如何点击一个按钮，画出一个圆？

[冬雷软件]

如何点击一个按钮，画出一个圆？请帮忙贴出代码。

[dlglmf]

要自己动手才能学好的，
首先你要学会事件机制，
然后在jpanel或者其他的组件上，像jbutton,jtextarea啊，都可以，画任意图形，不过首先你要得到哪个组件的graphics才行

[冬雷软件]

为什么没人帮我贴代码呢？

[giant216]

你要掌握按钮的事件机制，然后就是java2D的作图，其实就是点击按钮调用画圆的函数而已，在Swing和Applet中还有jsp页面中都可以实现。

[冬雷软件]

我的目的不在于这，请帮忙贴段代码好吗？画直线也可。

[dlglmf]

public class TestApp {
boolean packFrame = false;

//Construct the application
public TestApp() {
TestFrame frame = new TestFrame();
//Validate frames that have preset sizes
//Pack frames that have useful preferred size info, e.g. from their layout
if (packFrame) {
frame.pack();
}
else {
frame.validate();
}
//Center the window
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
Dimension frameSize = frame.getSize();
if (frameSize.height > screenSize.height) {
frameSize.height = screenSize.height;
}
if (frameSize.width > screenSize.width) {
frameSize.width = screenSize.width;
}
frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
frame.setVisible(true);
}

//Main method
public static void main(String[] args) {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}
catch(Exception e) {
e.printStackTrace();
}
new TestApp();
}
}

[dlglmf]

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

public class TestFrame extends JFrame {
JPanel contentPane;
JButton jbt = new JButton();
JScrollPane jScrollPane1 = new JScrollPane();
JTextArea jta = new JTextArea();

//Construct the frame
public TestFrame() {
enableEvents(AWTEvent.WINDOW_EVENT_MASK);
try {
jbInit();
}
catch(Exception e) {
e.printStackTrace();
}
}

//Component initialization
private void jbInit() throws Exception {
contentPane = (JPanel) this.getContentPane();
jbt.setBounds(new Rectangle(99, 22, 83, 28));
jbt.setText("jButton1");
jbt.addActionListener(new TestFrame_jbt_actionAdapter(this));
contentPane.setLayout(null);
this.setSize(new Dimension(400, 300));
this.setTitle("Frame Title");
jScrollPane1.setBounds(new Rectangle(25, 61, 341, 198));
jta.setText("jTextArea1");
contentPane.add(jbt, null);
contentPane.add(jScrollPane1, null);
jScrollPane1.getViewport().add(jta, null);
}

//Overridden so we can exit when window is closed
protected void processWindowEvent(WindowEvent e) {
super.processWindowEvent(e);
if (e.getID() == WindowEvent.WINDOW_CLOSING) {
System.exit(0);
}
}

void jbt_actionPerformed(ActionEvent e) {
// jta.setText("");
Graphics g=jta.getGraphics();
g.drawString("dlg",50,50);
g.drawOval(30,30,100,100);
}
}

class TestFrame_jbt_actionAdapter implements java.awt.event.ActionListener {
TestFrame adaptee;

TestFrame_jbt_actionAdapter(TestFrame adaptee) {
this.adaptee = adaptee;
}
public void actionPerformed(ActionEvent e) {
adaptee.jbt_actionPerformed(e);
}
}

[dlglmf]

两个文件放一起，运行哪个总不用说了吧

[冬雷软件]

呵，感谢雨魂，我明白了。

[dlglmf]

别客气，多讨论