Post overriding the paint method of the components

问题:

In java awt or swing when you want to change painting of some component you usually have to override the method paint(Graphics g) (in awt) or paintComponent(Graphics g) (in swing).
This is usually (maybe allways - I'm not sure) done when you are creating the component for example:

JPanel jPanel = new JPanel() {
                @Override
                protected void paintComponent(Graphics g) {

                    super.paintComponent(g);

                    Graphics2D g2d = (Graphics2D) g;
                    //... my implementation of paint, some transfromations, rotation, etc
                }   

            }; 

Imagine that you have container of components which could for example consists of some JLabels, some JTextFields, some image. Which will be all put on one component. By container I mean you have some list or map with ids or some similar structure in which are all components you will put on one JFrame.
The question is if I can change the painting method after creating with all of the components which are in this list in the moment when all of them are already created. For example I want do the rotation action (rotate), which is defined in Graphisc2D, with all of them.
So basicaly what I want is that I throught the list of componets I have and say: "All of you (components) which are in the list will be rotated by some angle". Is that possible? If yes how?

Edit:
This is my not correctly working solution:

  graphicalDisplayPanel = new JPanel() {
                    @Override
                    protected void paintComponent(Graphics g) {

                        super.paintComponent(g);


                        g2d = (Graphics2D) g;
                        g2d.rotate(Math.PI, anchorx, anchory);


                    }

                 @Override
                      public void paintChildren(Graphics g) {
                           super.paintChildren(g);
                           Graphics2D g2d2 = (Graphics2D) g;

                        g2d2.rotate(Math.PI, anchorx, anchory);

                      }

                };

    JFrame jFrame = JFrame();
    // ... setting dimension, position, visible etc for JFrame, it works correctly nonrotated

    jFrame.setContentPane(graphicalDisplayPanel);

回答1:

I have not tested this, but it seems like it would work. A JComponent's paint() method calls:

paintComponent(co);
paintBorder(co);
paintChildren(co);

where co is a Graphics object. In theory you create an image, retrieve the graphics object and then pass that into paintChildren(). you will have to call paintComponent() and paintBorder() yourself, if you do this. Then, just rotate the image and draw it into your component. You may have to crop the image or resize your component accordingly for this to work. It might look something like this:

BufferedImage myImage;

@Override
public void paint(Graphics g){
    myImage = new BufferedImage(getWidth(), getHeight(), BufferedImage.TRANSLUCENT);
    //using a transparent BufferedImage might not be efficient in your case
    Graphics myGraphics = myImage.getGraphics();
    super.paintComponent(g);
    super.paintBorder(g);
    super.paintChildren(myGraphics);
    //rotation code here
    //  ...
    //draw children onto your component
    g.drawImage(myImage, 0, 0,getWidth(), getHeight(), null);

}

I hope I didn't make any mistakes, please let me know if this works.

回答2:

So basicaly what I want is that I throught the list of componets I have and say: "All of you (components) which are in the list will be rotated by some angle".

If you want to rotate panel and therefore all the components on the panel as a single using then you need to do the custom painting in the paintComponent() method.

If you want to rotate, for example, individual images that each have a different angle of rotation then you can again do this in the paintComponent(...) method and change the angle for each component.

Or, in this second case you can use the Rotated Icon class. In this case the Icon is just added to a JLabel. Then you can change the degrees of rotation and repaint the label, so there is no custom painting (except in the Icon itself).