java - 从一个类调用另一个类的方法

Question

我知道这种问题已经在这里讨论过很多次了，但我很困惑。我完全是 Java 的初学者，老实说我不知道​​该怎么做，而且我承认我没有那么多时间阅读 Oracle 提供的整个文档。这是我的问题:

我正在尝试为我的程序编写一个 GUI，它将显示声波的干扰。数学功能在这里并不重要。我有两个类，称为“窗口”和“ slider ”。 Window 旨在成为“主 GUI 类”，而 Sliders 应该从它继承(？)。

这来自另一个问题，我需要在 Window 类中实现 ActionListener 并在 Sliders 类中实现 ChangeListener 。我听说一个类无法实现多个类，所以我创建了两个类。

现在，我写的这两个类有点困惑，但我不知道如何将它们结合起来。这真的很愚蠢，但是在 C++ 之后，我很困惑如何告诉程序它应该在一帧中显示 Window 类中定义的按钮和 Sliders 类中定义的 slider 。目前它只显示按钮，我想让它也显示 slider 。

对于困惑的伪代码，我感到非常抱歉，请帮忙。请尝试尽可能简单地解释。请随意忽略重写的方法，它们尚未完成。

import javax.swing.*;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.*;

public class Window extends JFrame implements ActionListener
{

private JButton showChord, playSound, getSample, getPlot;
private JLabel chordInfo;
private JPanel basicFunctions;

public Window()
{
    init();
}

private void init()
{
    setVisible(true);
    setSize(new Dimension(1000,500));
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    basicFunctions = new JPanel();
    FlowLayout basicLayout = new FlowLayout();
    basicFunctions.setLayout(basicLayout);

    showChord = new JButton("Akord");
    playSound = new JButton("Odtwórz");
    getSample = new JButton("Pobierz dźwięk");
    getPlot = new JButton("Pobierz wykres");

    showChord.addActionListener(this);
    playSound.addActionListener(this);
    getSample.addActionListener(this);
    getPlot.addActionListener(this);

    basicFunctions.add(showChord);
    basicFunctions.add(playSound);
    basicFunctions.add(getSample);
    basicFunctions.add(getPlot);
    add(basicFunctions);

    Sliders param = new Sliders();

}

public static void main(String[] args) 
{
    Window frame = new Window();
}

//Action Listener
@Override
public void actionPerformed(ActionEvent a) 
{
    Object event = a.getSource();

    if(event == showChord)
    {

    }

    else if(event == playSound)
    {

    }

    else if(event == getSample)
    {

    }

    else if(event == getPlot)
    {

    }
}


}

import java.awt.*;

import javax.swing.event.ChangeEvent;
import javax.swing.*;
import javax.swing.event.ChangeListener;


public class Sliders extends Window implements ChangeListener
{
private JPanel sliders, sliderSub;
private JTextField accAmplitude, accFrequency, accPhase;
private JSlider amplitude, frequency, phase;
private double amplitudeValue, frequencyValue, phaseValue;

public Sliders()
{
    sliders = new JPanel();
    sliders.setLayout(new FlowLayout());

    amplitude = new JSlider(0,100,0);

    amplitude.setMajorTickSpacing(10);
    amplitude.setMinorTickSpacing(5);
    amplitude.setPaintTicks(true);
    amplitude.setPaintLabels(true);

    frequency = new JSlider(0,10,0);

    frequency.setMajorTickSpacing(1);
    frequency.setMinorTickSpacing(1/10);
    frequency.setPaintTicks(true);
    frequency.setPaintLabels(true);

    phase = new JSlider(0,1,0);

    phase.setMinorTickSpacing(2/10);
    phase.setPaintTicks(true);
    phase.setPaintLabels(true);

    accAmplitude = new JTextField();
    accFrequency = new JTextField();
    accPhase = new JTextField();

    sliders.add(amplitude, BorderLayout.NORTH);
    sliders.add(frequency, BorderLayout.CENTER);
    sliders.add(phase, BorderLayout.SOUTH);
    add(sliders);
}

@Override
public void stateChanged(ChangeEvent arg0) 
{


}
}

<小时/>

到目前为止，我已经完成了此操作，但这些文本字段刚刚停止显示 slider 值，我不知道为什么。它们在Parameters 类和Window 类中定义。有人可以帮忙吗？此外，将来我希望使这些文本字段可编辑，以便您可以通过在文本字段中键入 slider 值来设置 slider 值。

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

import javax.swing.*;
import javax.swing.border.BevelBorder;
import javax.swing.event.*;

public class Window extends JPanel
{
private JMenuBar mainMenu = new JMenuBar();

private Plot plot = new Plot();
private Parameters param = new Parameters();

private JComboBox chooseChord = new JComboBox();

private JButton playSound = new JButton("Odtwórz");
private JButton getSample = new JButton("Pobierz dźwięk");
private JButton getPlot = new JButton("Pobierz wykres");

private JPanel mainPanel = new JPanel();
private JPanel subPanel = new JPanel();
private JPanel buttonsPanel = new JPanel();
private JPanel slidersPanel = new JPanel();

private JLabel chord = new JLabel("Akord:");

private JTextField aValue = new JTextField();
private JTextField fValue = new JTextField(); 
private JTextField pValue = new JTextField();

public Window() 
{
    mainPanel.setLayout(new FlowLayout());
    buttonsPanel.setLayout(new BoxLayout(buttonsPanel, BoxLayout.Y_AXIS));
    slidersPanel.setLayout(new BorderLayout());
    subPanel.setLayout(new BorderLayout());

    chooseChord.addItem("A");
    chooseChord.addItem("A#");
    chooseChord.addItem("Ab");
    chooseChord.addItem("B");
    chooseChord.addItem("Bb");
    chooseChord.addItem("C");
    chooseChord.addItem("C#");
    chooseChord.addItem("Cb");
    chooseChord.addItem("D");
    chooseChord.addItem("D#");
    chooseChord.addItem("E");
    chooseChord.addItem("F");
    chooseChord.addItem("F#");

    buttonsPanel.add(chord);
    buttonsPanel.add(chooseChord);
    buttonsPanel.add(Box.createRigidArea(new Dimension(0,10)));
    buttonsPanel.add(playSound);
    buttonsPanel.add(Box.createRigidArea(new Dimension(0,10)));
    buttonsPanel.add(getSample);
    buttonsPanel.add(Box.createRigidArea(new Dimension(0,10)));
    buttonsPanel.add(getPlot);
    buttonsPanel.setBorder(BorderFactory.createTitledBorder("Menu"));

    slidersPanel.add(param);

    JMenu langMenu = new JMenu("Język");
    mainMenu.add(langMenu);

    subPanel.add(buttonsPanel, BorderLayout.NORTH);
    subPanel.add(slidersPanel, BorderLayout.SOUTH);
    mainPanel.add(subPanel);
    mainPanel.add(plot);
    add(mainPanel);

    param.addAmplitudeListener(new ChangeListener()
    {
        public void stateChanged(ChangeEvent a)
        {
            double ampValue = param.getAmplitudeValue();
            aValue.setText(String.valueOf(ampValue));
        }
    }
    );


    param.addFrequencyListener(new ChangeListener()
    {
        public void stateChanged(ChangeEvent f)
        {
            double frValue = param.getFrequencyValue();
            fValue.setText(String.valueOf(frValue));
        }
    }
    );


    param.addPhaseListener(new ChangeListener()
    {
        public void stateChanged(ChangeEvent p)
        {
            double phValue = param.getPhaseValue();
            pValue.setText(String.valueOf(phValue));
        }
    }
    );


