Question

我在创建一个创建和操作数据库的类时遇到了麻烦！但方法create ()有问题说

“方法openOrCreateDatabase（String，int，null）未定义类型BancoDeDados“。

有人有任何建议可以解决这个问题吗？我的代码如下：

package com.example;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;

public class DataBase{
     private SQLiteDatabase db;
     private String DATABASE_NAME;
     private String TABLE_NAME;
     private String SQL_SELECT_ALL;
     private String SQL_SELECT_ID;
     private String SQL_CREATE;

     public DataBase(SQLiteDatabase db,String DATABASE_NAME,String TABLE_NAME,String SQL_SELECT_ALL,String SQL_SELECT_ID,String SQL_CREATE){
         this.db = db;
         this.DATABASE_NAME = DATABASE_NAME;
         this.TABLE_NAME = TABLE_NAME;
         this.SQL_SELECT_ALL = SQL_SELECT_ALL;
         this.SQL_SELECT_ID = SQL_SELECT_ID;
         this.SQL_CREATE = SQL_CREATE;
     }

     public void create(){
         this.db = openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
         this.db.execSQL(this.SQL_CREATE);
         this.db.close(); 
     }
}

Answer 1

SQLiteOpenHelper用于在Android中创建数据库。扩展此类后，您需要覆盖onCreate方法。 onCreate中的db.execSQL(TABLE_CREATE);创建数据库。 TABLE_CREATE是您的DDL字符串。

public class DbHelper extends SQLiteOpenHelper {

     //The database name and version can be parameterized in the constructor.
     public DbHelper(Context context, String databaseName, int databaseVersion) {
         super(context, databaseName, null, databaseVersion);
     }



    /*
     * (non-Javadoc)
     * 
     * @see
     * android.database.sqlite.SQLiteOpenHelper#onCreate(android.database.sqlite
     * .SQLiteDatabase)
     */
    @Override
    public void onCreate(SQLiteDatabase db) {

        try {
            // Create Database
            db.execSQL(TABLE_CREATE);


        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * android.database.sqlite.SQLiteOpenHelper#onUpgrade(android.database.sqlite
     * .SQLiteDatabase, int, int)
     */
    @Override
    public void onUpgrade(SQLiteDatabase arg0, int oldVersion, int newVersion) {

    }



}

Answer 2

创建此class to create and manipulate database的主要原因是repackage以及this class EXTENDS NO need no other!

Under My class after you solve the problem '. DataBase.java`

 import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;

 public class DataBase{
 private String DATABASE_NAME;
 private int DATABASE_VERSION;
 private String TABLE_NAME;
 private String SQL_SELECT_ALL;
 private String SQL_SELECT_ID;
 private String SQL_CREATE;

 public DataBase(String DATABASE_NAME,int DATABASE_VERSION,String TABLE_NAME,String SQL_SELECT_ALL,String SQL_SELECT_ID,String SQL_CREATE){
     this.DATABASE_NAME = DATABASE_NAME;
     this.DATABASE_VERSION = DATABASE_VERSION;
     this.TABLE_NAME = TABLE_NAME;
     this.SQL_SELECT_ALL = SQL_SELECT_ALL;
     this.SQL_SELECT_ID = SQL_SELECT_ID;
     this.SQL_CREATE = SQL_CREATE;
 }
 public DataBase(String DATABASE_NAME,int DATABASE_VERSION,String TABLE_NAME,String SQL_SELECT_ALL,String SQL_CREATE){
     this.DATABASE_NAME = DATABASE_NAME;
     this.DATABASE_VERSION = DATABASE_VERSION;
     this.TABLE_NAME = TABLE_NAME;
     this.SQL_SELECT_ALL = SQL_SELECT_ALL;
     this.SQL_CREATE = SQL_CREATE;
 }

public void onCreate(Context ctx,SQLiteDatabase db){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE, null);
     db.execSQL(this.SQL_CREATE); //Criando tabela caso não exista!!
     db.close();
 }

public void onUpgrade(Context ctx,SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + this.TABLE_NAME);

    // Create tables again
    onCreate(ctx,db);
 }

 public long onWrite(Context ctx,SQLiteDatabase db,String row,ContentValues ctv){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
     long lg = db.insert(this.TABLE_NAME,row,ctv);
     db.close();
     return lg;
 }

 public int onUpdate(Context ctx,SQLiteDatabase db,ContentValues ctv,String row,int id){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
      int x = db.update(this.TABLE_NAME, ctv, row, new String[]{String.valueOf(id)});
     db.close();
     return x;
 }

 public Cursor onSelecAll(Context ctx,SQLiteDatabase db){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
     Cursor cursor = db.rawQuery(this.SQL_SELECT_ALL, null);
     return cursor;
 }

 public Cursor onSelecId(Context ctx,SQLiteDatabase db,int id){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
     Cursor cursor = db.rawQuery(SQL_SELECT_ID, new String[]{String.valueOf(id)});
      return cursor;
  }

 public int onDelete(Context ctx,SQLiteDatabase db,String row,int id){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
     int x = db.delete(this.TABLE_NAME, row, new String[]{String.valueOf(id)});
     db.close();
     return x;
 }

 public void onClose(Context ctx,SQLiteDatabase db){
     db = ctx.openOrCreateDatabase(this.DATABASE_NAME,Context.MODE_PRIVATE,null);
     db.close();
 }
  }

在Main.java：

     import android...
     public class Main extends Activity {

 private SQLiteDatabase db;
 private Context ctx;
 private static final int DATABASE_VERSION = 1;
 private static final String DATABASE_NAME = "database.db";
 private static final String TABLE_NAME = "table";
 private static final String SQL_SELECT_ALL = "SELECT * FROM "+TABLE_NAME;
 private static final String SQL_SELECT_ID = "SELECT * FROM table WHERE _id = ?";
 /* SQL de criação do banco de dados. */
 private static final String SQL_CREATE = "CREATE TABLE IF NOT EXISTS table(" +
                    "_id INTEGER PRIMARY KEY, " +
                    "person VARCHAR(30), " 
                    "animal VARCHAR(30))";
 BancoDeDados BD = new BancoDeDados(DATABASE_NAME,DATABASE_VERSION,TABLE_NAME,SQL_SELECT_ALL,SQL_SELECT_ID,SQL_CREATE);
  @Override
   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);  
    ctx = getBaseContext(); //Context to use in class BancoDeDados
    BD.onCreate(ctx, db); // Create BD and table if needed!! 
   /* .... */
 }
}

对于DataBase类型，未定义openOrCreateDatabase（String，int，null）方法

2 个答案: