如何多次創建新的和部署jcomponents？

Question

（很抱歉，如果這個問題沒有正確地做，我是新的，但至少我問我自己的問題之前研究了很多）

你好。我正在用java編寫一個二十一點遊戲，並且它變得非常龐大。 我的問題是如何處理擺動組件的多個實例，我想你可以調用它。我無法弄清楚如何創建組件（如jpanels和jbuttons）作爲類級別或特定的方法。

如果我在他們相應的方法中創建它們，那麼我的動作偵聽器將無法看到它們，但是如果我將它們創建爲類級別，那麼當我調用dispose()時，它們會被刪除。

class BlackjackGame extends JFrame implements ActionListener{ 

    public void mainMenu(){ 

     JPanel menuPane = new JPanel(new GridBagLayout()); //Init of main menu 
     GridBagConstraints c = new GridBagConstraints(); 
     menuPane.setBackground(new Color(125,0,0)); 
     menuPane.setBounds(620,220,175,250); 

     JLabel menuTitle = new JLabel("Welcome to Blackjack!");//Main menu-content 
     c.gridx = 1; 
     c.gridy = 0; 
     c.insets = new Insets(0,0,20,0); 
     menuPane.add(menuTitle, c); 

     JButton playButton = new JButton("Play!"); 
     playButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 1; 
     c.gridwidth = 3; 
     c.ipadx = 25; 
     c.ipady = 25; 
     c.insets = new Insets(0,0,0,0); 
     menuPane.add(playButton, c); 

     JButton exitButton = new JButton("Exit!"); 
     exitButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 2; 
     c.gridwidth = 3; 
     menuPane.add(exitButton, c); 

     JButton rulesButton = new JButton("Set rules."); 
     rulesButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 3; 
     c.gridwidth = 3; 
     menuPane.add(rulesButton, c); 

     this.add(menuPane,0); 
    } 

    //This is where I get problems 
    public void actionPerformed (ActionEvent event){ 
     if(event.getSource() == playButton){ 
      //I want the menuPane to disappear, and a transition into the game. 
      menuPane.dispose(); 
      //Call method for the rest of the game. 

     }else if(event .getSource() etcetera etcetera){ 
      etcetera etcetera 
     } 
    } 
} 

當這樣做時，actionlistener找不到我的組件，比如playButton或menuPane。但是，如果我曾經引進了他們作爲一流水平的對象：

class BlackjackGame extends JFrame implements ActionListener{ 

    JPanel menuPane = new JPanel(new GridBagLayout()); 
    JLabel menuTitle = new JLabel("Welcome to Blackjack!"); 
    JButton playButton = new JButton("Play!"); 
    JButton exitButton = new JButton("Exit!"); 
    JButton rulesButton = new JButton("Set rules."); 

    public void mainMenu(){ 
     //Rest of code 
    } 

    public void actionPerformed(ActionEvent event){ 
     menuPane.dispose(); 
     //Rest of code 
    } 
} 

...然後我打電話menuPane.dispose()，我怎麼能找回來，當我想再次呼籲mainMenu()？如果我想回到主菜單，那麼我需要創建一個menuPane的新實例，以及所有的按鈕，但是因爲它們是課程級別並且已經處理了，所以我不能。

請幫助我，謝謝！

PS。如果它有幫助，我可以發佈完整的代碼，因爲它是atm。

編輯：丹的答案已被接受，因爲它確實是正確的答案，它的工作對我的具體方案非常好。謝謝你，聖誕快樂！

Answer 1

首先，除非我誤解你的代碼，menuPane.dispose()不應視爲JPanel工作沒有一個叫dispose()

，最好的辦法功能做你想做的，如果你想使用相同的menuPane做什麼爲菜單。代替menuPane.dispose();使用remove(menuPane);然後add(yourOtherPanel);

工作實施例

import java.awt.Color; 
import java.awt.EventQueue; 
import java.awt.GridBagConstraints; 
import java.awt.GridBagLayout; 
import java.awt.Insets; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 

