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Display not Changing [duplicate]

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I am working on this program that calculates the Beats per Minute (BPM) when you click the button. When you click two times, it is supposed to display the current BPM, and display the new one with every click after that. What the problem is, though, is that the display isn't changing. What do I need to do?
Here is my code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
public class BPM extends JPanel implements ActionListener {
JLabel label;
public String display;
public int bpm;
public int buttonPressed;
public int time1;
public int time2;
public int time3;
public int counter[];
public void addComponents(Container pane) {
JPanel buttons = new JPanel();
JButton bpmButton = new JButton("Click");
bpmButton.setSize(new Dimension(100, 50));
bpmButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
buttonPressed++;
counter = new int[2];
if (buttonPressed == 1) {
counter[0] = (int)(System.currentTimeMillis());
} else if (buttonPressed == 2) {
counter[1] = (int)(System.currentTimeMillis());
calculateTimeBetweenClicks();
setTime();
} else {
counter[0] = counter[1];
counter[1] = (int)(System.currentTimeMillis());
calculateTimeBetweenClicks();
setTime();
}
}
});
display = "0";
label = new JLabel(display, SwingConstants.CENTER);
label.setFont(label.getFont().deriveFont(100.0f)); // original 45
pane.add(label, BorderLayout.PAGE_START);
pane.add(bpmButton, BorderLayout.CENTER);
}
// Calculates the difference between the two saved clicks
public void calculateTimeBetweenClicks() {
if (buttonPressed == 1) {
time1 = counter[0];
} else {
time1 = counter[0];
time2 = counter[1];
}
time3 = time2 - time1;
}
// Calculates the BPM and changes the display accordingly
public void setTime() {
bpm = 60000 / time3;
display = "" + bpm + "";
label.setText(display);
}
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
public static void createAndShowGUI() {
// Creates the window
JFrame frame = new JFrame("BPM Calculator");
frame.setPreferredSize(new Dimension(300, 200)); // original (250, 130)
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Adds the components to the content pane
BPM window = new BPM();
window.addComponents(frame.getContentPane());
//Displays the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
// Turns off bold text
UIManager.put("swing.boldMetal", Boolean.FALSE);
// Allows the components to be used and interacted with
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}

The problem is in your addComponents method, you are creating a new array on each and every button click (so you end up with a new and empty array). This is throwing off your calculation. Simply move the instantiation of your array to somewhere outside of the ActionListener like this...
public void addComponents(Container pane) {
JPanel buttons = new JPanel();
counter = new int[2]; //Move this line to here...
JButton bpmButton = new JButton("Click");
bpmButton.setSize(new Dimension(100, 50));
bpmButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
buttonPressed++;
if (buttonPressed == 1) {
counter[0] = (int)(System.currentTimeMillis());
} else if (buttonPressed == 2) {
counter[1] = (int)(System.currentTimeMillis());
calculateTimeBetweenClicks();
setTime();
} //Removed the else - see edit below :-)
}
});
Additional
Your code as-is seems to get a litle confused after the 2nd click (the first BPM calculation) as it seems to take that 2nd click as the first click of the next set of 2 clicks if you get what I mean. I'm not sure if this is intended behaviour, but if not, I would reset everything in the calculateTimeBetweenClicks method after you've calculated the correct bpm ready for a new set of 2 clicks...
// Calculates the difference between the two saved clicks
public void calculateTimeBetweenClicks() {
if (buttonPressed == 1) {
time1 = counter[0];
} else {
time1 = counter[0];
time2 = counter[1];
//Reset here ready for next 2 clicks...
counter[0]=0;
counter[1]=0;
buttonPressed = 0;
}
time3 = time2 - time1;
}

JAVA - Trying to use a variable from inside an actionperformed outside the class

I am trying to access the (double) percentage variable outside my actionPerformed while retaining the changes that it goes through.
it is a drop down menu, and an ok button you press. once you press it, it calculates a value for percentage, which then i want to use later on in the program.
Here is a snippet of the code:
btn.addActionListener(
new ActionListener(){
public void actionPerformed(ActionEvent e){
String currentCountry = (String)cb.getSelectedItem();
double percentage = 0.00;
if(currentCountry.equals("Brazil") || currentCountry.equals("Argentina")) {
cb2.removeAllItems();
for(int i = 0; i < choicesSouthAmerica.length; i++) {
cb2.addItem(choicesSouthAmerica[i]);
}
}
else {
cb2.removeAllItems();
for(int i = 0; i < choicesEurope.length; i++) {
cb2.addItem(choicesEurope[i]);
}
}
btn.setEnabled(false);
btn2.setEnabled(true);
if(currentCountry.equals("Brazil") || currentCountry.equals("Argentina")){
percentage = 1/5;
System.out.println(percentage);
}
else{
percentage = 1/8;
System.out.println(percentage);
}
}
}
);
Thank you kindly