}

public JMenuBar getmainMenu()
{
    return mainMenu;
}

private static void GUI()
{
    Window mainPanel = new Window();
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(mainPanel);
    frame.setJMenuBar(mainPanel.getmainMenu());
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) 
{
    SwingUtilities.invokeLater(new Runnable() 
    {
         public void run()
         {
            GUI();
         }
      }
      );
}
}

class Parameters extends JPanel
{
    private JPanel pane = new JPanel();
    private JPanel ampPanel = new JPanel();
    private JPanel frPanel = new JPanel();
    private JPanel phPanel = new JPanel();

    private JSlider amplitude = new JSlider(0,100,0);
    private JSlider frequency = new JSlider(0,10000,0);
    private JSlider phase = new JSlider(0,180,0);

    private JLabel pLabel = new JLabel("Faza");
    private JLabel aLabel = new JLabel("Amplituda (dB)");
    private JLabel fLabel = new JLabel("Częstotliwość (Hz)");

    private JTextField preciseAmplitude = new JTextField(3);
    private JTextField preciseFrequency = new JTextField(4); 
    private JTextField precisePhase = new JTextField(3);

    public Parameters()
    {
        preciseAmplitude.setEditable(true);
        preciseFrequency.setEditable(true);
        precisePhase.setEditable(true);

        pane.setLayout(new BoxLayout(pane, BoxLayout.PAGE_AXIS));
        ampPanel.setLayout(new FlowLayout());
        frPanel.setLayout(new FlowLayout());
        phPanel.setLayout(new FlowLayout());

        amplitude.setMajorTickSpacing(10);
        amplitude.setMinorTickSpacing(5);
        amplitude.setPaintTicks(true);
        amplitude.setPaintLabels(true);

        frequency.setMajorTickSpacing(2000);
        frequency.setMinorTickSpacing(100);
        frequency.setPaintTicks(true);
        frequency.setPaintLabels(true);

        phase.setMajorTickSpacing(2/10);
        phase.setPaintTicks(true);
        phase.setPaintLabels(true);

        setBorder(BorderFactory.createTitledBorder("Parametry fali"));

        ampPanel.add(aLabel);
        ampPanel.add(preciseAmplitude);
        pane.add(ampPanel);
        pane.add(Box.createRigidArea(new Dimension(0,5)));
        pane.add(amplitude);
        pane.add(Box.createRigidArea(new Dimension(0,10)));

        frPanel.add(fLabel);
        frPanel.add(preciseFrequency);
        pane.add(frPanel);
        pane.add(Box.createRigidArea(new Dimension(0,5)));
        pane.add(frequency);
        pane.add(Box.createRigidArea(new Dimension(0,10)));

        phPanel.add(pLabel);
        phPanel.add(precisePhase);
        pane.add(phPanel);
        pane.add(Box.createRigidArea(new Dimension(0,5)));
        pane.add(phase);
        pane.add(Box.createRigidArea(new Dimension(0,10)));

        add(pane);

    }

    public int getAmplitudeValue()
    {
        return amplitude.getValue();
    }

    public int getFrequencyValue()
    {
        return frequency.getValue();
    }

    public int getPhaseValue()
    {
        return phase.getValue();
    }

    public void addAmplitudeListener(ChangeListener ampListener) 
    {
          amplitude.addChangeListener(ampListener);
    }

    public void addFrequencyListener(ChangeListener frListener) 
    {
          frequency.addChangeListener(frListener);
    }

    public void addPhaseListener(ChangeListener phListener) 
    {
          phase.addChangeListener(phListener);
    }
}

class Plot extends JPanel
{
private JPanel componentWave = new JPanel();
private JPanel netWave = new JPanel();
private JLabel componentLabel = new JLabel("Fale składowe");
private JLabel netLabel = new JLabel("Fala wypadkowa");
private JLabel wave = new JLabel("Wybierz falę składową");
private JPanel labels = new JPanel();
private JComboBox chooseWave = new JComboBox();

public Plot()
{
    labels.setLayout(new BoxLayout(labels, BoxLayout.PAGE_AXIS));

    componentWave.setBackground(new Color(255,255,255));
    netWave.setBackground(new Color(255,255,255));
    componentWave.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
    netWave.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));

    componentWave.setPreferredSize(new Dimension(400,200));
    netWave.setPreferredSize(new Dimension(400,200));

    labels.add(wave);
    labels.add(Box.createRigidArea(new Dimension(0,10)));
    labels.add(chooseWave);
    labels.add(componentLabel);
    labels.add(componentWave);
    labels.add(Box.createRigidArea(new Dimension(0,20)));
    labels.add(netLabel);
    labels.add(netWave);

    add(labels);
}
}

Answer 1

Window is intended to be a 'main GUI class' and Sliders is supposed to inherit (?) from it.

