i have to extract the data from sqlite and then compare it. but i have runtime error this is my code for retrieve data from sqlite but dont work i have two class 1-dbmanagerclass 2-mainactivity class this is my dbmanager class:
public class DBManager extends SQLiteOpenHelper {
static String dbName= "managmentdb";
static int dbVersion=1;
static String tblName= "user";
static String column_id= "_id";
static String column_username= "username";
static String column_password= "password";
SQLiteDatabase db;
Activity context;
public DBManager(Activity context) {
super(context, dbName, null, dbVersion);
this.context=context;
}
@Override
public void onCreate(SQLiteDatabase db) {
try { db.execSQL( " create table " + tblName + " ( " + column_id + "
integer primary key autoincrement , " + column_username + " text , " +
column_password + " text ); ");
Toast.makeText(context,"db is created",Toast.LENGTH_LONG).show();
}catch (Exception err){
Toast.makeText(context,err.toString(),Toast.LENGTH_LONG).show();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
void insert(String user, String pass) {
db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(column_username, user);
cv.put(column_password, pass);
try {
db.insert(tblName, null, cv);
Toast.makeText(context, "insert!!!", Toast.LENGTH_SHORT).show();
} catch (Exception ex) {
Toast.makeText(context, ex.toString(), Toast.LENGTH_SHORT).show();
}
}
Cursor selectAll(){
db=this.getReadableDatabase();
Cursor c=db.rawQuery("Select * from "+tblName,null);
return c;
}
Cursor select(){
db=this.getReadableDatabase();
Cursor c=db.rawQuery("Select * from "+tblName,);
return c;
}
}
and this is class for retrieve
public class MainActivity extends AppCompatActivity implements
View.OnClickListener {
DBManager dbManager;
String[] from =
{DBManager.column_id,DBManager.column_username,DBManager.column_password};
int[] to={R.id.txtid,R.id.txtuser,R.id.txtpass};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button register= (Button) findViewById(R.id.act_login_btnregister);
Button enter= (Button) findViewById(R.id.act_login_btnenter);
register.setOnClickListener(this);
enter.setOnClickListener(this);
}
@Override
public void onClick(View v) {
if(v.getId()==R.id.act_login_btnregister){
startActivity(new Intent(this,RegisterPage.class));
}
else if (v.getId()==R.id.act_login_btnenter){
DBManager dbManager=new DBManager(this);
Cursor cursor;
cursor=dbManager.selectAll();
String name=cursor.getString(1);
Toast.makeText(getApplicationContext(),name,Toast.LENGTH_LONG).show();
}
}
}
why my app have error and how i solved the problem
