Question

这里我是Android编程的新手，我想创建一个在listview中显示数据库的活动但是当我运行那个活动时我得到了一些错误：

Caused by: java.lang.IllegalArgumentException: column '_id' does not exist

我在google和Stackoverflow上搜索，我找到了一些答案

Cursor必须包含一个名为_id的列，否则该类不会工作。您可以尝试使用现有ID伪造它

我试过这种方式，但现在我还有一些错误说

Caused by: android.database.sqlite.SQLiteException: no such column: _id (code 1): , while compiling: SELECT CategName, _id FROM category_table

我不知道这个错误究竟发生了什么，但我希望有人可以帮助我.. 请用简单易懂的词语掌握一些解释。谢谢......

NB。这是我的活动，我得到了那些错误

public class CategorySetting extends ListActivity {
    private SQLiteDatabase db;

    private CursorAdapter currAdapter;
    private static Button BtnIAddCateg;
    private static Button BtnICancelCateg;
    private static final String TAG = CategorySetting.class.getSimpleName();
    DatabaseHelper dBHelper = new DatabaseHelper (this);
    private ListView list;

    private String tableName = DatabaseHelper.TABLE_Categ_NAME;
    private String columnName = DatabaseHelper.COL2;
    private CursorAdapter data_sumber;
    private static final String kolom[] = {"CategName"};


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       // setContentView(R.layout.activity_category_setting);
        //onButtonClickButtonListener();
        ListView list = getListView();
       // list = (ListView)findViewById(R.id.list);

        ListView view = getListView();
        view.addHeaderView(getLayoutInflater().inflate(R.layout.row, null));
        db = dBHelper.getWritableDatabase();
        this.muat_ulang();


    }


    public void muat_ulang()
    {
        Cursor data = db.query( tableName, kolom, null, null, null, null,null);
        data_sumber = new SimpleCursorAdapter(this, R.layout.row, data, kolom,new int[] { R.id.list });
        setListAdapter(data_sumber);
    }


    /*public void reload(){
        try {
            DatabaseHelper dbHelper = new DatabaseHelper(this.getApplicationContext());
            db = dbHelper.getWritableDatabase();
            Cursor c = db.rawQuery("SELECT CategName FROM " + tableName, null);
            if (c != null ) {
                if  (c.moveToFirst()) {
                    do {
                        String categName = c.getString(c.getColumnIndex("CategName"));
                    }while (c.moveToNext());
                }
            }
        } catch (SQLiteException se ) {
            Log.e(getClass().getSimpleName(), "Could not create or Open the database");
        } finally {
            if (db != null)
                db.execSQL("DELETE FROM " + tableName);
            db.close();
        }

    }*/



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_category_setting, menu);
        return true;
    }

    public void onButtonClickButtonListener(){

        BtnIAddCateg = (Button)findViewById(R.id.btnAddNewCateg);
        BtnIAddCateg.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intentAddCateg = new Intent ("com.example.ever_ncn.cashflow.AddCategory");
                        startActivity(intentAddCateg);
                    }
                }
        );

        BtnICancelCateg = (Button)findViewById(R.id.btnCancelCateg);
        BtnICancelCateg.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                    finish();
                    }
                }
        );
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

引起：java.lang.IllegalArgumentException：列'_id'不存在仍未解决

0 个答案: