android - 为什么我会收到错误 "table is not created?"有什么问题？

Question

这是我的数据库适配器类。我用它来连接和查询数据库。

package com.Coursework.AppointmentRecorder;

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 APP_TITLE = "title";
  public static final String APP_DATE = "date";
  public static final String APP_TIME = "time";
  public static final String APP_DETAILS = "details";
  private static final String TAG = "DBAdapter";
  private static final String DATABASE_NAME = "NewUser";
  private static final String DATABASE_TABLE = "Appointment";
  private static final int DATABASE_VERSION = 1;
  private static final String DATABASE_CREATE =
    "CREATE TABLE Appointment (_id integer primary key autoincrement, "
    + "title text not null, date text not null, time text not null, "
    + "details 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);
    }
  }

  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 insertAppointment(String title,String Date, String time, String details) {
    ContentValues initialValues = new ContentValues();
    initialValues.put(APP_TITLE, title);
    initialValues.put(APP_DATE, Date);
    initialValues.put(APP_TIME, time);
    initialValues.put(APP_DETAILS, details);
    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,
      APP_TITLE,
      APP_TIME,
      APP_DETAILS
    },
    null,
    null,
    null,
    null,
    null);
  }

  //---retrieves a particular title---
  public Cursor getTitle(long date) throws SQLException {
  Cursor mCursor = db.query(false, DATABASE_TABLE, new String[] {
    KEY_ROWID,
    APP_TITLE,
    APP_TIME,
    APP_DETAILS
  },
  APP_DATE + "=" + date,
  null,
  null,
  null,
  null,
  null);
  if (mCursor != null) {
    mCursor.moveToFirst();
    do {
    } while (mCursor.moveToNext());
  }
  return mCursor;
}

  //---updates a title---
  public boolean updateTitle(long rowId, String isbn, String title, String publisher) {
    ContentValues args = new ContentValues();
    args.put(APP_TITLE, isbn);
    args.put(APP_TIME, title);
    args.put(APP_DETAILS, publisher);
    return db.update(DATABASE_TABLE, args,
    KEY_ROWID + "=" + rowId, null) > 0;
  }
}

我遇到的问题是，当我在另一个类中创建一个条目时，首先打开数据库，我称之为:

final DBAdapter db = new DBAdapter(this);

然后我尝试执行此命令，但目录一直说没有这样的表并给我一个 SQL 异常。

db.open();
long id  = db.insertAppointment(Title.getText().toString(),
  String.valueOf(SDate),
  Jack.getText().toString(),
  details.getText().toString()
);
alertDialog.setTitle("Appoinment Manager");
alertDialog.setMessage("The Appointment Has Been Created.");
alertDialog.show();
db.close();

谁能告诉我错误在哪里以及为什么没有创建表？

Answer 1

我猜你修改了你的数据库结构而忘记了增加版本。这意味着您仍然会在没有新表的情况下使用旧数据库。

增加您的数据库版本并运行应用程序，以便 onUpgrade 方法运行并且您的问题应该消失。