I am making a program in which there is a square that changes its x and y positions when a key is pressed. The square moves but the the old square is still there. How do I remove/clear everything from a panel before I repaint it? Calling removeAll had no effect.
Presumably your code includes custom paintComponent() logic. The key thing to observe is what does your panel look like when you do not override paintComponent()? An empty (or cleared) panel:
Thus the solution is to invoke the paintComponent() method of the parent type on the panel, before executing your custom paintComponent() logic:
public class CustomPanel extends JPanel {
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g); // first draw a clear/empty panel
// then draw using your custom logic.
}
}
I think this should work.
g.clearRect (0, 0, panel.getWidth(), panel.getHeight());
Also, you could keep the old location of the square and just clear that rather than clear the whole background.
Related
I have the following code being called:
while(true){
view.onTick();
trySleep(55);
}
The onTick() method is described as such:
public void onTick() {
mainFrame.paintAll(mainFrame.getGraphics());
}
Here is where I set up my JFrame and JPanels etc (mainFrame is a JFrame):
private void runProgramSetup(){
JPanel canvas = new JPanel();
canvas.setLayout(new BoxLayout(canvas, BoxLayout.Y_AXIS));
mainFrame.getContentPane().add(canvas);
//create the main game panel
mapPanel = new MapPanel(model, this);
mapPanel.setPreferredSize(new Dimension(TOTAL_FRAME_WIDTH, MAP_PANEL_HEIGHT));
mapPanel.setBackground(Color.cyan);
//create the menu panel
menuPanel = new MenuPanel(model, this);
menuPanel.setLayout(new BoxLayout(menuPanel, 0));
menuPanel.setPreferredSize(new Dimension(TOTAL_FRAME_WIDTH, MENUS_PANEL_HEIGHT));
//add the panels to the window
canvas.add(mapPanel);
canvas.add(menuPanel);
//make both panels visible
mapPanel.setVisible(true);
menuPanel.setVisible(true);
}
Now here is my problem. Everything repaints when repaintAll() is called EXCEPT mapPanel's overridden paint(Graphics g) method:
#Override
public void paint(Graphics g) {
transformedImages.transformAndStoreImages(model);
paintGrid(g);
paintScenery(g);
paintElements(g);
paintDraggedElement(g);
paintUIOverlay(g);
}
It is only called once. That is it. However, every other component continues to repaint. It is only mapPanel that paints once. Here is what is even more strange. I am running on Ubuntu and get this problem. The rest of my team is running on Macs and they do not have this problem. The only way I have been able to solve this is to replace onTick() with two paint calls:
public void onTick() {
mainFrame.repaint();
mainFrame.paintAll(mainFrame.getGraphics());
}
This is all that has worked for me. I need both calls. Neither works alone. I don't like doing this though obviously because of inefficiency.. :/
Any ideas?
Thanks!
you should be overriding JPanel's
paintComponent(Graphics g)
not paint
The reason mainFrame.repaint() forces the map to refresh is because repaint() calls repaint(0, 0, 0, width, height), which marks the entire mainFrame's area to be marked as "dirty" for the RepaintManager. This is designed this way on purpose, because you usually do not want to repaint every pixel in the JFrame just to update a component. So, in onTick(), when mainFrame.paintAll() is being called, my guess is that the mapPanel's area has not been marked dirty, so the RepaintManager skips it, to save processing time. If you are very sure that you want to repaint the whole mapPanel every time onTick() is called, the simplest way would be to call mapPanel.repaint() inside of your onTick() method. This will mark the whole mapPanel as dirty so it will be redrawn asap. Also, if your menuPanel is just using regular swing JComponents, you don't need to manually cause them to repaint, they will be repainted when their values change, if you are using the API correctly.
I know this is a kind of old question, but I figured I'd answer in case anyone else runs into something similar.
I have a JPanel added to a JViewport, and the panel has several other panels added to it. I'm trying to implement a dragging selection, where you can select more than one component by dragging the mouse. The only problem I'm facing is that the selection rectangle is being painted behind the components added to the main JPanel. How can I paint over the top of them?
My structure is as follows: JFrame -> ContentPane -> JLayeredPane -> JScrollPane -> JPanel -> JPanel [].
Design draft for college assignment:
As you can see, the rectangle is behind the other panels.
This is what I'm already doing (on a much simpler level obviously), and Swing paints the rectangle underneath the components added to it.
This is one case where you should override the paint() method of the panel and not the paintComponent() method. Then the custom painting will be done AFTER all the child components have been painted.
Use a Layered Pane:
http://docs.oracle.com/javase/tutorial/uiswing/components/layeredpane.html
This allows you to create overlapping components.
Use a glass pane to handle the drag painting, and possibly events as well:
http://docs.oracle.com/javase/tutorial/uiswing/components/rootpane.html#glasspane
hot really sure what do you really needed and final effect, maybe is there two another ways painting to
1) GlassPane
2) Viewport
you can put that together, carrefully Insets to the visible Rectanle
Without seeing your actual code, it is difficult to say what you are doing wrong. However, I can still say what I would do:
Create a JPanel that represents the whole area where you want to draw, which — of course — contains every component.
Override that panel its paintComponents(Graphics) like this (EDITED, notice the s is now the last character from the method name):
#Override
public void paintComponents(Graphics g)
{ // ^
super.paintComponents(g);
// Draw your selection rectangle:
g.setColor(Color.RED);
g.drawRectangle(selectionRectangle);
}
Okay, this is what I've decided to do in the end:
I'm not sure if this is the best way to do it, but it seems to work okay.
Note: Using MigLayout.
In the constructor of the JPanel lying underneath the colored blocks.
...
this.add(new JPanel() {
#Override
public boolean isOpaque() {
return false;
}
#Override
public void paintComponent(Graphics g) {
if (dragShape != null) {
g.setColor(Colors.SECONDARY);
g.setStroke(new BasicStroke(2));
g.draw(dragShape);
}
}
}, "pos 0 0, width 100%, height 100%", 0);
...
Custom painting on top of Swing components is facilitated by JLayeredPane. This article describes an abstract base class that facilitates overpainting specific areas (like selection rectangles or component bounds).
I have a JPanel with a paintComponent() function. I'll call it once, then when the user clicks a different JButton, I'll set some flag and want to call this function again as it will do something slightly different after the flag is set.
So here's what I'm wondering: how do I clear the existing stuff from paintComponent? And to redraw, do I just call paintComponent again?
Currently I'm trying the following:
flag2 = true;
repaint(); //I expect (want) paintComponent to be called again
In paint component, I do stuff like:
if (flag2==true) {
g.drawRect(...);
} else {
g.drawLine(...);
}
But through testing it seems like there is something wrong with what I'm doing.
Thanks for any help.
When you change a property of the panel then you need to invoke:
panel.repaint();
to cause the component to be repainted.
Then the first statement in the paintComponent() method should be:
super.paintComponent(g);
This will paint the background so you can now do your custom painting.
If you need more help then post your SSCCE that demonstrates the problem.
To clear all previously drawn graphics, invoke g.clearRect(0, 0, getWidth(), getHeight()).
First, why not use an enum instead of a boolean?
enum Enum {
RECTANGLE,
LINE,
CIRCLE
}
Enum choice = RECTANGLE; //default to RECTANGLE
switch(choice) {
// case RECTANGLE, LINE, CIRCLE
}
With regards to your issue, can you answer my comments in your question?
I would suggest calling revalidate(); instead of repaint(). revalidate() needs to be called when changing the size / layout or when you add/remove objects onto your jpanel and will update all of it's children. From what I can tell, you're still using the same paint object tho but changing it's layout.
I'm writing a program that will be just a simple shape maker, I'm supposed to my main panel, ShapeMakerPanel, along with 2 panels on that one, controlPanel(which holds buttons for choosing the shape and clearing it, etc) and drawingArea (where the shapes are actually drawn), but no matter what I do, I can't get the paint to show up on drawingArea. If I just use paintComponent and comment out add(drawingArea) then the drawing stuff works, but on the bottom layer, how can I paint on the drawingArea Jpanel. Also, when I do draw the shapes, I can only have one at a time, because every time I start a new one, the panel is wiped clean`
super.paintComponent(g);
g.setColor(penColor);
if (p1 != null && p2 != null)
{
if (shapeChoice.getSelectedItem().equals("Line"))
{
Line line = new Line(p1.x, p1.y, p2.x, p2.y);
line.draw(g);
}
}
I know its the super.paintComponent(g) messing me up, but without that, as I drag the mouse, it draws hundreds of lines.
If you were wondering about the Line class, we had to make a class for each shape we drew, the draw() method just uses the coordinates of the line and puts them into drawLine().
Don't override paintComponent() in ShapeMakerPanel; override it in drawingArea's class (if drawingArea is a plain JPanel, then create a new subclass of JPanel). In general you need to subclass the component on which you're going to paint.
Also, when I do draw the shapes, I can only have one at a time, because every time I start a new one, the panel is wiped clean`
See Custom Painting Approaches for a couple of ways to solve this.
I have a simple animation program which moves some basic shapes on the Jframe. However, the program does not really move the shapes, but creates more instead. In other words, I need to force the Jframe to clean up the previous object. How to do so?
Have a look at this previous post.
Custom painting is done by overriding the paintComponent() method of a JPanel. The basic code is:
protected void paintComponent(Graphics g)
{
super.paintComponent(g); // this is what clears the screen.
// paint your shapes here
}
Then you add the panel to the frame.
Read the section from the Swing tutorial on "Custom Painting" for more information.