问题描述
我正在尝试创建一个小程序,它将生成与文本框中指定的数字一样多的椭圆。出现文本框,但在按Enter键时,我的paintComponent不会绘制。提前谢谢。
I'm trying to create an applet that will produce as many ovals as the number specified within a textbox. The textbox appears, but upon hitting enter, my paintComponent does not draw. Thank you in advance.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import net.miginfocom.layout.*;
import net.miginfocom.swing.MigLayout;
import java.awt.geom.*;
public class OvalDrawer extends JApplet
{
private JLabel numberL;
private JTextField numberTF;
private NumHandler numHandler;
public static final int WIDTH = 500;
public static final int HEIGHT = 500;
//Create Layout
public void init()
{
setLayout(new MigLayout("wrap 2"));
numberL = new JLabel("Enter number of ovals to draw:");
numberTF = new JTextField(7);
add(numberL);
add(numberTF);
numHandler = new NumHandler();
numberTF.addActionListener(numHandler);
setSize(500, 500);
}
//Event Handler
public class NumHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
repaint();
}
}
//Draw Ovals
public void paintComponent (Graphics g)
{
super.paintComponents(g);
int number;
int x = 10;
int y = 30;
int width = 20;
int height = 10;
number = Integer.parseInt(numberTF.getText());
for (int i = 0; i < number; i++)
{
g.drawOval(x, y, width, height);
x += 5;
y += 5;
width += 5;
height += 5;
}
}
}
推荐答案
JApplet类没有要覆盖的paintComponent方法。请注意,您的编译器不会让您调用实际的超级方法(您认为您可能正在执行此操作,但实际上您正在调用 super.paintComponents(...)
,一种完全不同的方法)。
A JApplet class does not have a paintComponent method to override. Note that your compiler won't let you call the actual super method (you think you may be doing this, but you're actually calling super.paintComponents(...)
, a completely different method).
一个糟糕的解决方案是覆盖JApplet的paint方法,但我强烈建议你不要这样做。相反,您应该绘制JPanel的paintComponent方法,然后让JApplet显示JPanel。此外,你会想养成使用 @Override
注释的习惯,以确保你实际上覆盖了你认为的方法。
A bad solution is to override the JApplet's paint method, but I strongly advise you not to do this. Instead you should draw in the paintComponent method of a JPanel and then have the JApplet display that JPanel. Also, you'll want to get into the habit of using the @Override
annotation to be sure that you're actually overriding methods you think are.
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