Java-悬停在图像事件

Question

我正在为当前正在设计的游戏创建菜单，并且使用在photoshop中设计的图像用作菜单按钮，但是我想知道是否有任何方法可以检测鼠标是否将鼠标悬停在图片上。

之前，我已经对常规矩形完成了此操作，但是此形状不是基本矩形（请点击此处查看该形状）。

使用Graphics2D将形状绘制为BufferedImage。

预先感谢您的帮助！

Answer 1

您可以将MouseListener添加到对象，并为MouseEntered事件编写代码。 当鼠标第一次进入组件的边界时会触发此事件，但单击时不会触发。 Oracle在此方面有很好的文档。

https://docs.oracle.com/javase/tutorial/uiswing/events/mouselistener.html

Answer 2

您可以绘制多边形并通过添加MouseListener来确定选择了哪个多边形。 下次重新绘制时，可以显示选择。

您可以使用以下方法检查事件的点是否包含在多边形中：

[Java文档] :: java.awt.Polygon.contains（Point）

这是一个例子：

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.*;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.*;

public class PolygonDetectorPanel extends JPanel implements MouseListener {
    private static final long serialVersionUID = -8929816396666863908L;
    private BufferedImage backgroundImage;
    private List<Polygon> shapes;
    private Polygon selectedPoly;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame("Polygon Detector");
                PolygonDetectorPanel panel = new PolygonDetectorPanel();

                frame.setContentPane(panel);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public PolygonDetectorPanel() {
        super();
        initialize();

        this.addMouseListener(this);
    }

    protected void initialize() {
        try {
            InputStream is = PolygonDetectorPanel.class.getClassLoader().getResourceAsStream("resources/buttons.png");
            this.backgroundImage = ImageIO.read(is);
        } catch (IOException e) {
            e.printStackTrace();
        }

        int width = this.backgroundImage.getWidth();
        int height = this.backgroundImage.getHeight();

        this.setPreferredSize(new Dimension(width, height));
        this.shapes = new ArrayList<Polygon>();

        int buttonStartX = 13;
        int buttonStartY = 54;
        int buttonOffset = 100;

        for (int i = 0; i < 4; i++) {
            int[] w  = { buttonStartX       , buttonStartY + 33 + (i * buttonOffset) };
            int[] nw = { buttonStartX +  50 , buttonStartY      + (i * buttonOffset) };
            int[] ne = { buttonStartX + 300 , buttonStartY      + (i * buttonOffset) };
            int[] e  = { buttonStartX + 350 , buttonStartY + 33 + (i * buttonOffset) };
            int[] se = { buttonStartX + 300 , buttonStartY + 66 + (i * buttonOffset) };
            int[] sw = { buttonStartX +  50 , buttonStartY + 66 + (i * buttonOffset) };

            int[] xPoints = { w[0], nw[0], ne[0], e[0], se[0], sw[0], w[0]};
            int[] yPoints = { w[1], nw[1], ne[1], e[1], se[1], sw[1], w[1]};

            this.shapes.add(new Polygon(xPoints, yPoints, 6));
        }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        if (this.backgroundImage != null) {
            g.drawImage(this.backgroundImage, 0, 0, null);
        }

        Graphics2D g2 = (Graphics2D) g;
        g2.setStroke(new BasicStroke(5, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND, 10.0f));

        for (Polygon poly : this.shapes) {
            if (poly == this.selectedPoly) {
                g.setColor(Color.GREEN);
            } else {
                g.setColor(Color.RED);
            }

            g.drawPolygon(poly);
        }
    }

    protected Polygon getClickedShape(Point point) {
        for (Polygon poly : this.shapes) {
            if (poly.contains(point)) {
                return poly;
            }
        }

        return null;
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        Polygon poly = getClickedShape(new Point(e.getX(), e.getY()));

        if (poly != null) {
            this.selectedPoly = poly;
        } else {
            this.selectedPoly = null;
        }

        repaint();
    }

    @Override
    public void mousePressed(MouseEvent e) { }

    @Override
    public void mouseReleased(MouseEvent e) { }

    @Override
    public void mouseEntered(MouseEvent e) { }

    @Override
    public void mouseExited(MouseEvent e) { }
}

这是屏幕截图。