关键是处理FontMetrics API。你能做的最好的就是查看这个参考文档。
这是演示此用法的示例代码。它根据一系列字符在“Hello world”文本周围绘制红线和蓝线。
文本位于 JLabel 中,但您可以在任何组件上调整绘制方法(但您必须调用graphics.drawChars
才能绘制文本。)
(代码不是很好,但演示了FontMetrics的用法)
package com.example.swing;
import javax.swing.*;
import java.awt.*;
public class DemoFontMetrics {
public static void main(String[] args){
JFrame frame = new JFrame();
DecoratedLabel label = new DecoratedLabel("hello world !",new int[]{2,4}, new int[]{6,9});
JPanel textContainer = new JPanel(new FlowLayout());
textContainer.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
textContainer.add(label);
frame.getContentPane().add(textContainer);
frame.pack();
frame.setVisible(true);
}
private static class DecoratedLabel extends JLabel{
int startBlue;
int endBlue;
int startRed;
int endRed;
private DecoratedLabel(String text, int[] blueRange, int[] redRange) {
super(text);
startBlue = blueRange[0];
endBlue = blueRange[1];
startRed = redRange[0];
endRed = redRange[1];
}
@Override
public void paint(Graphics g) {
super.paint(g); //draw text
//set line with : 3
Stroke stroke = new BasicStroke(3f);
((Graphics2D)g).setStroke(stroke);
FontMetrics fm = g.getFontMetrics();
int h = fm.getHeight();
//compute blue line coordonate
fm.stringWidth(getText().substring(0,startBlue));
int x1 = fm.stringWidth(getText().substring(0, startBlue));
int x2 = fm.stringWidth(getText().substring(0, endBlue));
g.setColor(Color.BLUE);
g.drawLine(x1,0,x2,0);// draw blue line
//compute red line coordonates
int x3 = fm.stringWidth(getText().substring(0,startRed));
int x4 = fm.stringWidth(getText().substring(0, endRed));
g.setColor(Color.RED);
g.drawLine(x3,h-1,x4,h-1); // draw redline
}
}
}