Develop Reference

Drawing Image on JPanel as Background

im trying to insert a gif as a background for my app. I cut all frames and renamed them f1/f2/f3/f4/f5/f6/..... I would use a timer to change the frame so it looks like an animation.
There is a total of 42 frames, so f42.png is the last frame. The code seems to be fine, but there is no result. Any help?
Global variables:
private String backgroundFile;
public JPanel backgroundPanel, areaImage;
private BufferedImage background;
private javax.swing.Timer timerBackground;
Constructor where the Timer is initialized:
public Game()
{
entryWindow();
this.setLayout(null);
timerBackground = new javax.swing.Timer(100,this);
timerBackground.stop();
}
Animation method code:
private void backgroundAnimation()
{
backgroundFile = "f"+backgroundNum+".png";
try{
background=ImageIO.read(new File(backgroundFile));
}
catch(IOException e)
{
}
backgroundPanel = new JPanel()
{
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(background, 0, 0, 1100,800,null);
}
};
backgroundPanel.setBackground(Color.BLACK);
backgroundPanel.setBounds(0, 0, 1100, 800);
if (backgroundNum>42)backgroundNum++;
else backgroundNum=1;
add(backgroundPanel);
backgroundPanel.setVisible(true);
}
Action Listener for timer:
if (ae.getSource() == timerBackground)
{
backgroundAnimation();
}

In order to show JPanel, you need to add it to something like JFrame with an BorderLayout for instance, then you need to show the JFrame. JFrame is a application window, the JPanel can be only added and drawn on Window, it can't be viewed without something on which it can draw (like app Window). Beside that you don't need to create new JPanel each time the animation changes, just make a setter for the current image to show, and after assigning the image call repaint(), the ImagePanel could be like this:
public class ImagePanel extends JPanel {
private volatile BufferedImage image;
public void showImage(BufferedImage image) {
this.image=image;
repaint();
}
public void paintComponent(Graphics g) {
g.drawImage(image, 0,0,getWidth(),getHeight(),null);
}
}
add it to your JFrame at application start, also set the LayoutManager of JFrame to BorderLayout preferably, because without that your panel will have size(0,0) since you didn't set it, and it could be one of reasons why you don't see it (you can't see something which is 0 pixel in size, can you?).
Then in your timer just call the ImagePanel method public void showImage(BufferedImage image) with the image to show. If that's don't solve your problem, then post your entire code. As without that i'm just guessing, but those are common problems, so there's big chance you hit something from this.

I can see a few issues here
1. Assuming your Game class is extending JFrame, You need to add the JPanel to the ContentPane of the JFrame. Use one of the approaches setContentPane(backgroundPanel); or getContentPane().add(backgroundPanel)
You are not using a LayoutManager. So either use a LayoutManager or set the Size of the 'JFrame' and 'JPanel' explicitly using setBounds() method. I would recommend using a LayoutManager.
The JPanel or any Component for that matter does not automatically refresh itself. Once you change the image, you need to call repaint() on your JPanel.
You dont need to create a new JPanel every time you change the image. Just extend the JPanel and override the paintComponent()like you have done. Use the Timer to change the image of that single instance and call repaint() with every change.
The complete example, with hat output you are seeing will help understand the problem better and give you a solution. Please see How to create a Minimal, Complete, and Verifiable example

There are multiple problems here, but first let me answer your question:
You are creating a new JPanel and add it to the Game on every run through. That is wrong, since you add infinite panels to your Game
Also in your if/else you have a wrong condition. You increase the iterator when it is greater 42. You probably mean lesser than 42.
Here is how I would do it:
public class BackgroundPanel extends JPanel {
private int currImage = 0;
private BufferedImage[] backgroundImages;
public BackgroundPanel() {
int numberOfImages = 42;
backgroundImages = new BufferedImage[42];
for(int i = 1; i <= numberOfImages; i++) {
String backgroundFile = "f" + i + ".png";
backgroundImages[i] = ImageIO.read(new File(backgroundFile));
}
}
public void nextImage() {
/*if(currImage <= 42) currImage++;
else currImage = 1;*/
if(currImage++ > 42) currImage = 1;
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(backgroundImages[currImage], 0, 0, getWidth(), getHeight(), null);
}
}
You need to add this panel ONCE to your "Game":
//Somewhere in your Game
private BackgroundPanel backgroundPanel;
...
...
public Game() {
entryWindow();
this.setLayout(null);
backgroundPanel = new backgroundPanel();
backgroundPanel.setSize(getWidth(), getHeight());
add(backgroundPanel);
timerBackground = new javax.swing.Timer(100,this);
timerBackground.stop();
}
Your timer:
if (ae.getSource() == timerBackground) {
backgroundPanel.nextImage();
}

