I have written some lines of code that supposed to show the image as a label in the JFrame. Here is the code.
ImageIcon image = new ImageIcon("funny.jpg");
JLabel label = new JLabel();
label.setIcon(image);
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500,500);
frame.setVisible(true);
frame.add(label);
As you were prompted in the comments of your question, I think you should take care of ensuring that the file exists in the specified location, and using getResource for example.
Other than that, you are not utilizing the image's observer pattern for the JLabel. Try setting the ImageObserver of the image to label, like so:
ImageIcon image = new ImageIcon("funny.jpg");
JLabel label = new JLabel();
label.setIcon(image);
image.setImageObserver(label); // <-- Added this line.
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500,500);
frame.setVisible(true);
frame.add(label);
Else, see the corresponding documentation on setImageObserver.
You can also check the corresponding tutorials' section.
That happens to be because, as far as I know, ImageIcon uses a MediaTracker to load the image asynchronously, so when you construct an instance of an ImageIcon it will return without first blocking until the image is fully loaded. Setting the ImageObserver of the ImageIcon will ensure that the ImageObserver you supplied will get notified about the state of loading the image when the state changes. The default implementation of Component (which is an ImageObserver) repaints itself so you will then be able to see the image fully loaded, when it is ready.
As an alternative, you can always use ImageIO#read which will block until the image is fully loaded into memory (but it will only return a single frame in an animated GIF image for example).
I did not test it though, but that's a problem I encouter very often so I think it should work. If it did or it didn't, let me know.
Related
First, to get it out of the way, I absolutely NEED to use heavyweight AWT component with a swing application. I need features from both of them.
The task is simple - render a heavyweight AWT Canvas (or any other element), render OpenGL scene directly onto it, then display Swing buttons above it for the UI.
My problem is that it works half-way.
I don't seem to have problems with Z-ordering. I am using jLayeredPanes for it, and I can move Canvas between layers and it actually works, popping on top or below other elements.
The problems are with transparency.
The thing is, Swing elements have Opaque parameter, and when it's set to false (non-opaque) - it should basically be transparent and you should see the next element below it. In my case, however, the AWT Canvas gets ignored, and you instead only see the next underlying SWING element.
Here are a couple of screenshots. They are taken from a standalone test project of mine. The canvas is stretched to the size of the frame, and in the upper left there is a JLayeredPane dummy element that is a simplified version of the menu.
On the first screenshot, the JLayeredPane's Opaque setting is set to true, and you can see that it's background property is set to Blue color.
On the second screenshot, everything is exactly the same but Opaque is set to false. Instead of displaying whatever is on the Canvas - what gets drawn in empty grey jFrame background.
Lastly, on the third screenshot I have put Canvas into a jPanel instead of leaving it on its own. As you can see, the Panel's orange color is seen through the transparent jLayeredPane, but the Canvas is yet again hidden.
Here's the code for the Frame layout. I would not post my rendering/context code right now
frame = new JFrame("AWT test");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.setPreferredSize(new Dimension(width, height));
canvas = new Canvas();
canvas.setSize(width,height);
//this part exists only in the third example
JPanel p = new JPanel();
p.setSize(width,height);
p.setBackground(Color.orange);
p.add(canvas);
// third example end
JLayeredPane pane = new JLayeredPane();
JLayeredPane paneMenu = new JLayeredPane();
JButton button = new JButton();
button.setSize(20,20);
paneMenu.setSize(200,200);
paneMenu.add(button, new Integer(1));
paneMenu.setBackground(Color.BLUE);
paneMenu.setOpaque(false); //True for the first example
pane.add(p, new Integer(1)); // canvas for the first two examples
pane.add(paneMenu, new Integer(2));
pane.setOpaque(false);
frame.add(pane);
frame.pack();
frame.setVisible(true);
frame.transferFocus();
Could anyone please explain me what is going on and how to do what I need to do.
