据我所知，重新查询（）技工，但我不明白的实现：

I understand the requery() mechanic, but i do not understand the implementation:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        datasource = new pollDataSource(this);
        datasource.open();

        Cursor values = datasource.getAllCategorie();

        String[] categorieColumns =
            {
                MySQLiteHelper.COLUMN_NOME   // Contract class constant containing the word column name

            };


            int[] mWordListItems = { R.id.categoria_label };


        SimpleCursorAdapter adapter = new SimpleCursorAdapter(
                getApplicationContext(),               // The application's Context object
                R.layout.single_list_item,             // A layout in XML for one row in the ListView
                values,                                // The result from the query
                categorieColumns,                      // A string array of column names in the cursor
                mWordListItems,                        // An integer array of view IDs in the row layout
                0);                                    // Flags (usually none are needed)


        setListAdapter(adapter);
    }




      public void onClick(View view) {
          categorie categoria = null;
        switch (view.getId()) {
        case R.id.add:

            categoria = datasource.createCategoria("pluto") ;
          break;


        case R.id.categoria_label:


          break;

        }

      }

在 categoria = datasource.createCategoria（冥王星）之后; 我要定义另一个：

SimpleCursorAdapter adapter = new SimpleCursorAdapter(
                    getApplicationContext(),               // The application's Context object
                    R.layout.single_list_item,             // A layout in XML for one row in the ListView
                    values,                                // The result from the query
                    categorieColumns,                      // A string array of column names in the cursor
                    mWordListItems,                        // An integer array of view IDs in the row layout
                    0);                                    // Flags (usually none are needed)


            setListAdapter(adapter);

PollDataSource

public class pollDataSource {
    // Database fields
      private SQLiteDatabase database;
      private MySQLiteHelper dbHelper;
      private String[] allCategorieColumns = { MySQLiteHelper.COLUMN_ID,
          MySQLiteHelper.COLUMN_PREF, MySQLiteHelper.COLUMN_NOME };   
      private String[] allSondaggiColumns = { MySQLiteHelper.COLUMN_ID,
              MySQLiteHelper.COLUMN_CATID, MySQLiteHelper.COLUMN_DOMANDA };   
      private String[] allRisposteColumns = { MySQLiteHelper.COLUMN_ID, 
              MySQLiteHelper.COLUMN_SONDID, MySQLiteHelper.COLUMN_RISPOSTA, 
              MySQLiteHelper.COLUMN_SELEZIONATA };


      public pollDataSource(Context context) {
            dbHelper = new MySQLiteHelper(context);
          }

      public void open() throws SQLException {
            database = dbHelper.getWritableDatabase();
          }

      public void close() {
            dbHelper.close();
          }

      public categorie createCategoria(String categoria) {
            ContentValues values = new ContentValues();
            values.put(MySQLiteHelper.COLUMN_NOME, categoria);
            values.put(MySQLiteHelper.COLUMN_PREF, 0);
            long insertId = database.insert(MySQLiteHelper.TABLE_CATEGORIE, null,
                values);
            Cursor cursor = database.query(MySQLiteHelper.TABLE_CATEGORIE,
                allCategorieColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
                null, null, null);
            cursor.moveToFirst();
            categorie newCategoria = cursorToCategorie(cursor);
            cursor.close();
            return newCategoria;
          } 

      public void deleteCategoria(categorie categoria) {
            long id = categoria.getId();
            System.out.println("Categoria cancellata, id: " + id);
            database.delete(MySQLiteHelper.TABLE_CATEGORIE, MySQLiteHelper.COLUMN_ID
                + " = " + id, null);
          }

      public sondaggi createSondaggio(String domanda, int catid) {
            ContentValues values = new ContentValues();
            values.put(MySQLiteHelper.COLUMN_DOMANDA, domanda);
            values.put(MySQLiteHelper.COLUMN_CATID, catid);
            long insertId = database.insert(MySQLiteHelper.TABLE_SONDAGGI, null,
                values);
            Cursor cursor = database.query(MySQLiteHelper.TABLE_SONDAGGI,
                allSondaggiColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
                null, null, null);
            cursor.moveToFirst();
            sondaggi newSondaggio = cursorToSondaggi(cursor);
            cursor.close();
            return newSondaggio;
          }


      public void deleteSondaggio(sondaggi sondaggio) {
            long id = sondaggio.getId();
            System.out.println("Sondaggio cancellato, id: " + id);
            database.delete(MySQLiteHelper.TABLE_SONDAGGI, MySQLiteHelper.COLUMN_ID
                + " = " + id, null);
          } 

      public Cursor getAllCategorie() {
            List<categorie> categorie = new ArrayList<categorie>();

            Cursor cursor = database.query(MySQLiteHelper.TABLE_CATEGORIE,
                allCategorieColumns, null, null, null, null, null);

            cursor.moveToFirst();
            while (!cursor.isAfterLast()) {
              categorie categoria = cursorToCategorie(cursor);
              categorie.add(categoria);
              cursor.moveToNext();
            }
            // Make sure to close the cursor
           // cursor.close();
            return cursor;
          }


      private categorie cursorToCategorie(Cursor cursor) {
          categorie categorie = new categorie();
          categorie.setId(cursor.getLong(0));
          categorie.setPreferita(cursor.getLong(1));
          categorie.setNome(cursor.getString(2));
            return categorie;
          }
      private sondaggi cursorToSondaggi(Cursor cursor) {
          sondaggi sondaggi = new sondaggi();
          sondaggi.setId(cursor.getLong(0));
          sondaggi.setDomanda(cursor.getString(1));
          sondaggi.setCatid(cursor.getLong(2));
          return sondaggi;
          }


}

使用相同的输入？所以基本上我也会有同样的确切code在两个不同的同一类的地方......我可以定义一个......程序或类？我很抱歉，如果我太天真了，我是一个真正的小白在此：D

with the same inputs?? so basically I will have the same exact code in two different places of the same class... May I define a... "procedure" or a class? I'm sorry if I'm too naive, I'm a real noob at this :D

推荐答案

在重新查询游标的方法去precated。但你说得对，你必须重新加载光标，然后确保你的新的光标正在psented到您的的ListView $ P $。一个快速'东经肮脏的解决方案，我建议你让你的适配器领域。然后使用下面的方法：

the requery cursor method is deprecated. but you're right you have to reload the cursor and then make sure that your new cursor is being presented to your ListView. for a quick 'n dirty solution, I suggest you make your adapter a field. and then use the following method:

private void requery() {
    Cursor values = datasource.getAllCategorie();
    adapter.changeCursor(values);
}

它的作用是重拍光标。然后通过调用 changeCursor 你换旧光标用于新的和旧的自动关闭。最起码，你做一个新的适配器救自己。与微调和修正我想一切会实现越是sophicated方法一 CursorLoader 这将在数据库中的内容已被更改自动执行的过程。

What it does is remake a cursor. then by calling changeCursor you swap the old cursor for the new one and the old one is closed automatically. at the very least, you save yourself from making a new adapter. The more sophicated approach with all the trim and fixes i suppose would be to implement a CursorLoader which would perform the process automatically when the database content has been changed.