I am trying to draw on my JFrame, but I can't get my super.paintComponents(g); to work. Also, nothing is drawing on my JFrame when I tell it to in my paintComponent() method.
Here is the code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class MTGSAMPServerReference extends JFrame implements ActionListener {
public static Toolkit tk = Toolkit.getDefaultToolkit();
static int ScrnWidth = ((int) tk.getScreenSize().getWidth());
static int ScrnHeight = ((int) tk.getScreenSize().getHeight());
private static final long serialVersionUID = 1L;
private static JList list1;
private static JButton next;
public MTGSAMPServerReference() {
// set flow layout for the frame
this.getContentPane().setLayout(new FlowLayout(FlowLayout.LEADING));
Object[]mainData = {"Vehicles", "Bikes/Bicycles", "Boats", "Houses", "Businesses", "Objects", "Jobs", "Ranks", "Licenses", "VIP"};
JPanel controls = new JPanel(new BorderLayout(5,5));
list1 = new JList<Object>(mainData);
list1.setVisibleRowCount(10);
next = new JButton("Next");
next.addActionListener(this);
controls.add(new JScrollPane(list1));
controls.add(next, BorderLayout.PAGE_END);
controls.setBorder(new EmptyBorder(25,25,0,0));
add(controls);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("Next")) {
int index = list1.getSelectedIndex();
System.out.println("Index Selected: " + index);
String s = (String) list1.getSelectedValue();
System.out.println("Value Selected: " + s);
}
}
public void createAndShowGUI() {
//Create and set up the window.
JFrame f = new MTGSAMPServerReference();
//Display the window.
f.pack();
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(1200, 800);
f.setLocationRelativeTo(null);
list1.setSize(250, 250);
list1.setLocation(0, 0);
next.setSize(75, 25);
next.setLocation(251, 276);
MTGSAMPServerReference.this.repaint();
}
protected void paintComponent(Graphics g) {
//super.paintComponent(g); << Can't seem to get this to work.
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.drawRect(0, 0, 50, 50);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
MTGSAMPServerReference gui = new MTGSAMPServerReference();
gui.createAndShowGUI();
}
});
}
}
I have worked with paintComponent() before, but still can't seem to figure out what I am doing wrong. I know that it has got to be a simple fix, but can't spot it for the life of me. Any ideas?
Any and all help is appreciated.
Thanks in advance!
Use the #Override annotation on your paintComponent method for a rude surprise. This is why using this annotation is very helpful, since it will flag you at compile time if you are not overriding a method when you think that you should be.
Solution: never "paint" in a JFrame for many reasons. Instead do what the tutorials tell you to do -- paint in a JPanel or JComponent's paintComponent(...) method. If you search this site you will find that we have told many folks here the same thing, and in fact I suggest that you do just that. I wouldn't be surprised if this question is closed as a duplicate since this is a fairly common question.
Note this won't "work" (and actually won't compile):
super.paintComponent(g); << Can't seem to get this to work.
for the same reason -- there is no super.paintComponent(g) for a JFrame.
Also, regarding,
I have worked with paintComponent() before, but still can't seem to figure out what I am doing wrong.
But if you look at your prior code, you'll see that this method was never used directly in a JFrame, and nor should it.
paintComponent() is a member of the JPanel class, not the JFrame class in which you are trying to call it.
That is why you are unable to call super.paintComponent(Graphics g). The compiler thinks you are creating your own completely unrelated method that also happens to be called paintComponent().
Create a class that inherits JPanel and copy and paster your paintComponent() method there.
Like Hovercraft Full Of Eels commented, you can check that you are correctly overriding methods by adding the #Override tag directly over the method header; if you receive an error, you are doing something wrong.
For more information about JPanel and JFrame, see my answer to this question.
Related
I'm trying to draw a line in a JFrame, but line isn't drawn.
I tried to use the method setOpaque(true) for contentPane, lblNewLabel and l but nothing changed. I also tried call repaint(); outside this class but the situation is still the same. Here's the code:
public class DrawingClass extends JFrame
{
private JPanel contentPane;
public DrawingClass(int n, int s, int p) {
Line l= new Line();
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setBounds(700, 300, 480, 640);
contentPane = new JPanel();
contentPane.setOpaque(true);
setResizable(false);
setContentPane(contentPane);
contentPane.setLayout(null);
JLabel lblNewLabel = new JLabel("");
lblNewLabel.setIcon(new ImageIcon("image.png"));
lblNewLabel.setBounds(0, 0, 480, 640);
contentPane.add(lblNewLabel);
l.setBounds(0,0,480,640);
contentPane.add(l);
repaint();
}
class Line extends JPanel
{
public void paintComponent(Graphics g) {
g.setColor(Color.BLUE);
g.fillRect(10, 10, 15, 12);
}
}
}
I expect a little line on the top left of the JFrame, above the background wallpaper, but nothing happen. It shows only the wallpaper.