you could use the putClientProperty(Object,Object) and getClientProperty(Object) functions as follow :
JButton btn = new JButton("Ok");
btn.putClientProperty("percentage",1.0);//or whatever initial value
btn.addActionListener(arg0 -> {
JButton source = (JButton) arg0.getSource();
double per = (double)source.getClientProperty("percentage");
per = (double)10/8;
source.putClientProperty("percentage",per);
});
double percentage = (double)btn.getClientProperty("percentage");//or use it in any other object that has access to the btn object

Sadly Java doesn't support closures, so you can not modify variables outside the scope of an anonymous class. But you can access final variables, so in principle you can do something like this:
class Percentage {
double p;
}
final Percentage p = new Percentage();
btn.addActionListener(
new ActionListener() {
public void actionPerformed(ActionEvent e) {
// [...]
p.p = 1/5;
// [...]
}
}
);
Then you can access the updated percentage via p.p outside of your anonymous class. (Btw. is it really a "percentage" or in fact a ratio?)
But this doesn't seem very idiomatic for Java, so the clean solution is probably just to make a proper class with a private instance variable and a getter and use this instead of the anonymous class.

I think what you actually need is just a static field (it can have whatever access modifiers you want). So something like this I think should work:
public class Test {
static double d = 0;
public static void main(String[] args) {
JButton b = new JButton("ASDF");
b.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent arg0) {
d = 5;
}
});
}
}

Calculator issue with simple logic

I'm new to Java and have set myself the task of trying to create a simple calculator (and GUI) to advance my understanding and skills of the language.
Take this code:
import java.awt.FlowLayout;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class calc extends JFrame {
public JTextField input;
public JTextField output;
public JPanel Window;
public JButton math_button[] = new JButton[5];
public JButton number_button[] = new JButton[10];
public String[] number_button_name = {"1","2","3","4","5","6","7","8","9","0"};
public String[] name = {"Add", "Mulitply", "Divide", "Subtract", "Equals"};
public JFrame frame = new JFrame();
public JPanel math_panel = new JPanel();
public JPanel number_panel = new JPanel();
public JTextField math_input = new JTextField();
boolean trrgger = false;
thehandler handler = new thehandler();
public void go()
{
for(int b=0; b<number_button.length; b++)
{
number_button[b] = new JButton(number_button_name[b]);
number_button[b].addActionListener(handler);
number_panel.add(number_button[b]);
}
for(int i=0; i<math_button.length;i++)
{
math_button[i] = new JButton(name[i]);
math_button[i].addActionListener(handler);
math_panel.add(math_button[i]);
}
frame.getContentPane().add(BorderLayout.NORTH, math_input);
frame.getContentPane().add(BorderLayout.SOUTH, math_panel);
frame.getContentPane().add(BorderLayout.CENTER, number_panel);
frame.setSize(400,400);
frame.setVisible(true);
}
//Method to handle the math and return the results of whichever 'button' was pressed
static int Math(String button_num, int first_num, int second_num)
{
int total = 0;
if(button_num == "Add")
{
total = first_num + second_num;
}
else if (button_num == "Mulitply") //multiply
{
total = first_num * second_num;
}
else if (button_num == "Divide") //divide
{
total = first_num / second_num;
}
else if (button_num == "Substract") //subtract
{
total = first_num - second_num;
}
else if (button_num == "Equals") //subtract
{
total = total;
}
return total;
}
//Action Events - Code that is triggered once the associated button is clicked
public class thehandler implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
for (int h = 0; h <math_button.length; h++)
{
if(event.getSource()==math_button[h])
{
int firstn = Integer.parseInt(math_input.getText());
math_input.setText("");
int secondn = Integer.parseInt(math_input.getText());
System.out.println(calc.Math(math_button[h].getText(), firstn, secondn));
}
}
for(int n=0; n<number_button.length; n++)
{
if(event.getSource()==number_button[n])
{
String number_clicked = (number_button[n].getText());
String number = math_input.getText();
math_input.setText(number + number_clicked);
}
}
}
}
}
The idea behind this code is to create a simple GUI and allows the user to input the desired amount of numbers and then press the 'equals' button to display the result. However, as stated I'm having a problem with the logic. I can get the first entered number from the JTextField, clear the text once the first variable has been initialized but this is where the program falls over. The variable 'second_num' is passed to the 'Math' method as blank (which throws up errors) because that's what I tell the ActionEvent to do in order to allow for more fluid use of the program, no user wants to have to keep clearing the input box when using a calculator.
Anybody got any ideas?
Thanks

