+id/size"
    android:layout_width="90dp"
    android:layout_height="wrap_content"
    android:textAlignment="center"
    android:textColor="#FFFFFF"
    android:textStyle="bold"
    tools:text="SIZE" />

<Button
    android:id="@+id/details"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/details" /></androidx.appcompat.widget.LinearLayoutCompat>

Answer 1

问题在于您的 getCount() 方法。由于您的 connectionsList 为空，它返回 0。如果您想使用硬编码数据进行测试，您可以像下面这样更改它。

@Override
public int getCount() {
    return 1; // or 2,5,10 any number of items you want
}