Question

我打算创建一个简单的gui，它会在窗口的顶部三分之一处绘制一个椭圆形，在中间三分之一处显示一个名称，并在底部三分之一处绘制一个矩形（稍后将完成）< / p>

到目前为止，我能够创建和显示的唯一部分是四个按钮，最终意味着切换对象和标签的可见性。

我遇到的问题是我无法看到标签或椭圆形，而且我不确定我错过了什么，以防止它们变得不可见

＆＃13;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.io.*;


public class Gui extends JFrame
	implements ActionListener
{
	private JButton bottomLeftButton;
	private JButton bottomMiddleLeftButton;
	private JButton bottomRightButton;
	private JButton bottomMiddleRightButton;
	private OtherPanel mypanel;
	private JLabel name;
	private JPanel panelOne;
	private boolean visible;
	
	public void actionPerformed(ActionEvent e)
	{
		if(e.getSource() == bottomLeftButton)
		{
			visible = name.isVisible();
			name.setVisible(visible);
		}
		else if(e.getSource() == bottomMiddleLeftButton)
		{
			
		}
		else if (e.getSource() == bottomMiddleRightButton)
		{
			
		}
		else if (e.getSource() == bottomRightButton)
		{
			
		}
		repaint();
	}
	public Gui()
	{
		setTitle("First GUI");
		setSize(800,800);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		Container contentPane = this.getContentPane();
		contentPane.setLayout(new BorderLayout());
		
		JPanel BottomPanel = new JPanel(new GridLayout(1,4));
		contentPane.add(BottomPanel, BorderLayout.SOUTH);
		
		bottomLeftButton = new JButton("Name");
		bottomLeftButton.addActionListener(this);
		BottomPanel.add(bottomLeftButton);
		
		bottomMiddleLeftButton = new JButton("Oval");
		bottomMiddleLeftButton.addActionListener(this);
		BottomPanel.add(bottomMiddleLeftButton);
		
		bottomMiddleRightButton = new JButton("Square");
		bottomMiddleRightButton.addActionListener(this);
		BottomPanel.add(bottomMiddleRightButton);
		
		bottomRightButton = new JButton("Special");
		bottomRightButton.addActionListener(this);
		BottomPanel.add(bottomRightButton);
		
		JPanel centerPanel = new JPanel();
		centerPanel.setLayout(new GridLayout(3,1));
		
		panelOne = new OtherPanel();
		
		name = new JLabel("Name");
		name.setHorizontalAlignment(SwingConstants.CENTER);
		
		JLabel label3 = new JLabel("Label3");
		
		centerPanel.add(panelOne);
		centerPanel.add(name);
		centerPanel.add(label3);
		
	}
	
	public static void main(String[] args)
	{
		Gui gui = new Gui();
		gui.setVisible(true);
	}
}

＆＃13;

（意为绘制椭圆形）

＆＃13;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class OtherPanel extends JPanel
{
	public void paintComponent(Graphics g)
	{
		int x = 10;
		int y = 10;
		int width = getWidth(); //ten pixels of spaces
		int height = getHeight();
		g.fillOval(x, y, width, height);
	}
}

＆＃13;

Answer 1

缺少一行代码来将对象添加到contentPane

contentPane.add（centerPanel）;在gui（）方法结束时

Java GUI：对象和标签不可见

1 个答案: