increase text font value with JButton issue

Question

I have to create an interface which allows the user to increase/decrease the size of a piece of text and to show the current font size value of that text.

I have two buttons, increase and decrease. I have two labels. One label has the text "X" which needs to change size every time a button is pressed. The other label has to display the current font size value of "X".

I have managed to implement the increase/decrease method for the text, however I cannot get the value of the text to increase after clicking. The value of the text when increased only allows the user to increase it once. I want the program to be able to increase it by 5 every time the button is activated.

I believe I have to somehow store the new value of the font size and use the new value to allow me to increase/decrease even more.

If anyone could tell me how to do this, or show a solution, it would be greatly appreciated.

package lab3;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class FontSize extends JFrame{
JButton increase, decrease;
JLabel sizeX, sizeValue;
public static void main (String[]args){
 FontSize changeFont = new FontSize();
 changeFont.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 changeFont.setTitle("Increase/Decrease Font Size");
 changeFont.setSize(900,700);
 changeFont.setVisible(true);
 changeFont.setLayout(new GridLayout(2,2));
}
public FontSize(){
 increase = new JButton("increase");
 increase.setBackground(Color.white);
 increase.setFont(increase.getFont().deriveFont(30.0f));
 add(increase);
 decrease = new JButton("decrease");
 decrease.setBackground(Color.white);
 decrease.setFont(decrease.getFont().deriveFont(30.0f));
 add(decrease);
 sizeX = new JLabel("X", SwingConstants.CENTER);
 sizeX.setBackground(Color.yellow);
 sizeX.setFont(sizeX.getFont().deriveFont(30.0f));
 add(sizeX);
 int temp = sizeX.getFont().getSize();
 sizeValue = new JLabel("",SwingConstants.CENTER);
 sizeValue.setText(String.valueOf(temp));
 sizeValue.setBackground(Color.yellow);
 sizeValue.setFont(sizeValue.getFont().deriveFont(30.0f));
 add(sizeValue);
 event e = new event();
 increase.addActionListener(e);
 decrease.addActionListener(e);
 }
public class event implements ActionListener {
 public void actionPerformed(ActionEvent e){
 String operation = e.getActionCommand();
 int temp = sizeX.getFont().getSize();
 int temp2 = sizeValue.getFont().getSize();
 if(operation.equals("increase"))
 { 
 temp = temp + 5;
 sizeX.setFont(new Font("Arial", Font.PLAIN, temp));
 temp2 = temp2 + 5;
 sizeValue.setText(String.valueOf(temp2));
 } 
 else if(operation.equals("decrease"))
 {
 temp = temp - 5;
 sizeX.setFont(new Font("Arial", Font.PLAIN, temp));
 temp2 = temp2 - 5;
 sizeValue.setText(String.valueOf(temp2));
 }
 }
 }
}

Answer 1

Simple fix really: on like 64 of the original code, you accidentaly are trying to count the variable temp2 as the size of the font of it, not the actual text. I've attached a slightly refactored, as well as corrected, version of the code.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class FontSize extends JFrame implements ActionListener {
 private JButton increase, decrease;
 private JLabel sizeX, sizeValue;
 public static void main (String[]args) {
 FontSize changeFont = new FontSize();
 changeFont.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 changeFont.setTitle("Increase/Decrease Font Size");
 changeFont.setSize(900,700);
 changeFont.setVisible(true);
 changeFont.setLayout(new GridLayout(2,2));
 }
 public FontSize(){
 increase = new JButton("increase");
 increase.setBackground(Color.white);
 increase.setFont(increase.getFont().deriveFont(30.0f));
 add(increase);
 decrease = new JButton("decrease");
 decrease.setBackground(Color.white);
 decrease.setFont(decrease.getFont().deriveFont(30.0f));
 add(decrease);
 sizeX = new JLabel("X", SwingConstants.CENTER);
 sizeX.setBackground(Color.yellow);
 sizeX.setFont(sizeX.getFont().deriveFont(30.0f));
 add(sizeX);
 int temp = sizeX.getFont().getSize();
 sizeValue = new JLabel("",SwingConstants.CENTER);
 sizeValue.setText(String.valueOf(temp));
 sizeValue.setBackground(Color.yellow);
 sizeValue.setFont(sizeValue.getFont().deriveFont(30.0f));
 add(sizeValue);
 increase.addActionListener(this);
 decrease.addActionListener(this);
 }
 public void actionPerformed(ActionEvent e) {
 String operation = e.getActionCommand();
 int temp = sizeX.getFont().getSize();
 int temp2 = Integer.parseInt(sizeValue.getText());
 if(operation.equals("increase")) { 
 temp += 5;
 sizeX.setFont(new Font("Arial", Font.PLAIN, temp));
 temp2 += 5;
 sizeValue.setText(String.valueOf(temp2));
 } else if(operation.equals("decrease")) {
 temp -= 5;
 sizeX.setFont(new Font("Arial", Font.PLAIN, temp));
 temp2 -= 5;
 sizeValue.setText(String.valueOf(temp2));
 }
 }
}

Hope this helped, and best of luck to you.

Answer 2

int temp2 = sizeValue.getFont().getSize(); isn't the size of the font you're changing, but is the size of the font which is been used to render the label.

Try using something more like instead...

 String operation = e.getActionCommand();
 int temp = sizeX.getFont().getSize();
 if (operation.equals("increase")) {
 temp = temp + 5;
 sizeX.setFont(new Font("Arial", Font.PLAIN, temp));
 sizeValue.setText(String.valueOf(temp));
 } else if (operation.equals("decrease")) {
 temp = temp - 5;
 sizeX.setFont(new Font("Arial", Font.PLAIN, temp));
 sizeValue.setText(String.valueOf(temp));
 }

You may also need to call revalidate(); and repaint(); at the end of the actionPerformed method to force a refresh, but it work okay without for me

Equally, you could just something like...

 Font font = sizeX.getFont();
 if (operation.equals("increase")) {
 font = font.deriveFont(font.getSize() + 5f);
 } else if (operation.equals("decrease")) {
 font = font.deriveFont(font.getSize() - 5f);
 }
 sizeX.setFont(font);
 sizeValue.setText(NumberFormat.getNumberInstance().format(font.getSize()));

Which allows you to maintain the font that the label was originally using, but increases/decreases it's size, but also relies on the actual Font size to update the display, rather the relying on calculated values...