paintComponent 问题 Java - Swing
issues with paintComponent Java - Swing
我正在尝试编写一个 swing gui，我可以通过按下两个不同的 JMenuItem、圆形和矩形在随机位置绘制形状。
我让它工作了，但我用了
Graphics2D gg = (Graphics2D) canvas.getGraphics();
有人建议我使用并覆盖 paintComponent()。所以我几个小时前就开始尝试了：D
我知道有很多关于这个的问题，但我真的读了很多，尝试和搜索但我无法帮助自己..
请查看我的 RandomDrawer Class，我发现我必须在那里实现 paintComponent()（我希望至少如此）。
进一步在下一个方法
public void actionPerformed(ActionEvent e)
我开始知道发生了什么动作，我可以或者我怎样才能告诉他之后画画？还是我的整个方法有缺陷？
这是我的代码。
感谢您的包容，非常感谢。
package plotterpackage;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.Random;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.WindowConstants;
import javax.swing.border.BevelBorder;
import javax.swing.text.JTextComponent;
public class PlotterApp implements ComponentListener {
private JFrame frame;
private JPanel canvas;
private JPanel statusBar;
private JTextField status;
/**
* Public default constructor.
*/
public PlotterApp() {
initialize();
}
/**
* Start of the application.
* @param args command line arguments
*/
public static void main(String[] args) {
PlotterApp app = new PlotterApp();
app.start();
}
/**
* Initialize the application.
*/
protected void initialize() {
frame = new JFrame("Main");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setBounds(50,50, 50+640, 50+480);
frame.setBackground(Color.GREEN);
frame.setJMenuBar(createMenuBar());
frame.getContentPane().add(createContent(), BorderLayout.CENTER);
frame.getContentPane().add(createStatusBar(),BorderLayout.SOUTH);
}
/**
* Start the graphical user interface.
*/
public void start() {
// show the GUI
frame.setVisible(true);
status.setText("Application started");
}
/**-*
* Internal helper to create the main content.
* @return component with application content.
*/
protected JComponent createContent() {
canvas = new JPanel();
canvas.addMouseListener(new Painter());
canvas.addMouseMotionListener(new Painter());
canvas.addComponentListener(this);
canvas.setBackground(new Color(128,218,255));
canvas.setForeground(Color.RED);
canvas.setBorder(new BevelBorder(BevelBorder.LOWERED));
return canvas;
}
/**
* Internal helper to create the statusbar and -fields.
* @return component with status/bar.
*/
protected JComponent createStatusBar() {
FlowLayout layout = new FlowLayout(FlowLayout.LEFT);
layout.setHgap(5);
statusBar = new JPanel(layout);
statusBar.add(new JLabel("Status: "));
status = new JTextField();
status.setPreferredSize(new Dimension(400,25));
status.setEditable(false);
status.setBorder(newBevelBorder(BevelBorder.RAISED,Color.MAGENTA,Color.LIGHT_GRAY));
status.getInsets().set(2, 10, 2, 10);
statusBar.add(status);
return statusBar;
}
/**
* Internal helper to create the frames menubar.
* @return menu bar
*/
protected JMenuBar createMenuBar() {
JMenuBar mb = new JMenuBar();
JMenuItem item;
JMenu menu;
// Action menu
menu = new JMenu("Actions");
mb.add(menu);
item = new JMenuItem("Draw RandomCircle");
item.addActionListener(new RandomDrawer());
menu.add(item);
item = new JMenuItem("Draw RandomRectangle");
item.addActionListener(new RandomDrawer());
menu.add(item);
menu.addSeparator();
item = new JMenuItem("Exit");
item.addActionListener(new AppCloser());
menu.add(item);
// Color menu not used so far
menu = new JMenu("Colors");
mb.add(menu);
// Help menu not used so far
menu = new JMenu("Help");
mb.add(menu);
return mb;
}
class AppCloser implements ActionListener {
/* (non-Javadoc)
* @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("application finished, bye-bye... ");
frame.setVisible(false);
frame.dispose();
System.exit(0);
}
}
class RandomDrawer extends JPanel implements ActionListener {
/* (non-Javadoc)
* @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLACK);
g2.drawOval(100, 100, 100, 100);
}
@Override
public void actionPerformed(ActionEvent e) {
Random generator = new Random();
int x = generator.nextInt(100)+100;
int y = generator.nextInt(100)+100;
int w;
if (e.getActionCommand()==("Draw RandomCircle")) {
System.out.printf("x = %d y = %d\n", x, y);
//status.setText(String.format("rnd draw x: y: "));
//gg.setColor(Color.BLACK);
//gg.drawOval(x, y, generator.nextInt(x), generator.nextInt(y));
