AsyncTask 中 PreparedStatement 的游标实现

Question

所以我正在尝试为我的 class 实现一个游标，以便我可以填充我的数据网格（当我需要为 SP 和准备好的语句使用可调用时，不确定这是否是正确的方法）这是我用这个 guide here 做的，但我得到了一个

DataGridActivity.Itemnumber is not abstract and does not override abstract method respond(Bundle) in Cursor

我不确定如何在这里实现抽象方法，因为我通常对我准备好的语句使用 getstring 方法想知道是否有某种方法可以代替填充我的网格而不是使用 Cursor

public class Itemnumber extends AsyncTask<String,String,String> implements Cursor {
    String z = "";
    @Override
    protected void onPreExecute() {
    }
    @Override
    protected void onPostExecute(String r) {
    }

    @Override
    protected String doInBackground(String... params) {
        try {
            Connection con = connectionClass.CONN();
            if (con == null) {
                z = "Error in connection with SQL server";
            } else {
                PreparedStatement preparedStatement = null;
                String sqli = "select ID,ItemNumber,Trashed,Sold from [file].[Item] where [ItemNumber] =?";
                preparedStatement = con.prepareStatement(sqli);
                preparedStatement.setString(1, "test");
                ResultSet rs = preparedStatement.executeQuery();
                if (rs.next()) {
                } else {
                }
            }
        } catch (Exception ex) {
            z = "Exceptions";
        }
        return z;
    }
    @Override
    public Bundle respond(Bundle extras){
        moveToFirst();
        return Bundle.EMPTY;
    }
}

我的数据网格activityclass

Cursor csr = new Itemnumber();
//create DataTable object
DataTable dtDataSource = new DataTable();
//define column
dtDataSource.addAllColumns(new String[]{"column_1", "column_2","column_3", "column_4});
//create DataRow
DataTable.DataRow drRow;

//populate data from cursor into DataSource
if(csr.moveToFirst()){
    do{
        drRow = dtDataSource.newRow();
        drRow.set("column_1", csr.getString(csr.getColumnIndex("field_1")));
        drRow.set("column_2", csr.getString(csr.getColumnIndex("field_2")));
        drRow.set("column_2", csr.getString(csr.getColumnIndex("field_3")));
        drRow.set("column_4", csr.getString(csr.getColumnIndex("field_4")));

        dtDataSource.add(drRow);
    } while(csr.moveToNext());
    csr.close();
}        
/**
 *  Prepare the DataGrid
 */
//initialize DataGrid
DataGrid dg = (DataGrid)findViewById(R.id.datagrid);
//define column style, bond each DataGrid column by DataTable column
dg.addColumnStyles(new DataGrid.ColumnStyle[]{
        new DataGrid.ColumnStyle(getString(R.string.ID), "column_1", 80),
        new DataGrid.ColumnStyle(getString(R.string.ItemNumber), "column_2", 120),
        new DataGrid.ColumnStyle(getString(R.string.Trashed), "column_3", 100),
        new DataGrid.ColumnStyle(getString(R.string.Sold), "column_4", 150)    
});
//set the DataTable as source
dg.setDataSource(dtDataSource);
//generate the DataGrid
dg.refresh();

Answer 1

您必须覆盖 Itemnumber class 中的最后一个方法。此方法在interface Cursor中，命名为：respond(Bundle)

因此，如果您的 class Itemnumber 实施了 Cursor，请添加

@Override
Bundle respond(Bundle extras){
   return Bundle.EMPTY; 
}

并实施，你的方法必须return

Answer 2

我想出了如何使用准备好的语句来做到这一点。

因为实现所有的抽象方法和接口似乎都不符合逻辑

public class DataGridActivity extends Activity {
    /** Called when the activity is first created. */
    ConnectionClass connectionClass;
    //define column
    DataTable.DataRow drRow;
    DataTable dtDataSource = new DataTable();
    Button btnsearch;
    DataGrid dg;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       setContentView(R.layout.datagridt);
        dg = (DataGrid)findViewById(R.id.datagrid);
        btnsearch = (Button) findViewById(R.id.btnsearch);
        connectionClass = new ConnectionClass(this.getApplicationContext());


        /**
         *  Prepare the DataGrid
         */
        //initialize DataGrid
        //define column style, bond each DataGrid column by DataTable column
                dg.addColumnStyles(new DataGrid.ColumnStyle[]{
                new DataGrid.ColumnStyle(getString(R.string.dito_nr), "column_1", 80),
                new DataGrid.ColumnStyle(getString(R.string.Biltype), "column_2", 120),
                new DataGrid.ColumnStyle(getString(R.string.kort_nr), "column_3", 100),
                new DataGrid.ColumnStyle(getString(R.string.Del_Type), "column_4", 150)

        });

    }


    public class Itemnumber extends AsyncTask<String,String,String> {
        String z = "";
        @Override
        protected void onPreExecute() {
            dtDataSource.addAllColumns(new String[]{"column_1", "column_2","column_3", "column_4"});
            drRow = dtDataSource.newRow();
            dtDataSource.add(drRow);
            dg.setDataSource(dtDataSource);
            dg.refresh();
        }
        @Override
        protected void onPostExecute(String r) {
        }

        @Override
        protected String doInBackground(String... params) {
            try {
                Connection con = connectionClass.CONN();
                if (con == null) {
                    z = "Error in connection with SQL server";
                } else {
                    PreparedStatement preparedStatement = null;
                    String sqli = "select ID,ItemNumber,Trashed,Sold from [file].[Item]";
                    preparedStatement = con.prepareStatement(sqli);
                    ResultSet rs = preparedStatement.executeQuery();
                    if (rs.next()) {
                        //create DataRow
                        drRow.set("column_1", rs.getString(1));
                        drRow.set("column_2", rs.getString(2));
                        drRow.set("column_3", rs.getString(3));
                        drRow.set("column_4", rs.getString(4));

                    } else {
                    }

                }
            } catch (Exception ex) {
                z = "Exceptions";
            }
            return z;

        }
    }

    public void btnsearch (View view) {
        // TODO Auto-generated method stub

        Itemnumber item = new Itemnumber();
        item.execute("");
    }
}

AsyncTask 中 PreparedStatement 的游标实现

Cursor implement on PreparedStatement in AsyncTask

java

android-asynctask

cursor

prepared-statement

implements