java 为 JPanel 使用 addMouseListener() 和paintComponent()
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时间：2020-10-31 08:03:18 来源:igfitidea点击:
Using addMouseListener() and paintComponent() for JPanel
提问by Alex
This is a follow-up to my previousquestion. I've simplified things as much as I could, and it still doesn't work! Although the good thing I got around using getGraphics().
这是对我之前的问题的跟进。我已经尽可能地简化了事情，但它仍然不起作用！尽管我使用getGraphics().
A detailed explanation on what goes wrong here is massively appreciated. My suspicion is that something's wrong with the the way I used addMouseListener()method here.
非常感谢对这里出了什么问题的详细解释。我怀疑我addMouseListener()在这里使用方法的方式有问题。
EDIT completely rewrote the code. Still does not work properly though.
EDIT 完全重写了代码。但是仍然不能正常工作。
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class RunClass{
static MainClass1 inst1 = new MainClass1();
public static void main(String args[]){
JFrame frame1 = new JFrame();
frame1.add(inst1);
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame1.setTitle("NewPaintToolbox");
frame1.setSize(200, 200);
frame1.setLocationRelativeTo(null);
frame1.setVisible(true);
}
}
class MainClass1 extends JPanel implements MouseListener, MouseMotionListener{
int xvar=30;
int yvar=30;
//static PaintClass22 inst1 = new PaintClass22();
@Override
public void mouseClicked(MouseEvent arg0) {
// TODO Auto-generated method stub
xvar = arg0.getX();
yvar = arg0.getY();
repaint(xvar,yvar,10,10);
}
@Override
public void mouseEntered(MouseEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void mouseExited(MouseEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void mousePressed(MouseEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseDragged(MouseEvent arg0) {
// TODO Auto-generated method stub
xvar = arg0.getX();
yvar = arg0.getY();
repaint(xvar,yvar,10,10);
}
@Override
public void mouseMoved(MouseEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void paintComponent(Graphics g){
super.paintComponent(g);
g.setColor(Color.RED);
g.fillRect(xvar, yvar, 10, 10);
}
}
回答by Andrew Thompson
This is not an immediate answer to your question, but knowing (or at least suspecting) what it is that you wish to offer (a simple paint program), I suggest starting with this approach based around a BufferedImageas the painting surface..
这不是对您问题的直接回答，但知道（或至少怀疑）您希望提供什么（一个简单的绘画程序），我建议从这种基于 aBufferedImage作为绘画表面的方法开始。
import java.awt.*;
import java.awt.RenderingHints.Key;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.filechooser.FileFilter;
import javax.swing.filechooser.FileNameExtensionFilter;
public class BasicPaint {
/** Reference to the original image. */
private BufferedImage originalImage;
/** Image used to make changes. */
private BufferedImage canvasImage;
/** The main GUI that might be added to a frame or applet. */
private JPanel gui;
/** The color to use when calling clear, text or other
* drawing functionality. */
private Color color = Color.WHITE;
/** General user messages. */
private JLabel output = new JLabel("You DooDoodle!");
private BufferedImage colorSample = new BufferedImage(
16,16,BufferedImage.TYPE_INT_RGB);
private JLabel imageLabel;
private int activeTool;
public static final int SELECTION_TOOL = 0;
public static final int DRAW_TOOL = 1;
public static final int TEXT_TOOL = 2;
private Point selectionStart;
private Rectangle selection;
private boolean dirty = false;
private Stroke stroke = new BasicStroke(
3,BasicStroke.CAP_ROUND,BasicStroke.JOIN_ROUND,1.7f);
private RenderingHints renderingHints;
public JComponent getGui() {
if (gui==null) {
Map<Key, Object> hintsMap = new HashMap<RenderingHints.Key,Object>();
hintsMap.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
hintsMap.put(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
hintsMap.put(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
renderingHints = new RenderingHints(hintsMap);
setImage(new BufferedImage(320,240,BufferedImage.TYPE_INT_RGB));
gui = new JPanel(new BorderLayout(4,4));
gui.setBorder(new EmptyBorder(5,3,5,3));
JPanel imageView = new JPanel(new GridBagLayout());
imageView.setPreferredSize(new Dimension(480,320));
imageLabel = new JLabel(new ImageIcon(canvasImage));
JScrollPane imageScroll = new JScrollPane(imageView);
imageView.add(imageLabel);
imageLabel.addMouseMotionListener(new ImageMouseMotionListener());
imageLabel.addMouseListener(new ImageMouseListener());
gui.add(imageScroll,BorderLayout.CENTER);
JToolBar tb = new JToolBar();
