Question

我有一个extends JPanel的课程。通过在类中添加以下方法来设置JPanel的大小：

@Override
public Dimension getPreferredSize() {
    return new Dimension(WIDTH, HEIGHT);
}

该课程的相关领域是：

int position = 0;

int randomSize = 0; 
int randomPositionX = 0;
int randomPositionY = 0;

public final static int MAX_SIZE = 100;
public final static int MIN_SIZE = 10;

public final static int WIDTH    = 500;
public final static int HEIGHT   = 500;

private Random rand = new Random();

String alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

我选择一个随机大小（最大值为100，最小值为10）和一个方法的随机坐标。我还为字符串alphabets选择了一个随机索引：

randomSize = MIN_SIZE + (rand.nextInt(MAX_SIZE - MIN_SIZE) + 1);

randomPositionX = rand.nextInt(WIDTH - randomSize);
randomPositionY = rand.nextInt(HEIGHT - randomSize);

position = rand.nextInt(alphabets.length());

我尝试绘制字母和圆圈：

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g); 
    g.fillOval(randomPositionX, randomPositionY, randomSize, randomSize);
    g.setFont(new Font("TimesRoman", Font.PLAIN, randomSize));
    g.setColor(Color.RED);
    g.drawString(alphabets.charAt(position) + "", randomPositionX + (randomSize/2), randomPositionY + (randomSize/2));
}

但它不会在圆圈的中心画出字母。简而言之，有问题的一行是

g.drawString(alphabets.charAt(position) + "", randomPositionX + (randomSize/2), randomPositionY + (randomSize/2));

我如何实现我的目标？

MCVE按要求：

import javax.swing.JFrame;
import javax.swing.JPanel;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Font;

import java.util.Random;

class MCVE{

    static int randomSize = 0; 
    static int randomPositionX = 0;
    static int randomPositionY = 0;

    static int position = 0;

    public final static int MAX_SIZE = 100;
    public final static int MIN_SIZE = 10;

    public final static int WIDTH    = 500;
    public final static int HEIGHT   = 500;

    private static Random rand = new Random();

    static String alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    public static void main(String[] argv){

        randomSize = MIN_SIZE + (rand.nextInt(MAX_SIZE - MIN_SIZE) + 1);

        randomPositionX = rand.nextInt(WIDTH - randomSize);
        randomPositionY = rand.nextInt(HEIGHT - randomSize);

        position = rand.nextInt(alphabets.length());

        JFrame frame = new JFrame("Test");
        JPanel panel = new JPanel(){
            @Override
            public void paintComponent(Graphics g) {
                super.paintComponent(g); 
                g.fillOval(randomPositionX, randomPositionY, randomSize, randomSize);
                g.setFont(new Font("TimesRoman", Font.PLAIN, randomSize));
                g.setColor(Color.RED);
                g.drawString(alphabets.charAt(position) + "", randomPositionX + (randomSize/2) - 15, randomPositionY + (randomSize/2) + 15);
            }
        };

        frame.add(panel);
        frame.setSize(WIDTH, HEIGHT);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

问题：字母没有画在圆圈的中心。

Answer 1

图形drawString在指定的位置绘制文本左下角的字符。你需要做一些数学计算，以便按照你想要的方式集中它们。

首先，我们需要从我们正在使用的FontMetrics对象中获取Graphics。据推测，您已经将字体更改为您想要的字体。

FontMetrics metrics = g.getFontMetrics(g.getFont());

现在，我们需要找到我们将要绘制的文本的大小：

Rectangle2D bounds = metrics.getStringBounds(text, g);

接下来，使用这些边界来偏移正在绘制的文本：

int offsetX = -bounds.getWidth()/2;
int offsetY = -bounds.getHeight()/2;
g.translate(offsetX, offsetY);
g.drawString(text, x, y);
g.translate(-offsetX, -offsetY);

或者，将偏移量直接捆绑到绘图调用中

int offsetX = -bounds.getWidth()/2;
int offsetY = -bounds.getHeight()/2;
g.drawString(text, x+offsetX, y+offsetY);

如何在随机大小和随机坐标的绘画圆圈内绘制一个字母？

1 个答案: