Develop Reference

Method called from first JFrame does nothing in second

I set JTextField "rfid" to setEnabled(false) in MainGUI class and created method setRfidEnabled to be able to enable textfield from another class called CardLayout.
When I try to call it from CardLayout by button event listener it does nothing, I mean to textfield, because System.out.print("LOL"); works fine. MainGUI contains JFrame and by button calls another JFrame in CardLayout class.
When I initialize MainGUI class, it has Thread[Thread-2,6,main], but when I call CardLayout it becomes Thread[AWT-EventQueue-0,6,main], same as CardLayout itself. I tried to make "rfid" volatile, no success.
---Edited code---
MainGUI:
public class MainGUI {
JTextField rfid;
JButton button;
final JFrame frame;
final JPanel pane;
LayoutChanger layout = new LayoutChanger();
public MainGUI() {
rfid = new JTextField("", 10);
button = new JButton("CardLayoutSwitch");
frame = new JFrame("Main GUI Panel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout(5,5));
pane = new JPanel(new GridLayout(5, 5));
frame.add(pane,BorderLayout.CENTER);
pane.add(rfid);
pane.add(button);
rfid.setEnabled(false);
button.setEnabled(true);
frame.pack();
frame.setVisible(true);
frame.setLocationRelativeTo(null);
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed (ActionEvent e){
layout.changeLayout(1);
}
});
}
public void setRfidEnabled() {
System.out.println("LOL");
rfid.setEnabled(true);
button.setEnabled(false);
}
}
LayoutChanger class:
public class LayoutChanger {
public static void main(String[] args) {
MainGUI gui = new MainGUI();
}
public void changeLayout(int i){
if (i == 1) {
CardLayout card = new CardLayout();
}
}
}
CardLayout class:
public class CardLayout {
JFrame frame;
JButton manual;
final JPanel pane;
MainGUI gui = new MainGUI();
public CardLayout() {
manual = new JButton("UID MANUAL");
frame = new JFrame("Card Scan Panel");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setLayout(new BorderLayout(5, 5));
pane = new JPanel(new BorderLayout(5, 5));
manual.setPreferredSize(new Dimension(50, 25));
frame.add(pane, BorderLayout.CENTER);
pane.add(manual);
frame.pack();
frame.setVisible(true);
frame.setLocationRelativeTo(null);
manual.addActionListener(new ActionListener() {
#Override
public void actionPerformed (ActionEvent e){
gui.setRfidEnabled();
}
});
}
}

As stated in the comments above by #matt
Every time you click on manual button, you're creating a new MainGUI().
You need to create a single instance, either in your constructor or in the ActionListener and ask if you already have an instance of it (i.e. a Singleton) and use it.
If you decide to use the first one, declare gui as a global variable:
MainGUI gui = new MainGUI();
And on your ActionListener have it changed as:
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(currentThread());
gui.setRfidEnabled();
//frame.dispose();
}
Then you have a single instance of it.
Also as stated by #Sergiy you don't really need all those threads
Here are some examples on how to use ActionListeners:
I'm trying to make a button to count characters in a text field
AppletViewer bugged and trying to involve a timer
Calculator returns 0.0 to all questions asked
Java - My action event doesn't work
Drawing shapes on a JForm java
Animated Sprites with Java Swing This one includes a Timer (Another thread that handles the animation but doesn't block the EDT)
As you can see in all the above examples, none of them required another Thread to handle the actions, the one that uses a thread is only for performing the animation and not to react to user clicks.
Recommended tutorial: How to use Actions

How to pass JTextField from JFrame into another JFrame?

I have two JFrame (JFrame1 and JFrame2) with two JTextField1 and JTextField2. My question is when I write "Hello world " on JTextField2 from Jframe2 and then click on OK button, I see "Hello world " on JTextField1 on Jframe1 class.
How can I do this? I'm sorry if this is a newbie question but I'm learning..
Here is my code:
JFrame2:
private JFrame1 jf1;
private void btn2ActionPerformed(java.awt.event.ActionEvent evt) {
jf1.setjTextField1(this.jTextField2);
}

What you are doing there is actually sending the reference to the actual JTextField from one frame to the other one.
That's probably not a good idea cause both frames would be end up referencing the same visual component.
What you probably want is to keep all visual components separate, but make the text of the second text field equal to the text in the first one.
Something like this:
private void btn2ActionPerformed(java.awt.event.ActionEvent evt) {
jf1.getjTextField1().setText(this.jTextField2.getText());
}

You could use an Observer Pattern or Producer/Consumer Pattern to solve the problem.
The basic idea is, you have something that generates a value and something that either wants to be notified or consume the generated value.
One of the other prinicples you should take the time to learn is also Code to interface (not implementation). This sounds stranger then it is, but the the idea is to reduce the unnecessary exposure of your objects (to unintended/controlled modifications) and decouple your code, so you can change the underlying implementation without affecting any other code which relies on it
Given the nature of your problem, an observer pattern might be more suitable. Most of Swing's listener's are based on the same principle.
We start by defining the contract that the "generator" will use to provide notification of changes...
public interface TextGeneratorObserver {
public void textGenerated(String text);
}
Pretty simple. This means we can safely provide an instance of any object that implements this interface to the generator and know that it won't do anything to our object, because the only thing it knows about is the textGenerated method.
Next, we need something that generates the output we are waiting for...
public class GeneratorPane extends JPanel {
private TextGeneratorObserver observer;
private JTextField field;
private JButton button;
public GeneratorPane(TextGeneratorObserver observer) {
this.observer = observer;
field = new JTextField(10);
button = new JButton("OK");
ActionListener listener = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
observer.textGenerated(field.getText());
}
};
button.addActionListener(listener);
field.addActionListener(listener);
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = GridBagConstraints.REMAINDER;
gbc.insets = new Insets(2, 2, 2, 2);
add(field, gbc);
add(button, gbc);
}
}
This is just a simple JPanel, but it requires you to pass a instance of TextGeneratorObserver to it. When the button (or field) triggers the ActionListener, the ActionListener calls the textGenerated to notify the observer that the text has been generated or changed
Now, we need someone to observer it...
public class ObserverPanel extends JPanel implements TextGeneratorObserver {
private JLabel label;
public ObserverPanel() {
label = new JLabel("...");
add(label);
}
#Override
public void textGenerated(String text) {
label.setText(text);
}
}
This is a simple JPanel which implements the TextGeneratorObserver interface and updates it's JLabel with the new text
Then, we just need to plumb it together
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
ObserverPanel op = new ObserverPanel();
op.setBorder(new CompoundBorder(new LineBorder(Color.RED), new EmptyBorder(10, 10, 10, 10)));
GeneratorPane pp = new GeneratorPane(op);
pp.setBorder(new CompoundBorder(new LineBorder(Color.GREEN), new EmptyBorder(10, 10, 10, 10)));
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridLayout(2, 1));
frame.add(pp);
frame.add(op);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
}

This is a complete working example I just coded out:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class FrameRunner
{
public static void main(String[] args){
MyFrame f1 = new MyFrame("Frame 1");
MyFrame f2 = new MyFrame("Frame 2");
f1.addRef(f2);
f2.addRef(f1);
}
}
class MyFrame extends JFrame{
JTextField txt = new JTextField(8);
JButton btn = new JButton("Send");
MyFrame f = null;
public MyFrame(String title){
super(title);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setLayout(new FlowLayout());
setPreferredSize(new Dimension(400, 300));
setVisible(true);
add(btn);
add(txt);
pack();
setLocationRelativeTo(null);
init();
}
public void addRef(MyFrame f){
this.f = f;
}
public void init(){
btn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
f.update(txt.getText());
}
});
}
public void update(String str){
txt.setText(str);
}
}
In order to make the code short and easier for you to understand. Many of the things I did not following the conventions and I did not modularize the codes. But this should give you a very good idea of how you can pass in the reference of another JFrame.
This code shows an example of how Frame1 has a reference on Frame2. Yet Frame2 also has a reference on Frame1.
Whatever things you type in JFrame1 can be send to JFrame2's textfield. Same for the other way round.

how to remove lines one by one from a JTextArea

How can i remove lines from a JTextArea one by one instead of all together?
I have a JTextArea which gets appended with string results from a thread, now i would like to remove one line at a time while the thread is executing.

You first need to decide what should trigger the line removal.
Should it be the addition of a new line, so that total line number is constant. If so then you should write your code to call the line removal code in the same location that where a new line is added.
Or should it be at a constant rate -- and if so, then you will want to use a Swing Timer for this.
Then you need to decide which line to remove. If not the first line, then you'll need to figure out how to calculate which line. The javax.swing.text.Utilities class can help you find out the start and finish location of every line of text in your JTextArea.
Edit
You ask:
the main concern is about how to remove it from the JTextArea, i have already calculated the start and end positions of a line that has to be deleted.But what function can assist in removing just that one line?
You would first get the JTextArea's Document by calling, getDocument()
Then you could call remove(int offs, int length) on the Document as per the Document API.

Try This :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class SwingControlDemo {
String [] m;
int i=0;
String append="";
private JFrame mainFrame;
private JLabel headerLabel;
private JLabel statusLabel;
private JPanel controlPanel;
Timer t;
public SwingControlDemo(){
prepareGUI();
}
public static void main(String[] args){
SwingControlDemo swingControlDemo = new SwingControlDemo();
swingControlDemo.showTextAreaDemo();
}
private void prepareGUI(){
mainFrame = new JFrame("Java Swing Examples");
mainFrame.setSize(400,400);
mainFrame.setLayout(new GridLayout(3, 1));
mainFrame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent windowEvent){
System.exit(0);
}
});
headerLabel = new JLabel("", JLabel.CENTER);
statusLabel = new JLabel("",JLabel.CENTER);
statusLabel.setSize(350,100);
controlPanel = new JPanel();
controlPanel.setLayout(new FlowLayout());
mainFrame.add(headerLabel);
mainFrame.add(controlPanel);
mainFrame.add(statusLabel);
mainFrame.setVisible(true);
}
private void showTextAreaDemo(){
headerLabel.setText("Control in action: JTextArea");
JLabel commentlabel= new JLabel("Comments: ", JLabel.RIGHT);
final JTextArea commentTextArea =
new JTextArea("This is a Swing tutorial "
+"\n to make GUI application in Java."+"\n to make GUI application in Java"+"\n to make GUI application in Java",5,20);
JScrollPane scrollPane = new JScrollPane(commentTextArea);
JButton showButton = new JButton("Show");
showButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String s=commentTextArea.getText();
m=s.split("\n");
t.start();
}
});
t=new Timer(1000,new ActionListener(){
public void actionPerformed(ActionEvent e)
{
i++;
append="";
if(i<=m.length)
{
for(int j=i;j<m.length;j++)
{
append=append+m[j];
}
commentTextArea.setText(append);
}
else
{
t.stop();
}
}});
controlPanel.add(commentlabel);
controlPanel.add(scrollPane);
controlPanel.add(showButton);
mainFrame.setVisible(true);
}
}

