A rotated square panel in Java GUI

问题

I wonder if it is possible to implement a GUI panel (possibly JPanel) that is of square shape but rotated 90 degrees. Obviously, there will be a top-level container which contains this panel, and visually the main panel is this rotated square panel within.

More specifically, I would divide a panel (called 'A') into 4 equal square sub-panels, and fill these sub-panels with JLabels, for which I am thinking to use GridLayout. And lastly, I would rotate 'A' 90 degrees to give what I want.

From my reading of other similar questions, it seems that you cannot rotate JPanel itself, but you can rotate what is contained within. Is this applicable to my case here? Would appreciate if someone could point out. Thanks.

回答1:

The critical thing seems to be painting the components after rotating the graphics context. Here's an example:

Addendum 1:As @Atreys comments, the rotated components are drawn, but interact poorly. If the components must remain usable, event coordinates should also be transformed. Compare this (considerably) more complex example that mirrors components.

Addendum 2: If you also need to transform the mouse coordinates, this example may be helpful.

Addendum 3: Alternatively, consider the drawString() examples examined here.

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

/** @see https://stackoverflow.com/questions/6333464 */
public class RotatePanel extends JPanel {

    public RotatePanel() {
        this.setPreferredSize(new Dimension(320, 240));
        this.add(new JLabel("Hello World!", JLabel.CENTER));
    }

    @Override
    public void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        int w2 = getWidth() / 2;
        int h2 = getHeight() / 2;
        g2d.rotate(-Math.PI / 2, w2, h2);
        super.paintComponent(g);
    }

    private void display() {
        JFrame f = new JFrame("RotatePanel");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new RotatePanel().display();
            }
        });
    }
}

回答2:

Check out JXTransformer in the SwingHelper project over at java.net. This class acts as a component decorator that allows you to apply an arbitrary affine transform to a component.

回答3:

Yes, you would have to have the top-level container (JPanel or other container) be the item that rotates the contents. Really you aren't rotating the items, you are rotating to the painting of the items.

回答4:

If all you need to do is rotate the text on a JLabel you could use a Rotated Icon, then you don't have to worry about rotating the panel.

来源：https://stackoverflow.com/questions/6333464/a-rotated-square-panel-in-java-gui