There are several errors in your code:
You're extending JFrame but you're not changing its behavior, so why are you doing that? JFrame is a rigid component, so it's never a good idea to extend from it, build your GUI based on JPanels instead. See: Extends JFrame vs. creating it inside the program
Don't explicitly set the size of the JFrame, call pack() on it and instead override getPreferredSize from the JPanel, see: Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?
You don't need to call setOpaque(...) in this case.
Don't use a null-layout, it might lead to strange errors, because null Layout is Evil and frowned upon
We don't have access to your image so we cannot test the ImageIcon and it's also not related to your question. However you should load your images as resources
Don't explicitly set the bounds of each element, this is related to point (4) and you should use a Layout Manager or combinations of them to get your desired GUI.
Don't call repaint() that way, it has no effect, it is supposed to repaint your UI when there's a change in it. However there is no change at the start of your program.
You're breaking the paint-chain by not calling super.paintComponent(...) inside your paintComponent(...) method. Check the Tutorial on Custom Painting in Swing so that you learn how to do it properly
And be careful, as paintComponents(...) (With a trailing s) is different from paintComponent(...) (Look at your title)
So, after doing all of the above changes, we get to this simple program:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class DrawingClass {
private JPanel contentPane;
private JFrame frame;
public static void main(String args[]) {
SwingUtilities.invokeLater(() -> new DrawingClass().createAndShowGUI());
}
public void createAndShowGUI() {
frame = new JFrame(getClass().getSimpleName());
Line line = new Line();
frame.add(line);
frame.setResizable(false);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
class Line extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(10, 10, 15, 12);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(480, 640);
}
}
}
Which produces the following output:
I'm trying to understand what actually paints components in Swing. I read this article about painting in AWT and Swing and now tried to write the following simple program:
//A simple wrapper to understan how paint() works
public class MyButton extends JButton{
/**
* Default serialVersionUID
*/
private static final long serialVersionUID = 1L;
private final JButton jButton;
public MyButton(JButton jButton) {
this.jButton = jButton;
}
#Override
public void paint(Graphics g){
jButton.paint(g);
}
}
But when I try to add MyButton to frame
JFrame frame = new JFrame("Hello swing");
JPanel panel = new JPanel();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.add(new MyButton(button));
frame.add(panel);
it renders nothing
But after deleting
#Override
public void paint(Graphics g){
jButton.paint(g);
}
it renders the empty button:
QUESTION: Why does it behave that way? Why does the delegating cause rendering to fail?
First of all when you post a question you should post a proper SSCCE that demonstrates the problem. We can't copy/compile random lines of code. Until a problem is solved, you don't know what part of the code is causing the problem.
Why does the delegating cause rendering to fail?
My guess would be that the size of the button is (0, 0) so there is nothing to paint.
When you get rid of the custom paint method, then the real button can be painted because it does have a size because the layout manager has done its job.
public class Demo extends JFrame{
public static void main(String[] args)
{
JPanel panel = new JPanel();
getContentPane().setLayout(new BorderLayout());
panel.add(new JButton("Test"));
this.getContentPane().add(panel, BorderLayout.CENTER);
this.setSize(200,200);
this.setVisible(true);
}
}
If you want to add UI Components do it like that, don't use paint in any way.
If you want to paint for example a rectangle follow this tutorial: https://docs.oracle.com/javase/tutorial/uiswing/painting/
Your paint method does not draw the MyButton object, but instead draws the JButton which is member of your class. The problem now is, that this Button has not been added to the panel and so it's drawn on nothing. By removing your paint method, super.paint(g) is called because your class has no paint method and so your button, but not the member JButton is drawn.
I hope you understand what I am trying to explain to you.
I am new to Java. I am trying to make text appear on a JLabel after a virtual button is clicked. However, I can't seem to find a solution to this. When I use the if statement it won't work. How can I make the text appear after the button was pressed?
import java.awt.event.*;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JButton;
import javax.swing.JPanel;
import java.awt.Graphics;
public class autos extends JLabel implements ActionListener
{
private static final long serialVersionUID = 1L;
int now=0;
public autos(){
JLabel l=new JLabel("");
JFrame f=new JFrame("the title");
JPanel p=new JPanel();
JButton b=new JButton("click");
f.setBounds(400,500,400,500);
f.setVisible(true);
p.add(b);
f.add(p);
b.addActionListener(this);
p.setVisible(true);
p.add(l);
f.add(l);
if(now==1)
{
l.setText("hello");
l.setOpaque(true);
}
p.setBounds(200,200,200,200);
l.setBounds(100,100,100,100);
l.setOpaque(true);
f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.drawRect(200,300,89,90);
g.drawString("buv",80,80);
repaint();
}
public static void main(String[] args)
{
new autos();
}
#Override
public void actionPerformed(ActionEvent e) {
now=1;
System.out.println("worked");
System.out.println(now);
}
}
You are setting up your label in your constructor code, which executes before the event handler which sets the now variable to 1.