It's easier to put the background on JLabel. It requires only 3 lines of code and works fine! :) Hope it helps for anyone that will have the same problem :)
All you have to do is copy this code, change the name (i have all pictures in a folder called "Images") with any kind of Java supported picture/video/.... (just change the suffix .gif to your file format) and at last the size. Good luck! :)
public JLabel backgroundGIF;
backgroundGIF = new JLabel(new ImageIcon(getClass().getResource("Images/background.gif")));
backgroundGIF.setBounds(0,0,1100,800);
add(backgroundGIF);

overriding JComponent methods

after running this code appears windows sized 0x0.
i can fix it by writting "f.setSize(640, 480);" in the main method.
i hear its bad pratice, so.. is there way to make this overriding work?
public class Gui {
public static void main(String[] args) throws IOException {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().setBackground(Color.BLACK);
f.add(new DrawingPad());
f.setVisible(true);
}
}
class DrawingPad extends JComponent{
Image img = new ImageIcon("res/icon.jpg").getImage();
Dimension d = new Dimension(640, 480);
public void paintComponent(Graphics g){
g.drawImage(img, 50, 50, null);
}
#Override
public Dimension getPreferredSize(){return d;}
}

Call f.pack() before making the frame visible.
Quote from the javadoc:
Causes this Window to be sized to fit the preferred size and layouts of its subcomponents. The resulting width and height of the window are automatically enlarged if either of dimensions is less than the minimum size as specified by the previous call to the setMinimumSize method.
Also, you should not use swing components from the main thread. Only from the event dispatch thread. Read http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html

How do I call a graphical class in Java?

I've been coding a simulation for a traffic flow network in Java, and the class that is supposed to graphically model the network looks as follows:
public class Map extends JPanel {
BufferedImage truck1;
public Map() throws IOException{
truck1 = ImageIO.read(getClass().getResource("Truck.png"));
}
protected void paintcomponent (Graphics g) {
super.paintComponent(g);
g.drawImage(truck1, 50, 100, 300, 300, this);
}
}
In my main() function, I instance the object as follows at the very beginning of the function:
Frame F1 = new Frame();
F1.setLayout(new FlowLayout());
F1.setSize(500,500);
F1.setVisible(true);
Map map = new Map();
map.setOpaque(true);
F1.add(map);
F1.setVisible(true);
However, when I run the program, the only output is a blank window with a slightly darker grey small square exactly in the middle at the top of the window. I've added Truck.png to the project, and I can't see any reason why it shouldn't display properly. What am I doing wrong?

Components should be added to the frame before the frame is made visible.
You are using a FlowLayout for your frame. A FlowLayout respects the preferred size of all components. Your Map class doesn't have a preferred size so the size defaults to (0, 0) so there is nothing to paint. Override the getPreferredSize() method of the Map class to return the appropriate size for the component.

Basic paintComponent not being called by repaint()?

I'm using the book Headfirst java, and I have put together a program that I thought would compile fine. But when the window is created, the background or oval isn't showing up.
import javax.swing.*;
import java.awt.*;
public class setup {
public static void main(String[] args) {
JFrame f = new JFrame();
System.out.println("Created Frame");
JPanel myJPan = new JPanel();
System.out.println("Created Panel");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(300,300);
System.out.println("Set Size");
f.setLocationRelativeTo(null);
f.setContentPane(myJPan);
f.setVisible(true);
System.out.println("Made Visible");
myJPan.repaint();
}
// #Override ???
// "protected void" ??
public void paintComponent(Graphics g) {
// super.paintComponent(); ???
g.fillRect(0,0,300,300);
System.out.println("painted");
int red = (int) (Math.random()*255);
int green = (int) (Math.random()*255);
int blue = (int)(Math.random()*255);
System.out.println("Got Random Colors");
Color randomColor = new Color(red, green, blue);
g.setColor(randomColor);
System.out.println("Set Random Colors");
g.fillOval(70,70,100,100);
System.out.println("Filled Oval");
}
}

See my answer to this question . It provides an example of the proper way to set up a JPanel.
Like other commenters/answerers have stated, paintComponent belongs to the JPanel class. What this means for you is that you need to create a class (let's call it MyPanel) that extends JPanel. (Note: you can either make a new .java file for this class if you are in eclipse or make it an inner class, it should work either way).
Once you have done that, simply cut the paintCOmponent method from your setup class and paste it into your new MyPanel class.
And finally, within your setup class, instead of creating a JPanel object, create a MyPanel.
Basically, this MyPanel object is your own custom JPanel object that does whatever you want it to! It's almost like magic!
On a side note (this will hopefully help you better format your code in the future), and hopefully more experience Java programmers will agree with me on this, I would also recommend that you create your own custom JFrame object as well. Only for this one, you won't override any methods other than the constructor. Instead, in your constructor for this custom JFrame, you will make all of the specifications for the window (such as your setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE and setSize(300,300) calls). This constructor is also where you will instantiate your MyPanel object (as well as any other component objects in your window) and maybe give it a few ActionListeners.
Then, in another class (such as your setup class), have a main method that has 1 line: one that instantiates a 'JFrame` object. This will automagically create the window.
Oh and one more vitally import thing: you must call setVisible(true) on your JFrame if you want it to display. I am not sure why it is setup that way.

BG image with Swing without overriding paintComponent

I'm currently designing a menu with several screens with multiple buttons on each screen. To use buttons on top of the background image, which is in a jLabel (by default, I can't put buttons on TOP of the jLabel), I used GridBagLayout with two panels/menu screen, one panel containing the buttons (opaque = false) and one panel with the background image, or jLabel. In order to switch the current panels being displayed, depending on where the user is in the menu, I made each menu screen (aka. every 2 panels) in separate methods, not classes.
Now, I've come to the point where I'm working on parts of the interface that are unnecessarily complicated, and I don't feel GridBag will serve my purposes, so I was wondering if there was a different way to draw my background image, still being able to use my buttons on top of the image.
The most popular way I looked up was overriding the paintComponent method, but I can't do that, since I've made my JPanels in separate methods, not classes. They're all contained in my original JFrame.
Help would be greatly appreciated, thank you!
Just added this code, but my background remains white for some reason? Trying the other suggestion right now, thanks guys!
private void mainPanel() {
icon = new ImageIcon(getClass().getResource("/phantasma/menuv1.png"));
mainContainer1 = new javax.swing.JPanel() {
#Override
protected void paintComponent(Graphics g) {
g.drawImage(icon.getImage(), 0,0, null);
super.paintComponent(g);
}
};

BG image with Swing without overriding paintComponent
I have no idea why all the postings suggest doing custom painting for this. You would only do custom painting if you need to automatically scale the background image.
If you want the image painted at its real size then use a JLabel.
I can't put buttons on TOP of the jLabel),
Sure you can. Just set a LayoutManager for the JLabel and then you can add any component to it the same way you add components to a panel.

In my comment above I state:
You can always create an anonymous inner JPanel-derived class and override the paintComponent method there if need be.
As an example of what I mean, you can override paintComponent in any JPanel that you create whether it's derived from a stand-alone class or created within a method. For e.g.,
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.*;
public class AnonInnerPanel {
private static void createAndShowGui() {
JPanel mainPanel = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 200);
}
};
JFrame frame = new JFrame("AnonInnerPanel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}