Query always returns false in Sqlite Android - android-sqlite

Question

I want to check the username and password with sqlite table,In my case query always returns false...
This is my Query...
public boolean validateUser(String u_name, String p_word){
Cursor c = getReadableDatabase().rawQuery(
"SELECT FNAME,PASSWORD FROM " + TABLE_NAME + " WHERE "
+ fname + "='" + u_name+"'AND "+ password +"='"+ p_word+"'" , null);
if (c!=null)
{
return true;
}
else{
return false;
}
}

Answer 1

Checking whether or not the Cursor is null is basically useless as a valid Cursor will be returned by rawQuery. That is no data to extract will result in an empty Cursor with no rows, whilst if data has been extracted the Cursor will have 1 or more rows.
You should check whether or not the Cursor is empty by using the Cursor getCount() method which will return 0 if there are no rows or the number of rows. Alternately you could use some of the Cursor's move methods which will return true/false depending upon whether the move can be performed. e.g if (c.moveToFirst) { ... //row(s) exist} else { ... //no rows exists }.
You should also close the Cursor before returning. So perhaps use :-
public boolean validateUser(String u_name, String p_word){
Cursor c = getReadableDatabase().rawQuery(
"SELECT FNAME,PASSWORD FROM " + TABLE_NAME + " WHERE "
+ fname + "='" + u_name+"'AND "+ password +"='"+ p_word+"'" , null);
int count = c.getCount(); // get the number of rows
c.close(); // Close the Cursor
return count > 0; // return result (no data found = false, else true)
Many would recommend not using rawQuery but rather the convenience Cursor query method. This could be :-
public boolean validateUser(String u_name, String p_word) {
String[] columns = new String[]{
FNAME,
PASSWORD
};
String whereclause = FNAME + "=? AND " + PASSWORD + "=?";
String[] whereargs = new String[]{
u_name,
p_word
};
Cursor c = this.getWritableDatabase().query(
TABLE_NAME,
columns,
whereclause,
whereargs,
null,null,null
);
int count = c.getCount();
c.close();
return count > 0;
}
Note the above code is in-principle code and hasn't been tested so it may contain typing errors.
The above code assumes that the method is within the Database Helper class (i.e. a subclass of SQLiteOpenHelper).
The assumption has been made that FNAME and PASSWORD are the correct String variables to be used for the column names as opposed to fname and password
Assumptions have been made due to the limited code made available.