I want to remove all the values from sqlite table. For doing this i have created one method:-
public void deleteCourse() {
// on below line we are creating
SQLiteDatabase db = this.getWritableDatabase();
// a variable to write our database.
db.execSQL("DELETE FROM "+TABLE_NAME);
db.close();
}
But delete query is not working. Is there any solution to do so?
below is my complete code is database.java file
public class DBHandler extends SQLiteOpenHelper {
// creating a constant variables for our database.
// below variable is for our database name.
private static final String DB_NAME = "testdb";
public static ArrayList<String> arrayList=new ArrayList<>();
public static ArrayList<Double> arraysum=new ArrayList<>();
// below int is our database version
private static final int DB_VERSION = 1;
static String error;
public static String getError(){
return error;
}
// below variable is for our table name.
private static final String TABLE_NAME = "hello";
// below variable is for our id column.
// below variable is for our course name column
private static final String NAME_COL = "name";
private static final String NAME_NUM = "count";
private String[] hello;
// creating a constructor for our database handler.
public DBHandler(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
// below method is for creating a database by running a sqlite query
@Override
public void onCreate(SQLiteDatabase db) {
// on below line we are creating
// an sqlite query and we are
// setting our column names
// along with their data types.
String query = "CREATE TABLE " + TABLE_NAME + " ("
+ NAME_COL + " TEXT ,"+NAME_NUM+" int )";
// at last we are calling a exec sql
// method to execute above sql query
db.execSQL(query);
}
// this method is use to add new course to our sqlite database.
public void addNewCourse(String courseName,int num) {
// on below line we are creating a variable for
// our sqlite database and calling writable method
// as we are writing data in our database.
SQLiteDatabase db = this.getWritableDatabase();
// on below line we are creating a
// variable for content values.
ContentValues values = new ContentValues();
// on below line we are passing all values
// along with its key and value pair.
values.put(NAME_COL, courseName);
values.put(NAME_NUM,num);
// after adding all values we are passing
// content values to our table.
db.insert(TABLE_NAME, null, values);
// at last we are closing our
// database after adding database.
db.close();
}
// we have created a new method for reading all the courses.
public ArrayList<CourseModal> readCourses() {
// on below line we are creating a
// database for reading our database.
SQLiteDatabase db = this.getReadableDatabase();
// on below line we are creating a cursor with query to read data from database.
Cursor cursorCourses = db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
// on below line we are creating a new array list.
ArrayList<CourseModal> courseModalArrayList = new ArrayList<>();
// moving our cursor to first position.
if (cursorCourses.moveToFirst()) {
do {
// on below line we are adding the data from cursor to our array list.
courseModalArrayList.add(new CourseModal(cursorCourses.getString(0),cursorCourses.getString(1)));
arrayList.add(cursorCourses.getString(0));
arraysum.add(cursorCourses.getDouble(1));
} while (cursorCourses.moveToNext());
// moving our cursor to next.
}
// at last closing our cursor
// and returning our array list.
cursorCourses.close();
return courseModalArrayList;
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// this method is called to check if the table exists already.
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
public void deleteCourse() {
// on below line we are creating
SQLiteDatabase db = this.getWritableDatabase();
// a variable to write our database.
db.execSQL("DELETE FROM "+TABLE_NAME);
db.close();
}
}
