Question

public void onSave(View v){  // this is the activity which calls sqllite 
     Connectivity cn = new Connectivity(getApplicationContext());
     SQLiteDatabase sqlDb = cn.getWritableDatabase();
}

在我执行数据库操作的sqllite open helper类中在下面的代码中，我无法访问＆＃34; OnCreate＆＃34;或＆＃34; OnUpdate＆＃34;方法，以及我的应用程序如何正常工作，没有任何异常或错误

public class Connectivity extends SQLiteOpenHelper {
final static String db_name="Attendence";
SQLiteDatabase sqlDb;
Context cn = null;
Connectivity(Context context){
    super(context,db_name , null, 1);
    cn = context;
    toast.message(cn, "constructor called");

}
@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    try{
    db.execSQL("create table class_ref(id number primarykey autoincrement," +
            "class_name varchar(20),no_students int,reg_no text");
    }catch(Exception e){
        toast.message(cn, "EXCEPTION:"+e.toString());
    }
    toast.message(cn, "onCreate method called");    
}

我没有收到上面宣布的任何一个Toast消息

@Override
public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {
    // TODO Auto-generated method stub
    try{
        toast.message(cn, "onupgrade called");
        db.execSQL("drop table class_ref if exists");
        onCreate(db);
    }catch(Exception e){
        toast.message(cn, "EXCEPTION:"+e.toString());
    }toast.message(cn, "on update method called");  
}

}

输出：

toast message 'constructor called '

Answer 1

只有当发送给构造函数的版本代码发生更改时，才会调用Android SQLite数据库的生命周期方法。

调试时，请尝试动态更改版本以触发生命周期方法，而不是设置常量。

Connectivity(Context context, int version){
    super(context,db_name , null, version);
    cn = context;
    toast.message(cn, "constructor called");
}

SQLiteOpenHelper接口，访问覆盖方法＆＃39; onCreate＆＃39;

1 个答案: