我在java swing中创建了三个类（一个用于main，frame，用于面板）。添加组件后，它们在框架中不可见。为什么？ [英] I have created three classes(one for main, frame, for panel) in java swing. After adding components they are not visible in the frame. Why?

问题描述

//Main Class:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Order
{
	public static void main(String[] args)
	{
		OrderFrame frame = new OrderFrame();
	}
}

//Frame Class:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class OrderFrame extends JFrame
{
	OrderFrame()
	{
		setTitle("Place Order");
		setLayout(null);
		setSize(500,500);
		this.add(new OrderPanel());
		setVisible(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
}

//Panel Class:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class OrderPanel extends JPanel implements ActionListener
{	
	JLabel l1,l2;
	JButton b1;
	public OrderPanel()
	{
		l1 = new JLabel("Welcome to Online Food Delivery System");
		b1 = new JButton("Close Window");
		b1.addActionListener(this);
		add(l1);
		add(b1);
	}
	public void actionPerformed(ActionEvent e) 
	{
		System.exit(0);
	}
}

我的尝试：



我仍​​然要编写很多代码，但如果我运行Main Class（类名 - 顺序），我应该得到一个带有Label和按钮的GUI。但我得到一个空白的GUI。我尝试编写this.add（b1）和this.add（l1），但没有改变。我错过了什么？

What I have tried:

I still have to write a lot of code, but I if I run the Main Class(Class name - order) I should get a GUI with a Label and a button. But I get a blank GUI. I tried writing this.add(b1) and this.add(l1) but with no change. What am I missing?

推荐答案

我建​​议你阅读： Java JButton - javatpoint [ ^ ]

I'd suggest to read this: Java JButton - javatpoint[^]

import java.awt.event.*;
import javax.swing.*;
public class ButtonExample {
public static void main(String[] args) {
    JFrame f=new JFrame("Button Example");
    final JTextField tf=new JTextField();
    tf.setBounds(50,50, 150,20);
    JButton b=new JButton("Click Here");
    b.setBounds(50,100,95,30);
    b.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
            tf.setText("Welcome to Javatpoint.");
        }
    });
    f.add(b);f.add(tf);
    f.setSize(400,400);
    f.setLayout(null);
    f.setVisible(true);
}
}

根据以上代码，你错过了这一行：

Based on above code, you missed this line:

jcontrol.setBounds(50,50, 150,20);

这篇关于我在java swing中创建了三个类（一个用于main，frame，用于面板）。添加组件后，它们在框架中不可见。为什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！