为什么JOptionPanes没有显示出来？

huangapple
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英文:

Why do the JOptionpanes not appear?

问题

import javax.swing.*;
import javax.swing.border.LineBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MusicGenre extends JFrame {

    String MusicGenre[] = {"Lo-Fi", "Future-House", "Deep-House", "Anderes"};

    public MusicGenre() {

        setTitle("Genre-Auswahl");
        setSize(250, 250);
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(4, 2));

        JLabel frage = new JLabel("An welches Genre denkst du?");
        panel.add(frage);

        JComboBox genreAuswahl = new JComboBox(MusicGenre);
        panel.add(genreAuswahl);

        JButton okBtn = new JButton("Okay");
        okBtn.setBackground(Color.BLACK);
        okBtn.setForeground(Color.GREEN);
        okBtn.setBorder(new LineBorder(Color.RED));
        okBtn.setOpaque(true);

        JButton backBtn = new JButton("Zurück");
        backBtn.setBackground(Color.BLACK);
        backBtn.setForeground(Color.RED);
        backBtn.setBorder(new LineBorder(Color.RED));
        backBtn.setOpaque(true);


        okBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent actionEvent) {

                String selectedGenre = genreAuswahl.getSelectedItem().toString();

                if (selectedGenre.equals("Lo-Fi")) {
                    int lofi = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
                    if (lofi == JOptionPane.YES_OPTION) {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle einen Lo-Fi Beat");
                        System.exit(0);
                    } else {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Hör dir Lo-Fi an");
                        System.exit(0);
                    }
                } else if (selectedGenre.equals("Future-House")) {
                    int fh = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
                    if (fh == JOptionPane.YES_OPTION) {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle einen Future-House Beat");
                    } else {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Hör dir Future-House an");
                    }
                } else if (selectedGenre.equals("Deep-House")) {
                    int dh = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
                    if (dh == JOptionPane.YES_OPTION) {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle einen Deep-House Beat");
                    } else {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Hör dir Deep-House an");
                    }
                } else if (selectedGenre.equals("Anderes")) {
                    int other = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
                    if (other == JOptionPane.YES_OPTION) {
                        JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle Musik deiner Wahl");
                    } else {
                        JOptionPane.showMessageDialog(null, "Hör dir Musik deiner Wahl an");
                    }
                }
            }
        });

        backBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                dispose();
            }
        });

        panel.add(okBtn);
        panel.add(backBtn);

        add(panel);
        setVisible(true);
    }
}
英文:

I have created a JCombobox and want that when a certain item is selected in the box, the respective ConfirmDialogs/MessageDialogs appear. What have I done wrong? Because unfortunately nothing happens when I click on my button "okBtn" :/
I have already tried a lot of things, but unfortunately I am still stuck and would appreciate any help (:
My Code:

import javax.swing.*;
import javax.swing.border.LineBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class MusicGenre extends JFrame {
String MusicGenre[] = {"Lo-Fi", "Future-House", "Deep-House", "Anderes"};
public MusicGenre() {
setTitle("Genre-Auswahl");
setSize(250, 250);
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(4, 2));
JLabel frage = new JLabel("An welches Genre denkst du?");
panel.add(frage);
JComboBox genreAuswahl = new JComboBox(MusicGenre);
panel.add(genreAuswahl);
JButton okBtn = new JButton("Okay");
okBtn.setBackground(Color.BLACK);
okBtn.setForeground(Color.GREEN);
okBtn.setBorder(new LineBorder(Color.RED));
okBtn.setOpaque(true);
JButton backBtn = new JButton("Zurück");
backBtn.setBackground(Color.BLACK);
backBtn.setForeground(Color.RED);
backBtn.setBorder(new LineBorder(Color.RED));
backBtn.setOpaque(true);
okBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent actionEvent) {
if (genreAuswahl.equals("Lo-Fi")){
int lofi = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
if (lofi == JOptionPane.YES_OPTION){
JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle einen Lo-Fi Beat");
System.exit(0);
}else {
JOptionPane.showMessageDialog(null, "Meine Idee: Hör dir Lo-Fi an");
System.exit(0);
}
if (genreAuswahl.equals("Future-House")){
int fh = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
if (fh == JOptionPane.YES_OPTION){
JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle einen Future-House Beat");
}else {
JOptionPane.showMessageDialog(null, "Meine Idee: Hör dir Future-House an");
}
if (genreAuswahl.equals("Deep-House")){
int dh = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
if (dh == JOptionPane.YES_OPTION){
JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle einen Deep-House Beat");
}else {
JOptionPane.showMessageDialog(null, "Meine Idee: Hör dir Deep-House an");
}
if (genreAuswahl.equals("Anderes")){
int other = JOptionPane.showConfirmDialog(null, "Produzierst du selber Musik?");
if (other == JOptionPane.YES_OPTION){
JOptionPane.showMessageDialog(null, "Meine Idee: Erstelle Musik deiner Wahl");
}else {
JOptionPane.showMessageDialog(null, "Hör dir Musik deiner Wahl an");
}
}
}
}
}
}
});
backBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent actionEvent) {
dispose();
}
});
panel.add(okBtn);
panel.add(backBtn);
add(panel);
setVisible(true);
}
}

答案1

得分: 4

在你的 if 语句中，不要像你在代码中所做的那样将 JComboBox 对象与字符串进行比较，比如下面的代码：

genreAuswahl.equals("Lo-Fi")

而是要比较实际选择的项目（它是一个 String 对象）：

genreAuswahl.getSelectedItem().equals("Lo-Fi")

对其他的 if 控制语句也采取同样的做法，你的代码应该能够按预期工作。我在本地尝试过，对我来说有效。

你的 if 语句不起作用的原因是 JComboBox 永远不可能等于一个 String 对象。

英文:

In your if statement, instead of comparing a JComboBox object with a string like you do in your code as follows:

genreAuswahl.equals("Lo-Fi")

Compare the actual selected item (which is a String object):

genreAuswhal.getSelectedItem().equals("Lo-Fi")

Do this for other if controls too and your code should work as expected. I tried it locally and worked for me.

The reason any of your if statements won't work is that the JComboBox can never be equal to a String object.

huangapple
  • 本文由 发表于 2020年10月7日 21:52:48
  • 转载请务必保留本文链接：https://go.coder-hub.com/64245544.html
  • java
  • jcombobox
  • joptionpane
  • swing
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