Question

我试图运行我的第一个数据库连接程序，这是我面临的问题。

Couldn't read row 0, col -1 from CursorWindow.

这是我在调用showData（）函数时得到的错误，我猜这意味着它试图从第0行和第-1列获取第一个元素值。

为什么它从-1开始，以及如何从column = 1开始 package com.example.garegin.data;

 public class MainActivity extends Activity {

SQLiteDatabase db;
String fName, sName, mail;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    db=openOrCreateDatabase("MyDB1",MODE_PRIVATE, null);
    db.execSQL("CREATE TABLE IF NOT EXISTS Student(fName VARCHAR, sName VARCHAR, mail VARCHAR);");

    Button save = (Button) findViewById(R.id.save);
    save.setOnClickListener(new View.OnClickListener() {


        @Override
        public void onClick(View view) {
            addData(view);
        }
    });

    Button list = (Button) findViewById(R.id.list);
    list.setOnClickListener(new View.OnClickListener() {


        @Override
        public void onClick(View view) {
            showData(view);
        }
    });

}

private void addData(View view){
    EditText text1 = (EditText) findViewById(R.id.fname);
    EditText text2 = (EditText) findViewById(R.id.sname);
    EditText text3 = (EditText) findViewById(R.id.mail);
    fName=text1.getText().toString();
    sName=text2.getText().toString();
    mail=text3.getText().toString();
    db.execSQL("INSERT INTO  Student VALUES('"+fName+"', '"+sName+"', '"+mail+"')");
}

private void showData(View view){
    Cursor c = db.rawQuery("SELECT * from Student", null);
    int count = c.getCount();
        c.moveToFirst();
        TableLayout tableLayout = new TableLayout(getApplicationContext());
        tableLayout.setVerticalScrollBarEnabled(true);
        TableRow tableRow;
        TextView textView,textView1,textView2,textView3,textView4,textView5;tableRow = new TableRow(getApplicationContext());
        textView=new TextView(getApplicationContext());
        textView.setText("Firstname");
        textView.setTextColor(Color.RED);
        textView.setTypeface(null, Typeface.BOLD);
        textView.setPadding(20, 20, 20, 20);
        tableRow.addView(textView);

        textView4=new TextView(getApplicationContext());
        textView4.setText("LastName");
        textView4.setTextColor(Color.RED);
        textView4.setTypeface(null, Typeface.BOLD);
        textView4.setPadding(20, 20, 20, 20);
        tableRow.addView(textView4);

        textView5=new TextView(getApplicationContext());
        textView5.setText("Email");
        textView5.setTextColor(Color.RED);
        textView5.setTypeface(null, Typeface.BOLD);
        textView5.setPadding(20, 20, 20, 20);
        tableRow.addView(textView5);
        tableLayout.addView(tableRow);

        for (Integer j = 0; j < count; j++)
        {
            tableRow = new TableRow(getApplicationContext());
            textView1 = new TextView(getApplicationContext());
            textView1.setText(c.getString(c.getColumnIndex("fName")));
            textView2 = new TextView(getApplicationContext());
            textView2.setText(c.getString(c.getColumnIndex("sName")));
            textView3 = new TextView(getApplicationContext());
            textView3.setText(c.getString(c.getColumnIndex("mail")));

            textView1.setPadding(20, 20, 20, 20);
            textView2.setPadding(20, 20, 20, 20);
            textView3.setPadding(20, 20, 20, 20);


            tableRow.addView(textView1);
            tableRow.addView(textView2);
            tableRow.addView(textView3);
            tableLayout.addView(tableRow);
            c.moveToNext() ;
        }
        setContentView(tableLayout);
        db.close();

}
public void close(View view){
    System.exit(0);
}

}

Answer 1

当您致电getColumnIndex()时，您将获得Cursor中不存在的列名的索引-1。尝试在第一行列索引-1上检索值会产生错误。

确保您的查询中包含您引用的列名称。

在添加代码后编辑：好像你有一个旧版本的数据库文件，没有全部。如果已存在具有相同名称的表，CREATE TABLE IF NOT EXISTS将无法创建表。旧表格没有您尝试访问的列。要解决此问题，请删除旧数据库：卸载您的应用，或使用应用管理器清除其数据。

为什么CursorWindow列等于-1？

1 个答案: