I'm studying advanced Java and trying to write a program that utilizes the MVC design pattern. The program needs to draw a string which can be modified by a user's input in a JTextField. The user can also adjust the color and font size of the text through a JComboBox and a JSpinner respectively.
Here is what I have so far:
public class MVCDemo extends JApplet {
private JButton jBtnController = new JButton("Show Controller");
private JButton jBtnView = new JButton("Show View");
private TextModel model = new TextModel();
//constructor
public MVCDemo(){
//set layout and add buttons
setLayout(new FlowLayout());
add(jBtnController);
add(jBtnView);
jBtnController.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
JFrame frame = new JFrame("Controllor");
TextController controller = new TextController();
controller.setModel(model);
frame.add(controller);
frame.setSize(200, 100);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
jBtnView.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
JFrame frame = new JFrame("View");
TextView view = new TextView();
view.setModel(model);
frame.add(view);
frame.setSize(500, 200);
frame.setLocation(200, 200);
frame.setVisible(true);
}
});
}
public static void main(String[] args){
MVCDemo applet = new MVCDemo();
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle("MVCDemo");
frame.getContentPane().add(applet, BorderLayout.CENTER);
frame.setSize(400, 90);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
public class TextModel {
private String text = "Your Student ID #";
//utility field used by event firing mechanism
private ArrayList<ActionListener> actionListenerList;
public void setText(String text){
this.text = text;
//notify the listener for the change on text
processEvent(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "text"));
}
public String getText(){
return text;
}
//register an action event listener
public synchronized void addActionListener(ActionListener l){
if (actionListenerList == null)
actionListenerList = new ArrayList<ActionListener>();
}
//remove an action event listener
public synchronized void removeActionListener(ActionListener l){
if (actionListenerList != null && actionListenerList.contains(l))
actionListenerList.remove(l);
}
//fire TickEvent
private void processEvent(ActionEvent e){
ArrayList<ActionListener> list;
synchronized (this){
if (actionListenerList == null)
return;
list = (ArrayList<ActionListener>)(actionListenerList.clone());
}
}
}
public class TextView extends JPanel{
private TextModel model;
//set a model
public void setModel(TextModel model){
this.model = model;
if (model != null)
//register the view as listener for the model
model.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
repaint();
}
});
}
public TextModel getModel(){
return model;
}
@Override
public void paintComponent(Graphics g){
if (model != null){
super.paintComponent(g);
//g.setColor(model.getColor());
g.drawString(model.getText(), 190, 90);
}
}
}
public class TextController extends JPanel {
String[] colorStrings = { "Black", "Blue", "Red" };
private TextModel model;
private JTextField jtfText = new JTextField();
private JComboBox jcboColorList = new JComboBox(colorStrings);
//constructor
public TextController(){
//panel to group labels
JPanel panel1 = new JPanel();
panel1.setLayout(new GridLayout(3, 1));
panel1.add(new JLabel("Text"));
panel1.add(new JLabel("Color"));
panel1.add(new JLabel("Size"));
//panel to group text field, combo box and spinner
JPanel panel2 = new JPanel();
panel2.setLayout(new GridLayout(3, 1));
panel2.add(jtfText);
panel2.add(jcboColorList);
setLayout(new BorderLayout());
add(panel1, BorderLayout.WEST);
add(panel2, BorderLayout.CENTER);
//register listeners
jtfText.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
if (model != null)
model.setText(jtfText.getText());
}
});
/*jcboColorList.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
if (model != null)
model.set
}
});*/
}
public void setModel(TextModel model){
this.model = model;
}
public TextModel getModel(){
return model;
}
}
At this moment I've only implemented the JTextField component (yet to figure out how to do the JComboBox and JSpinner properly), and even that is hardly perfect.
When I first launch the program and turn on both view and controller panels, the default string of "Your Student ID #" is shown correctly in the view. But when I type some other string into the JTextField and hit enter, the output string in TextView does not update unless I close the view panel and reopen it. Could someone point out what is causing this behavior?
I suspect it probably has something to do with the event handling part of my program. But I'm still quite new to GUI programming and have a very basic understanding of how events are triggered and handled. So I would be really grateful if someone could explain the underlying cause of the problem in a beginner-friendly fashion.