int firstn = Integer.parseInt(math_input.getText());
math_input.setText("");
int secondn = Integer.parseInt(math_input.getText());
What exactly do you expect the above lines to do? You are getting the text from math_input. Then you set it to an empty string. And by immediately getting the string back you are expecting to get something other than empty string?
The correct approach would be:
First time the handler is called (i.e. a "math" button is clicked) collect the input. Store it somewhere.
Next time this handler will be called you will have your next input. And so on until the user clicks on "=" to evaluate the whole expression.
Advice: If you are new to java, you might find it easier to create a calculator on the command line first. The functionality of a calculator does not require a GUI. In command line collecting the input is more simple. If you get that working then you can proceed to more fancy stuff like Swing

I looked at your code but its sound complicated for me. I recommend you to use IDE like Netbeans. Create swing application. To add two number all you need to do is as follow
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
int input_1 = Integer.parseInt(jTextField1.getText());
int input_2 = Integer.parseInt(jTextField2.getText());
jTextField3.setText(String.valueOf((input_1+input_2)));
}
http://i.stack.imgur.com/1G4v7.jpg

Java - Listen to variable change

First of all i am brand new to Java : /
I have been trying to solve this problem on my own for about 2 days now but cant get around it the problem is i am trying to implement a variable change listener. I have tried without successes to implement Observer and Observable to my project but whit no successes at best i came up by wrapping some elements of the code in to while loops but that well fails.
Any how this is my class and if you look at it i have some global variables defined after the constructor i need to listen for a change in all of those global variables if one changes i would like to execute a method.
I have been told JavaFX has methods that can listen to variables can someone confirm this.
Anyhow thanks for help in advance.
public class Tower_Controller {
public Tower_Controller() {
}
//Global variables
String isSelected = null;
int hasModules = 0;
int cap_s = 0;
int cpu_s = 0;
int cap = 0;
int cpu = 0;
int shield = 0;
int armor = 0;
double em = 00.00;
double th = 00.00;
double ki = 00.00;
double ex = 00.00;
public void invoke() {
Invoke_GUI runnable = new Invoke_GUI();
final JLabel tower_name = runnable.tower_name;
final JComboBox tower_select = runnable.tower_select;
final JTree module_browser = runnable.module_browser;
final JTree selected_modules = runnable.selected_modules;
final JProgressBar cap_bar = runnable.cap_bar;
final JProgressBar cpu_bar = runnable.cpu_bar;
final JLabel em_res = runnable.em;
final JLabel th_res = runnable.thermic;
final JLabel ki_res = runnable.kinetic;
final JLabel ex_res = runnable.explosive;
tower_select.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (isSelected != null) {
Events evt = new Events();
evt.towerSelected(isSelected);
} else {
tower_name.setText(tower_select.getSelectedItem().toString());
isSelected = tower_name.toString();
}
}
});
removeTower(tower_name);
runnable.setVisible(true);
}
public void updateValues(final JProgressBar cap_bar, final JProgressBar cpu_bar, final JLabel em_res,
final JLabel th_res, final JLabel ki_res, final JLabel ex_res){
cap_bar.setMaximum(cap);
cap_bar.setString(cap_s + " / " + cap);
cap_bar.setStringPainted(true);
cpu_bar.setMaximum(cpu);
cpu_bar.setString(cpu_s + " / " + cpu);
cpu_bar.setStringPainted(true);
String em_v = String.valueOf(em);
em_res.setText(em_v);
String th_v = String.valueOf(th);
th_res.setText(th_v);
String ki_v = String.valueOf(ki);
ki_res.setText(ki_v);
String ex_v = String.valueOf(ex);
ex_res.setText(ex_v);
}
public void updateList(final ArrayList<String> nodes, final JTree selected_modules) {
DefaultMutableTreeNode nod = new DefaultMutableTreeNode();
for (int i = 0; i < nodes.size(); i++) {
nod.add(new DefaultMutableTreeNode(nodes.get(i)));
}
selected_modules.setModel(new DefaultTreeModel(nod));
}
public void removeTower(final JLabel tower_name) {
tower_name.addMouseListener(new MouseListener() {
#Override
public void mouseClicked(MouseEvent e) {
if (hasModules == 1 & isSelected != null) {
Events evt = new Events();
evt.towerHasModules();
} else if (isSelected == null) {
} else {
tower_name.setText("No Control Tower selected");
isSelected = null;
}
}
#Override
public void mousePressed(MouseEvent e) {
}
#Override
public void mouseReleased(MouseEvent e) {
}
#Override
public void mouseEntered(MouseEvent e) {
}
#Override
public void mouseExited(MouseEvent e) {
}
});
}
public JLabel setTowerName(JLabel a, String name) {
a.setText(name);
return a;
}
}

