如何使用 JMenuItem 将另一个 class 调用到我的主菜单 class？

Question

我不知道如何使用 JMenuItem 调用与我的主要 class (Lista) 在同一包中的另一个 class（称为 Calc）。如果我需要更具体一些，我不知道如何使用我的 Lista class.

上的 JMenuItem 将我的 class Calc 调用到我的 Lista class

下面的代码是我的Listaclass，对不起英文的家伙

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

    import javax.swing.event.MenuEvent;
    import javax.swing.event.MenuListener;

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

    public class Lista extends JFrame{
      public Lista(){
        super("Menu");

        // Menu Bar
        JMenuBar barra = new JMenuBar();
        setJMenuBar(barra);

        // Menu
        JMenu opcoes = new JMenu("Options");

        // Menu Item
        JMenuItem item = new JMenuItem("Item 1");

        // actionlistener
        item.addActionListener(
          new ActionListener(){
            public void actionPerformed(ActionEvent e){
              //I think that is in here where i must write the code
            }
          }
        );

        opcoes.add(item);

        // Adds
        barra.add(opcoes);

        setSize(300, 150);
        setVisible(true);    
      }

      public static void main(String args[]){
        Lista app = new Lista();
        app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      }
    }

另一个class，Calc，它只是我用这段代码制作的一个简单的计算器： public class Calc 扩展了 JFrame {

public Calc(){
    super("Calculadora");
    Container tela = getContentPane();
    setLayout(null);

    JLabel rotulo1 = new JLabel("1 numero: ");
    JLabel rotulo2 = new JLabel("2 numero: ");
    JLabel showup = new JLabel("");

    JTextField texto1 = new JTextField(5);
    JTextField texto2 = new JTextField(5);

    JButton somar = new JButton ("+");
    JButton subtrair = new JButton("-");
    JButton dividir = new JButton("/");
    JButton multiplicar = new JButton("x");
    JButton exibir = new JButton("=");

    rotulo1.setBounds(30,20,100,20); rotulo2.setBounds(30,60,100,20);
    texto1.setBounds(100,20,200,20); texto2.setBounds(100,60,200,20);
    showup.setBounds(125,100,200,20);
    somar.setBounds(230,100,45,45);//coluna, linha, largura, comprimento
    subtrair.setBounds(280,100,45,45);
    dividir.setBounds(230,155,45,45);
    multiplicar.setBounds(280,155,45,45);
    exibir.setBounds(255,205,45,45);


    setVisible(true);
    setLocationRelativeTo(null);

    tela.add(rotulo1); tela.add(rotulo2);
    tela.add(texto1); tela.add(texto2); tela.add(showup);
    tela.add(exibir); tela.add(somar); tela.add(subtrair); tela.add(dividir);tela.add(multiplicar);

    setSize(350,300);

    somar.addActionListener( new ActionListener(){
        public void actionPerformed(ActionEvent e){
            double numero1, numero2, soma;
            soma=0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            soma = numero1+numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText()+""+"+"+""+texto2.getText()+""+"="+soma);
            texto1.setText(null); texto2.setText(null); texto1.requestFocus(); //funcao limpar e focar
        }
    }
    );

    subtrair.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            double numero1, numero2, subtrair;
            subtrair=0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            subtrair = numero1 - numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText()+""+"-"+""+texto2.getText()+""+"="+subtrair);
            texto1.setText(null); texto2.setText(null); texto1.requestFocus();
        }
    });

    multiplicar.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            double numero1, numero2, multiplicar;
            multiplicar=0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            multiplicar = numero1*numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText()+""+"x"+""+texto2.getText()+""+"="+multiplicar);
            texto1.setText(null); texto2.setText(null); texto1.requestFocus();
        }
    });

    dividir.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            double numero1, numero2, dividir;
            dividir=0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            dividir=numero1/numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText()+""+"/"+""+texto2.getText()+""+"="+dividir);
            texto1.setText(null); texto2.setText(null); texto1.requestFocus();
        }
    });


}

public static void main (String [] args){
    Calc app = new Calc();
    app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}}

我唯一想做的是：当我在 Lista 代码中单击 JMenuItem 时，我的计算器程序 (Calc class) 被调用。我已经尝试过："Calc calc = new Calc(); calc.Visible(true);" 或 "item = calc;" 但失败了。我是初学者程序员，抱歉，我认为这很简单。

Answer 1

从另一个 class 调用方法的一种简单方法是获取对另一个 class 的引用并调用该方法。如果另一个 class 的对象已经存在，则不要通过创建新对象来执行此操作，而是将现有对象的引用传递给此 class。具体如何完成将取决于您尚未向我们展示的代码。

请注意，您的代码只能运行来自一个主要方法，我敢打赌，它不会是您发布的代码中的主要方法，而是来自另一个 class 中的另一个主要方法，但同样，所有这些 将取决于您尚未向我们展示的代码 。你可能在这里检测到一个主题，你应该考虑改进你的问题，显示更相关的代码，包括你打算如何启动这个 class，它会从另一个 class 启动吗，什么other class 看起来像，你想从另一个 class 中调用什么方法....

