I would like to have a vertical line drawn over a JPanel, and make it glide over it, without this process invoking the paintComponent() of the JPanel. I have thought of using the GlassPane but I don't think it is the correct way since there are other components in the frame containing the JPanel, and so it isn't specific to it (and I'm not actually sure it wouldn't call the paintComponent() anyway).
Any ideas?
Maybe you should be using Layered Panes if you just want to isolate the line painting code from the rest of your painting code.
If your painting code is expensive, then maybe you should be creating a BufferedImage and then just redraw the image in your paintComponent() code. This is faster than repainting from scratch every time.
Even with a GlassPane the underlying component would have to be repainted at some point. There is not a nice way to avoid a paintComponent call to JPanel.
However, the JPanel should not be doing things in paintComponent other than painting. If you are trying to avoid calling it, then it sounds like you have something in the paintComponent method that needs to be changed or cached somehow.
Is there a reason why you do not want to call the paintComponent() method on the JPanel? Repainting the object to render the line gliding over it will most likely be the easiest solution.
Related
How do I convert a paintComponent to something that I can manipulate with a layout in a JFrame?
So, I'm running into an issue. I haven't really been taught (and don't have access to a book) how to use layouts/GUI stuff in my courses yet.
My issue is this: I have a program that the user inputs a number. Based on this number, the program calculates a circle and draws it out with a paintComponent method that has a for loop inside of it. The "pixels" that the circle is drawn with are actually fillRect methods. The current method of getting a user-input that I am using is a JOptionPane showInputDialog. This is MOSTLY fine, but I want the user to be able to select from a set of pre-defined numbers. Somebody suggested that I use a JComboBox, but I don't know how I would convert the paintComponent to something that would be usable by a layout manager (which a JComboBox must use, as far as I've learned). I know the dimensions of the paintComponent (805px by 805px) and there is no situation where it will change. If I could get some help with this bit, I am confident that I can figure out using a layout manager myself.
Another way to paint (besides custom painting) is to paint to a BufferedImage. The image can then be displayed in a JLabel.
Examples:
Painting in a BufferedImage inside Swing A fairly complicated one.
Dynamic Graphics Object Painting Another one.
Yet another one.
You don't know the dimensions of paintComponent because it's a method, and methods don't have dimensions. You probably know the dimensions of a JPanel or a JFrame or whatever your component is.
You should separate the panel where you do the painting, and a different panel which would contain any comboboxes or other inputs you decide to put in. That way you can keep your drawing panel as is, and they won't interfere with each other. You'll want to search for the tutorial on LayoutManagers.
So the intial setup for this issue is that there's a JDialog, and inside that I've placed a JPanel that would house the rest of the components (since painting the JDialog itself is apparently a bad idea). This JPanel has an overriden paintComponent(Graphics g) method that only paints the background and adds a faint border for aesthetic purposes.
Now inside that is a series of JPanels that categorize the contained form components, and each JPanel has an overridden paintComponent(Graphics g) as well, painting a semi-transparent background.
Inside each of those JPanels is where I start to have some issues, presumably with transparency. I have JTextFields, JCheckBoxes, JLabels, JSliders, etc inside these panels, and when you interact with one (hover, click, etc), the background goes from transparent to opaque, with an occassional ghosted image from another field (which appears slightly random sometimes). I'm using a custom LAF called Web, but I tested with other built-in LAFs and the same thing happens.
Is this a glitch with Java or did I mess something up? If so, how can I patch this up? I can paste code fragments later if necessary, but I've used several custom classes and nine-patch style image stitching which may make the code fragments hard to follow. Thanks in advance!
If you are painting components with a transparent background it is very important that the component is marked as transparent (setOpaue(false)) so that the repaint manager knows that it must paint the components below it.
It is also very important that when you are performing custom painting that you call super.paintComponent first.
This is especially important in the case of transparent components, as this prepares the Graphics context for painting.
Graphics is a shared resource. All the components painted in your window will share the same Graphics object, meaning that if you don't allow paintComponent to first prepare it, then you will see what was previously painted on it.
Is it possible to position a BufferedImage that is drawn by the PaintComponent method? For instance, if it is an image drawn in the overridden PaintComponent method, is it possible to use a layout manager (i.e. BoxLayout, BorderLayout, FlowLayout, GridBagConstrains, GridBagLayout) for that? Or do you have to translate the image to a JComponent (i.e. JLabel)?
Is it possible to position a BufferedImage that is drawn by the PaintComponent method?
Yes it is possible. You would get the dimensions of the drawing component in its paintComponent(...) method via getWidth() and getHeight(), and then use those dimensions to position things. Also, the Graphics#drawImage(...) method has overloads that simplify this for you.
For instance, if it is an image drawn in the overridden PaintComponent method, is it possible to use a layout manager (i.e. BoxLayout, BorderLayout, FlowLayout, GridBagConstrains, GridBagLayout) for that?
No, not directly since layout managers are for laying out child components only.
Or do you have to translate the image to a JComponent (i.e. JLabel)?
You could easily do that -- put your Image in an ImageIcon and that in a JLabel, and position that in a container using whatever nested components and their layout managers that work best.
Edit 1
You ask in a comment:
How do I get the dimensions?
Again, inside of the paintComponent(...) method simply call getSize() or getHeight() and getWidth() and you've got your dimensions. Nothing could be easier really.
And could you provide a snippet of code of your first instance paintComponent(...)?
I would suggest that you go first. Show us some of your code that compiles and runs, and tries to demonstrate your problem, and let's work with that.
I have a canvas that is drawing everything in a paintComponent() method.
Is it possible to draw outside of paintComponent (without calling a method within paintComponent?)
If so how do you go about doing this?
It depends what you mean and why you need it. For example, it is possible to create a BufferedImage, get the Graphics2D object, Graphics.paint() everything that should be on the image, then drop the image into a JLabel.
But since I do not know what you are trying to achieve (as opposed to what you are trying to do) I cannot know if that answer solves the unstated problem.
I found out how to solve this issue.
What I did was make JPanel an inner class to my JFrame class.
In JPanels paintComponent I had it calling a method from the outer class which did some updating of the graphics, by passing paintComponents Graphics2D object.
This has allowed me to paint "outside" of paintComponent, just as I needed.
Hi
I have a panel on my frame which you can draw something on it.and also i have a "clean" button which clean my panel completely.but I don't know how can I do this work ?
I use netbeans .
thanks
Well, this really depends on the how you have got your panel to draw. Usually, someone would override the paint method of the panel and draw the screen based on Points or other geometric elements.
To clean the panel, you would need to clear the points, and then force a redraw, using the panel's repaint() method.
This however really depends on how you have implemented the first part of your solution. We really need more information to give a more precise answer.
Use the clearRect method to draw the background color over the whole area
Custom Painting Approaches shows two common approaches to do custom painting. It also shows the common approaches to clear the painting.