}
else if (e.getActionCommand()==("Draw RandomRectangle")) {
System.out.printf("x = %d y = %d\n", x, y);
//status.setText(String.format("rnd draw x: y: "));
//Graphics2D gg = (Graphics2D) canvas.getGraphics();
//gg.setColor(Color.BLACK);
//gg.drawRect(x, y, generator.nextInt(x), generator.nextInt(y));
}
}
}
class Painter extends MouseAdapter implements MouseMotionListener {
Point start, end;
int startX, startY, oldX, oldY, oldWidth, oldHeight;
public void mousePressed(MouseEvent e) {
start = e.getPoint();
oldX = startX;
oldY = startY;
startX = e.getX();
startY = e.getY();
status.setText(String.format("Mouse start: " + start));
}
public void mouseDragged(MouseEvent e) {
Graphics2D gc = (Graphics2D)canvas.getGraphics();
gc.setColor(new Color(128, 218, 255));
gc.drawOval(oldX, oldY, oldWidth, oldHeight);
System.out.printf("oldWidth ist = %3d, oldHeight ist = %3d\n", oldWidth, oldHeight);
oldWidth = e.getX();
oldHeight = e.getY();
gc.setColor(Color.BLACK);
gc.drawOval(startX, startY, e.getX(), e.getY());
}
public void mouseReleased(MouseEvent e) {
end = e.getPoint();
status.setText(String.format("Mouse end: " + end));
}
}
@Override
public void componentHidden(ComponentEvent e) {
// TODO Auto-generated method stub
}
@Override
public void componentMoved(ComponentEvent e) {
// TODO Auto-generated method stub
}
@Override
public void componentResized(ComponentEvent e) {
// TODO Auto-generated method stub
}
@Override
public void componentShown(ComponentEvent e) {
// TODO Auto-generated method stub
}
}
您可以将形状放在某种容器中，例如 ArrayList。
在 paintComponent(Graphics g) 中，你应该从该列表中绘制每个形状，在 actionPerformed(ActionEvent e) 中，你应该使用 repaint () 对象上的方法，您在其上绘制。
不要做...
Graphics2D gg = (Graphics2D) canvas.getGraphics();
这不是自定义绘画的方式。 Swing 会在需要绘制某些东西时询问您，您应该重新绘制组件的当前状态。
首先查看 Painting in AWT and Swing and Performing Custom Painting 了解更多详情
基本上，您需要覆盖JPanel的paintComponent方法（确保首先调用super.paintComponent）并绘制组件的当前状态。
您需要以对您的（List 或自定义对象甚至 Image）最有用的任何形式存储状态
您可以在更改状态后通过调用 repaint 请求 API 更新 UI
我正在尝试编写一个 swing gui，我可以通过按下两个不同的 JMenuItem、圆形和矩形在随机位置绘制形状。 我让它工作了，但我用了
Graphics2D gg = (Graphics2D) canvas.getGraphics();
有人建议我使用并覆盖 paintComponent()。所以我几个小时前就开始尝试了：D 我知道有很多关于这个的问题，但我真的读了很多，尝试和搜索但我无法帮助自己..
请查看我的 RandomDrawer Class，我发现我必须在那里实现 paintComponent()（我希望至少如此）。 进一步在下一个方法
public void actionPerformed(ActionEvent e)
我开始知道发生了什么动作，我可以或者我怎样才能告诉他之后画画？还是我的整个方法有缺陷？
这是我的代码。
感谢您的包容，非常感谢。
package plotterpackage;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.Random;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.WindowConstants;
import javax.swing.border.BevelBorder;
import javax.swing.text.JTextComponent;
public class PlotterApp implements ComponentListener {
private JFrame frame;
private JPanel canvas;
private JPanel statusBar;
private JTextField status;
/**
* Public default constructor.
*/
public PlotterApp() {
initialize();
}
/**
* Start of the application.
* @param args command line arguments
*/
public static void main(String[] args) {
PlotterApp app = new PlotterApp();
app.start();
}
/**
* Initialize the application.
*/
protected void initialize() {
frame = new JFrame("Main");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setBounds(50,50, 50+640, 50+480);
frame.setBackground(Color.GREEN);
frame.setJMenuBar(createMenuBar());
frame.getContentPane().add(createContent(), BorderLayout.CENTER);
frame.getContentPane().add(createStatusBar(),BorderLayout.SOUTH);
}
/**
* Start the graphical user interface.
*/
public void start() {
// show the GUI
frame.setVisible(true);
status.setText("Application started");
}
/**-*
* Internal helper to create the main content.
* @return component with application content.
*/
protected JComponent createContent() {
canvas = new JPanel();
canvas.addMouseListener(new Painter());
canvas.addMouseMotionListener(new Painter());
canvas.addComponentListener(this);
canvas.setBackground(new Color(128,218,255));
canvas.setForeground(Color.RED);
canvas.setBorder(new BevelBorder(BevelBorder.LOWERED));
return canvas;
}
/**
* Internal helper to create the statusbar and -fields.
* @return component with status/bar.
*/
protected JComponent createStatusBar() {
FlowLayout layout = new FlowLayout(FlowLayout.LEFT);
layout.setHgap(5);
statusBar = new JPanel(layout);
statusBar.add(new JLabel("Status: "));
status = new JTextField();
status.setPreferredSize(new Dimension(400,25));
status.setEditable(false);
status.setBorder(newBevelBorder(BevelBorder.RAISED,Color.MAGENTA,Color.LIGHT_GRAY));
status.getInsets().set(2, 10, 2, 10);
statusBar.add(status);
return statusBar;
}
/**
* Internal helper to create the frames menubar.
* @return menu bar
*/
protected JMenuBar createMenuBar() {
JMenuBar mb = new JMenuBar();
JMenuItem item;
JMenu menu;
// Action menu
menu = new JMenu("Actions");
mb.add(menu);
item = new JMenuItem("Draw RandomCircle");
item.addActionListener(new RandomDrawer());
menu.add(item);
item = new JMenuItem("Draw RandomRectangle");
item.addActionListener(new RandomDrawer());
menu.add(item);
menu.addSeparator();
item = new JMenuItem("Exit");
item.addActionListener(new AppCloser());
menu.add(item);
// Color menu not used so far
menu = new JMenu("Colors");
mb.add(menu);
// Help menu not used so far
menu = new JMenu("Help");
mb.add(menu);
return mb;
}
class AppCloser implements ActionListener {
/* (non-Javadoc)
* @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("application finished, bye-bye... ");
frame.setVisible(false);
frame.dispose();
System.exit(0);
}
}
class RandomDrawer extends JPanel implements ActionListener {
/* (non-Javadoc)
* @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLACK);
g2.drawOval(100, 100, 100, 100);
}
@Override
public void actionPerformed(ActionEvent e) {
Random generator = new Random();
int x = generator.nextInt(100)+100;
int y = generator.nextInt(100)+100;
int w;
if (e.getActionCommand()==("Draw RandomCircle")) {
System.out.printf("x = %d y = %d\n", x, y);
//status.setText(String.format("rnd draw x: y: "));
//gg.setColor(Color.BLACK);
//gg.drawOval(x, y, generator.nextInt(x), generator.nextInt(y));
}
else if (e.getActionCommand()==("Draw RandomRectangle")) {
System.out.printf("x = %d y = %d\n", x, y);
//status.setText(String.format("rnd draw x: y: "));
//Graphics2D gg = (Graphics2D) canvas.getGraphics();
//gg.setColor(Color.BLACK);
//gg.drawRect(x, y, generator.nextInt(x), generator.nextInt(y));
}
}
}
class Painter extends MouseAdapter implements MouseMotionListener {
Point start, end;
int startX, startY, oldX, oldY, oldWidth, oldHeight;
public void mousePressed(MouseEvent e) {
start = e.getPoint();
oldX = startX;
oldY = startY;
startX = e.getX();
startY = e.getY();
status.setText(String.format("Mouse start: " + start));
}
public void mouseDragged(MouseEvent e) {
Graphics2D gc = (Graphics2D)canvas.getGraphics();
gc.setColor(new Color(128, 218, 255));
gc.drawOval(oldX, oldY, oldWidth, oldHeight);
System.out.printf("oldWidth ist = %3d, oldHeight ist = %3d\n", oldWidth, oldHeight);
oldWidth = e.getX();
oldHeight = e.getY();
gc.setColor(Color.BLACK);
gc.drawOval(startX, startY, e.getX(), e.getY());
}
public void mouseReleased(MouseEvent e) {
end = e.getPoint();
status.setText(String.format("Mouse end: " + end));
}
}
@Override
public void componentHidden(ComponentEvent e) {
// TODO Auto-generated method stub
}
@Override
public void componentMoved(ComponentEvent e) {
// TODO Auto-generated method stub
}
@Override
public void componentResized(ComponentEvent e) {
// TODO Auto-generated method stub
}
@Override
public void componentShown(ComponentEvent e) {
// TODO Auto-generated method stub
}
}
您可以将形状放在某种容器中，例如 ArrayList。 在 paintComponent(Graphics g) 中，你应该从该列表中绘制每个形状，在 actionPerformed(ActionEvent e) 中，你应该使用 repaint () 对象上的方法，您在其上绘制。
不要做...
Graphics2D gg = (Graphics2D) canvas.getGraphics();
这不是自定义绘画的方式。 Swing 会在需要绘制某些东西时询问您，您应该重新绘制组件的当前状态。
首先查看 Painting in AWT and Swing and Performing Custom Painting 了解更多详情
基本上，您需要覆盖JPanel的paintComponent方法（确保首先调用super.paintComponent）并绘制组件的当前状态。
您需要以对您的（List 或自定义对象甚至 Image）最有用的任何形式存储状态
您可以在更改状态后通过调用 repaint 请求 API 更新 UI