What you can do is to move this code:
l.setText("hello");
l.setOpaque(true);
To here:
#Override
public void actionPerformed(ActionEvent e) {
now=1;
System.out.println("worked");
System.out.println(now);
l.setText("hello");
l.setOpaque(true);
}
This is a minimally working example of updating the text on button click. See the comments in code for the variety of changes.
import java.awt.event.*;
import javax.swing.*;
/* There is no need to extend label here. */
// public class autos extends JLabel implements ActionListener
public class autos implements ActionListener {
private static final long serialVersionUID = 1L;
int now = 0;
// this is now a class attribute, accessible to any method of this class.
JLabel l;
public autos() {
// this no longer declares a local variable, but instead
// creates an instance of the class attribute.
l = new JLabel("");
JFrame f = new JFrame("the title");
JPanel p = new JPanel();
JButton b = new JButton("click");
f.setBounds(400, 500, 400, 500); // this needs fixing!
f.setVisible(true);
p.add(b);
f.add(p);
b.addActionListener(this);
p.setVisible(true);
p.add(l);
f.add(l);
p.setBounds(200, 200, 200, 200); // this needs fixing!
l.setBounds(100, 100, 100, 100); // this needs fixing!
l.setOpaque(true);
f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
}
/* I cannot tell what this was trying to achieve, but whatever it was,
this was the wrong way to go about it. Never call repaint() from within
the paintComponent method as this creates an infinite loop! */
/*
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawRect(200, 300, 89, 90);
g.drawString("buv", 80, 80);
repaint();
}
*/
public static void main(String[] args) {
// Swing GUIs should be created and updated on the EDT
new autos();
}
#Override
public void actionPerformed(ActionEvent e) {
/* This logic is questionable, but it denpends on what you are trying
to achieve here, something I'm not clear on. */
now = 1;
if (now == 1) {
l.setText("hello");
l.setOpaque(true);
}
System.out.println("worked");
System.out.println(now);
}
}
Edit
You added two comments at the setBounds part saying this needs fixing!. There I tried to resize the JPanel and JLabel but it's obvious it doesn't work.
How should I proceed here?
Here are some 'copy/paste comments' I regularly use:
Java GUIs have to work on different OS', screen size, screen resolution etc. using different PLAFs in different locales. As such, they are not conducive to pixel perfect layout. Instead use layout managers, or combinations of them along with layout padding and borders for white space.
See Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing? (Yes.)
Provide ASCII art or a simple drawing of the intended layout of the GUI at minimum size, and if resizable, with more width and height.
Now, to expand on those comments for this use-case:
That is advice I offer for people trying to make a null layout, but it also applies here.
This is relevant because there is one component (the custom painted one, if it exists) that needs to #Override the getPreferredSize(..) method to return a size as a suggestion to the layout managers or for packing the top level container.
The 3rd comment is because it is hard to advise how to code this GUI without knowing the end effect that is required.
Of course, I should point out: Each SO thread is expected to be a single, specific question. I really should have told you to start a new question on the other matters, but let it slide for this edit.
I have been playing around with Java's 2d painting tools and have hit a snag. I am attempting to move the objects. Here is the code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Test extends JPanel{
private int[] location = new int[2];
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.red);
g.fillArc(location[0], location[1], 100, 100, 45, 90);
g.setColor(Color.black);
g.fillArc((location[0]+50-10),(location[1]+50-10), 20, 20, 0, 360);
new Timer(2000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setLocation((location[0]+50),50);
repaint();
System.out.println("repainting");
}
}).start();
}
public void setLocation(int x, int y){
this.location[0] = x;
this.location[1] = y;
}
public static void main(String[] args){
JFrame jf=new JFrame();
jf.setDefaultCloseOperation
(JFrame.EXIT_ON_CLOSE);
jf.setPreferredSize(new Dimension(300,500));
jf.setLocation(100,100);
jf.add(new Test());
jf.pack();
jf.setVisible(true);
}
}
This only paints one of the two objects to the screen... it seems to be the second one as when I change the parameters of setLocation on [1] the one object it does paint moves. Any thoughts? Thanks
Edit: Edited above code to reflect what was said below.
You are adding two components to the JFrame in a default way. This will add the components BorderLayout.CENTER and so the second component will cover and obscure the first. You will want to read up on layout managers to fix this. Also read up on Swing Timers for simple animations, since your code, even if written correctly would do no animation.
If you want to move the drawing, then
Use only one Test JPanel
Override JPanel's paintComponent(...) method, not paint(...) method.
call the super.paintComponent(g) method first thing in your paintComponent method override.
Give the Test JPanel public methods to allow outside classes to change the location without having them directly futz with the field. Make the location field (name should begin with a lower-case letter) private just to be safe.
Use a Swing Timer to periodically call this method and change location, then call repaint() on the JPanel.
I've looked at the other examples on here but the revalidate() or repaint() after I create all of my components. I've also tried the this.setVisible(this); and that didn't work. I've tried creating my components in a createGUI() method and running that from the init() method within a try/catch statement.
EDIT
I tried all of your examples, as you can see in the comments. But from what everyone has said why does this now work?
package basic;
import java.awt.*;
//import java.applet.*;
import java.applet.Applet;
import javax.swing.*;
import java.awt.event.*;
public class Shapes extends Applet implements ActionListener
{
JButton rectBtn = new JButton("Rectangle");
JButton circBtn = new JButton("Circle");
JLabel rectLbl = new JLabel("Rectangle"), circLbl = new JLabel("Circle");
JLabel widthLbl = new JLabel("Width"), heightLbl = new JLabel("Height");
JTextField widthTF = new JTextField(6), heightTF = new JTextField(6), colorTF;
boolean rectOn;
boolean circOn;
int x,y, width, height;
String xcord, ycord, widthSize, heightSize;
public void init()
{
JPanel TotalGUI = new JPanel(new GridLayout(2,0));
TotalGUI.add(rectLbl); TotalGUI.add(rectBtn);
rectBtn.addActionListener(this);
TotalGUI.add(circLbl); TotalGUI.add(circBtn);
circBtn.addActionListener(this);
TotalGUI.add(widthLbl); TotalGUI.add(widthTF);
TotalGUI.add(heightLbl); TotalGUI.add(heightTF);
add(TotalGUI, BorderLayout.WEST);
//this.setVisible(true);
TotalGUI.repaint();
//pack();
}
//#Override
public void paintComponent(Graphics g)
{
//super.paintComponent(g);
//Graphics g2 = getGraphics();
if(rectOn)//if Rectangle has been pressed
{
g.drawRect(x,y, width,height);
}
if(circOn)//if Circle has been pressed
{
g.drawOval(x,y, width, height);
}
}
public void actionPerformed(ActionEvent e)
{
if(e.getSource() == rectBtn)
{
rectOn = true;
}
if(e.getSource() == circBtn)
{
circOn = true;
}
//Reads coordinates and sizes as Strings and converts to integers
try{
widthSize = widthTF.getText();
width = Integer.parseInt(widthSize);
heightSize = heightTF.getText();
height = Integer.parseInt(heightSize);
}
catch(Exception err) { JOptionPane.showMessageDialog(null, "Enter a number!"); }
repaint();
}
}
Thank you for your help!
The main problem with your original code was that your overrode the paint() method without invoking super.paint(g). When you changed that method to paintComponent() the code worked because that method doesn't even exits in an Applet so it was dead code.
The problems with your code:
You should be extending JApplet for a Swing applet
You should NOT override the paint() (or paintComponent()) method of an Applet. If you need to do custom painting then you override the paintComponent() method of a JPanel (or JComponent) and add the panel to the content pane of the applet.
The code should be executed on the EDT.
The applet will display the components automatically, there is no need to invoke repaint)
Never use getGraphics() to do custom painting. Use the Graphics object of the paintComponent() method.
When you attempt to override a method don't forget to use the #Override annontation before the method signature to make sure you override the method correctly.
Start by reading the Swing tutorial for a better explanation and working example. Start with the sections on:
How to Make Applets
Performing Custom Painting
You should call repaint() on TotalGUI.
The reason your gui refreshes after resize, is that resize automatically calls repaint() for you. However, if you want you gui changes to appear instantly, you should call repaint();
A preferred approach, however, is to use in your totalGUI's paint(Graphics g)/paintComponent(Graphics g) method/s:
super.paintComponent(g);
as described by these posts:
JPanel repaint issue
http://www.sitepoint.com/forums/showthread.php?273522-super.paintComponent()