Question

我制作的程序可以在用户鼠标按下时再次改变矩形的颜色按下默认颜色我在jpanel上画了这个绘制组件方法的帮助。我用鼠标适配器写了鼠标按下的方法。但是如何制作一个当用户鼠标按在矩形上时，将矩形颜色改为红色的功能在再次按下时也会出现默认颜色。这是图片
enter image description here
代码：

    public class A extends JPanel{
    public void paintComponent(Graphics g){
            super.paintComponents(g);

            g.setColor(Color.BLACK);
            g.fillRect(6, 10, 66, 70);

            addMouseListener(new MouseAdapter(){

            public void mousePressed(MouseEvent e){


            }
            });
            }
    }

主：

public class Main {

    public static void main(String[] args) {

        JFrame obj = new JFrame();
        A object = new A();
        obj.add(object);

        obj.setSize(450, 400);
        obj.setResizable(false);
        obj.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        obj.setLocationRelativeTo(null);

        obj.setVisible(true);
        }
}

Answer 1

添加到Gosu的答案：

如果您希望仅在单击矩形时切换颜色，则只需在if内添加MouseListener语句。

    frame.addMouseListener(new MouseAdapter() {

        public void mousePressed(MouseEvent e) {

             // Check if the point where the mouse was clicked is contained
             // within the drawing Rectangle.                          
             if (new Rectangle(6, 10, 66, 70).contains(e.getPoint())) {
                    object.switchColor();
                    object.revalidate();
                    object.repaint();
             }
         }
    });

但是，请记住，在实际的应用程序中，您不应该像本例中的矩形那样硬编码。

Answer 2

试试这个：

public class QuickTester {

    public static void main(String[] args) {

        JFrame frame = new JFrame();
        final A object = new A();
        frame.add(object);

        frame.setSize(450, 400);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);

        frame.addMouseListener(new MouseAdapter() {

            public void mousePressed(MouseEvent e) {

                object.switchColor();
                //object.revalidate();
                object.repaint();
            }
        });

        frame.setVisible(true);
    }
}

class A extends JPanel {

    private Color currColor = Color.BLACK;

    public void switchColor() {
        currColor = (currColor == Color.BLACK) ? Color.RED : Color.BLACK;
    }

    public void paintComponent(Graphics g) {
        super.paintComponents(g);

        g.setColor(currColor);
        g.fillRect(6, 10, 66, 70);
    }
}

只要您在框架内单击，矩形就会在黑色和红色之间切换。

Answer 3

你需要另一个JPanel（或类似的东西）用于必须改变颜色的方块。否则，您将无法注册广场内发生的鼠标事件以及外部发生的事件。以下是一个小工作示例。

public class A extends JPanel {
    private Color currColor = Color.BLACK;
    JPanel p = new JPanel();
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        p.setSize(new Dimension(66,70));
        p.setLocation(6, 10);
        p.setBackground(currColor);

        p.addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                switchColor();
                p.revalidate();
                p.repaint();
            }
        });
        add(p);
    }

    public void switchColor() {
        currColor = (currColor == Color.BLACK) ? Color.RED : Color.BLACK;
    }

    public static void main(String [] args) {
        JFrame frame = new JFrame();
        A t = new A();
        frame.add(t);
        frame.setSize(450,400);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

Java：JPanel Rectangle问题？

3 个答案: