Question

根据java Graphics2D drawString 描绘出的字符串得到字符串所围成成的矩形

各位大神好，这是小弟第一次提问题，因为是初学。

我想通过java Graphics2D相关类来实现以下功能：Graphics2D 的drawString方法在图片上描绘了许多文字，有些文字也是倾斜显示的（我通过Graphics2D 的rotate来做到的），但是有些文字有时候存在交叉重叠的现象，我想避免图片上有些文字重叠，只需要大神们告诉我如何判断会重叠就好。

目前已知信息是每个字符串的起始x、y坐标，终点x、y坐标，字符串宽、高。但是需要考虑的是字体大小调整后起始点坐标不会变，终点坐标就会伸缩有变化，所以考虑进去有必要。

小弟的想法是想根据字符串来得到所围成的矩形，然后通过待插入的字符串所为的矩形判断是否会与矩形相交，但是查阅API发现drawString方法返回值是void，所以又想通过数学中的几何图形特点来算，亦无果。

跪求大神们施以援手，谢谢！

Answer 1

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
final class StringPaintDemo extends JFrame {
    final static private Dimension SIZE = new Dimension(800, 600);
    public String getTitle() {return "StringPaintDemo";}
    public Dimension getPreferredSize() {return SIZE;}
    public Dimension getMinimumSize() {return SIZE;}
    public Dimension getMaximumSize() {return SIZE;}
    public Dimension getSize() {return SIZE;}
    private Canvas canvas;private JCheckBox checkBox;
    private Brush brush;
    StringPaintDemo() throws HeadlessException {
        init();
        attachListeners();
        doLay();
        setVisible(true);
    }

    private void init() {
        brush=new StringBoundBrush();
        canvas=new Canvas(brush);
        checkBox=new JCheckBox("是否绘制文本边框?");
        checkBox.addChangeListener(evt->{
            brush.update(null, checkBox.isSelected());
        });
    }

    private void attachListeners() {
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(1);
            }
        });
    }

    private void doLay() {
        Container container=getContentPane();
        container.add(canvas,BorderLayout.CENTER);
        container.add(checkBox,BorderLayout.NORTH);
        pack();
    }

    public static void main(String... args) {
        System.setProperty("swing.defaultlaf", "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        SwingUtilities.invokeLater(StringPaintDemo::new);
    }
    
    private interface Brush extends Observer {
        /**
         * do paint action
         * @param g the graphics context in you application
         */
        void paint(Graphics g);

        /**
         * The component that this brush hold
         * @return component instance
         */
        Component getOwner();

        void setOwner(Component owner);
    }

    private static final class StringBoundBrush implements Brush{
        private Component owner;
        private Object contentObj;
        private boolean isBorderPainted=false;
        public Component getOwner() {
            return owner;
        }

        public void setOwner(Component owner) {
            this.owner=owner;
        }

        public void paint(Graphics g) {
            Graphics2D g2= (Graphics2D)g.create();
            g2.fill(getOwner().getBounds());
            g2.translate(100, 100);
            g2.rotate(Math.PI / 3);
            g2.setColor(Color.BLUE);
            g2.setFont(g2.getFont().deriveFont(33f));
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

            String s = contentObj ==null?"Null?": contentObj.toString();

            if (isBorderPainted) {
                g2.setColor(Color.ORANGE);
                g2.draw(g2.getFontMetrics().getStringBounds(s, g2));
            }

            g2.setColor(Color.RED);
            g2.drawString(s,0,0);
            g2.dispose();
        }

        public void update(Observable o, Object arg) {
            if(arg instanceof Boolean)
                isBorderPainted= (boolean)arg;
            else
                contentObj = arg;

            if (owner!=null) owner.repaint();
        }
    }

    /**
     * you canvas
     */
    private class Canvas extends JComponent{
        private Brush brush;
        private Canvas(Brush brush) {
            super();
            this.brush=brush;
            brush.setOwner(this);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (brush == null)return;
            brush.paint(g);
        }
    }
}