Develop Reference

Java - how to zoom in/zoom out text in JTextArea

I am writing in a notepad. And I want to implement text scaling in my notepad. But I don't know how to do it. I'm trying to find it but everyone is suggesting to change the font size. But I need another solution.
I am create new project and add buttons and JTextArea.
package zoomtest;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JTextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class zoom {
private JFrame frame;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
zoom window = new zoom();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public zoom() {
initialize();
}
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
frame.getContentPane().add(panel, BorderLayout.NORTH);
JButton ZoomIn = new JButton("Zoom in");
ZoomIn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
//Code here...
}
});
panel.add(ZoomIn);
JButton Zoomout = new JButton("Zoom out");
Zoomout.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
//Code here...
}
});
panel.add(Zoomout);
JTextArea jta = new JTextArea();
frame.getContentPane().add(jta, BorderLayout.CENTER);
}
}

Introduction
Oracle has a helpful tutorial, Creating a GUI With Swing. Skip the Learning Swing with the NetBeans IDE section. Pay close attention to the Laying Out Components Within a Container section.
I reworked your GUI. Here's how it looks when the application starts. I typed some text so you can see the font change.
Here's how it looks after we zoom out.
Here's how it looks after we zoom in.
Stack Overflow scales the images, so it's not as obvious that the text is zooming.
Explanation
Swing was designed to be used with layout managers. I created two JPanels, one for the JButtons and one for the JTextArea. I put the JTextArea in a JScrollPane so you could type more than 10 lines.
I keep track of the font size in an int field. This is a simple application model. Your Swing application should always have an application model made up of one or more plain Java getter/setter classes.
Code
Here's the complete runnable code.
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class ZoomTextExample {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
new ZoomTextExample();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
private int pointSize;
private Font textFont;
private JFrame frame;
private JTextArea jta;
private JTextField pointSizeField;
public ZoomTextExample() {
this.pointSize = 16;
this.textFont = new Font(Font.DIALOG, Font.PLAIN, pointSize);
initialize();
}
private void initialize() {
frame = new JFrame("Text Editor");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createButtonPanel(), BorderLayout.NORTH);
frame.add(createTextAreaPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createButtonPanel() {
JPanel panel = new JPanel(new FlowLayout());
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
JButton zoomIn = new JButton("Zoom in");
zoomIn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent event) {
incrementPointSize(+2);
updatePanels();
}
});
panel.add(zoomIn);
panel.add(Box.createHorizontalStrut(20));
JLabel label = new JLabel("Current font size:");
panel.add(label);
pointSizeField = new JTextField(3);
pointSizeField.setEditable(false);
pointSizeField.setText(Integer.toString(pointSize));
panel.add(pointSizeField);
panel.add(Box.createHorizontalStrut(20));
JButton zoomOut = new JButton("Zoom out");
zoomOut.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent event) {
incrementPointSize(-2);
updatePanels();
}
});
panel.add(zoomOut);
return panel;
}
private JPanel createTextAreaPanel() {
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
jta = new JTextArea(10, 40);
jta.setFont(textFont);
JScrollPane scrollPane = new JScrollPane(jta);
panel.add(scrollPane, BorderLayout.CENTER);
return panel;
}
private void updatePanels() {
pointSizeField.setText(Integer.toString(pointSize));
textFont = textFont.deriveFont((float) pointSize);
jta.setFont(textFont);
frame.pack();
}
private void incrementPointSize(int increment) {
pointSize += increment;
}
}

How do I update a JLabel during run time

the JLabel's name is set to an int which changes as the user modifies the number, i tried label.revalidate and Label.repaint after the user changes the int value. i have seen in similar questions people suggest creating a new jlabel everytime, but im wondering if there is a simpler way? the code is very long so i will summerize when needed.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class officia {
static JFrame Frame;
static JPanel Panel;
static JTextField healthPlace;
static String health="0";
static JButton begin;
static JLabel heart;
static int loop;
public static void main(String[] args) {
Panel = new JPanel();
Frame = new JFrame();
Frame.setSize(500,1000);
Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Frame.add(Panel);
Panel.setLayout(null);
//adds panel and frame
healthPlace = new JTextField();
healthPlace.setBounds(170, 130, 165, 25);
Panel.add(healthPlace);
begin = new JButton("Begin");
begin.setBounds(217, 185, 70, 25);
Panel.add(begin);
while(loop==1)
loop=0;
heart = new JLabel(health);
heart.setBounds(150, -85, 500, 500);
Panel.add(heart);
Frame.setVisible(true);
//inputs gui's
ActionListener beginPressed = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
health = healthPlace.getText();
loop=1;
}
};
begin.addActionListener(beginPressed);
}
}

