android - 日志 : column _id does not exist (SQL related)

Question

我的应用程序目前遇到一个非常烦人的问题:目标是根据用户单击的按钮从数据库中读取 ListView 中的不同信息。不幸的是，我的应用程序总是崩溃，我在 stackoverflow 上的类似问题中找不到有效的解决方案(尝试更改数据库版本，添加一些关于光标的行等)。

这是我的代码的相关部分:

A.数据库适配器类:

public class DatabaseAdapter {

public static final String DATABASE_TABLE = "Restaurants";

public static final String COL_CAT1 = "cat1";
public static final String KEY_ROWID = "_id";
public static final String COL_CAT2 = "cat2";
public static final String COL_NAME = "name";
public static final String COL_COMMENTS = "comments";

private Context myContext;
private SQLiteDatabase myDatabase;
private DatabaseHelper dbHelper;
private Cursor c;

// Constructor
public DatabaseAdapter(Context context) {
    this.myContext = context;

}

public DatabaseAdapter open() throws SQLException {
    dbHelper = new DatabaseHelper(myContext);
    // TODO: or maybe?
    // database = dbHelper.getWritableDatabase();
    try {
        dbHelper.createDatabase();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    myDatabase = dbHelper.getReadableDatabase();
    return this;
}

public void close() {
    if (c != null) {   
        c.close();
    }
    try {
        dbHelper.close();
        myDatabase.close();
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}


public Cursor findNameInTable(int myVariable) {
    c = myDatabase
            .query(DATABASE_TABLE, new String[] { COL_NAME , COL_COMMENTS }, 
                    COL_CAT1+"=?",
                    new String[] { Integer.toString(myVariable) }, null,
                    null, null);
    return c;
}

B. ResultListViewActivity(结果应该通过 ListView 中的此 Activity 显示):

public class ResultListViewActivity extends Activity {

private SimpleCursorAdapter cursorAdapter;
private DatabaseAdapter dbHelper;
ListView listview;


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

    dbHelper = new DatabaseAdapter(this); // open() method is in DatabaseAdapter

    dbHelper.open();


    displayListView();
}

private void displayListView() {

    Bundle bundle = getIntent().getExtras();
    int myVariable = bundle.getInt("myVariable");

    Cursor c = dbHelper.findNameInTable(myVariable);
    // the desired columns to be bound
    String[] columns = new String[] { DatabaseAdapter.COL_NAME,
            DatabaseAdapter.COL_COMMENTS, };
    // the XML defined views which the data will be bound to
    int[] to = new int[] { R.id.name, R.id.comments, };
    // create the adapter using the cursor pointing to the desired data
    // as well as the layout information
    cursorAdapter = new SimpleCursorAdapter(this, R.layout.poi_info, c,
            columns, to, 0);

    ListView listView = (ListView) findViewById(R.id.listview);
    // Assign adapter to ListView
    listView.setAdapter(cursorAdapter);
}

我的数据库图片:如你所见，实际上有一个 _id 列:

最后，在以下情况下，我的 logcat 的图片:

如果您想查看我代码的其他部分，请告诉我。在此先感谢您提供任何帮助!

Answer 1

每个 ListView 在其选择查询中都需要一个 _id 列。您必须在列表查询中包含一个 _id 列

将您的查询更改为:

c = myDatabase
        .query(DATABASE_TABLE, new String[] { KEY_ROWID,COL_NAME , COL_COMMENTS }, 
                COL_CAT1+"=?",
                new String[] { Integer.toString(myVariable) }, null,
                null, null);