java - 没有创建SQLite数据库。为什么？

我试图将我从某些特定消息中接收到的数据添加到SQLite数据库中。
但是，当我运行我的应用程序时，我得到的错误提示是：致命异常：主要由DBAdapter.java中InsertTitle函数处的Java空指针异常引起

这是我的DBAdapter类

package com.lalsoft.janko;

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.util.Log;

public class DBAdapter
{
public static final String KEY_ROWID = "_id";
public static final String KEY_GQTY = "gqty";
public static final String KEY_NQTY = "nqty";
public static final String KEY_DATE = "ddate";
private static final String TAG = "DBAdapter";

private static final String DATABASE_NAME = "lalaqua";
private static final String DATABASE_TABLE = "nsales";
private static final int DATABASE_VERSION = 1;

private static final String DATABASE_CREATE =
    "create table titles (_id integer primary key autoincrement, "
    + "gqty text not null, nqty text not null, "
    + "ddate text not null);";

private final Context context;

private DatabaseHelper DBHelper;
private SQLiteDatabase db;

public DBAdapter(Context ctx)
{
    this.context = ctx;
    DBHelper = new DatabaseHelper(context);
}

private static class DatabaseHelper extends SQLiteOpenHelper
{
    DatabaseHelper(Context context)
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db)
    {
        db.execSQL(DATABASE_CREATE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion,
    int newVersion)
    {
        Log.w(TAG, "Upgrading database from version " + oldVersion
                + " to "
                + newVersion + ", which will destroy all old data");
        db.execSQL("DROP TABLE IF EXISTS titles");
        onCreate(db);
    }
}

//---opens the database---
public DBAdapter open() throws SQLException
{
    db = DBHelper.getWritableDatabase();
    return this;
}

//---closes the database---
public void close()
{
    DBHelper.close();
}

//---insert a title into the database---
public long insertTitle(String gqty, String nqty, String ddate)
{
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_GQTY, gqty);
    initialValues.put(KEY_NQTY, nqty);
    initialValues.put(KEY_DATE, ddate);
    return db.insert(DATABASE_TABLE, null, initialValues);
}

//---deletes a particular title---
public boolean deleteTitle(long rowId)
{
    return db.delete(DATABASE_TABLE, KEY_ROWID +
            "=" + rowId, null) > 0;
}

//---retrieves all the titles---
public Cursor getAllTitles()
{
    return db.query(DATABASE_TABLE, new String[] {
            KEY_ROWID,
            KEY_GQTY,
            KEY_NQTY,
            KEY_DATE},
            null,
            null,
            null,
            null,
            null);
}

//---retrieves a particular title---
public Cursor getTitle(long rowId) throws SQLException
{
    Cursor mCursor =
            db.query(true, DATABASE_TABLE, new String[] {
                    KEY_ROWID,
                    KEY_GQTY,
                    KEY_NQTY,
                    KEY_DATE
                    },
                    KEY_ROWID + "=" + rowId,
                    null,
                    null,
                    null,
                    null,
                    null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

//---updates a title---
public boolean updateTitle(long rowId, String gqtr,
String nqty, String ddate)
{
    ContentValues args = new ContentValues();
    args.put(KEY_GQTY, gqtr);
    args.put(KEY_NQTY, nqty);
    args.put(KEY_DATE, ddate);
    return db.update(DATABASE_TABLE, args,
                     KEY_ROWID + "=" + rowId, null) > 0;
}
}

这是从BroadcastReceiver扩展的类，该类正在调用inserttitle函数。

package com.lalsoft.janko;

import java.util.Calendar;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.gsm.SmsManager;
import android.telephony.gsm.SmsMessage;
import android.util.Log;

public class SMSReceiver extends BroadcastReceiver
{
public String SendMsgBody;
private static final String LOG_TAG = "JankoSMS";
public DBAdapter db;
public Integer isDone=0;
public Double GrossQty,NetQty;

@Override
public void onReceive(Context context, Intent intent)
{
    db = new DBAdapter(context);
    //---get the SMS message passed in---
    Bundle bundle = intent.getExtras();
    SmsMessage[] msgs = null;
    String str = "";
    String PhNo;
    String MsgBody;
    if (bundle != null)
    {
        //---retrieve the SMS message received---
        Object[] pdus = (Object[]) bundle.get("pdus");
        msgs = new SmsMessage[pdus.length];
        for (int i=0; i<msgs.length; i++){
            msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);
            str += "SMS from " + msgs[i].getOriginatingAddress();
            PhNo=msgs[i].getOriginatingAddress();
            str += " :";
            str += msgs[i].getMessageBody().toString();
            MsgBody=msgs[i].getMessageBody().toString();
            str += "\n";
           // EncodeSMS(MsgBody);

             String GQtyS,NQtyS,sDate;
             GQtyS="Ok";
             NQtyS="Done";
             sDate=getDate();
             Log.i(LOG_TAG, "Date" +" "+ sDate +" "+ GQtyS +" "+ NQtyS);
             long id;
             id = db.insertTitle(GQtyS ,NQtyS,sDate);

        }

    }
}
public static String getDate()
{
    Calendar c = Calendar.getInstance();

    String sDate = c.get(Calendar.DAY_OF_MONTH) + "-"
    + c.get(Calendar.MONTH)
    + "-" + c.get(Calendar.YEAR);

    //+ " at " + c.get(Calendar.HOUR_OF_DAY)
    //+ ":" + c.get(Calendar.MINUTE);
    return sDate;
}
}

另外我已经检查了数据库没有被创建..
那么，这个问题的可能原因是什么？我该如何解决呢？请帮我摆脱这个麻烦。

最佳答案

问题出在db.insert()方法的insertTitle()行中。 You have to assign the value of db before using so use open the database before using by calling open()作为insertTitle（）方法中的第一条语句

您的代码将如下所示

public long insertTitle(String gqty, String nqty, String ddate)
{
    open();
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_GQTY, gqty);
    initialValues.put(KEY_NQTY, nqty);
    initialValues.put(KEY_DATE, ddate);
    return db.insert(DATABASE_TABLE, null, initialValues);
}