不:这是对继承的滥用，只会导致问题，因为 Sliders 本质上是 Windows 实例，与显示的 Windows 实例完全不同。您需要做的就是传递引用。

例如，以下代码使用 JButton 和 JMenuItem 操作的外部类(操作类似于类固醇上的 ActionListener)，并使用一个包含 JSlider 的类，该 JSlider 允许其外部类将监听器附加到 slider 。

import java.awt.Component;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class Foo extends JPanel {
   private static final long serialVersionUID = 1L;
   private Action helloAction = new HelloAction("Hello", KeyEvent.VK_H);
   private Action exitAction = new ExitAction("Exit", KeyEvent.VK_X);
   private JMenuBar menuBar = new JMenuBar();
   private JTextField sliderValueField = new JTextField(10);
   private Bar bar = new Bar();

   public Foo() {
      sliderValueField.setEditable(false);
      sliderValueField.setFocusable(false);

      add(new JButton(helloAction));
      add(new JButton(exitAction));
      add(new JLabel("Slider Value: "));
      add(sliderValueField);
      add(bar);

      JMenu fileMenu = new JMenu("File");
      fileMenu.setMnemonic(KeyEvent.VK_F);
      fileMenu.add(new JMenuItem(exitAction));
      fileMenu.add(new JMenuItem(helloAction));
      menuBar.add(fileMenu);

      bar.addSliderListener(new ChangeListener() {

         @Override
         public void stateChanged(ChangeEvent e) {
            int sliderValue = bar.getSliderValue();
            sliderValueField.setText(String.valueOf(sliderValue));
         }
      });
   }

   public JMenuBar getJMenuBar() {
      return menuBar;
   }

   private static void createAndShowGui() {
      Foo mainPanel = new Foo();

      JFrame frame = new JFrame("Foo");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.setJMenuBar(mainPanel.getJMenuBar());
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

class HelloAction extends AbstractAction {

   public HelloAction(String name, int mnemonic) {
      super(name); // sets name property and gives button its title
      putValue(MNEMONIC_KEY, mnemonic);
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      JOptionPane.showMessageDialog(null, "Hello!");
   }
}

class ExitAction extends AbstractAction {
   private static final long serialVersionUID = 1L;

   public ExitAction(String name, int mnemonic) {
      super(name);
      putValue(MNEMONIC_KEY, mnemonic);
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      Component component = (Component) e.getSource();
      Window win = SwingUtilities.getWindowAncestor(component);
      if (win == null) {
         // if no window, then a JMenuItem held in a JPopupMenu
         JPopupMenu popup = (JPopupMenu) component.getParent();
         component = popup.getInvoker();
         win = SwingUtilities.getWindowAncestor(component);
      }
      win.dispose();
   }
}

class Bar extends JPanel {
   private JSlider slider = new JSlider(0, 100, 50);

   public Bar() {
      slider.setPaintLabels(true);
      slider.setPaintTicks(true);
      slider.setMajorTickSpacing(20);
      slider.setMinorTickSpacing(5);
      slider.setSnapToTicks(true);
      setBorder(BorderFactory.createTitledBorder("Slider Panel"));
      add(slider);
   }

   public int getSliderValue() {
      return slider.getValue();
   }

   // one way to let outside classes listen for changes
   public void addSliderListener(ChangeListener listener) {
      slider.addChangeListener(listener);
   }
}

<小时/>

您询问十进制标签，是的，这可以完成，但需要使用标签表。例如，

  JSlider slider = new JSlider(0, 100, 50);
  slider.setPaintLabels(true);
  slider.setPaintTicks(true);
  slider.setMajorTickSpacing(20);
  slider.setMinorTickSpacing(2);

  Dictionary<Integer, JLabel> labels = new Hashtable<>();
  for (int i = 0; i <= 100; i += 20) {
     labels.put(i, new JLabel(String.format("%.1f", i / 200.0)));
  }

  slider.setLabelTable(labels);

显示为:

您还必须将值从 int 转换回其相应的 float 。