I will repeat again - I have to use heavyweight component as render target. I am aware of solutions like JOGL's GLPanel which is a lightweight Swing-compatible component. But I tried that method and the performance is really slow, because instead of directly rendering onto it as a context target - it reads FrameBuffer from memory, flips it, and then paints it as BufferedImage. This path is not fitting for the limited resources of an embedded system that I'll be running on.
c0der said: Please post minimal reproducible example
Errrrm.... Didn't I?
Here, you can have it in complete java class form if you want, but I literally changed some variables for constants.
import javax.swing.*;
import java.awt.*;
public class Main
{
public static void main(String[] args)
{
JFrame frame = new JFrame("AWT test");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.setPreferredSize(new Dimension(500, 500));
Canvas canvas = new Canvas();
canvas.setSize(500,500);
canvas.setBackground(Color.RED);
//this part exists only in the third example
JPanel p = new JPanel();
p.setSize(500,500);
p.setBackground(Color.orange);
p.add(canvas);
// third example end
JLayeredPane pane = new JLayeredPane();
JLayeredPane paneMenu = new JLayeredPane();
JButton button = new JButton();
button.setSize(20,20);
paneMenu.setSize(200,200);
paneMenu.add(button, new Integer(1));
paneMenu.setBackground(Color.BLUE);
paneMenu.setOpaque(false); //True for the first example
pane.add(p, new Integer(1)); // canvas for the first two examples
pane.add(paneMenu, new Integer(2));
pane.setOpaque(false);
frame.add(pane);
frame.pack();
frame.setVisible(true);
frame.transferFocus();
}
}
A little update:
I initially suspected that because Swing elements delegate all their drawing to the underlying heavyweight element (In my case JFrame), then what happens is that the frame generates a single frameBuffer for itself and then displays on top of Canvas. Canvas itself is not handled in this generation and thus the frame "covers" over the canvas.
That doesn't seem to be the case. I tried making the JFrame undecorated, all panels non-opaque, and display the picture. The result - canvas is still "cut", and through the hole you can see the underlying IDE menu.
This makes me think that somewhere during Drawing, the Canvas itself detects that it is obscured by another element, and that it doesn't need to draw that area. So it "optimizes" itself and doesn't update these pixels.
Maybe I'm wrong. But here's another screenshot. This is the same example as before, but I took out 3d rendering and simply trying to display Canvas with background set to Red.
Once again, going to reply to my own question.
It turned out that I need to do
setComponentMixingCutoutShape(paneMenu, new Rectangle());
for the menu pane that lies underneath the button. That essentially tells java not to cut out the element from the heavyweight underlying component.
I'm a somewhat novice programmer and I'm have some trouble adding an image to my frame. While I know how to add images generally, this specific case it does not work.
public class Tutorial extends JFrame{
Tutorial(){
JFrame frame = new JFrame("ImageTutorial");
frame.setVisible(true);
frame.setSize(750,850);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
ImageIcon image = new ImageIcon(getClass().getResource("Green Block.png"));
JLabel imagelabel = new JLabel(image);
imagelabel.setBounds(10, 10, 75, 75);
imagelabel.setOpaque(true);
frame.add(imagelabel);
Now, I've located the problem but I don't understand 'why' its a problem. When I remove
frame.setSize(750,850);
the image shows, but when its there it doesn't. How can the frame's size impact the image showing and how can I get around it?
Just curious, logically, what makes you think a frame should be visible before you add any components? Logically speaking, wouldn't it seem right to add your components first, then make the frame visible. It's like displaying a painting in an art gallery even before the painter has painted anything on it. It just makes no sense. I highly doubt setting the size has anything to do with it. IF you don't set the size of the frame, then the frame appears as small as possible. When you resize the frame, it causes a repaint, then showing the label you add. But generally, you want to always set frame visible after all you components are added, to avoid this problem.
Side note: You should stay away from null layouts. You need to learn to use Layout Managers and let them do the dynamic sizing and locating for you.
