Android Studio-从SQLite数据库加载RecyclerView并在Edittext中输入单词

Question

我正在使用Android Studio，并且在我的项目的DB SQLite上有一个表，其中包含3条记录。

public class BaseDeDatos extends SQLiteOpenHelper {

public BaseDeDatos(Context context, String s, Context applicationContext, int i) {
    super(context, "verbos.db", null, 10);
}

@Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table verbos(id integer, verbos text, referencia text, eu text, voce text, nos text)");
        db.execSQL("insert into verbos values(1, 'agito', 'abalo', 'abala', 'abalamos', 'abalam')," +
                "(1, 'agito', 'abalava', 'abalava', 'abalávamos', 'abalavam')," +
                "(1, 'agito', 'abalei', 'abalou', 'abalamos', 'abalaram')");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {
        db.execSQL("DROP TABLE IF EXISTS verbos");
        db.execSQL("create table verbos(id integer, verbos text, referencia text, eu text, voce text, nos text)");
        db.execSQL("insert into verbos values(1, 'agito', 'abalo', 'abala', 'abalamos', 'abalam')," +
                "(1, 'agito', 'abalava', 'abalava', 'abalávamos', 'abalavam')," +
                "(1, 'agito', 'abalei', 'abalou', 'abalamos', 'abalaram')");
    }
}

这是我正在工作的“ Verbos2”活动：

public class Verbos2 extends AppCompatActivity {

ArrayList<Item> listaItem;
RecyclerView recyclerViewItem;
EditText etVerbos;
Button mostrar;

BaseDeDatos conn;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.verbos2);

    etVerbos = findViewById(R.id.etIngresar);
    mostrar = findViewById(R.id.bnMostrar);

    conn = new BaseDeDatos(getApplicationContext(),"verbos.db",null,10);

    listaItem = new ArrayList<>();
    recyclerViewItem=findViewById(R.id.rvListItems);
    recyclerViewItem.setLayoutManager(new LinearLayoutManager(this));


    mostrar.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
    consultarListaItems();

    RecyclerViewAdapter adapter = new RecyclerViewAdapter(listaItem);
    recyclerViewItem.setAdapter(adapter);
}

private void consultarListaItems(){
    SQLiteDatabase db = conn.getReadableDatabase();
    Item item = null;
    String[] parametros = {etVerbos.getText().toString()};
    Cursor cursor=db.rawQuery("select * from verbos WHERE verbos =?", parametros);

    while (cursor.moveToNext()){
        item = new Item();
        item.setVerbo(cursor.getString(0));
        item.setReferencia(cursor.getString(1));
        item.setEu(cursor.getString(2));

        listaItem.add(item);
    }
}

});
}
}

当我在EditText中设置单词“ agito”时，我试图用SQLite数据库中的数据加载Recycler View（（它应该带给我数据库中3条记录的信息，因为字段“ verbo”在所有记录中），但是当我编写并单击该按钮时，什么也没有发生，并且控制台将显示以下消息：

“ E / RecyclerView：未连接适配器；正在跳过布局”

这是recyclerview布局的图片，可以更好地理解我：

这是我的“回收者视图”活动：

public class RecyclerViewAdapter extends RecyclerView.Adapter {
private ArrayList<Item> listItem ;



public RecyclerViewAdapter(ArrayList<Item> listItem) {
    this.listItem = listItem;
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View contentView = LayoutInflater.from(parent.getContext()).inflate(R.layout.lista, null);
    System.out.println("CREATE VIEW HOLDER: " + viewType);
    return new Holder(contentView);

}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    Item item = listItem.get(position);
    Holder Holder = (Holder) holder;
    Holder.tvVerbo.setText(item.getVerbo());
    Holder.tvReferencia.setText(item.getReferencia());
    Holder.tvEu.setText(item.getEu());

    System.out.println("BIND VIEW HOLDER: " + position);
}

@Override
public int getItemCount() {
    return listItem.size();
}

public class Holder extends RecyclerView.ViewHolder{
    TextView tvVerbo;
    TextView tvReferencia;
    TextView tvEu;


    public Holder(View itemView) {
        super(itemView);
        tvVerbo = itemView.findViewById(R.id.tvLista1);
        tvReferencia = itemView.findViewById(R.id.tvLista2);
        tvEu = itemView.findViewById(R.id.tvLista3);
    }
}

}

除了错误，我不确定在“ Verbos2”中我是否正在做正确的事情，以便从SQLite数据库中获取数据并将其加载到我的Recycler View中。

如果您能帮助我，我会非常感激。

Answer 1

您正在代码中的某处使用context.getSystemService。您正在使用的上下文为null。

Answer 2

尝试将attachToRoot中的onCreateViewHolder设置为false将是：

 View contentView = LayoutInflater.from(parent.getContext()).inflate(R.layout.lista, false);