创建数据库时出错[关闭]

Question

我正在尝试在我的 android 应用程序中创建 SQLite 数据库，但是当我创建数据库时应用程序意外停止工作。

package com.example.expenditurelogs;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.text.format.Time;
import android.widget.TextView;
public class CTable extends Activity{
    public static  final String KEY_SNO = "SNo.";
    public static  final String KEY_ITEM = "Item";
    public static  final String KEY_PRICE = "Price";
    public static  final String KEY_TIME = "Time";
    private static  final String DATABASE_NAME = "CExpenditureLogs";
    private static  final String DATABASE_CTABLE = "CanteenTable";
    private static  final int DATABASE_VERSION = 1;

    private CDBHelper cdb;
    private  final Context con;
    private SQLiteDatabase canteendb;
    private static class CDBHelper extends SQLiteOpenHelper
    {
        public CDBHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);

        }
        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL("CREATE TABLE "+ DATABASE_CTABLE+ " ("+KEY_SNO+" INTEGER PRIMARY KEY AUTOINCREMENT, "+ KEY_ITEM + " TEXT NOT NULL, "+ KEY_PRICE+
                    " TEXT NOT NULL, "+KEY_TIME+" TEXT NOT NULL);");

        }
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("DROP TABLE IF EXISTS "+DATABASE_CTABLE);
            onCreate(db);

        }

    }
    public CTable(Context c)
    {
        con = c;
    }
    public CTable open() throws SQLException
    {
        cdb = new CDBHelper(con);
        canteendb = cdb.getWritableDatabase();
        return this;
    }
    public void close()
    {
        cdb.close();
    }
    public long createEntry(String item,String price)
    {
        ContentValues cv = new ContentValues();
        cv.put(KEY_ITEM,item);
        cv.put(KEY_PRICE,price);
        Time t = new Time(Time.getCurrentTimezone());
        t.setToNow();
        String time = ""+t.month;   
        cv.put(KEY_TIME,time);
        return canteendb.insert(DATABASE_CTABLE,null,cv);
    }
    public void getData()
    {
        TextView sno,item,price,time;
        sno = (TextView) findViewById(R.id.tSno);
        item = (TextView) findViewById(R.id.tItem);
        price = (TextView) findViewById(R.id.tPrice);
        time = (TextView) findViewById(R.id.tDateandTime);

        sno.setText("");
        item.setText("");
        price.setText("");
        time.setText("");

        String[] columns = { KEY_SNO,KEY_ITEM,KEY_PRICE,KEY_TIME };
        Cursor c = canteendb.query(DATABASE_CTABLE,columns,null,null,null,null,null);
        int iSno = c.getColumnIndex(KEY_SNO);
        int iItem = c.getColumnIndex(KEY_ITEM);
        int iPrice = c.getColumnIndex(KEY_PRICE);
        int iTime = c.getColumnIndex(KEY_TIME);
        for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext())
        {
            sno.setText(sno+ c.getString(iSno) +"."+"\n");
            item.setText(item+c.getString(iItem)+"\n");
            price.setText(price+c.getString(iPrice)+"\n");
            time.setText(time+c.getString(iTime)+"\n");
        }

    }
}

Answer 1

SNo. 不是有效的列名。

为了能够在标识符中使用特殊字符，您必须引用它：

public static final String KEY_SNO = "\"SNo.\"";

但最好不要使用句号：

public static final String KEY_SNO = "SNo";