java JLabel 不显示

JLabel doesn't show up

提问by James L.

I'm working on a program but my JLabel doesn't show up. My JButton works perfectly (it appears) but for some reason the JLabel does not appear. I have checked on internet but I Haven't found anything.

我正在开发一个程序，但我的 JLabel 没有出现。我的 JButton 工作正常（它出现）但由于某种原因 JLabel 没有出现。我已经在互联网上检查过，但我没有找到任何东西。

package com.hinx.client;

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

public class Main {

    public static void main(String [] args) 
    {
        createWindow();
    }       

    static void createWindow()
    {           

        //Create panel
        JPanel content = new JPanel();
        content.setLayout(null);

        //Build the frame
        JFrame frame = new JFrame("Hinx - A marketplace for apps - Client ALPHA_0.0.1");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(700, 400);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.add(content);
        frame.setVisible(true);

        //Add the login button
        JButton login = new JButton("Login");
        login.setBounds(0, 342, 150, 30);

        //Create login label
        JLabel loginlabel = new JLabel("Login Area");

        //Create login panel
        JPanel loginpanel = new JPanel();
        loginpanel.setLayout(null);
        loginpanel.setBounds(0, 0, 150, 400);
        loginpanel.setBackground(Color.gray);
        loginpanel.add(login);
        loginpanel.add(loginlabel);         

        content.add(loginpanel);
    }       
}

回答by Alexis C.

Set a layoutfor your panel. Per example :

设置一个layout你panel。每个例子：

loginpanel.setLayout(new BorderLayout());

You can learn more about layouts here.

您可以在此处了解有关布局的更多信息。

Here's what I get :

这是我得到的：

回答by mKorbel

I have checked on internet but I Haven't found anything.

我已经在互联网上检查过，但我没有找到任何东西。

• JFrame is visible before JComponents (frame.add(content);) are added / created

• move code line frame.setVisible(true);(better everything about JFrame) to the end of constuctor

• JFrame 在frame.add(content);添加/创建JComponents ( )之前是可见的

• 将代码行frame.setVisible(true);（更好的关于 JFrame 的所有内容）移动到构造函数的末尾

回答by Branislav Lazic

1. Use layouts. FlowLayoutshould be fine in this case. Do not call setBounds()and do not set layout as a null.

2. Add label and button on JPanel

3. Then add JPanelon JFrame

4. Call pack()instead of setSize()

5. Call setVisible(true)in the end.

1. 使用布局。FlowLayout在这种情况下应该没问题。不要调用setBounds()并且不要将布局设置为null.

2. 添加标签和按钮 JPanel

3. 然后添加JPanel上JFrame

4. 调用pack()而不是setSize()

5. 最后打电话setVisible(true)。

Good luck!

祝你好运！

回答by Amarnath

You are making setLayout null.

您正在制作 setLayout null。

    JPanel loginpanel = new JPanel();
    loginpanel.setLayout(null);

Use this,

用这个，

    JPanel loginpanel = new JPanel();
    loginpanel.setLayout(new BorderLayout());        

Run the UI on the EDTinstead of running on the main thread. Read this post.

EDT在主线程上运行 UI而不是在主线程上运行。阅读这篇文章。

Example:

例子：

public static void main(String [] args) 
    {
        Runnable r  = new Runnable() {

            @Override
            public void run() {
                createWindow();
            }
        };

        EventQueue.invokeLater(r);
    }