I want to re-draw my screen (JForm) on button click. Due to some logic its not possible to do with repaint. Is there any other way to do so ?
When i Will click Save Pattern button. Shape should be redrawn.
If any one want to know why i cant do with paint the see this question
Painting is done by overriding one of the paint methods of a component (preferably a component that extends from JComponent and by overriding paintComponent).
One possible solution is to render output to a BufferedImage, which allows you to do offscreen rendering and which you can control and when you want to, simply use Graphics#drawImage or even JLabel to render the BufferedImage to the screen
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How to define multiple JButton actions from a different class
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So the program draws a car and I'm going to make three buttons, one for flash to initialize the flashing ability, one left, to move the car one space to the left and one right, to move the car one space to the right. My question is how do I make it change color each time I press the button? So to sum it up, I don't know how to have an object change it's color each time the button is pressed while flashing is on. I assume I use paint()
Any help would be appreciated.
If you are drawing an image, you will need to load a different image file which is a different color, and then draw that image instead. You will do this inside whatever method you are currently using to draw the car.
If you are drawing a shape or text of some kind, you can call g.setColor() on the graphics object passed to the paint() or paintComponent() method before drawing the shape.
There are any number of ways to do it. The basic requirement though, is to have a Object of some kind which you can tell when it should change color, it would then undertake the appropriate action and update the UI accordingly.
You could...
Use a simple JPanel as the representation of the object and simply call it's setBackground color method when you want it to change color.
This assumes you want to make use of a LayoutManager to position the panel. While it is certainly doable, it will require some thought into the overall design
You could...
Use a JPanel and override it's paintComponent method and paint the color change there. At the simplest level, this is overkill, but if you also want to draw a "car" or an image of "car", then this becomes a little more meaningful, especially if you want to rotate the car based on the direction it's moving
See Painting in AWT and Swing, Performing Custom Painting and 2D Graphics for more details
Flashing
I assume you mean you want the object to be animated in some way and "blink" on and off.
This can easily be accomplished through the use of a Swing Timer which can be used to change the state of a simple flag which changes the way in which the component is rendered.
See How to use Swing Timers for more details
The important concept to take away from this is to create a object which encapsulates the requirements in away which is ease for you to use, so when you enable flashing for example, all you do is call the setFlashing(boolean) method and the object takes care of the rest
I have a component on which I'm drawing a BufferedImage on all the surface.
I would like to draw something more over it, following the mouse when it passes over the area.
To do it, I'm adding a MouseMotionListener on the component and implement mouseMove method. Inside mouseMoved method I'm calling repaint() at the end of the drawing of the drawing of the cursor image. I would like to know if there is a better way to do it, cause the image following the cursor is really small, and I'm repainting every thing each time.
Add a JLabel containing an Icon to the panel with the buffered image.
Then when you move the mouse you just change the location of the label. Swing will repaint the last location so the buffered image shows through, then it will repaint the label at the new location. So let Swing manage the repaint.
Since you know the coordinate of your mouse and the small image you gonna paint over your background, you can optimize like this [pseudo-code]:
void mouseMoved(event) {
lastCoordinates = currentCoordinates;
currentCoordinates = event.coordinates;
image.repaint(lastCoordinates.x, lastCoordinates.y, smallImage.width, smallImage.height);
image.repaint(currentCoordinates.x, currentCoordinates.y, smallImage.width, smallImage.height);
}
that way you only repaint the two regions you actually care about instead of the whole background.
Also, reading the javadoc it seems the code above my actually trigger 2 separate calls to painting stuff, which would be inefficient. You may want to try to pass in a 10 milliseconds value or so to make sure the 2 paints execute together.
Check out javadoc for repaint() that takes 4 and 5 arguments:
4-argument version
5-argument version
In Java, is it possible to use paintIcon to put an icon into a canvas, and then move that icon around using keyboard events like you would a game character?
Once you paint something on the canvas, it stays there, and what was there beneath that location is lost. To "move" the icon, you need to repaint the canvas (or at least what was originally at the location of the icon) and draw the icon at its new position.
This would work better with an applet by registering keylisteners.
and overridding the paint method
I want to create a number of straight lines connecting small circle shapes. then I want to change the color and width of the lines from within my program. I was thinking of using Canvas to do this but there does not seem to be a way to access individual shapes drawn on canvas to change their attributes after they are drawn. What would be an easy way to implement this?
First of all, what version of Java and which UI toolkit? AWT's Canvas is very dumb, it will not even "remember" what you have painted; when you minimize and restore the window, it will send a paint() event because it wants to be repainted.
The easiest way (if you are using AWT and stuck to Canvas) is to have a List of your shapes (either one list for all or one for circles and one for lines, or whatever you like) and make your paint method draw all of them. Then update the objects in your list. When you are done updating, call repaint() on your canvas and it will call paint() for you again.
You don't paint shapes onto a Canvas if you're using Graphics and Graphics2D functions like drawRect, drawPolygon, drawOval, etc. Once they're drawn, they don't exist as shapes anymore. You just have an image with filled-in pixels.
As mihi said, you may have to keep track of the shapes you're trying to draw, then regenerate your image if it changes. Perhaps you could also "unpaint" a shape you're trying to change by painting over it in the background color and repainting the changed shape.
I have to create a special TextFieldUI that draws an image as the background. That image contains some alpha components. However, whenever a character is written in that text field, first it redraws the background and then draws the character. This is fine when the background contains no alpha components, but after a few characters have been typed, the alpha areas sum up to become black.
The only way I can see around this is in the paintBackground method of TextfieldUI (which I'm overriding), I have to first sample the color of the background at that location, paint the entire graphics component that color, and then paint my background.
Does anyone know how to sample the color of a pixel when all I have access to is the Graphics object?
Is there a better way to draw a custom image as the textfield background other than overriding paintBackground in TextfieldUI?
Thanks
I haven't tried it before, but Swing is built on top of AWT, and the Robot class had a way of sampling specific pixels in the AWT
Well, I don't know what your custom code looks like in the paintBackground method, but I would make sure you fill in the text field background before you draw the image.
I'll let you decide if its "better" or not, but you can use the Background Panel which allows you to add an image to a panel. Then you add the text field to the panel (the text field is automatically made non-opaque so the image shows through). Then you add the panel to the GUI.
If that doesn't work then it would be nice to have a demo of your code so we can see whats actually happening.
When you override paintBackground, you're calling the superclass version first, right? It already lays down a background-color rectangle that would give your image a fresh-start.
Rather than 'sampling' the background color, it's probably already correct (the superclass paintBackground code gets it from the parent component if not locally set). If that default is not correct, set it in initial interface construction. (Your field isn't being overlaid on other complicated arbitrary interface of unknown solid colors, is it?)