[英]confused with java graphics paint
我对 java 非常熟悉。我试图在 jpanel 中画一条线(使用 netbean ide)。而不是在主窗体上,而是在面板中..如何修改此代码,这是我的代码
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package graphic;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
/**
*
* @author nisansala
*/
public class grapix extends javax.swing.JFrame {
/**
* Creates new form grapix
*/
public grapix() {
initComponents();
}
@Override
public void paint(Graphics g) {
Graphics2D ga = (Graphics2D)g;
ga.setPaint(Color.red);
ga.drawLine(200,100,200,300);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("paint");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(153, 153, 153)
.addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 94, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(153, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(108, 108, 108)
.addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(149, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
Graphics gg = null;
// TODO add your handling code here:
// grap(gg);
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(grapix.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(grapix.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(grapix.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(grapix.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new grapix().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
// End of variables declaration
}
这是一个可以帮助您的示例:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Line2D;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
*
* @author David
*/
public class Test {
private static void createAndShowGUI() {
JFrame frame = new JFrame("Frame");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
final LinePanel linePanel = new LinePanel();
JPanel buttonPanel = new JPanel();
JButton buttonDrawRandomLine = new JButton("Draw Random Line");
final Random rand = new Random();
buttonDrawRandomLine.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
Line2D line = new Line2D.Double(rand.nextInt(200), rand.nextInt(200), rand.nextInt(200), rand.nextInt(200));
linePanel.addLine(line);
}
});
buttonPanel.add(buttonDrawRandomLine);
frame.add(buttonPanel, BorderLayout.SOUTH);
frame.add(linePanel, BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
createAndShowGUI();
}
});
}
}
class LinePanel extends JPanel {
ArrayList<Line2D> lines = new ArrayList<>();
public void addLine(Line2D l) {
lines.add(l);
repaint();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
for (Line2D l : lines) {
g2d.draw(l);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
}
1) 我不建议通过 Netbeans 拖放来学习 Swing,首先要手工学习,而不是使用拖放来让你的生活更轻松,一旦你了解了它是如何工作的。
2) 不要扩展JFrame
(对于 OOP 最佳实践)我们不扩展类,除非我们向它们添加他们不支持的功能
3)除非绝对必要,否则不要覆盖JFrame
paint
,而是使用像JPanel
这样的JComponent
并覆盖paintComponent
问题:您的按钮事件处理程序中没有事件代码。
单击按钮时修改状态变量。
private void jButton1ActionPerformed( java.awt.event.ActionEvent evt) { Graphics gg = null; // TODO add your handling code here: showLine = (true) ? false : true;
}
向paint方法添加条件检查。
@Override public void paint(Graphics g) { Graphics2D ga = (Graphics2D)g;
if (showLine) { ga.setPaint(Color.red); ga.drawLine(200,100,200,300); }
}
请添加要从按钮侦听器调用的适当方法。 还要在要画线的地方添加面板。 这似乎是以下内容的可能重复:-
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