tb.setFloatable(false);
JButton colorButton = new JButton("Color");
colorButton.setMnemonic('o');
colorButton.setToolTipText("Choose a Color");
ActionListener colorListener = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
Color c = JColorChooser.showDialog(
gui, "Choose a color", color);
if (c!=null) {
setColor(c);
}
}
};
colorButton.addActionListener(colorListener);
colorButton.setIcon(new ImageIcon(colorSample));
tb.add(colorButton);
setColor(color);
final SpinnerNumberModel strokeModel =
new SpinnerNumberModel(3,1,16,1);
JSpinner strokeSize = new JSpinner(strokeModel);
ChangeListener strokeListener = new ChangeListener() {
@Override
public void stateChanged(ChangeEvent arg0) {
Object o = strokeModel.getValue();
Integer i = (Integer)o;
stroke = new BasicStroke(
i.intValue(),
BasicStroke.CAP_ROUND,
BasicStroke.JOIN_ROUND,
1.7f);
}
};
strokeSize.addChangeListener(strokeListener);
strokeSize.setMaximumSize(strokeSize.getPreferredSize());
JLabel strokeLabel = new JLabel("Stroke");
strokeLabel.setLabelFor(strokeSize);
strokeLabel.setDisplayedMnemonic('t');
tb.add(strokeLabel);
tb.add(strokeSize);
tb.addSeparator();
ActionListener clearListener = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
int result = JOptionPane.OK_OPTION;
if (dirty) {
result = JOptionPane.showConfirmDialog(
gui, "Erase the current painting?");
}
if (result==JOptionPane.OK_OPTION) {
clear(canvasImage);
}
}
};
JButton clearButton = new JButton("Clear");
tb.add(clearButton);
clearButton.addActionListener(clearListener);
gui.add(tb, BorderLayout.PAGE_START);
JToolBar tools = new JToolBar(JToolBar.VERTICAL);
tools.setFloatable(false);
JButton crop = new JButton("Crop");
final JRadioButton select = new JRadioButton("Select", true);
final JRadioButton draw = new JRadioButton("Draw");
final JRadioButton text = new JRadioButton("Text");
tools.add(crop);
tools.add(select);
tools.add(draw);
tools.add(text);
ButtonGroup bg = new ButtonGroup();
bg.add(select);
bg.add(text);
bg.add(draw);
ActionListener toolGroupListener = new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
if (ae.getSource()==select) {
activeTool = SELECTION_TOOL;
} else if (ae.getSource()==draw) {
activeTool = DRAW_TOOL;
} else if (ae.getSource()==text) {
activeTool = TEXT_TOOL;
}
}
};
select.addActionListener(toolGroupListener);
draw.addActionListener(toolGroupListener);
text.addActionListener(toolGroupListener);
gui.add(tools, BorderLayout.LINE_END);
gui.add(output,BorderLayout.PAGE_END);
clear(colorSample);
clear(canvasImage);
}
return gui;
}
/** Clears the entire image area by painting it with the current color. */
public void clear(BufferedImage bi) {
Graphics2D g = bi.createGraphics();
g.setRenderingHints(renderingHints);
g.setColor(color);
g.fillRect(0, 0, bi.getWidth(), bi.getHeight());
g.dispose();
imageLabel.repaint();
}
public void setImage(BufferedImage image) {
this.originalImage = image;
int w = image.getWidth();
int h = image.getHeight();
canvasImage = new BufferedImage(w,h,BufferedImage.TYPE_INT_ARGB);
Graphics2D g = this.canvasImage.createGraphics();
g.setRenderingHints(renderingHints);
g.drawImage(image, 0, 0, gui);
g.dispose();
selection = new Rectangle(0,0,w,h);
if (this.imageLabel!=null) {
imageLabel.setIcon(new ImageIcon(canvasImage));
this.imageLabel.repaint();
}
if (gui!=null) {
gui.invalidate();
}
}
/** Set the current painting color and refresh any elements needed. */
public void setColor(Color color) {
this.color = color;
clear(colorSample);
}
private JMenu getFileMenu(boolean webstart){
JMenu file = new JMenu("File");
file.setMnemonic('f');
JMenuItem newImageItem = new JMenuItem("New");
newImageItem.setMnemonic('n');
ActionListener newImage = new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
BufferedImage bi = new BufferedImage(
360, 300, BufferedImage.TYPE_INT_ARGB);
clear(bi);
setImage(bi);
}
};
newImageItem.addActionListener(newImage);
file.add(newImageItem);
if (webstart) {
//TODO Add open/save functionality using JNLP API
} else {
//TODO Add save functionality using J2SE API
file.addSeparator();
ActionListener openListener = new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
if (!dirty) {
JFileChooser ch = getFileChooser();
int result = ch.showOpenDialog(gui);
if (result==JFileChooser.APPROVE_OPTION ) {
try {
BufferedImage bi = ImageIO.read(
ch.getSelectedFile());
setImage(bi);
} catch (IOException e) {
showError(e);
e.printStackTrace();
}
}
} else {
// TODO
JOptionPane.showMessageDialog(
gui, "TODO - prompt save image..");
}
}
};
JMenuItem openItem = new JMenuItem("Open");
openItem.setMnemonic('o');
openItem.addActionListener(openListener);
file.add(openItem);
ActionListener saveListener = new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
JFileChooser ch = getFileChooser();
int result = ch.showSaveDialog(gui);
if (result==JFileChooser.APPROVE_OPTION ) {
try {
File f = ch.getSelectedFile();
ImageIO.write(BasicPaint.this.canvasImage, "png", f);
BasicPaint.this.originalImage = BasicPaint.this.canvasImage;
dirty = false;
} catch (IOException ioe) {
showError(ioe);
ioe.printStackTrace();
}
}
}
};
JMenuItem saveItem = new JMenuItem("Save");
saveItem.addActionListener(saveListener);
saveItem.setMnemonic('s');
file.add(saveItem);
}
if (canExit()) {
ActionListener exit = new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
System.exit(0);
}
};
JMenuItem exitItem = new JMenuItem("Exit");
exitItem.setMnemonic('x');
file.addSeparator();
exitItem.addActionListener(exit);
file.add(exitItem);
}
return file;
}
private void showError(Throwable t) {
JOptionPane.showMessageDialog(
gui,
t.getMessage(),
t.toString(),
JOptionPane.ERROR_MESSAGE);
}
JFileChooser chooser = null;
public JFileChooser getFileChooser() {
if (chooser==null) {
chooser = new JFileChooser();
FileFilter ff = new FileNameExtensionFilter("Image files", ImageIO.getReaderFileSuffixes());
chooser.setFileFilter(ff);
}
return chooser;
}
public boolean canExit() {
boolean canExit = false;
SecurityManager sm = System.getSecurityManager();
if (sm==null) {
canExit = true;
} else {
try {
sm.checkExit(0);
canExit = true;
} catch(Exception stayFalse) {
}
}
return canExit;
}
public JMenuBar getMenuBar(boolean webstart){
JMenuBar mb = new JMenuBar();
mb.add(this.getFileMenu(webstart));
return mb;
}
public static void main(String[] args) {
Runnable r = new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(
UIManager.getSystemLookAndFeelClassName());
} catch (Exception e) {
// use default
}
BasicPaint bp = new BasicPaint();
JFrame f = new JFrame("DooDoodle!");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setContentPane(bp.getGui());
f.setJMenuBar(bp.getMenuBar(false));
f.pack();
f.setMinimumSize(f.getSize());
f.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
public void text(Point point) {
String text = JOptionPane.showInputDialog(gui, "Text to add", "Text");
if (text!=null) {
Graphics2D g = this.canvasImage.createGraphics();
g.setRenderingHints(renderingHints);
g.setColor(this.color);
g.setStroke(stroke);
int n = 0;
g.drawString(text,point.x,point.y);
g.dispose();
this.imageLabel.repaint();
}
}
public void draw(Point point) {
Graphics2D g = this.canvasImage.createGraphics();
g.setRenderingHints(renderingHints);
g.setColor(this.color);
g.setStroke(stroke);
int n = 0;
g.drawLine(point.x, point.y, point.x+n, point.y+n);
g.dispose();
this.imageLabel.repaint();
}
class ImageMouseListener extends MouseAdapter {
@Override
public void mousePressed(MouseEvent arg0) {
// TODO Auto-generated method stub
if (activeTool==BasicPaint.SELECTION_TOOL) {
selectionStart = arg0.getPoint();
} else if (activeTool==BasicPaint.DRAW_TOOL) {
// TODO
draw(arg0.getPoint());
} else if (activeTool==BasicPaint.TEXT_TOOL) {
// TODO
text(arg0.getPoint());
} else {
JOptionPane.showMessageDialog(
gui,
"Application error. :(",
"Error!",
JOptionPane.ERROR_MESSAGE);
}
}
@Override
public void mouseReleased(MouseEvent arg0) {
if (activeTool==BasicPaint.SELECTION_TOOL) {
selection = new Rectangle(
selectionStart.x,
selectionStart.y,
arg0.getPoint().x,
arg0.getPoint().y);
}
}
}
class ImageMouseMotionListener implements MouseMotionListener {
@Override
public void mouseDragged(MouseEvent arg0) {
reportPositionAndColor(arg0);
if (activeTool==BasicPaint.SELECTION_TOOL) {
selection = new Rectangle(
selectionStart.x,
selectionStart.y,
arg0.getPoint().x-selectionStart.x,
arg0.getPoint().y-selectionStart.y);
} else if (activeTool==BasicPaint.DRAW_TOOL) {
draw(arg0.getPoint());
}
}
@Override
public void mouseMoved(MouseEvent arg0) {
reportPositionAndColor(arg0);
}
}
private void reportPositionAndColor(MouseEvent me) {
String text = "";
if (activeTool==BasicPaint.SELECTION_TOOL) {
text += "Selection (X,Y:WxH): " +
(int)selection.getX() +
"," +
(int)selection.getY() +
":" +
(int)selection.getWidth() +
"x" +
(int)selection.getHeight();
} else {
text += "X,Y: " + (me.getPoint().x+1) + "," + (me.getPoint().y+1);
}
output.setText(text);
}
}
This source is very patchy.
