如何解决初始化后如何在JFrame中添加组件?
我有一个JFrame。首次启动时,它不会(故意)加载按钮,因为它取决于布尔值sessionExists,默认情况下为false。当用户单击“添加”以启动jdialog并在该jdialog中单击“确定”时,它将把JFrame的sessionExists值设置为true。
我想要代码做什么:
单击Ok之后,我希望JFrame进行更新,并使用text“ new button”显示该按钮,因为sessionExists现在为true。
当前行为:
当前,用户单击“确定”,jdialog将退出,但父JFrame将保持不变,并且按钮不会出现。
我尝试的解决方案:
我尝试在JFrame中使用.validate和.repaint()刷新它,以便显示按钮,但似乎不起作用。
我应该如何实现预期的行为?我应该使用cardlayout吗?
我使用以下代码重现了该问题。我的实际程序依赖于文件是否存在而不是布尔变量。
JFrame
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;
import javax.swing.jdialog;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class MainMenu extends JFrame {
private JPanel contentPane;
MainMenu thisFrame = this;
boolean sessionExists = false;
public static void main(String[] args) {
EventQueue.invokelater(new Runnable() {
public void run() {
try {
MainMenu frame = new MainMenu();
frame.setVisible(true);
} catch (Exception e) {
e.printstacktrace();
}
}
});
}
public MainMenu() {
setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100,100,450,300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5,5,5));
contentPane.setLayout(new BorderLayout(0,0));
setContentPane(contentPane);
if (sessionExists == true) {
JButton btnNewButton = new JButton("New button");
contentPane.add(btnNewButton,BorderLayout.CENTER);
}
JButton btnNewButton_1 = new JButton("Add Button");
btnNewButton_1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
Add newTask = new Add(thisFrame);
newTask.setDefaultCloSEOperation(jdialog.disPOSE_ON_CLOSE);
newTask.setTitle("Add Task");
newTask.setVisible(true);
}
});
contentPane.add(btnNewButton_1,BorderLayout.soUTH);
}
public void refresh() {
this.validate();
this.repaint();
}
}
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.jdialog;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class Add extends jdialog {
private final JPanel contentPanel = new JPanel();
public Add(MainMenu parentJFrame) {
setBounds(100,300);
getContentPane().setLayout(new BorderLayout());
contentPanel.setLayout(new FlowLayout());
contentPanel.setBorder(new EmptyBorder(5,5));
getContentPane().add(contentPanel,BorderLayout.CENTER);
{
JPanel buttonPane = new JPanel();
buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
getContentPane().add(buttonPane,BorderLayout.soUTH);
{
JButton okButton = new JButton("OK");
okButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
parentJFrame.sessionExists = true;
parentJFrame.refresh();
dispose();
}
});
okButton.setActionCommand("OK");
buttonPane.add(okButton);
getRootPane().setDefaultButton(okButton);
}
{
JButton cancelButton = new JButton("Cancel");
cancelButton.setActionCommand("Cancel");
buttonPane.add(cancelButton);
}
}
}
}
解决方法
在尝试添加if(session == true)时没有调用它。取而代之的是,创建诸如adding()之类的新函数,然后从Add JDialog类中调用它,它将起作用。(您会注意到您不必使用session == true,因为您可以通过这种方式调用该函数直接。但是根据您的理解,我没有更改。) 示例代码:
MainMenu:
public class MainMenu extends JFrame {
private JPanel contentPane;
MainMenu thisFrame = this;
boolean sessionExists = false;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
MainMenu frame = new MainMenu();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public MainMenu() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100,100,450,300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5,5,5));
contentPane.setLayout(new BorderLayout(0,0));
setContentPane(contentPane);
JButton btnNewButton_1 = new JButton("Add Button");
btnNewButton_1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
Add newTask = new Add(thisFrame);
newTask.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
newTask.setTitle("Add Task");
newTask.setVisible(true);
}
});
contentPane.add(btnNewButton_1,BorderLayout.SOUTH);
}
public void adding() {
if (sessionExists == true) {
JButton btnNewButton = new JButton("New button");
contentPane.add(btnNewButton,BorderLayout.CENTER);
}
}
public void refresh() {
this.validate();
this.repaint();
}
}
添加:
public class Add extends JDialog {
private final JPanel contentPanel = new JPanel();
public Add(MainMenu parentJFrame) {
setBounds(100,300);
getContentPane().setLayout(new BorderLayout());
contentPanel.setLayout(new FlowLayout());
contentPanel.setBorder(new EmptyBorder(5,5));
getContentPane().add(contentPanel,BorderLayout.CENTER);
{
JPanel buttonPane = new JPanel();
buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
getContentPane().add(buttonPane,BorderLayout.SOUTH);
{
JButton okButton = new JButton("OK");
okButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
parentJFrame.sessionExists = true;
parentJFrame.adding();
parentJFrame.refresh();
dispose();
}
});
okButton.setActionCommand("OK");
buttonPane.add(okButton);
getRootPane().setDefaultButton(okButton);
}
{
JButton cancelButton = new JButton("Cancel");
cancelButton.setActionCommand("Cancel");
buttonPane.add(cancelButton);
}
}
}
}
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