Android ต้องการเขียนให้ login เสร้จเเล้วเด้งข้ามไปอีกหน้าครับ ผมดู code มาจากใน internet ลองมาหลายวิธีเเล้วครับ เเนะนำด้วยครับ

public class MainActivity extends Activity
{
    ConnectionClass connectionClass;
    EditText edtuserid,edtpass;
    Button btnlogin;
    ProgressBar pbbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        connectionClass = new ConnectionClass();
        edtuserid = (EditText) findViewById(R.id.et_username);
        edtpass = (EditText) findViewById(R.id.et_password);
        btnlogin = (Button) findViewById(R.id.btn_Login);
        pbbar = (ProgressBar) findViewById(R.id.pbbar);
        pbbar.setVisibility(View.GONE);

        btnlogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                DoLogin  doLogin = new DoLogin();
                doLogin.execute("");

            }
        });
    }


    public class DoLogin extends AsyncTask<String,String,String> {
        String z = "";
        Boolean isSuccess = false;
        String userid = edtuserid.getText().toString();
        String password = edtpass.getText().toString();

        @Override
        protected void onPreExecute() {pbbar.setVisibility(View.VISIBLE);}
        @Override
        protected void onPostExecute(String r) {
            pbbar.setVisibility(View.GONE);
            Toast.makeText(MainActivity.this, r, Toast.LENGTH_SHORT).show();
            if (isSuccess) {
                Toast.makeText(MainActivity.this, r, Toast.LENGTH_SHORT).show();
            }
        }
        @Override
        protected String doInBackground(String... params) {
            if (userid.trim().equals("") || password.trim().equals(""))
                z = "Please enter User Id and Password";
            else {
                try {
                    Connection con = connectionClass.CONN();
                    if (con == null) {
                        z = "Error in connection with SQL server";
                    } else {
                        String query = "select * from doc_users where users_name='" + userid + "' and users_pass='" + password + "'";
                        Statement stmt = con.createStatement();
                        ResultSet rs = stmt.executeQuery(query);
                        if (rs.next()) {
                           z = "Login successfull";
                           isSuccess = true;
                        } else {
                            z = "Invalid Credentials";
                            isSuccess = false;
                        }
                    }
                } catch (Exception ex) {
                    isSuccess = false;
                    z = "Exceptions";
                }
            }
            return z;
        }



    }}