Develop Reference

Java JTabbedPane or how to get the custom Object that created the Tab

I am often struggling with the same problem of custom Objects that creates a e.g. gui Component. And I never know what is the best way to get from the gui Component back to the object.
So multiple hacks and tricks are welcome.
Let me explain it to you:
This is my custom Object I need to find afterwards
public class MyObject {
int yearOfBirth;
String name;
public MyObject(int yearOfBirth, String name) {
this.yearOfBirth = yearOfBirth;
this.name = name;
}
public int getYearOfBirth() {
return yearOfBirth;
}
public Component getPanel() {
Component panel1 = makeTextPanel("This is the personal tab of "+name);
return panell;
}
}
This is where I need to find it through the Tab I am focusing
public class MyTabControl implements ChangeListener {
JTabbedPane myTabPane = new JTabbedPane();
public MyTabControl(){
//This will add a Listener for clicking on one Tab
myTabPane.addChangeListener(this);
}
public void oneMoreTab(MyObject myObject) {
myTabPane.addTab(myObject.name, myObject.getPanel())
}
public void stateChanged(ChangeEvent arg0) {
System.out.println("Focus of Tab changed");
int actualFocusedTabIndex = myTabPane.getSelectedIndex();
Component acutalFocusedComponent = myTabPane.getComponentAt(actualFocusedTabIndex);
//This works fine, I can get the Tab. Or at least the Component.
//But how do I get the yearOfBirth or better the Object itself?
int yearOfBirthOfTheSelectedTab = ???
}
}
This is just the main function
public static void main(String[] args) {
//Commands to start and create the GUI
MyTabControl myTabControl = new MyTabControl();
MyObject mother = new MyObject(1960, "Helen");
myTabControl.oneMoreTab(mother);
MyObject father = new MyObject(1955, "James");
myTabControl.oneMoreTab(father);
}
EDIT:
1 not working solution: Extend Component class
I have tried to extend the class Component. But this will create a failure (see comment in code):
public class ComponentWithExtras extends Component {
MyObject myObject;
public void addMyObject(MyObject myObject) {
this.myObject = myObject;
}
}
// The following line will create failure: Can't cast Component to ComponentWithExtras
ComponentWithExtras componentWithExtras = (ComponentWithExtras) myObject.getPanel();
componentWithExtras.addMyObject(myObject);
myTabPane.addTab(myObject.name, componentWithExtras);

How to update and view current window in MVC

I know this question has been covered in many posts here.
However, something is still not clear to me, so i wanted to ask you my problem in detail.
I have to develop a java application using Swing and using the MVC model.
The application is mainly divided into two parts:
login part
questionnaire part (after login, a questionnaire is displayed)
So following MVC model i divided my code into 3 packages containing the following classes:
Model
LoginModel
QuestionModel
View
LoginView
QuestionView
Controller
LoginController
QuestionController
After developing these classes, i didn't know how to set the window that the program was current working on (login, questionnaire or other future implementations).
So i thought about implementing 3 other classes that use the Observer pattern:
MainModel - Observable
MainView
MainController - Observer
But now i'm not sure how to change the current window.
For example when login is successful, the window must change from LOGIN to QUESTION, so "MainModel.window = Window.QUESTION" and send it to the View.
Should it be added in LoginModel.login() by extending LoginModel with MainModel?
Or how can I do this?
My code:
public class main {
public static void main(String[] args) {
MainView view = new MainView();
MainModel model = new MainModel();
MainController controller = new MainController(view, model);
}
}
public class MainView {
private JFrame window;
public MainView() {
window = new JFrame();
window.setLayout(new CardLayout(0, 0));
LoginView login = new LoginView(); // init window at opening
QuestionView question = new QuestionView();
window.add(login);
window.add(question);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}
public void update(Window window) {
// ??
}
}
public class MainModel {
private List<Observer> observers = new ArrayList<>();
private Window window;
public MainModel() {
window = Window.LOGIN; // init window at opening
}
public void addObserver(Observer observer) {
observers.add(observer);
}
public void removeObserver(Observer observer) {
observers.remove(observer);
}
public void setWindow(Window newWindow) {
newWindow = window;
for (Observer o : observers)
o.update(newWindow);
}
}
public class MainController implements Observer {
private MainView view;
private MainModel model;
public MainController(MainView view, MainModel model) {
this.view = view;
this.model = model;
this.model.addObserver(this);
}
#Override
public void update(Window window) {
this.view.update(window);
}
}
public class LoginView extends JPanel {
private JButton btnLogin;
// ... other attributes
public LoginView() {
btnLogin = new JButton("Login");
new LoginController(this);
}
public JButton getBtnLogin() {
return btnLogin;
}
public void ShowResult(boolean bResult) {
// print result with JOptionPane.showMessageDialog
}
}
public class LoginController {
private LoginView view;
public LoginController(LoginView view) {
this.view = view;
setActionListener();
}
public void setActionListener() {
ActionListener loginButton;
loginButton = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
LoginModel model = new LoginModel();
boolean bResult = model.login(view.getUserNameField(), view.getPasswordField());
view.ShowResult(bResult);
}
};
view.getBtnLogin().addActionListener(loginButton);
}
}
public class LoginModel {
// ... attributes etc
public boolean login(String username, String password) {
boolean bResult;
// ... Some operation etc (useless for this example)
bResult = true; // Simulation login successful
if (bResult)
// ? Change window model to Window.QUESTION.
// But how?
// LoginModel extends MainModel? To call "super.setWindow(Window.QUESTION)?
return bResult;
}
}
// My Observer class
public interface Observer {
public void update(Window window);
}
// My Window class
public enum Window {
LOGIN,
QUESTION,
}
// Questionnaire classes code is very similar to the Login code
public class QuestionView extends JPanel {
private JButton btn;
// ...
new QuestionController(this);
// ...
}
public class QuestionController {
private QuestionView view;
// ...
setActionListener();
// ...
}
So in conclusion is it correct to use this approach? Or how else could i view/update the current window better?

In Swing, the MVC pattern looks like this:
The view reads from the model
The view may not update the model
The controller updates the model and the view
The MVC name implies that you create the model first, then the view, then the controllers.
There's usually not one controller to "rule them all". Each listener is responsible for its own part of the model and the view.
You usually have one application model. An application model is made up of one or more plain Java getter/setter classes. In your case, it looks like a Person class and a Questionaire class. You would probably also have a Question class, to hold one question, several possible answers, and the chosen answer. You may have additional plain Java getter/setter classes I'm not thinking about now.
You would have one JFrame, one JPanel to hold a question and possible answers, and a JDialog for the login and password. You may need multiple JPanels for different types of answers (not different questions), so you might need a main JPanel with a CardLayout.
Your controllers will be the ActionListener for the login JButton, and the "I'm finished answering this question" JButton. You may have other listeners that I'm not thinking about now.

StyleableProperty: how to change value programatically at runtime?

My use-case:
a custom property on a control that should be configurable via css
the property must be changeable at runtime
for a given instance of the control, the programmatic change must not be reverted on re-applying the css
A custom StyleableProperty looks like a perfect match to implement the requirement. Below is an example that implements (taken without change from the class javadoc of StyleablePropertyFactory).
All is fine except for the last requirement: on applyCss, the default value from the stylesheet is reapplied. To reproduce:
run the example, note that the initial "selected" state (the checkbox' selected is bound it) of the MyButton is true
click the custom button, note that the "selected" doesn't change to false (though the actionHandler changes it)
click on the second ("toggle") button, note that the selected state of the custom button changes to false
hover the mouse over the custom button, note that the selected state falls back to true
The reason for falling back to true (the value set via style), can be traced to applyCss which happens on state changes ... which is understandable and might be the correct thingy-to-do most of the times, but not in my context.
So the questions:
am I on the right track with using StyleableProperty?
if so, how to tweak such that it's not re-apply after a manual change has happened?
if not, what else to do?
or maybe asking the wrong questions altogether: maybe properties which are settable via css are not meant to be (permanently) changed by code?
The example:
public class StyleableButtonDriver extends Application {
/**
* example code from class doc of StyleablePropertyFactory.
*/
private static class MyButton extends Button {
private static final StyleablePropertyFactory<MyButton> FACTORY
= new StyleablePropertyFactory<>(Button.getClassCssMetaData());
MyButton(String labelText) {
super(labelText);
getStyleClass().add("my-button");
setStyle("-my-selected: true");
}
// Typical JavaFX property implementation
public ObservableValue<Boolean> selectedProperty() { return (ObservableValue<Boolean>)selected; }
public final boolean isSelected() { return selected.getValue(); }
public final void setSelected(boolean isSelected) { selected.setValue(isSelected); }
// StyleableProperty implementation reduced to one line
private final StyleableProperty<Boolean> selected =
FACTORY.createStyleableBooleanProperty(
this, "selected", "-my-selected", s -> s.selected);
#Override
public List<CssMetaData<? extends Styleable, ?>> getControlCssMetaData() {
return FACTORY.getCssMetaData();
}
public static List<CssMetaData<? extends Styleable, ?>> getClassCssMetaData() {
return FACTORY.getCssMetaData();
}
}
private Parent createContent() {
MyButton button = new MyButton("styleable button");
button.setOnAction(e -> {
// does not work: reset on applyCss
boolean isSelected = button.isSelected();
button.setSelected(!isSelected);
});
CheckBox box = new CheckBox("button selected");
box.selectedProperty().bind(button.selectedProperty());
Button toggle = new Button("toggle button");
toggle.setOnAction(e -> {
boolean isSelected = button.isSelected();
button.setSelected(!isSelected);
});
BorderPane content = new BorderPane(button);
content.setBottom(new HBox(10, box, toggle));
return content;
}
#Override
public void start(Stage stage) throws Exception {
stage.setScene(new Scene(createContent(), 300, 200));
//same behavior as setting the style directly
// URL uri = getClass().getResource("xstyleable.css");
// stage.getScene().getStylesheets().add(uri.toExternalForm());
// not useful: would have to override all
// Application.setUserAgentStylesheet(uri.toExternalForm());
stage.setTitle(FXUtils.version());
stage.show();
}
public static void main(String[] args) {
launch(args);
}
#SuppressWarnings("unused")
private static final Logger LOG = Logger
.getLogger(StyleableButtonDriver.class.getName());
}

You are on the right track, but since you need to override the default priority of the style origins (user agent stylesheet < programmatically assigned < css stylesheet < Node.style property), you cannot use SyleablePropertyFactory for creating this property. You need to create a CssMetaData object that indicates a property as non-setable, if the property was programatically assigned.
private static class MyButton extends Button {
private static final List<CssMetaData<? extends Styleable, ?>> CLASS_CSS_METADATA;
private static final CssMetaData<MyButton, Boolean> SELECTED;
static {
SELECTED = new CssMetaData<MyButton, Boolean>("-my-selected", StyleConverter.getBooleanConverter()) {
#Override
public boolean isSettable(MyButton styleable) {
// not setable, if bound or set by user
return styleable.selected.getStyleOrigin() != StyleOrigin.USER && !styleable.selected.isBound();
}
#Override
public StyleableProperty<Boolean> getStyleableProperty(MyButton styleable) {
return styleable.selected;
}
};
// copy list of button css metadata to list and add new metadata object
List<CssMetaData<? extends Styleable, ?>> buttonData = Button.getClassCssMetaData();
List<CssMetaData<? extends Styleable, ?>> mybuttonData = new ArrayList<>(buttonData.size()+1);
mybuttonData.addAll(buttonData);
mybuttonData.add(SELECTED);
CLASS_CSS_METADATA = Collections.unmodifiableList(mybuttonData);
}
MyButton(String labelText) {
super(labelText);
getStyleClass().add("my-button");
setStyle("-my-selected: true");
}
// Typical JavaFX property implementation
public ObservableValue<Boolean> selectedProperty() { return selected; }
public final boolean isSelected() { return selected.get(); }
public final void setSelected(boolean isSelected) { selected.set(isSelected); }
// StyleableProperty implementation reduced to one line
private final SimpleStyleableBooleanProperty selected = new SimpleStyleableBooleanProperty(SELECTED, this, "selected");
#Override
public List<CssMetaData<? extends Styleable, ?>> getControlCssMetaData() {
return CLASS_CSS_METADATA;
}
public static List<CssMetaData<? extends Styleable, ?>> getClassCssMetaData() {
return CLASS_CSS_METADATA;
}
}

StackOverflow Error at java.util.AbstractColllection.<init>(Unknown Source)

I fixed my prior problem yesterday by just separating all the classes into separate files. Nevertheless, I wrote all the code down and seeing no errors was able to compile the program. Or so I thought.
Here's the error code:
Exception in thread "main" java.lang.StackOverflowError
at java.util.AbstractCollection.<init>(Unknown Source)
at java.util.AbstractList.<init>(Unknown Source)
at java.util.Vector.<init>(Unknown Source)
at java.util.Vector.<init>(Unknown Source)
at java.util.Vector.<init>(Unknown Source
Here are the spots where my I get the errors(marked with problem?)
public class GameWorld implements IObservable, IGameWorld
{
// create collections class
public Vector<GameObject> GameObjectList = new Vector<GameObject>(); // PROBLEM
private Vector<IObserver> ObserverList = new Vector<IObserver>();
// declare objects
Tank pTank = new Tank(10, 10);
// other objects and variables to declare
public GameWorld()
{
// add objects to GameObjectList
}
// accessors/mutators
}
I get another error here
public class Tank extends Movable implements ISteerable
{
private int armorStrength;
private int missileCount;
public Tank()
{}
public Tank(int armStr, int misslCt) // problem?
{
armorStrength = armStr; // default armorStrength
missileCount = misslCt; // default missileCount
}
public void setDirection(int direction)
{
this.setDirection(direction); // get input from left turn or right turn
// updateValues();
}
// access/mutators here
I'm stumped on what to do here.
here's the main code
public class Starter {
public static void main (String args[])
{
Game g = new Game();
}
}
which has a Game class that is basically the GUI of the program
public class Game extends JFrame {
private GameWorld gw;
private MapView mv; // new in A2
private ScoreView sv; // new in A2
public Game() {
gw = new GameWorld(); // create “Observable”
mv = new MapView(); // create an “Observer” for the map
sv = new ScoreView(gw); // create an “Observer” for the game state data
gw.addObserver(mv); // register the map Observer
gw.addObserver(sv); // register the score observer
// code here to create menus, create Command objects for each command,
// add commands to Command menu, create a control panel for the buttons,
// add buttons to the control panel, add commands to the buttons, and
// add control panel, MapView panel, and ScoreView panel to the frame
setVisible(true);
}
}
and has a lot of references to other functions.

access object method from another class

I'm new to Java and oriented-object and I'm trying to create a chat program. Here's what I'm trying to do:
Somewhere in my Main.java
Window window = new Window;
Somewhere in my Window.java
History history = new History()
Somewhere in my History.java:
public History()
{
super(new GridBagLayout());
historyArea = new JTextArea(15, 40);
historyArea.setEditable(false);
JScrollPane scrollPane = new JScrollPane(historyArea);
/* some other code... */
}
public void actionPerformed(ActionEvent event)
{
String text = entryArea.getText();
historyArea.append(text + newline);
entryArea.selectAll();
historyArea.setCaretPosition(historyArea.getDocument().getLength());
}
public JTextArea getHistoryArea()
{
return historyArea;
}
public void addToHistoryArea(String pStringToAdd)
{
historyArea.append(pStringToAdd + newline);
historyArea.setCaretPosition(historyArea.getDocument().getLength());
}
Now that I'm in Server.java, I want to use the method addToHistoryArea. How can I do that without making my historyArea static? Because if I understand well how static works, I couldn't have different historyArea even if I create a new History...
Thanks for your help and tell me if I got it all wrong!

In your Server constructor, send the instance of your History object (e.g new Server (history), and then you can invoke, history.addToHistoryArea, other option would be have a setter method which sets an instance of history to an instance variable, and then just call the addToHistoryArea method
public class Server{
private History history;
public Server(History history){
this.history = history;
}
public void someMethod(){
this.history.addToHistoryArea();
}
}
Another way
public class Server{
private History history;
public void setHistory(History history){
this.history = history;
}
public void someMethod(){
this.history.addToHistoryArea();
}
}

In someplace in Server you can have History
public class Server{
private History history;
public void setHistory(History history){
this.history= history;
}
public void someMethod(){
history.addToHistoryArea();
}
}
Or if you don't want to have an instance in Server
public void someMethod(History history){
history.addToHistoryArea();
}
Or if you want to be more decoupled you can take approach with the observer pattern or perhaps a mediator if they are colleagues.

You may want to create a History object in the Server class and then call the addToHistoryArea() method on that history instance.
public class Server{
private History history;
public void setHistory(History history){
this.history = history;
}
public void methodCall(){
history.addToHistoryArea();
}
}