Question

每次制作新的JFrame对象时，框架都会显示在0,0位置。我已经尝试使用setLocationRelativeTo（）查找如何使窗口居中，但我尝试在容器上调用的所有内容都显示为不可编译的代码。这是我正在使用的课程之一：

package Ginfo;

import java.awt.*;
import java.awt.event.*;
import java.io.*;

import javax.swing.*;

public class EditUsers extends JFrame implements ActionListener
{
    Container EU;

    JPanel modUsers, button, output;
    JLabel user, password;
    JTextField tuser, tpassword;
    JTextArea toutput;
    JButton addAdmin, addStand, editPass, removeUser, exit;

    ObjectOutputStream oout;
    ObjectInputStream oin;

    Message m;
    ConnectInfo c;

public EditUsers (ObjectOutputStream oout2, ObjectInputStream oin2, Message m2, ConnectInfo a)
{
    super("User Modifications");
    EU = getContentPane();
    oout = oout2;
    try 
    {
        oout.reset();
    } 
    catch (IOException e)
    {
        e.printStackTrace();
    }
    oin = oin2;
    m = m2;
    c = a;

    buildUserInfoPanel();
    buildOutputPanel();
    buildButtonPanel();
    EU.add(modUsers, BorderLayout.NORTH);
    EU.add(output, BorderLayout.CENTER);
    EU.add(button, BorderLayout.SOUTH);
    pack();
    setVisible(true);

}

private void buildUserInfoPanel()
{
    modUsers = new JPanel();
    modUsers.setLayout(new GridLayout (2,2));
    user = new JLabel ("Enter the username you wish to edit: ");
    tuser = new JTextField (15);
    password = new JLabel("Enter their new password: ");
    tpassword = new JTextField(15);

    modUsers.add(user);
    modUsers.add(tuser);
    modUsers.add(password);
    modUsers.add(tpassword);
}

private void buildOutputPanel()
{
    output = new JPanel();
    toutput = new JTextArea();
    toutput.setPreferredSize(new Dimension (400,100));

    output.add(toutput);
}

private void buildButtonPanel()
{
    button = new JPanel();
    addAdmin = new JButton ("Add user as administrator");
    addStand = new JButton ("Add user as standard");
    editPass = new JButton ("Change password");
    removeUser = new JButton ("Remove user");
    exit = new JButton ("Back");

    button.add(addAdmin);
    button.add(addStand);
    button.add(editPass);
    button.add(removeUser);
    button.add(exit);

    addAdmin.addActionListener(this);
    addStand.addActionListener(this);
    editPass.addActionListener(this);
    removeUser.addActionListener(this);
    exit.addActionListener(this);
}

public void actionPerformed(ActionEvent e) 
{
    if (e.getSource() == addAdmin)
    {
        m.type = Message.ADDADMIN;
        m.main = tuser.getText();
        m.setPassword = tpassword.getText();
        m.setPermission = 1;
    }
    else if (e.getSource() == addStand)
    {
        m.type = Message.ADDSTANDARD;
        m.main = tuser.getText();
        m.setPassword = tpassword.getText();
        m.setPermission = 2;
    }
    else if (e.getSource() == editPass)
    {
        m.type = Message.CHANGEPASSWORD;
        m.main = tuser.getText();
        m.setPassword = tpassword.getText();
    }
    else if (e.getSource() == removeUser)
    {
        m.type = Message.REMOVEUSER;
        m.main = tuser.getText();
    }
    else if (e.getSource() == exit)
    {
        new WhatToDo (oout, oin, m, c);
        dispose();
        return;
    }
    try 
    {
        oout.writeObject(m);
        m = (Message)oin.readObject();
        toutput.setText(m.response);
    } 
    catch (IOException e1) 
    {
        e1.printStackTrace();
    } 
    catch (ClassNotFoundException e1) 
    {
        e1.printStackTrace();
    }
}
}

当我运行此代码时，窗口从（0,0）位置开始。我想做的是，将窗口大小调整为运行计算机分辨率大小的1/4，并重置窗口的位置，使窗口的中心位于屏幕的中心。如果分辨率为1000x1000，窗口应为250x250，位于（500 - 250/2）X，（500 - 250/2）Y（左上角）乘（500 + 250/2）X，（500 + 250/2 ）Y（右下角）

