setValue of a Non-editable comboBox - combobox

Question

Can someone share some sample codes on how to set the value of a non-editable Combobox? It is similar to this, but when I tried to insert it in my code. It returns a null value
Code
ObservableList<City> data = FXCollections.observableArrayList();
data = AddressGetWay.getCityByProvince("Batanes")
cmbCity.setItems(data); // set the items from the database
cmbCity.setConverter(new StringConverter<City>() {
#Override
public String toString(City object) {
return object.getCityName();
}
#Override
public City fromString(String string) {
return cmbCity.getItems().stream().filter(ap
-> ap.getCityName().equals(string)).findFirst().orElse(null);
}
});
cmbCity.valueProperty().addListener(
(ObservableValue<? extends City> observable, City oldValue, City newVal) -> {
if (newVal != null) {
//
}
}
);
// TODO: get the data stored in the database (Column City)
// and set the value of the ComboBox.
Predicate<City> predicate = city -> city.getCityName() == "Itbayat"; // Let's assume that the data stored in the database is "Itbayat"
Optional<City> opt = data.stream().filter(predicate).findAny();
cmbCity.getSelectionModel().select(opt.orElse(null)); // the ComboBox value should be "Itbayat".
I'm using a Singleton Class (correct me if I'm wrong) to retrieve the data from the database
public class AddressGetWay {
static Connection con; //connect to the database
static PreparedStatement pst = null;
static ResultSet rs = null;
public static ObservableList<City> getCityByProvince(String prov) {
ObservableList<City> listData = FXCollections.observableArrayList();
String sql = "SELECT pk_cit_id, cit_nm, zip_code FROM city_mun WHERE prov_code = (SELECT prov_code FROM provinces WHERE prov_nm = ?)";
try {
pst = con.prepareStatement(sql);
pst.setString(1, prov);
rs = pst.executeQuery();
while (rs.next()) {
listData.add(new City(
rs.getInt(1),
rs.getString(2),
rs.getInt(3)
));
}
} catch (SQLException ex) {
Logger.getLogger(AddressGetWay.class.getName()).log(Level.SEVERE, null, ex);
} finally {
try {
pst.close();
rs.close();
} catch (SQLException ex) {
Logger.getLogger(AddressGetWay.class.getName()).log(Level.SEVERE, null, ex);
}
}
return listData;
}
}
This should be my desired Output
But I got this output using the above code
As for my naming conventions. I tried to do this if there's something I need to correct, feel free to pinpoint.

Answer 1

It seems that you are having issue on this code block,
ObservableList<City> data = AddressGetWay.getCityByProvince("Batanes");
//....
Predicate<City> predicate = city -> city.getCityName() == "Itbayat";
Optional<City> opt = data.stream().filter(predicate).findAny();
cmbCity.getSelectionModel().select(opt.orElse(null));
I suspect some loop-holes that is overcoming the null-value.
As you retrieving data through province Batanes i.e. ObservableList<City> data = AddressGetWay.getCityByProvince("Batanes"), maybe it's not retrieving any data.
Your predicate is comparing cityName Itbayat, which may not be getting matched with the retrieved data.
Please check the database value for the city table as to compare those data as well
AddressGateWay
public class AddressGateWay {
private static Connection connection;
private static PreparedStatement statement = null;
private static ResultSet result = null;
static {
connection = loadConnection();
}
public static ObservableList<City> getCityByProvince(String prov) {
ObservableList<City> listData = FXCollections.observableArrayList();
String sql = "SELECT pk_cit_id, cit_nm, zip_code FROM city_mun WHERE prov_code = (SELECT prov_code FROM provinces WHERE prov_nm = ?)";
try {
statement = connection.prepareStatement(sql);
statement.setString(1, prov);
result = statement.executeQuery();
while (result.next()) {
listData.add(new City(
result.getInt(1),
result.getString(2)
));
}
} catch (SQLException ex) {
Logger.getLogger(AddressGateWay.class.getName()).log(Level.SEVERE, null, ex);
} finally {
try {
statement.close();
result.close();
} catch (SQLException ex) {
Logger.getLogger(AddressGateWay.class.getName()).log(Level.SEVERE, null, ex);
}
}
return listData;
}
// for editing
public static ObservableList<Address> selectedItem(int item) {
ObservableList<Address> listData = FXCollections.observableArrayList();
String sql = "SELECT prov_nm, city_nm FROM emp_address WHERE pk_address_id = ?";
try {
statement = connection.prepareStatement(sql);
statement.setString(1, item);
result = statement.executeQuery();
if (result.next()) {
listData.add(new Address(
result.getString(1),
result.getString(2)
));
}
} catch (SQLException ex) {
Logger.getLogger(AddressGateWay.class.getName()).log(Level.SEVERE, null, ex);
} finally {
try {
statement.close();
result.close();
} catch (SQLException ex) {
Logger.getLogger(AddressGateWay.class.getName()).log(Level.SEVERE, null, ex);
}
}
return listData;
}
}
City
public class City {
private int id;
private String cityName;
public City(int id, String cityName) {
this.id = id;
this.cityName = cityName;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCityName() {
return cityName;
}
public void setCityName(String cityName) {
this.cityName = cityName;
}
}
Controller Logic Code
ObservableList<City> cities = AddressGateWay.getCityByProvince(provinceComboBox.getValue()); // assume the value is "Batanes"
cityComboBox.setItems(cities);
cityComboBox.setConverter(new StringConverter<City>() {
#Override
public String toString(City object) {
return object.getCityName();
}
#Override
public City fromString(String string) {
return cityComboBox.getItems().stream().filter(ap
-> ap.getCityName().equals(string)).findFirst().orElse(null);
}
});
cityComboBox.valueProperty().addListener(
(ObservableValue<? extends City> observable, City oldValue, City newVal) -> {
if (newVal != null) {
//
}
}
);
City city = cities
.stream()
.filter(c -> c.getCityName() == "Itbayat")
.findAny()
.orElse(null);
cityComboBox.getSelectionModel().select(city);
// summing up the below updates and your codes,
// I have set the value of cityComboBox by using . . .
Address ads = new Address();
ads = AddressGetWay.selectedItem(item); // the item to be edit
// assume the value from the database is "Itbayat"
Predicate<City> predicate = city -> city.getCityName() == ads.getCity().getCityName();
Optional<City> opt = cities.stream().filter(predicate).findAny();
cityComboBox.getSelectionModel().select(opt.orElse(null));
// Thank you, it finally work :)
Some key points based on the updated code
Refactoring code based on unnecessary code
Implementing basic Java naming Conventions
Missing connection initialization (need to load based on your database)
Inined code (for Predicate, and Optional)
EDIT
Province
public class Province {
private String provinceCode;
private String provinceName;
//Constructors
//Getters and Setters
}
Address
public class Address {
private City city;
private Province province;
//Constructors
//Getters and Setters
}