I have a shell that contains a canvas, which in turn draws some text in its PaintListener. The problem is, when I dynamically reduce size of the shell with its setBounds method (this is going to happen every once in a while), the text doesn't get redrawn. In fact, the canvas' PaintListener doesn't get called again.
Is there a way to force repaint? I've tried calling canvas.redraw() but this does not work.
Hmm, it appears that I did not set a layout on the shell. After setting a FillLayout, it works.
Related
Some animations (such as some gif files) only store in each frame the pixels that change from the previous frame. To draw these animations correctly, you have to paint the first frame, then paint the succeeding frames on top of them without erasing the previous frames. JPanels, however, always redraw the background when you call repaint(), erasing the previous frames. Is there a way to prevent a JPanel from redrawing the background? I've been told that calling super.paintComponent(g) in the JPanels paintComponent(Graphics g) method is what redraws the background, but I tried commenting that out and it lead to some strange behaviour, so I'm assuming it does more than just repaint the background.
I'd recommend to build your code upon the already existent code provided by the API instead of messing with it. Just store the image as BufferedImage. This allows you to display it using an ImageIcon, so it's an additional simplification. This allows you to update single pixels without any hassles with the API. If you absolutely insist on excluding the JPanel from the repaint-routine, this question might help.
In general:
Follow the conventional use of the API. If you want to permanently store data of an image, us a BufferedImage. JComponents are supposed to be entirely overridden every time the frame is updated.
Depending on your exact requirement there are two common approaches:
Draw on a BufferedImage and then display the BufferedImage
Keep an ArrayList of Objects you want to paint and paint all the Objects in the list every time paintComponent() is invoked.
Check out Custom Painting Approaches for more information and working examples of each approach.
I have problem with SWT StyledText. I draw new element on StyledText's GC whenever resize or paint event take place. What's more I also force redraw of the whole StyledText in every second.
My problem is that this redraw is sometimes visible because StyledText sometimes funny "blinks".
My question is, is it somehow possible in SWT to redraw only part of the widget, like it is possible in Swing?
You can call redraw(x, y, width, height, false) on the StyleText control to ask for just a part of the control to be redrawn.
I have an application that uses a JLabel and a JPanel. These components have a MatteBorder. When the components are created, the border is the default. When I click on the components, I set the border to a different thickness to make a select appearance. The problem comes when I want to unselect and I set the border to another thickness. This time the border is not modified and looks the same.
I'm not seeing what the problem is, because the first modification of the border thickness works fine.
Although this might be a hacky approach, try to repaint() the view, sometimes it just glitches.
I read this:
http://docs.oracle.com/javase/tutorial/uiswing/components/border.html
when working on my program.
So I wrote a small program for a class. I designed it as a JApplet inside an undecorated JFrame, not in a browser. Other than that, it's a simple drawing program of sorts. You click two points to draw the selected shapes, then it calls a repaint. The problem I'm having is that when you draw while the program has been moved to my secondary monitor, the entire JApplet seems to disappear, only displaying the drawn shape. It only disappears after the 2nd point is selected, so I presume it does this on repaint().
My secondary monitor is using the exact same brand and resolution, even color profile.
Any other technical details, I'm using Java 1.7 (Can't recall which update off the top of my head), Windows 8 Enterprise 64x, using Eclipse's Run button to test.
Thanks in advance for any help!
I am indeed calling getGraphics(); in the init() method of the JApplet..
That is the problem. The Graphics object is a transient thing that will be repainted the very next time the JVM thinks there is any need to do so. That might be triggered by:
Changing the size or location of the window.
Covering it with another program and then removing the covering app.
Adding new components or changing values that are displayed.
See Performing Custom Painting for more details on how to do what you are attempting to achieve. OTOH Swing has a JLabel that can show a BufferedImage. You can use the BufferedImage in the way you want. When it is updated, call repaint() on the label to see the effect.
i wanted to ask, if somebody might have a solution about a problem i face. I am working at an application, which draws an animation - for instance a map with objects moving onto. My problem is, that on top of the drawing, a Jtable, Jlist as well as other Components are also placed.
In my particular example all of those components have been added to the Panel, which holds the map. In result each component gets redrawn as often as good my fps is. Therefore making one of the tables invisible reduces the already high cpu usage of sometimes around 50% to less than 30%.
My question is, how can i avoid calling somewhat static visual contents paintComponent() method, without having the "background" - the map - whited out the menu.
Since the animation redraws permanently the menu is not shown at all, if its separated from the corresponding JPanel.
First thoughts move into following directions:
Clipping - actually not as good as i would like to, since id like to enable moving around the menus.
JLayeredPane - already tried but seemed to turn out, that the paintComponent method of menus still gets called frequently.
JWindow/Internal Frame - had that thought a couple of minutes ago. Having a complete independent container shall be able to handle my regard, or?
I am looking forward, if somebody has an elegant idea, how to fix that and reduce the cpu usage significantly.
Thanks!!
Best regards.
I would create a custom Shape for clip. Use Area class and subtract from the Area all the children components' bounds.
For painting over JComponent(s) placed into JPanel you have look at
JLayer (Java7) based on JXLayer(Java6)
GlassPane, notice all JComponents must be lightweight, otherwise is GlassPane behind heavyweight (J)Components
is possible painting to the JViewport,
EDIT
you have to use Swing Timer for moving with Icon (in the JLabel) placed into JXLayer, GlassPane or JViewport, don't use Runnable#Thread and never, not by using plain Thread.sleep(int)