（请注意，我正在为每个窗口使用不同的类，我正在打开并在进程完成时关闭它，所以没有其他类，这将无法完全编译。我传递的是ObjectOutputStream，ObjectInputStream，我称之为Message的对象，另一个我称之为ConnectInfo的对象。输出和输入流是为了使连接保持活动状态，Message是来回发送的序列化信息，ConnectionInfo基本上保存cookie信息（用户连接，会话信息，权限级别等。）

好的，我现在

package Ginfo;

import java.awt.*;
import java.awt.event.*;
import java.io.*;

import javax.swing.*;

public class EditUsers implements ActionListener
{

Container EU;

JFrame myJFrame;

JPanel modUsers, button, output;
JLabel user, password;
JTextField tuser, tpassword;
JTextArea toutput;
JButton addAdmin, addStand, editPass, removeUser, exit;

ObjectOutputStream oout;
ObjectInputStream oin;

Message m;
ConnectInfo c;

public EditUsers (ObjectOutputStream oout2, ObjectInputStream oin2, Message m2, ConnectInfo a)
{
    myJFrame = new JFrame("User Modifications");
    EU = myJFrame.getContentPane();
    oout = oout2;
    try 
    {
        oout.reset();
    } 
    catch (IOException e)
    {
        e.printStackTrace();
    }
    oin = oin2;
    m = m2;
    c = a;

    buildUserInfoPanel();
    buildOutputPanel();
    buildButtonPanel();
    EU.add(modUsers, BorderLayout.NORTH);
    EU.add(output, BorderLayout.CENTER);
    EU.add(button, BorderLayout.SOUTH);
    myJFrame.add(EU);
    myJFrame.pack();
    myJFrame.setVisible(true);

}

private void buildUserInfoPanel()
{
    modUsers = new JPanel();
    modUsers.setLayout(new GridLayout (2,2));
    user = new JLabel ("Enter the username you wish to edit: ");
    tuser = new JTextField (15);
    password = new JLabel("Enter their new password: ");
    tpassword = new JTextField(15);

    modUsers.add(user);
    modUsers.add(tuser);
    modUsers.add(password);
    modUsers.add(tpassword);
}

private void buildOutputPanel()
{
    output = new JPanel();
    toutput = new JTextArea();
    toutput.setPreferredSize(new Dimension (200,100));

    output.add(toutput);
}

private void buildButtonPanel()
{
    button = new JPanel();
    addAdmin = new JButton ("Add user as administrator");
    addStand = new JButton ("Add user as standard");
    editPass = new JButton ("Change password");
    removeUser = new JButton ("Remove user");
    exit = new JButton ("Back");

    button.add(addAdmin);
    button.add(addStand);
    button.add(editPass);
    button.add(removeUser);
    button.add(exit);

    addAdmin.addActionListener(this);
    addStand.addActionListener(this);
    editPass.addActionListener(this);
    removeUser.addActionListener(this);
    exit.addActionListener(this);
}

public void actionPerformed(ActionEvent e) 
{
    if (e.getSource() == addAdmin)
    {
        m.type = Message.ADDADMIN;
        m.main = tuser.getText();
        m.setPassword = tpassword.getText();
        m.setPermission = 1;
    }
    else if (e.getSource() == addStand)
    {
        m.type = Message.ADDSTANDARD;
        m.main = tuser.getText();
        m.setPassword = tpassword.getText();
        m.setPermission = 2;
    }
    else if (e.getSource() == editPass)
    {
        m.type = Message.CHANGEPASSWORD;
        m.main = tuser.getText();
        m.setPassword = tpassword.getText();
    }
    else if (e.getSource() == removeUser)
    {
        m.type = Message.REMOVEUSER;
        m.main = tuser.getText();
    }
    else if (e.getSource() == exit)
    {
        new WhatToDo (oout, oin, m, c);
        myJFrame.dispose();
        return;
    }
    try 
    {
        oout.writeObject(m);
        m = (Message)oin.readObject();
        toutput.setText(m.response);
    } 
    catch (IOException e1) 
    {
        e1.printStackTrace();
    } 
    catch (ClassNotFoundException e1) 
    {
        e1.printStackTrace();
    }
}
}

现在问题在于myJFrame.add（EU）它说“java.lang.IllegalArgumentException：将容器的父级添加到自身”。感谢您提前提供任何帮助。

Answer 1

尝试myJFrameObject.setLocationRelativeTo(null);

来自JavaDoc

如果组件为null，或者与此组件关联的GraphicsConfiguration为null，则窗口将放置在屏幕的中心。可以使用GraphicsEnvironment.getCenterPoint方法获取中心点。
如果组件不为null，但当前未显示，则窗口将放置在与此组件关联的GraphicsConfiguration定义的目标屏幕的中心。
如果组件不为空并显示在屏幕上，则窗口的位置使得窗口的中心与组件的中心重合。

修改

我刚刚在这个（不太高级的）构造函数上测试了你的代码，它看起来像你想要的那样（至少那是我希望的）。我在setLocationRelativeTo(null)之前放置setVisible(true)以确保Frame包含其所有元素并知道在居中时使用的大小。

public EditUsers() {
    super("User Modifications");
    //I removed some not GUI operations

    EU = getContentPane();

    buildUserInfoPanel();
    buildOutputPanel();
    buildButtonPanel();
    EU.add(modUsers, BorderLayout.NORTH);
    EU.add(output, BorderLayout.CENTER);
    EU.add(button, BorderLayout.SOUTH);
    pack();
    //put setLocationRelativeTo before setVisible() 
    setLocationRelativeTo(null);
    setVisible(true);
}

Answer 2

你必须在GUI构造函数中调用最后的代码行

JFrame#pack();
JFrame#setLocationRelativeTo(null); // Windows OS
//or JFrame#setLocationByPlatform(true); //depends of Native OS
JFrame#setVisible(true);

另一个建议

不扩展JFrame，创建局部变量，实例
不要为JTextArea, better would be to set for Column and row instead
可能为GridLayout设置button = new JPanel();，JPanel默认为FlowLayout

修改

将代码行EditUsers eu = new EditUsers();放在主类中，返回带有JFrame的新GUI实例，包装代码创建GUI到InitialThread，希望别的： - ）

   public static void main(String[] a_args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                EditUsers eu = new EditUsers();
            }
        });
    }

EDIT2

修改后的代码返回

enter image description here

来自代码

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;

public class EditUsers implements ActionListener {

    private JFrame myJFrame;
    private JPanel modUsers, button, output;
    private JLabel user, password;
    private JTextField tuser, tpassword;
    private JTextArea toutput;
    private JButton addAdmin, addStand, editPass, removeUser, exit;
    private ObjectOutputStream oout;
    private ObjectInputStream oin;
    //private Message m;
    //private ConnectInfo c;

    public static void main(String[] a_args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                EditUsers eu = new EditUsers();
            }
        });
    }

    public EditUsers() {
        //editUsers(oout2, oin2, m2, a);
        buildUserInfoPanel();
        buildOutputPanel();
        buildButtonPanel();
        myJFrame = new JFrame("User Modifications");
        myJrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        myJFrame.add(modUsers, BorderLayout.NORTH);
        myJFrame.add(output, BorderLayout.CENTER);
        myJFrame.add(button, BorderLayout.SOUTH);
        myJFrame.pack();
        myJFrame.setLocationRelativeTo(null);
        myJFrame.setVisible(true);
    }

    /*private void editUsers(ObjectOutputStream oout2, 
          ObjectInputStream oin2, Message m2, ConnectInfo a) {
        oout = oout2;
        try {
            oout.reset();
        } catch (IOException e) {
            e.printStackTrace();
        }
        oin = oin2;
        m = m2;
        c = a;
    }*/

编辑3

JTextArea应该在JScrollPane，

Answer 3

在窗口或多或少初始化后，应调用setLocationRelativeTo。

关于您在pack命令后直接采样。 pack()命令可能会重新排列您的框架。

将JFrame容器对象居中

3 个答案:

修改