问题描述
我觉得一切正常,但由于某种原因,什么都没有正确显示,也许我错过了一些东西,但我不确定为什么它不起作用,有人可以帮我吗?
** 任务 **
通过添加两个来改进您的程序 框架中的组合框。通过组合框,用户应该能够 选择他们喜欢的字体和字体大小。然后将更新显示的文本 相应地(见下图)。
import javax.swing.*;
import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.JTextField;
import java.awt.*;
import java.awt.event.*;
public class ComboGUI extends JFrame implements ActionListener {
public JButton update;
public JTextField textField;
public JLabel textLabel;
public JComboBox<String> fontBox;
public JComboBox sizeBox;
public String font;
public String size;
public ComboGUI()
{
components();
panels();
actionListener();
}
public void components()
{
this.update = new JButton("update");
this.textField=new JTextField(20);
this.textField.setText("hello");
this.textLabel= new JLabel("GUI");
this.font="Arial";
this.size="20";
this.textLabel.setFont(new Font(this.font,Font.PLAIN,Integer.parseInt(this.size)));
this.fontBox=new JComboBox();
this.fontBox.addItem("Times New Roman");
this.fontBox.addItem("Calibri");
this.sizeBox= new JComboBox();
this.sizeBox.addItem("20");
this.sizeBox.addItem("30");
this.sizeBox.addItem("40");
this.setSize(400,400);
this.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
this.setLocationRelativeto(null);
}
public void panels(){
JPanel northPanel =new JPanel();
JLabel fontLabel =new JLabel("Font: ");
JLabel sizeLabel =new JLabel("size: ");
northPanel.add(fontLabel);
//center
BGPanel centerPanel =new BGPanel();
centerPanel.add(this.textLabel);
this.add(centerPanel,BorderLayout.CENTER);
//south
BGPanel southPanel =new BGPanel();
southPanel.add(this.textLabel);
this.add(southPanel,BorderLayout.CENTER);
}
public void actionListener(){
this.update.addActionListener(this);
this.fontBox.addActionListener(this);
this.sizeBox.addActionListener(this);
}
@Override
public void actionPerformed(ActionEvent e){
if(e.getSource()==this.update){
this.textLabel.setText(this.textField.getText());
}
if(e.getSource()==this.fontBox || e.getSource()==this.sizeBox){
this.font=this.fontBox.getSelectedItem().toString();
this.size=this.sizeBox.getSelectedItem().toString();
this.textLabel.setFont(new Font(this.font,Integer.parseInt(this.size)));
}
this.repaint();
}
public static void main(String[] args) {
ComboGUI comb =new ComboGUI();
combo.setVisible(true);
}
}
this is what im getting instead
解决方法
看起来你缺少 this.setVisible(true);在构造函数的末尾。
您的代码应如下所示:
public ComboGUI()
{
components();
panels();
actionListener();
this.setVisible(true);
}
,
如果有人试图做类似的事情,这就是完整的解决方案
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JComboBox;
public class ComboGUI extends JFrame implements ActionListener{
public void updateLabelText(){
size = fSize.getItemAt(fSize.getSelectedIndex());
font = fStyles.getItemAt(fStyles.getSelectedIndex());
updateLabel.setFont(new Font(font,Font.PLAIN,size));
}
public static BGPanel centrePanel;
public JComboBox<String> fStyles;
public JComboBox<Integer> fSize;
public JButton updateButton;
public JLabel updateLabel;
public JLabel fontLabel;
public JLabel sizeLabel;
public JTextField textField;
public JPanel BottomPanel;
public JPanel topPanel;
private String font;
private int size;
public ComboGUI() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(400,400);
this.setLocation(0,0);
//Top
topPanel = new JPanel();
fontLabel = new JLabel("Font:");
sizeLabel = new JLabel("Font Size:");
fStyles = new JComboBox<String>();
fStyles.addItem("Arial");
fStyles.addItem("TimesRoman");
fStyles.addItem("Serif");
fStyles.addItem("Monospaced");
fStyles.addActionListener(this);
fSize = new JComboBox<Integer>();
fSize.addItem(10);
fSize.addItem(20);
fSize.addItem(30);
fSize.addItem(40);
fSize.addActionListener(this);
topPanel.add(fontLabel);
topPanel.add(fStyles);
topPanel.add(sizeLabel);
topPanel.add(fSize);
//CentrePanel setup
centrePanel = new BGPanel();
updateLabel = new JLabel("I love PDC :)");
centrePanel.add(updateLabel);
//Bottom
BottomPanel = new JPanel();
updateButton = new JButton("Update");
textField = new JTextField(20);
textField.setText("I love PDC :)");
updateButton.addActionListener(this);
BottomPanel.add(textField);
BottomPanel.add(updateButton);
this.add(centrePanel,BorderLayout.CENTER);
this.add(BottomPanel,BorderLayout.SOUTH);
this.add(topPanel,BorderLayout.NORTH);
updateLabelText();
}
public static void main(String[] args) {
ComboGUI combo = new ComboGUI();
combo.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e) {
if(e.getSource() == updateButton){
updateLabel.setText(textField.getText().trim());
}
if(e.getSource() == fStyles){
updateLabelText();
}
if (e.getSource() == fSize){
updateLabelText();
}
}
}