这个来源非常不完整。
- It has many parts with
// TODO - A
dirtyattribute is declared but never used in any meaningful way. ..
- 它有很多部分
// TODO - 一个
dirty属性声明，但任何有意义的方式从来没有使用过。..
It is just something I hacked together today and thought should be shown before it hit the posting limit.
这只是我今天一起破解的东西，我认为应该在达到发布限制之前显示。
Oh, and don't go looking for any 'OO design' since I did not put any in. If there is any, it is only by accident. This code is intended to demonstrate what is possible and how to start doing it.
哦，不要去寻找任何“OO 设计”，因为我没有放入任何东西。如果有，那只是偶然。此代码旨在演示什么是可能的以及如何开始这样做。
回答by kleopatra
You must add the mouseListener to the panel. That doesn't happen by default as you might have expected ;-)
您必须将 mouseListener 添加到面板。这在默认情况下不会发生，如您所料;-)
MainClass1() {
addMouseListener(this);
}
BTW: it's not recommended to expose public api that's only meant to be used internally. So instead of letting the panel implement MouseListener (which enforces the public exposure), let the panel create and use a MouseListener:
顺便说一句：不建议公开仅供内部使用的公共 API。因此，与其让面板实现 MouseListener（强制公开曝光），不如让面板创建并使用 MouseListener：
private MouseListener mouseListener;
MainClass1() {
mouseListener = createMouseListener();
addMouseListener(mouseListener);
}
protected MouseListener createMouseListener() {
MouseListener l = new MouseListener() {
}
return l;
}
BTW 2: calling the repaint on the limited area isn't exactly what you want (?) - it temporarilyadds the squares to the painting, they are lost whenever the whole panel is repainted (same effect as with getGraphics). Depending on what you really want,
BTW 2：在有限区域上调用重绘并不是你想要的（？） - 它暂时将方块添加到绘画中，每当整个面板重绘时它们都会丢失（与 getGraphics 的效果相同）。看你真正想要的是什么
- paint a single square at the most recently clicked position: call repaint()
- paint squares at all locations ever clicked: store the locations in a list and implement repaint to loop over that list. Here you may call the repaint with parameters, but why bother?
- 在最近点击的位置绘制一个正方形：调用 repaint()
- 在单击过的所有位置绘制方块：将位置存储在列表中并实现重绘以循环遍历该列表。在这里你可以调用带参数的重绘，但何必呢？
回答by Robin
Note the typo in your method:
请注意您的方法中的错字：
public void paintComponent(Graphics g){
super.paintComponents(g);
g.setColor(Color.RED);
g.fillRect(varx, vary, 10, 10);
}
Your method is named paintComponentwhile you are calling super.paintComponents(plural). If you override a method (and I would strongly suggest to add an @Overridetag to avoid that due to a typo you are actually overriding nothing) like paintComponent, make sure to call the supermethod (the same method, and not another one).
您的方法paintComponent在您调用时已命名super.paintComponents（复数）。如果您覆盖了一个方法（我强烈建议添加一个@Override标签以避免由于打字错误而导致您实际上没有覆盖任何内容），例如paintComponent，请确保调用该super方法（相同的方法，而不是另一个方法）。
回答by MadProgrammer
Firstly, the PaintClass11is never used...
首先，PaintClass11从未使用过...
Secondly even if it was, you create two separate instances of the PaintClass22, one that is placed on the frame and one which you are trying to update...so no updates will ever occur on the screen.
其次，即使是这样，您也创建了两个单独的 实例PaintClass22，一个放置在框架上，另一个您尝试更新......因此屏幕上永远不会发生更新。
You don't need two separate classes. Merge PaintClass11and PaintClass22into a single class and add that to your frame
您不需要两个单独的类。合并PaintClass11并PaintClass22成一个类，并添加到您的框架
