我正在尝试将鼠标操作添加到我的面板中。 这就是该计划应该做的事情：
编写一个程序，允许用户通过三次鼠标按下指定三角形。第一次鼠标按下后，画一个小点。第二次鼠标按下后，绘制一条连接前两点的线。第三次鼠标按下后，绘制整个三角形。第四次鼠标按下删除旧三角形并开始一个新三角形。
答案 0 :(得分：2)
我强烈建议您先阅读How to Write a Mouse Listener。当你遇到困难时，这些教程（以及JavaDocs）是开始的最佳场所
您的问题的“直接”答案是，您需要在您的组件中注册MouseListener的实例，可能类似......
private JPanel createCenterPanel() {
panel.addMouseListener(new MouseListen());
//panel.setLayout(null);
return panel;
}
这将“回答”您当前的问题。
但是，您会发现很难尝试将MouseListener的操作与面板结合起来，而面板需要绘制结果。
更好的解决方案可能是从JPanel开始管理它自己的MouseListener
此外，Graphics g = panel.getGraphics()不是应该如何执行自定义绘画。看看Performing custom painting for more details
所以，相反，它可能看起来更像......
public class TrianglePanel extends JPanel {
private List<Point> points = new ArrayList<>(3);
public TrianglePanel() {
addMouseListener(new MouseListen());
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g); //To change body of generated methods, choose Tools | Templates.
if (points.size() < 1) {
return;
}
for (int index = 0; index < points.size(); index++) {
Point nextPoint = points.get(index);
g.fillOval(nextPoint.x - 2, nextPoint.y - 2, 4, 4);
}
Point startPoint = points.get(0);
Point lastPoint = startPoint;
for (int index = 1; index < points.size(); index++) {
Point nextPoint = points.get(index);
g.drawLine(lastPoint.x, lastPoint.y, nextPoint.x, nextPoint.y);
lastPoint = nextPoint;
}
g.drawLine(lastPoint.x, lastPoint.y, startPoint.x, startPoint.y);
}
class MouseListen extends MouseAdapter {
public void mouseReleased(MouseEvent e) {
if (points.size() < 3) {
points.add(e.getPoint());
repaint();
}
}
}
}
答案 1 :(得分：1)
我没有看到你实例化类MouseListen的任何地方。您还需要调用addMouseListener（）。
以下是我前一段时间写过的内容中的行：
public class ColorPanel extends JPanel implements MouseListener {
. . .
ColorPanel(JTextField jTextFieldColor) {
super();
this.jTextField = jTextFieldColor;
addMouseListener(this);
}
@Override
public void mouseClicked(MouseEvent evt) {
System.out.println("Instance of ColorPanel clicked.");
jColorChooser = new JColorChooser(this.getBackground());
this.add(jColorChooser);
int retval = JOptionPane.showConfirmDialog(null,
jColorChooser,
"JOptionPane Example : ",
JOptionPane.OK_CANCEL_OPTION,
JOptionPane.PLAIN_MESSAGE);
if (retval == JOptionPane.OK_OPTION) {
jTextField.setText(Utils.hexStringFromColor(jColorChooser.getColor()));
}
}
请参阅https://docs.oracle.com/javase/tutorial/uiswing/events/mouselistener.html上的教程。
此外，基于https://docs.oracle.com/javase/tutorial/uiswing/events/eventsandcomponents.html，您可以让您的JFrame实现MouseListener，这将使您的代码更简单。 （你根本不需要类MouseListen。）
通过过去的Java代码快速写一下我写的确认你可以
public class MyFrame extends JFrame implements MouseListener
所以你可能想看看这个。
答案 2 :(得分：0)
我对Swing并不是很熟悉。作为一名新程序员，我只使用过JavaFX。
但是，您在程序的任何位置都没有引用MouseListener。你可能忘了实例化它。
答案 3 :(得分：0)
您必须使用 addMouseListener 方法向Jpanel注册侦听器对象。 更多信息;
答案 4 :(得分：0)
使用JDialog，因为我希望它是模态的;不要那么打扰你。
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.GroupLayout;
import javax.swing.JDialog;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.WindowConstants;
public class RectSelectGUI extends JDialog implements MouseListener, ActionListener, WindowListener {
private static final long serialVersionUID = 1L;
public int overheadWd;
public int overheadHt;
public ImageJPanel imagePanel;
private JMenu jMenuSelection;
private JMenuBar jMenuBar1;
private Dimension mouseDownLoc;
private String errorString;
public RectSelectGUI(String imgFileName) {
initComponents(imgFileName);
}
private void initComponents(String imgFileName) {
imagePanel = new ImageJPanel(imgFileName);
jMenuBar1 = new JMenuBar();
jMenuSelection = new JMenu();
JMenuItem jMenuItemSave = new JMenuItem();
jMenuItemSave.setActionCommand("Save");
jMenuItemSave.addActionListener(this);
jMenuItemSave.setText("Save");
jMenuSelection.add(jMenuItemSave);
JMenuItem jMenuItemCancel = new JMenuItem();
jMenuItemCancel.setActionCommand("Cancel");
jMenuItemCancel.addActionListener(this);
jMenuItemCancel.setText("Cancel");
jMenuSelection.add(jMenuItemCancel);
mouseDownLoc = new Dimension();
errorString = "No selection";
imagePanel.addMouseListener(this);
this.setModal(true);
this.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
this.addWindowListener(this);
GroupLayout jPanel1Layout = new GroupLayout(imagePanel);
imagePanel.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING).addGap(0, 524, Short.MAX_VALUE));
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING).addGap(0, 370, Short.MAX_VALUE));
jMenuSelection.setText("Selection");
jMenuBar1.add(jMenuSelection);
setJMenuBar(jMenuBar1);
GroupLayout layout = new GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup().addContainerGap()
.addComponent(imagePanel, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addContainerGap()));
layout.setVerticalGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup().addContainerGap()
.addComponent(imagePanel, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addContainerGap()));
pack();
overheadWd = this.getWidth() - imagePanel.getWidth();
overheadHt = this.getHeight() - imagePanel.getHeight();
}
public String getSelectionString() {
if (errorString.isEmpty()) {
double rectWd = (double) imagePanel.rectWd;
double rectHt = (double) imagePanel.rectHt;
double rectX = (double) imagePanel.rectX;
double rectY = (double) imagePanel.rectY;
if (Math.abs(RectSelect.displayFactor - 1.0) > 0.001) {
System.out.println("Adjusting by displayFactor (" + RectSelect.displayFactor + ")");
rectWd /= RectSelect.displayFactor;
rectHt /= RectSelect.displayFactor;
rectX /= RectSelect.displayFactor;
rectY /= RectSelect.displayFactor;
}
return Math.round(rectWd) + "x" + Math.round(rectHt) + "+" + Math.round(rectX) + "+" + Math.round(rectY);
} else {
return "ERROR: " + errorString;
}
}
@Override
public void mouseClicked(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mousePressed(MouseEvent evt) {
mouseDownLoc.setSize(evt.getX(), evt.getY());
}
@Override
public void mouseReleased(MouseEvent evt) {
Dimension mouseUpLoc = new Dimension(evt.getX(), evt.getY());
if (mouseDownLoc.width < mouseUpLoc.width) {
imagePanel.rectX = mouseDownLoc.width;
imagePanel.rectWd = mouseUpLoc.width - mouseDownLoc.width;
} else {
imagePanel.rectX = mouseUpLoc.width;
imagePanel.rectWd = mouseDownLoc.width - mouseUpLoc.width;
}
if (mouseDownLoc.height < mouseUpLoc.height) {
imagePanel.rectY = mouseDownLoc.height;
imagePanel.rectHt = mouseUpLoc.height - mouseDownLoc.height;
} else {
imagePanel.rectY = mouseUpLoc.height;
imagePanel.rectHt = mouseDownLoc.height - mouseUpLoc.height;
}
imagePanel.haveNewRect = true;
imagePanel.repaint();
errorString = "";
}
@Override
public void actionPerformed(ActionEvent evt) {
String cmd = evt.getActionCommand();
switch (cmd) {
case "Save":
break;
case "Cancel":
errorString = "Cancelled";
break;
default:
System.out.println("Unknown action command " + cmd);
}
this.setVisible(false);
}
@Override
public void windowClosing(WindowEvent e) {
errorString = "Cancelled";
this.setVisible(false);
}
@Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void windowOpened(WindowEvent e) {
try {
Thread.sleep(100);
} catch (InterruptedException e1) {
}
this.repaint();
}
@Override
public void windowClosed(WindowEvent e) {
// TODO Auto-generated method stub
}
@Override
public void windowIconified(WindowEvent e) {
// TODO Auto-generated method stub
}
@Override
public void windowDeiconified(WindowEvent e) {
// TODO Auto-generated method stub
}
@Override
public void windowActivated(WindowEvent e) {
}
@Override
public void windowDeactivated(WindowEvent e) {
// TODO Auto-generated method stub
}
}
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import javax.swing.JPanel;
public class ImageJPanel extends JPanel {
private static final long serialVersionUID = 1L;
public Image localImage;
private int origWd;
private int origHt;
private int displayWd;
private int displayHt;
public int rectX;
public int rectY;
public int rectWd;
public int rectHt;
public boolean haveNewRect;
private Toolkit toolkit;
ImageJPanel(String imageFileName) {
toolkit = Toolkit.getDefaultToolkit();
localImage = toolkit.getImage(imageFileName);
}
protected void paintComponent(Graphics g1D) {
Graphics2D g;
g = (Graphics2D) g1D;
// Draw the image using the Graphics object provided
g.drawImage(localImage, 0, 0, getDisplayWd(), getDisplayHt(), null);
/*
* Optional label.
Font font = new Font("SansSerif", Font.BOLD, 24);
g1D.setFont(font);
FontMetrics metrics = g1D.getFontMetrics();
int ht = metrics.getHeight();
int wd = metrics.stringWidth(this.imageFileName);
g.setColor(Color.LIGHT_GRAY);
g.fillRect(this.getWidth() - wd - 10, this.getHeight() - ht, wd + 10, ht);
g1D.setColor(new Color(55, 11, 160));
g1D.drawString(this.imageFileName, this.getWidth() - wd - 10, this.getHeight() - ht + 20);
*/
// Draw a selection rectangle if requested.
if (haveNewRect) {
g.drawRect(rectX, rectY, rectWd, rectHt);
haveNewRect = false;
}
}
public int getDisplayWd() {
return displayWd;
}
public void setDisplayWd(int displayWd) {
this.displayWd = displayWd;
}
public int getDisplayHt() {
return displayHt;
}
public void setDisplayHt(int displayHt) {
this.displayHt = displayHt;
}
public int getOrigWd() {
return origWd;
}
public void setOrigWd(int origWd) {
this.origWd = origWd;
}
public int getOrigHt() {
return origHt;
}
public void setOrigHt(int origHt) {
this.origHt = origHt;
}
}