I would like to know how to put a JLabel on top of another JLabel at a specific position, in a class that extends JPanel in Java. People have asked for help with this before but the solutions that I found do not satisfy me. I am using GridLayout, here is some of my code:
//imports
public class Game extends JPanel implements MouseListener {
Icon background = new ImageIcon(getClass().getResource("/background.jpg"));
Icon foreground = new ImageIcon(getClass().getResource("/foreground.jpg"));
JLabel backgr = new JLabel(background);
JLabel foregr = new JLabel(foreground);
JFrame frame = new JFrame("Game");
public Game() {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridBagLayout());
backgr.addMouseListener(this);
frame.setLayout(new FlowLayout());
frame.setPreferredSize(new Dimension(200,200));
frame.pack();
frame.setVisible(true);
frame.addMouseListener(this);
backgr.setLayout(new BorderLayout());
frame.add(backgr);
backgr.add(foreground);
}
}
(I have a lot of other methods in this class, such as some mouse stuff, but I don't include them here since they are not relevant to this problem.)
Currently the code almost works as I want, the foreground picture is displayed on top of the background, right in the middle of it. But I would like the foreground picture to be displayed at specific coordinates on the background picture. I thought that if I wanted to display the foreground at coordinates (50, 50), I could say backgr.add(foreground, 50,50), this compiles but returns an error when I run the program. Any tips of what to do? It would be really appreciated.
Edit: I discovered that by saying backgr.setLayout(null), backgr.add(foregr) and then foregr.setLocation(50,50), we can do what I was looking for. But since not using a layout manager is discouraged, I am looking for better solutions, so that I can use the coordinates on the backgr Icon.
People have asked for help with this before but the solutions that I found do not satisfy with me since they require me to set the frame layout to null, but I am using GridBagLayout
The frame is using a GridBagLayout.
You are adding the foreground JLabel, so the background JLabel. The background label can use any layout (including null) that you wish.
the foreground picture is displayed on top of the background, right in the middle of it.
That is because you are using a BorderLayout and are adding the foreground to the CENTER, which is the default when you don't specify a constraint.
I keep trying all this example code and none of it works, it always wants me to have a try/catch which means I have to ini. the variable anyway and I am tearing my hair out on the one, I have a jframe the exact size of my image, all I want is it to fill the entire jframe, also, could you make it so that if the image is transparent, that you can see though the entire jframe.
Thanks in advance
frame.add(new JLabel(new ImageIcon("path/to/image.png"));
There is a class called ImageIcon that can be used for images in Swing. Javadocs for ImageIcon
There are also many other ways to use ImageIcon.
From your saying that your example code want's you to use try / catch blocks, I'm guessing you are using the ImageIO class. It returns you with a BufferedImage which is not able to added to the frame. See the ImageIcon class here which you can use with the JLabel
frame.add(new JLabel(new ImageIcon("my_image.png"));
This should work if your image is outside of your jar. If it's included in the jar, use the classloader to get the resource for you.
URL url = getClass().getClassLoader().getResource("my_image.png");
ImageIcon icon = new ImageIcon(url);
frame.add(new JLabel(icon));
Hope this works.
So I am currently making a login screen that has a cool looking background effect made using the Graphics object and a 'game loop'. When I add in a JTextField though, it is seen underneath everything and not above. Is there anyway to to make the graphics draw underneath all components inside of the JFrame?
Here is an image of the graphics:
The text field is there, just underneath everything being drawn to the surface of the frame. I want to somehow reorder this so it draws underneath components.
Here is my current frame code:
frame = new JFrame("Login");
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.getContentPane().setPreferredSize(new Dimension(450, 200));
frame.getContentPane().setBackground(Color.black);
frame.setBackground(Color.black);
frame.setLayout(new FlowLayout());
JTextField user = new JTextField(20);
user.setLocation(100, 200);
user.setVisible(true);
frame.add(user);
frame.pack();
frame.setVisible(true);
frame.createBufferStrategy(2);
buff = frame.getBufferStrategy();
Painter painter = new Painter();
frame.add(painter);
Any help please?
AnimationTest shows one approach. It overrides paintComponent() and invokes super.paintComponent() to ensure that components are rendered atop the background. Click anywhere to position a text field; resize to see how the default FlowLayout works. JPanel is double buffered by default using the existing buffer strategy.