The general procedure to be notified of a change to a variable is as follows:
First, make the variables private.
Create two methods for each variable, one which sets its value to an argument (often called setX(), where X is the variable name), the other which retrieves its value (getX())
Everywhere you need to read or set the variable, call the methods instead.
In the setX() method, call notifyObserver() on your Observers, in a loop.
And there you go! Now every time the variable is changed, registered Observers are notified. The key part of this solution is that the variables have to be private, so that no code can set their values without going through the setX() methods.

Changing JLabels between classes

My first post, so forgive any incorrect etiquette. I'm currently doing my year end project for school and I need a bit of help. I am making a GUI java app in Netbeans. I have two classes. One is a class that controls a timer, the other is a class that is a scoreboard screen. I need to update the scoreboard timerLabel with the time that is being counted down in the timerClass. Its quite messy as there is another timer label in the Timer class which does update. My problem is that I cannot get timerLabel in MatchScreen() to update. Here is my code :
Timer Class
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class TimerClass extends JFrame {
Timer timer;
JLabel promptLabel, timerLabel;
int counter;
JTextField tf;
JButton button;
MatchScreen call = null;
public TimerClass() {
call = new MatchScreen();
setLayout(new GridLayout(4, 4, 7, 7));
promptLabel = new JLabel(""
+ "Enter number of seconds for the timer",
SwingConstants.CENTER);
add(promptLabel);
tf = new JTextField(5);
add(tf);
button = new JButton("Start");
add(button);
timerLabel = new JLabel("waiting...",
SwingConstants.CENTER);
add(timerLabel);
event e = new event();
button.addActionListener(e);
System.out.println("Button pressed");
}
public class event implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.out.println("Action performed");
int count = (int) (Double.parseDouble(tf.getText()));
timerLabel.setText("Time left: " + count);
call.setTimerLabel(count);
System.out.println("Passed count to tc");
TimeClass tc = new TimeClass(count);
timer = new Timer(1000, tc);
System.out.println("Timer.start");
timer.start();
//throw new UnsupportedOperationException("Not supported yet.");
}
/*public void actionPerformed(ActionEvent e) {
throw new UnsupportedOperationException("Not supported yet.");
}*/
}
public class TimeClass implements ActionListener {
int counter;
public TimeClass(int counter) {
this.counter = counter;
}
public void actionPerformed(ActionEvent e) {
counter--;
if (counter >= 1) {
call.setTimerLabel(counter);
} else {
timerLabel.setText("END");
timer.stop();
Toolkit.getDefaultToolkit().beep();
}
}
}
public static void main(String args[]) {
TimerClass gui = new TimerClass();
gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
gui.setSize(250, 150);
gui.setTitle("Time Setup");
gui.setVisible(true);
}
}
And now the ScoreBoard Screen
public class MatchScreen extends javax.swing.JFrame {
int redScore = 0, blueScore = 0, blueCat1 = 0,
blueCat2 = 0, redCat1 = 0, redCat2 = 0, winner = 0;
public MatchScreen() {
initComponents();
}
//Determine Winner of the match
public int getWinner() {
if (redScore > blueScore) {
winner = 1;
} else {
winner = 2;
}
return winner;
}
public void setTimerLabel(int a) {
int time = a;
while (time >= 1) {
timerLabel.setText("" + time);
}
if (time < 1) {
timerLabel.setText("End");
}
}
private void jButton13ActionPerformed(java.awt.event.ActionEvent evt) {
//Creates an object of the timerClass
TimerClass gui = new TimerClass();
gui.setSize(300, 175);
gui.setTitle("Time Setup");
gui.setVisible(true);
}
}
Some code that I felt is irrelevant was left out from the MatchScreen().
Many thanks

Managed to solve the general problem. I put all the code into one class. Not ideal, but it works :/ Anyway, deadlines are looming.
Sincere thanks.

You have a while loop in the setTimerLabel method, which I don't think you intended to put there. Also, you take the parameter a and assign it to time and then never use a again, why not just rename your parameter to time and bypass that additional variable?
EDIT
Sorry, I forgot to explain what I'm seeing :P If you say call.setTimerLabel(10) then you hit that while loop (while(time >= 1) which is essentially running while(10 >= 1) which is an infinite loop. Your program is never leaving the method setTimerLabel the first time you call it with a value >= 1.