@SuppressWarnings("serial") 
public class BlackjackGame extends JFrame implements ActionListener { 
    private JPanel menuPane; 
    private JLabel menuTitle; 
    private JButton playButton; 
    private JButton exitButton; 
    private JButton rulesButton; 

    private JPanel otherPane; 
    private JLabel otherTitle; 
    private JButton otherButton; 

    public BlackjackGame() { 
     mainMenu(); 
     otherPanel(); 
     setSize(400, 400); 
     setVisible(true); 
    } 

    private void mainMenu() { 

     menuPane = new JPanel(new GridBagLayout()); 
     GridBagConstraints c = new GridBagConstraints(); 
     menuPane.setBackground(new Color(125,0,0)); 
     menuPane.setBounds(620,220,175,250); 

     menuTitle = new JLabel("Welcome to Blackjack!"); 
     c.gridx = 1; 
     c.gridy = 0; 
     c.insets = new Insets(0,0,20,0); 
     menuPane.add(menuTitle, c); 

     playButton = new JButton("Play!"); 
     playButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 1; 
     c.gridwidth = 3; 
     c.ipadx = 25; 
     c.ipady = 25; 
     c.insets = new Insets(0,0,0,0); 
     menuPane.add(playButton, c); 

     exitButton = new JButton("Exit!"); 
     exitButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 2; 
     c.gridwidth = 3; 
     menuPane.add(exitButton, c); 

     rulesButton = new JButton("Set rules."); 
     rulesButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 3; 
     c.gridwidth = 3; 
     menuPane.add(rulesButton, c); 

     add(menuPane); 
    } 

    private void otherPanel() { 
     otherPane = new JPanel(new GridBagLayout()); 
     GridBagConstraints c = new GridBagConstraints(); 
     otherPane.setBackground(new Color(125,0,0)); 
     otherPane.setBounds(620,220,175,250); 

     otherTitle = new JLabel("Welcome to Second Pane!"); 
     c.gridx = 1; 
     c.gridy = 0; 
     c.insets = new Insets(0,0,20,0); 
     otherPane.add(otherTitle, c); 

     otherButton = new JButton("Go Back!"); 
     otherButton.addActionListener(this); 
     c.gridx = 0; 
     c.gridy = 1; 
     c.gridwidth = 3; 
     c.ipadx = 25; 
     c.ipady = 25; 
     c.insets = new Insets(0,0,0,0); 
     otherPane.add(otherButton, c); 
    } 

    public void actionPerformed (ActionEvent event) { 
     if(event.getSource() == playButton) { 
      remove(menuPane); 
      add(otherPane); 
      validate(); 
      repaint(); 

     } else if(event.getSource() == otherButton) { 
      remove(otherPane); 
      add(menuPane); 
      validate(); 
      repaint(); 
     } 
    } 

    public static void main(String[] args) { 
     EventQueue.invokeLater(() -> new BlackjackGame()); 
    } 
} 

編輯徵求意見

因此Java方法remove()僅刪除從容器，在這種情況下是對象JFrame。此方法不會影響其移動的對象，因此稍後可以重新使用該對象。因此，爲什麼在我上面的代碼可以只使用remove()和add()方法，而沒有重新聲明或改造menuPane和otherPane。

至於爲什麼我宣佈的對象這樣

`private JPanel menuPane;` 

然後初始化這樣

menuPane = new JPanel(new GridBagLayout()); 

這是因爲我希望ActionListener能夠看清物體，而不直接初始化它們遠。行private JPanel menuPane;使對象成爲一個全局變量，行menuPane = new JPanel(new GridBagLayout());使它成爲我將要使用的內容。這樣做而不是JPanel menuPane = new JPanel(new GridBagLayout());也意味着我可以在多個方法中重用相同的變量。例如

private JPanel panel; 

private void createPanelOne() { 
    panel = new JPanel(new FlowLayout()); 
    ... 
    add(panel); 
} 

private void createPanelTwo() { 
    panel = new JPanel(new GridBagLayout()); 
    ... 
    add(panel); 
} 

這樣做後，您將有兩個JPanel在你JFrame，他們會有所不同，但你只需要使用一個JPanel

這是宣佈它和它的另一種方式使局部變量。除非您傳遞方法，否則局部變量對您所用方法之外的其他方法不可見。

JPanel panel = new JPanel(); 

我不會說這是一絲不苟。我認爲有時候在一個方法中使用局部變量是很好的，而這個方法對其他方法是不可見的。

最後，要將局部變量傳遞給其他方法，您可以在所做的方法中使用參數。例如

public void setSomeValue(int val) { 
    someValue = val; 
}