Question

我正在创建一个具有Sqlite数据库方法的类对象，但是当我调用该类时，我的构造函数被调用但是调用不在onCreate方法中。

我的电话再次返回给来电课程......请告诉我我在接下来的电话中接听电话

我使用：

调用KotDBHelper类

QueryListBean queryListBean=new QueryListBean();
            queryListBean.setQueryList(queryList);

             db=new KotDBHelper(context,queryListBean);
             db.getWritableDatabase();

my code for sqlite helper class

    public class KotDBHelper extends SQLiteOpenHelper {

        private static final int DB_VERSION = 3; 
        private static final String DB_NAME = "eKOT";
        ArrayList<String> queryList;
        KotDBHelper objKotDBHelper;
        BeanInterface bean;
        /*private static final String TABLE_CATEGORIES="category_master";
        private static final String TABLE_KOT="kot_master";
        private static final String TABLE_ITEM="item_master";
        private static final String TABLE_KOT_DETAIL="kot_detail";
        private static final String TABLE_WAITER_MASTER="waiter_master";
        private static final String TABLE_TABLE_MASTER="table_master";
        private static final String TABLE_CONFIGURATION_MASTER="configuration_master";
        private static final String TABLE_USER_MASTER="user_master";*/


        public KotDBHelper(Context context,BeanInterface bean){
                    super(context, DB_NAME, null, DB_VERSION);
                    this.bean=bean;

        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            try{
                String address;
                BluetoothAdapter adpt=BluetoothAdapter.getDefaultAdapter();
                address=adpt.getAddress();
// casting bean here
            QueryListBean objBean=(QueryListBean)bean;
            objBean.getQueryList();


                AsyncClass objAsyncClass=new AsyncClass(objKotDBHelper,null,address);
                objAsyncClass.execute("");

                for(int i=0;i<queryList.size();i++){
                    db.execSQL(queryList.get(i));
                }
                /*db.execSQL(CREATE_TABLE_CATEGORIES);
                db.execSQL(CREATE_TABLE_ITEM);
                db.execSQL(CREATE_WAITER_MASTER);
                db.execSQL(CREATE_TABL_KOT);
                db.execSQL(CREATE_TABLE_KOT_DETAIL);
                db.execSQL(CREATE_TABLE_MASTER);
                db.execSQL(CREATE_CONFIGURATION_MASTER);
                db.execSQL(CREATE_USER_MASTER);
                db.execSQL("insert into table_master(table_no,curDate,type) values(1,'','Room')");
                db.execSQL("insert into table_master(table_no,curDate,type) values(10,'','Table')");
                db.execSQL("insert into user_master(username,password) values('admin','admin')");*/ 
            }catch(Exception e){
                e.printStackTrace();
            }
        }

Answer 1

这是使用sqlite帮助程序类在android中创建数据库的示例代码：

public class SQLite_Helper extends SQLiteOpenHelper {
    // All Static variables
    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "mydb.db";

    // Contacts table name


    private static final String USER_TABLE = "User";
    public static final String TABLE_ACCOUNT = "Account";

     static String CREATE_TABLE_TRANSACTION = "CREATE TABLE " + TABLE_TRANSACTION + "("
                + TRAN_ID + " INTEGER PRIMARY KEY NOT NULL," + PAYEE + " TEXT," + CATEGORY + " TEXT," + AMOUNT + " NUMERIC,"
                + DUEDATE + " TEXT," + PAYFROM + " TEXT," + NOTES + " TEXT,"  + IS_REPEAT + " TEXT," + TYPE + " TEXT,"    + " FOREIGN KEY ("+TRAN_ID+") REFERENCES "+USER_TABLE+" ("+USER_ID+"));";




    String CREATE_USER_TABLE = "CREATE TABLE " + USER_TABLE + "("
            + USER_ID + "  INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," + FIRST_NAME + " TEXT not null unique," + LAST_NAME + " TEXT not null unique," + EMAIL + " TEXT not null unique,"
            + PASSWORD + " TEXT not null unique" + ")";

    static String CREATE_TABLE_ACCOUNT = "CREATE TABLE " + TABLE_ACCOUNT + "("
            + ACCT_ID + " INTEGER PRIMARY KEY NOT NULL," + ACCT_NAME + " TEXT,"
            + ACCT_HEAD_NAME + " TEXT," + OPEN_BAL + " TEXT,"+ ACCOUNT_EMAIL + " TEXT," + " FOREIGN KEY ("+ACCT_ID+") REFERENCES "+USER_TABLE+" ("+USER_ID+"));";



    public SQLite_Helper(Context context) {
        super(context, "login.db", null, 1);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

        db.execSQL(CREATE_TABLE_ACCOUNT);
        db.execSQL(CREATE_USER_TABLE);
        db.execSQL(CREATE_TABLE_TRANSACTION); 
    }
//      code or methods something here...
}

Answer 2

数据库助手onCreate()在

时运行一次

使用getWritableDatabase()或getReadableDatabase()和
数据库文件不存在。

一旦onCreate()成功返回而不抛出，则认为数据库已创建。

了解更多信息：When is SQLiteOpenHelper onCreate() / onUpgrade() run?

在onCreate()中执行除数据库设置之外的其他操作是不正确的。只需创建表并使用一些默认值（如果有）填充它们。从onCreate()删除所有其他代码。

通过捕获异常来隐藏问题是不正确的。如果在设置数据库时出现问题，onCreate()应该将问题（异常）传播到框架。删除try-catch。

在构造函数之后不调用的create方法

2 个答案: