select from db in sqlite database

Question

what is wrong with this code

when i run it the program don,t response

    public Cursor checkauth(String username,String password)
{
    Ecommerce=getReadableDatabase();
//  Cursor curser =Ecommerce.rawQuery("select * from customer where username = ? and password =?", new String []{username,password});
    //String [] details={"id","custname","gender"};
    Cursor c = Ecommerce.rawQuery("select id  from customer where username = ? AND password = ?" , new String[] {username,password });
    //Cursor cursor = Ecommerce.query(true, "customer",details,"username = ? AND password = ?", new String[] { username, password },null, null, null, null, null);
    while(c != null)
    {
    c.moveToFirst();
    }
    return c;
}

in activity

public void onClick(View arg0) {
            // TODO Auto-generated method stub

            user_name=username.getText().toString();
            passwords=password.getText().toString();
            Cursor c=data.checkauth(user_name, passwords);
            while(!c.isAfterLast())
            {
              username.setText(String.valueOf(c.getInt(0)));
              c.moveToNext();
            }
            }

![enter image description here][1]

laalto · Accepted Answer · 2014-12-09 13:45:38Z

1

You're blocking your UI thread.

This loop never completes:

while(c != null)
    {
    c.moveToFirst();
    }

The while condition is always true. The loop doesn't seem to be doing anything useful, you can probably just leave a plain c.moveToFirst() there.

answered Dec 9, 2014 at 13:45

laalto

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marc_s · Accepted Answer · 2016-01-31 21:07:04Z

1

Try with this..

String selectQuery = "Write select query" ;
SQLiteDatabase db = this.getWritableDatabase();

Cursor cursor = db.rawQuery(selectQuery, null);
boolean result = false;

if (cursor.moveToFirst())
{
        do
        {
            result = true;
        } while (cursor.moveToNext());
    }
    else
    {
        result = false;
    }

edited Jan 31, 2016 at 21:07

marc_s

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answered Dec 9, 2014 at 13:56

Amitabha Biswas

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Comments

stealthjong · Accepted Answer · 2014-12-09 14:16:33Z

Even though this question is answered already, I'd like to suggest a simple improvement. What you're doing is kind of useless. Your goal is to know whether or not a user exists and what his or her id is.

public int checkAuth(String username, String password) {
    String sql = "select id from customer where username = ? AND password = ?";
    Ecommerce = getReadableDatabase(); //field names never start with uppercase
    Cursor c;
    try {
        c = Ecommerce.rawQuery(sql, new String[] { username, password });
        if (c.moveToFirst()) //if the cursor has any records, this returns true, else false
            return c.getInt(0); //so if a user exists with given params, we can return an id
        else
            return -1; //if not, we return -1, which means: user/pass-combination not found
    }
    finally { //but after the whole method, we need to do some things: 
        if (c != null && !c.isClosed())
            c.close(); //close the cursor
        closeDatabase(); //and close the database
    }
}

This way you keep your UI code separated from your database code. A cursor shouldn't appear in UI-code. Which above modifications, the UI code looks a lot cleaner

int i = data.checkAuth(username, password);
if (i == -1) {
    //alert of some kind
}
else
    username.setText(String.valueOf(i));

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