javaswing绘制箭头

在Java Swing中绘制箭头可以通过创建Arrow类和LineArrow、CurvedArrow子类来实现。可以使用Graphics2D类的draw方法来绘制箭头。

下面是一个简单的示例代码，用于在Java Swing中绘制箭头：

public abstract class Arrow {
    public abstract void draw(Graphics2D g, int x1, int y1, int x2, int y2);
}

public class LineArrow extends Arrow {
    public void draw(Graphics2D g, int x1, int y1, int x2, int y2) {
        g.drawLine(x1, y1, x2, y2);
        drawArrow(g, x1, y1, x2, y2);
    }

    private void drawArrow(Graphics2D g, int x1, int y1, int x2, int y2) {
        double dx = x2 - x1, dy = y2 - y1;
        double angle = Math.atan2(dy, dx);
        int len = 10;
        int x = (int) (x2 - len * Math.cos(angle));
        int y = (int) (y2 - len * Math.sin(angle));
        g.drawLine(x2, y2, x, y);
        x = (int) (x2 - len * Math.cos(angle - Math.PI / 8));
        y = (int) (y2 - len * Math.sin(angle - Math.PI / 8));
        g.drawLine(x2, y2, x, y);
        x = (int) (x2 - len * Math.cos(angle + Math.PI / 8));
        y = (int) (y2 - len * Math.sin(angle + Math.PI / 8));
        g.drawLine(x2, y2, x, y);
    }
}

public class CurvedArrow extends Arrow {
    public void draw(Graphics2D g, int x1, int y1, int x2, int y2) {
        QuadCurve2D.Double curve = new QuadCurve2D.Double();
        curve.setCurve(x1, y1, (x1 + x2) / 2, (y1 + y2) / 2, x2, y2);
        g.draw(curve);
        drawArrow(g, x1, y1, (x1 + x2) / 2, (y1 + y2) / 2);
    }

    private void drawArrow(Graphics2D g, int x1, int y1, int x2, int y2) {
        double dx = x2 - x1, dy = y2 - y1;
        double angle = Math.atan2(dy, dx);
        int len = 10;
        int x = (int) (x2 - len * Math.cos(angle));
        int y = (int) (y2 - len * Math.sin(angle));
        g.drawLine(x2, y2, x, y);
        x = (int) (x2 - len * Math.cos(angle - Math.PI / 8));
        y = (int) (y2 - len * Math.sin(angle - Math.PI / 8));
        g.drawLine(x2, y2, x, y);
        x = (int) (x2 - len * Math.cos(angle + Math.PI / 8));
        y = (int) (y2 - len * Math.sin(angle + Math.PI / 8));
        g.drawLine(x2, y2, x, y);
    }
}

public class ArrowTest extends JPanel {
    private Arrow[] arrows = { new LineArrow(), new CurvedArrow() };

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        int width = getWidth();
        int height = getHeight();
        for (int i = 0; i < arrows.length; i++) {
            arrows[i].draw(g2, 0, i * height / arrows.length, width, (i + 1) * height / arrows.length);
        }
    }
}

在上面的代码中，Arrow是一个抽象类，它有一个抽象方法draw，用于绘制箭头。LineArrow和CurvedArrow是Arrow的两个子类，分别用于绘制直线箭头和曲线箭头。在draw方法中，先使用Graphics2D的drawLine方法绘制线条，然后调用drawArrow方法绘制箭头。

在ArrowTest类中，创建了一个Arrow数组，包含了LineArrow和CurvedArrow两个实例。在paintComponent方法中，遍历Arrow数组，调用draw方法绘制箭头。