使用Java在鼠标单击时绘制形状

我正在尝试创建一个java程序，当用户单击JFrame时，它将在JFrame上绘制一个形状。我已经到了可以接受不同形状并识别点击的程度，但是我很难弄清楚如何实现形状的绘制

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;
import javax.swing.JComponent;

public class StamperFrame extends JFrame {

    private JButton circleButton, ovalButton, squareButton, rectButton;
    private int buttonValue = 0;

    public StamperFrame() {
        setTitle("Shape Stamper");
        setSize(500, 500);

        //Setting up the buttons and positioning them.
        JPanel buttonPanel = new JPanel();

        circleButton = new JButton("Circle");
        ovalButton = new JButton("Oval");
        squareButton = new JButton("Square");
        rectButton = new JButton("Rectangle");

        buttonPanel.add(circleButton);
        buttonPanel.add(ovalButton);
        buttonPanel.add(squareButton);
        buttonPanel.add(rectButton);
        getContentPane().add(buttonPanel, BorderLayout.SOUTH);
        //end button init



        //Setting up button logic
        circleButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                buttonValue = 1;
                System.out.println(buttonValue);
            }
        });
        ovalButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                buttonValue = 2;
                System.out.println(buttonValue);
            }
        });
        squareButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                buttonValue = 3;
                System.out.println(buttonValue);
            }
        });
        rectButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                buttonValue = 4;
                System.out.println(buttonValue);
            }
        });
        //end button click configuration

        getContentPane().addMouseListener(new MouseAdapter() {

            @Override
            public void mouseClicked(MouseEvent e) {
                if (buttonValue == 1) {
                    System.out.println("Circle added at: " + e.getX() + "," + e.getY());
                } else if (buttonValue == 2) {
                    System.out.println("Oval added at: " + e.getX() + "," + e.getY());
                }else if (buttonValue == 3) {
                    System.out.println("Square added at: " + e.getX() + "," + e.getY());
                }else if (buttonValue == 4) {
                    System.out.println("Rectangle added at: " + e.getX() + "," + e.getY());
                }
            }
        });

    }
}

我知道它需要以某种方式进入我的鼠标事件，但我不知道如何

我的框架当前看起来如下所示：

如有任何建议，将不胜感激。

有关定制喷漆的两种方法，请参阅：

将要绘制的对象添加到ArrayList 将对象直接绘制到BuffereImage上。

---

链接中的示例只绘制了一个矩形，因此您显然需要修改代码以支持不同的形状，但它应该会给您一些想法。

您将在内容窗格中添加一个新的JPanel，可能位于中心

JPanel drawingPanel = new JPanel();
getContentPane().add(drawingPanel, BorderLayout.CENTER);

然后，在每个按钮的action listerner代码处调用代码以绘制JPanel的图形：

rectButton.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
           Graphics2D g = Graphics2D drawingPanel.getGraphics2D(); 
           g.draw(new java.awt.Rectangle(42,42,20,40);

        }
    });

等等

---

您需要熟悉Java2D才能完成FinalExam包的工作。

好的。真正完整的aswer now：

TL；DR：复制并粘贴以下代码：

package FinalExam;

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;

public class StamperFrame extends JFrame {

    private final JButton circleButton, ovalButton, squareButton, rectButton;

    private final JPanel shapesPanel;

    private Shape shape;
    private final int w = 100;
    private final int h = 200;

    private Object lastButtonPressed;

    public StamperFrame() {
        setTitle("Shape Stamper");
        setSize(500, 500);

        final Container contentPane = getContentPane();

        //Setting up the buttons and positioning them.
        JPanel buttonPanel = new JPanel();

        circleButton = new JButton("Circle");
        ovalButton = new JButton("Oval");
        squareButton = new JButton("Square");
        rectButton = new JButton("Rectangle");

        buttonPanel.add(circleButton);
        buttonPanel.add(ovalButton);
        buttonPanel.add(squareButton);
        buttonPanel.add(rectButton);

        contentPane.add(buttonPanel, BorderLayout.SOUTH);
        //end button init

        shapesPanel = new JPanel(){
            @Override
            public void paintComponent(Graphics graphics) {
                Graphics2D g = (Graphics2D) graphics;
                super.paintComponent(g); 
                if(shape != null) g.draw(shape);
            }

        };
        contentPane.add(shapesPanel, BorderLayout.CENTER);

        final ActionListener buttonPressed = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                lastButtonPressed = event.getSource();
            }
        };

        circleButton.addActionListener(buttonPressed);
        ovalButton.addActionListener(buttonPressed);
        squareButton.addActionListener(buttonPressed);
        rectButton.addActionListener(buttonPressed);

        contentPane.addMouseListener(new MouseAdapter() {

            @Override
            public void mouseClicked(MouseEvent e) {

                int x = e.getX();
                int y = e.getY();

                if(lastButtonPressed == circleButton){
                    shape = new Ellipse2D.Double(x, y, w, w);
                    echo("Circle",x,y);
                } else if(lastButtonPressed == ovalButton){
                    shape = new Ellipse2D.Double(x, y, w, h);
                    echo("Oval",x,y);
                } else if (lastButtonPressed == squareButton){
                    shape = new Rectangle2D.Double(x, y, w, w);
                    echo("Square",x,y);
                } else if (lastButtonPressed == rectButton){
                    echo("Rectangle",x,y);
                    shape = new Rectangle2D.Double(x, y, w, h);
                } 

                shapesPanel.repaint();
            }

            private void echo(String shape, int x, int y){
                System.out.println(shape + " added at: " + x + "," + y);
            }

        });

    }
}

长篇大论

我们不需要一个可变的buttonValue来记住按下了哪个按钮。按钮是事件源，所以我们只需存储它，然后就可以知道按下了哪个按钮。 我们不需要每个按钮都有一个ActionListener的4个实例，因为它们都做相同的事情来存储事件源作为按下的按钮' 绘图技巧是通过使用JPanel和shapePanel变量作为绘图画布来完成的。我们扩展了JPanel以覆盖paintComponent。此方法将使用Graphics2D的形状绘制API。 在contentPane中添加的ActionListener将获得单击的x和y坐标，根据上次按下的按钮创建要绘制的形状，将其存储在variable Shape中，并要求ShapePanel重新绘制自身。

---

-1、不应使用getGraphics进行绘制。您所做的任何绘制都是临时的，并且在Swing第一次确定组件需要重新绘制时将丢失。您是对的。我想应该重写paintComponentGraphics g，检查怪异的buttonValue属性并绘制形状。当然，重画应该在某个地方进行。我讨厌期末考试。嘿，谢谢你的反馈。实际上，我提出了一个新问题，因为我让程序在单击“立即”时绘制，但重新绘制方法导致了一个我需要解决的问题。问题在于重新喷漆，但我不确定修复方法。我一定会采纳你的建议，减少行动听众的数量。