You're working in a event driven environment, that is, something happens and you respond to it.
This means, you're while-loop is ill-conceived and is probably the source of your issue. How can the ActionListener for the button be added when the loop is running, but you seem to using the ActionListener to exit the loop...
I modified you code slightly, so when you press the button, it will update the label.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class officia {
static JFrame Frame;
static JPanel Panel;
static JTextField healthPlace;
static String health = "0";
static JButton begin;
static JLabel heart;
static int loop;
public static void main(String[] args) {
Panel = new JPanel();
Frame = new JFrame();
Frame.setSize(500, 1000);
Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Frame.add(Panel);
Panel.setLayout(null);
//adds panel and frame
healthPlace = new JTextField();
healthPlace.setBounds(170, 130, 165, 25);
Panel.add(healthPlace);
begin = new JButton("Begin");
begin.setBounds(217, 185, 70, 25);
Panel.add(begin);
// This is ... interesting, but a bad idea
// while (loop == 1) {
// loop = 0;
// }
heart = new JLabel(health);
heart.setBounds(150, -85, 500, 500);
Panel.add(heart);
Frame.setVisible(true);
//inputs gui's
ActionListener beginPressed = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
health = healthPlace.getText();
loop ++;
heart.setText(Integer.toString(loop));
}
};
begin.addActionListener(beginPressed);
}
}
JLabel#setText is what's known as a stateful property, that is, it will trigger an update that will cause it to be painted, so, if it's not updating, you're doing something wrong.
Possible runnable example (of what I think you want to do)
You're working a very rich UI framework. One if it's, many, features, is the layout management framework, something you should seriously take the time to learn to understand and use.
See Laying Out Components Within a Container for more details.
Below is a relatively simple example which shows one way you might "swicth" between views based on a response to a user input
import java.awt.CardLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new BasePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class BasePane extends JPanel {
private CardLayout cardLayout;
public BasePane() {
cardLayout = new CardLayout();
setLayout(cardLayout);
StartPane startPane = new StartPane(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
cardLayout.show(BasePane.this, "HeartPane");
}
});
HeartPane heartPane = new HeartPane();
add(startPane, "StartPane");
add(heartPane, "HeartPane");
}
}
public class StartPane extends JPanel {
public StartPane(ActionListener actionListener) {
setBorder(new EmptyBorder(10, 10, 10, 10));
setLayout(new GridBagLayout());
JButton start = new JButton("Begin");
add(start);
start.addActionListener(actionListener);
}
}
public class HeartPane extends JPanel {
private JTextField heartTextField;
private JLabel heartLabel;
public HeartPane() {
setBorder(new EmptyBorder(10, 10, 10, 10));
setLayout(new GridBagLayout());
heartLabel = new JLabel("Heart");
heartTextField = new JTextField(10);
add(heartLabel);
add(heartTextField);
}
}
}

How to close jframe panel or window

I have 2 frames/windows, I have Exit button on window 2, an from window 1 I launch window 2 and then exit it i.e setVisible(false);
When I execute window 2 I can easily click button exit and hide the current window, however when I launch window 2 from window 1, and then click exit button I get NullPointerException Error. then I instantiated it in the beginning with static and this error was gone, however the window 2 is not being closed/hidden its still there with no effect of button.
Window 1 code:
package com.my.jlms;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class LibrarianMenu extends JFrame {
private JPanel contentPane;
private static LibrarianMenu frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
frame = new LibrarianMenu();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public LibrarianMenu() {
setTitle("Librarian");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 385, 230);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JButton btnPasswd = new JButton("Change Pass");
btnPasswd.setBounds(202, 76, 146, 39);
contentPane.add(btnPasswd);
btnPasswd.addActionListener(
new ActionListener() {
public void actionPerformed(ActionEvent e) {
ChangePwd framee = new ChangePwd();
framee.setVisible(true);
}
});
}
}
Window 2 Code:
package com.my.jlms;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;
public class ChangePwd extends JFrame {
private JPanel contentPane;
private static ChangePwd frame = new ChangePwd();;
private JButton btnExit;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
frame = new ChangePwd();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public ChangePwd() {
setResizable(false);
setTitle("Password!");
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setBounds(100, 100, 266, 154);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
btnExit = new JButton("Exit");
btnExit.setBounds(20, 80, 89, 30);
contentPane.add(btnExit);
btnExit.addActionListener(
new ActionListener() {
public void actionPerformed(ActionEvent ae) {
frame.setVisible(false);
}
});
}
}
Is there a solution I can set window 2 to hide ?

The problem here is that you are creating your frame, as your class, and not on the object frame, but you hide the frame which represents the object frame.
Change this line (in your actionListener's actionPerformed() method):
frame.setVisible(false);
to:
setVisible(false);

You can use dispose function for the purpose.see how dispose works.

If you want to close a JFrame, you could use the dispose() method.
Example:
public void actionPerformer(ActionEvent e)
{
if(e.getSource().equals(closeFrameButton)
{
dispose(); //This will close the current JFrame
}
}
NOTE: this is different to System.exit(0);. Using this will close the Java virtual machine. if you just want to close the frame, use dispose()

Grey screen on repaint() and revalidate()

My application gives a grey screen after the timer is run. As advised, I have now a MainPage which extends JFrame and a MenuPage that extends JPanel. I wish to load MenuPage after MainPage is run. repaint() and revalidate() does not work out for me. Please point me in the right direction.
import java.awt.*;
import java.awt.event.*;
import java.io.File;
import javax.swing.*;
import javax.swing.border.Border;
import javax.swing.border.EmptyBorder;
public class MainPage extends JFrame {
private static JPanel contentPane;
//timer
private final static int interval = 40;
private int i;
private Timer t;
private JProgressBar pbar;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
MainPage frame = new MainPage();
frame.setVisible(true);
}
catch (Exception e) {
e.printStackTrace();
}
}
});
}
public MainPage() {
dim = Toolkit.getDefaultToolkit().getScreenSize();
System.out.println(dim);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(null);
contentPane.setBounds(0,0,dim.width,dim.height);
setContentPane(contentPane);
this.setExtendedState(JFrame.MAXIMIZED_BOTH);
pbar = new JProgressBar (0,20);
pbar.setBounds(600, 500, 200, 45);
pbar.setValue(0);
pbar.setStringPainted(true);
pbar.setForeground(Color.RED);
Border border = BorderFactory.createTitledBorder("Loading...");
pbar.setBorder(border);
t = new Timer (interval, new ActionListener(){
public void actionPerformed(ActionEvent e) {
if (i == 20){
t.stop();
//start.setEnabled(true);
//refresh + load next page
contentPane.removeAll();
MenuPage menuPage = new MenuPage();
//setContentPane(menuPage);
contentPane.add(menuPage);
contentPane.revalidate();
contentPane.repaint();
contentPane.setVisible(true);
}
else{
i++;
pbar.setValue(i);
}
}
});
t.start();
contentPane.add(pbar, BorderLayout.NORTH);
contentPane.add(lblTitle);
contentPane.add(imgLogo);
contentPane.add(imgBackground);
}
}
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class MenuPage extends JPanel {
private JPanel contentPane;
public MenuPage() {
//setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setSize(500, 500);
contentPane.setLayout(null);
add (contentPane);
JButton btnSadfsafsa = new JButton("sadfsafsa");
btnSadfsafsa.setBounds(10, 52, 89, 23);
btnSadfsafsa.setEnabled(true);
btnSadfsafsa.setVisible(true);
contentPane.add(btnSadfsafsa);
}
}

Your MenuPage constructor is the problem.
You create a new JPanel - contentPane but never add it and never set the size. So in fact you just create an empty panel.

I hope this helps others in future. Yes null layout is not to be recommended. Applied setContentPane() instead of contentPane.add() in my case.
//refresh + load next page
contentPane.removeAll();
contentPane.revalidate();
contentPane.repaint();
setContentPane(new MenuPage());

Center panel when window resized

I would like to keep a panel I have created using an absolute layout in the center of my window even when the window is resized (if possible). I've come across a couple of suggestions here and [here][2] but no dice! Below is my sample code, any ideas or suggestions? I have no problems centered a single component like a JLable but I want to center a panel with many components!
import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.BorderFactory;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.border.Border;
import javax.swing.JLabel;
public class TestPanel extends JFrame {
private JLabel lblSetupTitle;
private Border compoundBorder, outlineColorBorder, outlineBorder;
private JTextArea txtrManageData;
private JPanel childPanel;
public TestPanel()
{
setBackground(Color.white);
outlineColorBorder = BorderFactory.createLineBorder(Color.gray);
outlineBorder = BorderFactory.createEmptyBorder(20, 20, 20, 20);
compoundBorder = BorderFactory.createCompoundBorder(outlineColorBorder, outlineBorder);
lblSetupTitle = new JLabel("Setup");
lblSetupTitle.setBounds(443, 288, 44, 23);
txtrManageData = new JTextArea("Text Area Text");
txtrManageData.setBounds(393, 322, 142, 61);
childPanel = new JPanel();
childPanel.setLocation(89, 38);
childPanel.setSize(921, 452);
childPanel.setBorder(compoundBorder);
setupGUIElements();
setupPanel();
}
private void setupGUIElements()
{
txtrManageData.setBackground(null);
txtrManageData.setLineWrap(true);
txtrManageData.setWrapStyleWord(true);
}
private void setupPanel()
{
getContentPane().setLayout(new GridBagLayout()); // set layout of parent panel to GridBagLayout
childPanel.setLayout(null); // set layout of child panel to AbsoluteLayout
childPanel.add(lblSetupTitle);
childPanel.add(txtrManageData);
getContentPane().add(childPanel, new GridBagConstraints());
this.setSize(1020, 500);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
TestPanel ex = new TestPanel();
ex.setVisible(true);
}
});
}
}
EDIT: Any tips, links, guidance on creating something like this

I'd nest layouts.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;
public class ThreeButtonTextFieldCombo {
private JPanel ui = null;
ThreeButtonTextFieldCombo() {
initUI();
}
public final void initUI() {
if (ui!=null) return;
ui = new JPanel(new GridBagLayout());
ui.setBorder(new TitledBorder("Parent Panel"));
JPanel controls = new JPanel(new GridLayout(1,0,10,10));
ui.add(controls);
controls.setBackground(Color.RED);
controls.setBorder(new TitledBorder("Child Panel"));
for (int ii=1; ii<4; ii++) {
addLabelAndField(controls, "String " + ii);
}
}
public JComponent getUI() {
return ui;
}
private void addLabelAndField(JPanel panel, String text) {
JPanel controls = new JPanel(new BorderLayout(3, 3));
controls.setBorder(new EmptyBorder(20,20,20,20));
JLabel l = new JLabel(text);
controls.add(l, BorderLayout.PAGE_START);
JTextArea ta = new JTextArea(text, 2, 8);
controls.add(new JScrollPane(ta));
panel.add(controls);
}
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
JFrame f = new JFrame("Three Button/Text Field Combo");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
ThreeButtonTextFieldCombo tbtfc =
new ThreeButtonTextFieldCombo();
f.setContentPane(tbtfc.getUI());
f.pack();
f.setMinimumSize(f.getSize());
f.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}

The first problem with your code is that you are adding your child panel using an empty instantiation of GridBagConstraints. I have never seen it used like that before.
getContentPane().add(childPanel, new GridBagConstraints());
Do not set any layout to content pane and just add it like this :
getContentPane().add(childPanel);
Now if you run it you will get the two components in the middle, where you defined them using the setBounds(..) method.
Like almost everyone commenting on your question, you should not use null layout, and use some other layout instead. I would use a GridBagLayout to organise the three buttons and three textfields in your diagram. You could then setBounds(..) on your child panel.
If you really must use absolute layout then you will have to do a bit of maths.
If your first label is like this :
labell1.setBounds(443, 288, 44, 23);
then your second label should be something like this :
labell2.setBounds(443 + someXDisplacement, 288, 44, 23);
..and third :
labell3.setBounds(443 + (someXDisplacement x 2), 288, 44, 23);
You get the picture.