有种更好的处理方法，包括 M-V-C，但是在现阶段这可能只会让您感到困惑，但您最好了解一下我在上面建议的当前解决方案虽然简单，但并不是最干净的。

看起来您可能正在尝试使用此代码创建和显示第二个 JFrame，如果是这样，您不想这样做。请参阅：The Use of Multiple JFrames, Good/Bad Practice?.

事实上，您最好不要让 Lista 扩展 JFrame，而是让它创建并生成一个 JMenu，然后您可以将其放置在需要的地方和时间，但话又说回来，要完全回答您的问题需要从您尚未向我们展示的代码中获得的知识。

Answer 2

您能否在 classes 中进行以下更改并查看结果：

1) Lista.java

 public static void main(String args[]){
    Lista app = new Lista();        
    app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    app.setLocationRelativeTo(null); //so that the JFrame appears at the center of screen
  }

2) Lista.java

// actionlistener
item.addActionListener(
      new ActionListener(){
        public void actionPerformed(ActionEvent e){
          //I think that is in here where i must write the code              
          Calc calc=new Calc(Lista.this); // pass owner JFrame i.e. an instance of Lista
          calc.setVisible(true);
        }
      }
 );

3) Calc.java

import java.awt.Container;
import java.awt.Frame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Calc extends JDialog {

private JLabel rotulo1;
private JLabel rotulo2;
private JLabel showup;
private JTextField texto1;
private JTextField texto2;
private JButton somar;
private JButton subtrair;
private JButton dividir;
private JButton multiplicar;
private JButton exibir;

public Calc(Frame owner) {
    super(owner, "Calculadora");
    Container tela = getContentPane();
    setLayout(null);

    rotulo1 = new JLabel("1 numero: ");
    rotulo2 = new JLabel("2 numero: ");
    showup = new JLabel("");

    texto1 = new JTextField(5);
    texto2 = new JTextField(5);

    somar = new JButton("+");
    subtrair = new JButton("-");
    dividir = new JButton("/");
    multiplicar = new JButton("x");
    exibir = new JButton("=");

    rotulo1.setBounds(30, 20, 100, 20);
    rotulo2.setBounds(30, 60, 100, 20);
    texto1.setBounds(100, 20, 200, 20);
    texto2.setBounds(100, 60, 200, 20);
    showup.setBounds(125, 100, 200, 20);
    somar.setBounds(230, 100, 45, 45);// coluna, linha, largura, comprimento
    subtrair.setBounds(280, 100, 45, 45);
    dividir.setBounds(230, 155, 45, 45);
    multiplicar.setBounds(280, 155, 45, 45);
    exibir.setBounds(255, 205, 45, 45);

    setVisible(true);
    setLocationRelativeTo(null);

    tela.add(rotulo1);
    tela.add(rotulo2);
    tela.add(texto1);
    tela.add(texto2);
    tela.add(showup);
    tela.add(exibir);
    tela.add(somar);
    tela.add(subtrair);
    tela.add(dividir);
    tela.add(multiplicar);

    setSize(350, 300);

    somar.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            double numero1, numero2, soma;
            soma = 0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            soma = numero1 + numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText() + "" + "+" + "" + texto2.getText() + "" + "=" + soma);
            texto1.setText(null);
            texto2.setText(null);
            texto1.requestFocus(); // funcao limpar e focar
        }
    });

    subtrair.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            double numero1, numero2, subtrair;
            subtrair = 0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            subtrair = numero1 - numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText() + "" + "-" + "" + texto2.getText() + "" + "=" + subtrair);
            texto1.setText(null);
            texto2.setText(null);
            texto1.requestFocus();
        }
    });

    multiplicar.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            double numero1, numero2, multiplicar;
            multiplicar = 0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            multiplicar = numero1 * numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText() + "" + "x" + "" + texto2.getText() + "" + "=" + multiplicar);
            texto1.setText(null);
            texto2.setText(null);
            texto1.requestFocus();
        }
    });

    dividir.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            double numero1, numero2, dividir;
            dividir = 0;
            numero1 = Double.parseDouble(texto1.getText());
            numero2 = Double.parseDouble(texto2.getText());
            dividir = numero1 / numero2;
            showup.setVisible(true);
            showup.setText(texto1.getText() + "" + "/" + "" + texto2.getText() + "" + "=" + dividir);
            texto1.setText(null);
            texto2.setText(null);
            texto1.requestFocus();
        }
    });

  }

}

解释：

Calc.java

中有许多细微的变化

class 用于扩展 JDialog 而不是 JFrame
构造函数已更改，因此它需要所有者 JFrame (Lista) 作为参数。
JTextField、JButton的局部变量较多， JLabel等，都是实例变量