Java- How to add more textfields by clicking a button?

I have created a frame in Java which has some textfields and buttons in it. Assuming that user wants more textfields (for example to add more data), I want to put a button and when a user clicks the button, then a new textfield should appear. then user can fill data in it and again by clicking that button another textfield should appear.
How can I do this ? What code I need to write for the button to show more and more text fields by clicking button?
Thank you !

It would be wise that instead of adding components to your JFrame directly, you add them to a JPanel. Though related to your problem, have a look at this small example, hopefully might be able to give you some hint, else ask me what is out of bounds.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class JFrameExample
{
private JFrame frame;
private JButton button;
private JTextField tfield;
private String nameTField;
private int count;
public JFrameExample()
{
nameTField = "tField";
count = 0;
}
private void displayGUI()
{
frame = new JFrame("JFrame Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridLayout(0, 1, 2, 2));
button = new JButton("Add JTextField");
button.addActionListener(new ActionListener()
{
#Override
public void actionPerformed(ActionEvent ae)
{
tfield = new JTextField();
tfield.setName(nameTField + count);
count++;
frame.add(tfield);
frame.revalidate(); // For JDK 1.7 or above.
//frame.getContentPane().revalidate(); // For JDK 1.6 or below.
frame.repaint();
}
});
frame.add(button);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
#Override
public void run()
{
new JFrameExample().displayGUI();
}
});
}
}

Supposing that you have a main container called panel and a button variable button which is already added to panel, you can do:
// handle the button action event
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// create the new text field
JTextField newTextField = new JTextField();
// add it to the container
panel.add(newTextField);
panel.validate();
panel.repaint();
}
});
When adding the new text field, you may need to mention some layout related characteristics, depending on the layout manager you are using (for instance if you use GridBagLayout, you will need to specify the constraints).

Custom JLabel Cleanup

I need to clean my labelResult each time on textField Action, but on the first time it adds 'null' in front of string and then - prints new string right after. Please help.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Frame extends JFrame implements ActionListener {
boolean isDirect = true;
String[] typeStr = {"direct", "invert"};
JLabel labelTip = new JLabel("Choose 'direct' OR 'invert' to print your next line in direct order or inverted respectively.");
JTextField textField = new JTextField("Some text!", 40);
JComboBox comboBox = new JComboBox(typeStr);
EventProcessing eventProcessing = new EventProcessing();
JLabel labelResult = new JLabel();
public Frame() {
setLayout(new BorderLayout());
getContentPane().add(labelTip, BorderLayout.PAGE_START);
getContentPane().add(comboBox, BorderLayout.CENTER);
getContentPane().add(textField, BorderLayout.AFTER_LINE_ENDS);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
textField.addActionListener(this);
pack();
}
public void actionPerformed(ActionEvent e) {
getContentPane().remove(labelResult);
labelResult = new JLabel();
labelResult.setText("");
if (!(comboBox.getSelectedItem()).equals("direct")) {
isDirect = false;
}
else {
isDirect = true;
}
labelResult.setText(eventProcessing.action(isDirect, textField.getText()));
getContentPane().add(labelResult, BorderLayout.PAGE_END);
pack();
}
}

#Tim I know that in official tutorial about JComboBox is used ActionListener, but for any of actions from JComboBox to the GUI is better look for ItemListener, there you are two states (always be called twice, but you can filtering between thes two options SELECTED / DESELECTED by wraping to the if ... else)
and your code should be only
Runnable doRun = new Runnable() {
#Override
public void run() {
labelResult.setText(eventProcessing.action(isDirect, textField.getText()));
add(labelResult, BorderLayout.PAGE_END);
//1) this.pack(); if you want to re-layout with effect to size of JFrame too
//2a revalidate();
//2b plus in most cases
//2b repaint(); relayout Container with fitting JComponents inside Container,
//2b but without resize of JFrame
}
};
SwingUtilities.invokeLater(doRun);

Without the code to EventProcessing.action() it's hard to determine, but I would guess you attempt to concatenate two strings, the first of which is null. Null strings get converted to the literal string "null."