希望对您有所帮助。

Answer 3

Felipe，这对我有用...它基于 Sanjeev Saha 的回答...

enter 

import java.awt.Container;
import java.awt.Frame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Calc extends JDialog {

private JLabel rotulo1;
private JLabel rotulo2;
private JLabel showup;
private JTextField texto1;
private JTextField texto2;
private JButton somar;
private JButton subtrair;
private JButton dividir;
private JButton multiplicar;
private JButton exibir;

public Calc(Frame owner) {
super(owner, "Calculadora");
Container tela = getContentPane();
setLayout(null);

rotulo1 = new JLabel("1 numero: ");
rotulo2 = new JLabel("2 numero: ");
showup = new JLabel("");

texto1 = new JTextField(5);
texto2 = new JTextField(5);

somar = new JButton("+");
subtrair = new JButton("-");
dividir = new JButton("/");
multiplicar = new JButton("x");
exibir = new JButton("=");

rotulo1.setBounds(30, 20, 100, 20);
rotulo2.setBounds(30, 60, 100, 20);
texto1.setBounds(100, 20, 200, 20);
texto2.setBounds(100, 60, 200, 20);
showup.setBounds(125, 100, 200, 20);
somar.setBounds(230, 100, 45, 45);// coluna, linha, largura, comprimento
subtrair.setBounds(280, 100, 45, 45);
dividir.setBounds(230, 155, 45, 45);
multiplicar.setBounds(280, 155, 45, 45);
exibir.setBounds(255, 205, 45, 45);

setVisible(true);
setLocationRelativeTo(null);

tela.add(rotulo1);
tela.add(rotulo2);
tela.add(texto1);
tela.add(texto2);
tela.add(showup);
tela.add(exibir);
tela.add(somar);
tela.add(subtrair);
tela.add(dividir);
tela.add(multiplicar);

setSize(350, 300);

somar.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        double numero1, numero2, soma;
        soma = 0;
        numero1 = Double.parseDouble(texto1.getText());
        numero2 = Double.parseDouble(texto2.getText());
        soma = numero1 + numero2;
        showup.setVisible(true);
        showup.setText(texto1.getText() + "" + "+" + "" + texto2.getText() + "" + "=" + soma);
        texto1.setText(null);
        texto2.setText(null);
        texto1.requestFocus(); // funcao limpar e focar
    }
});

subtrair.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        double numero1, numero2, subtrair;
        subtrair = 0;
        numero1 = Double.parseDouble(texto1.getText());
        numero2 = Double.parseDouble(texto2.getText());
        subtrair = numero1 - numero2;
        showup.setVisible(true);
        showup.setText(texto1.getText() + "" + "-" + "" + texto2.getText() + "" + "=" + subtrair);
        texto1.setText(null);
        texto2.setText(null);
        texto1.requestFocus();
    }
});

multiplicar.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        double numero1, numero2, multiplicar;
        multiplicar = 0;
        numero1 = Double.parseDouble(texto1.getText());
        numero2 = Double.parseDouble(texto2.getText());
        multiplicar = numero1 * numero2;
        showup.setVisible(true);
        showup.setText(texto1.getText() + "" + "x" + "" + texto2.getText() + "" + "=" + multiplicar);
        texto1.setText(null);
        texto2.setText(null);
        texto1.requestFocus();
    }
});

dividir.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        double numero1, numero2, dividir;
        dividir = 0;
        numero1 = Double.parseDouble(texto1.getText());
        numero2 = Double.parseDouble(texto2.getText());
        dividir = numero1 / numero2;
        showup.setVisible(true);
        showup.setText(texto1.getText() + "" + "/" + "" + texto2.getText() + "" + "=" + dividir);
        texto1.setText(null);
        texto2.setText(null);
        texto1.requestFocus();
    }
});

  }

}

和 Lista class...

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

import javax.swing.event.MenuEvent;
import javax.swing.event.MenuListener;

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

public class Lista extends JFrame{
  public Lista(){
    super("Menu");

    // Menu Bar
    JMenuBar barra = new JMenuBar();
    setJMenuBar(barra);

    // Menu
    JMenu opcoes = new JMenu("Options");

    // Menu Item
    JMenuItem item = new JMenuItem("Item 1");

    // actionlistener
    item.addActionListener(
      new ActionListener(){
        public void actionPerformed(ActionEvent e){
          new Calc(Lista.this);
        }
      }
    );

    opcoes.add(item);

    // Adds
    barra.add(opcoes);

    setSize(300, 150);
    setVisible(true);    
  }

  public static void main(String args[]){
    Lista app = new Lista();
    app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }
}

如何使用 JMenuItem 将另一个 class 调用到我的主菜单 class？

How to call another class to my main menu class using the JMenuItem?

java

swing

jmenu

jmenuitem

jmenubar