如何通過點擊JButton添加JPanel？

Question

我試圖創建一個小的GUI，它有2個JButtons和2個JPanels，每個都有一些繪圖動畫。默認情況下，它必須顯示第一個JPanel，並通過點擊第二個JButton我想看到我的第二個JPanel。所以：我創建了JFrame，Panel1和Panel2，在其中繪製了我的動畫，創建了Button1和Button2並向它們添加了ActionListeners。我也有一個字段變量i的MainPanel。通過改變這個「我」我的構造函數添加到MainPanel要麼Panel1（默認）或Panel2（通過點擊JButton2我改變我）。比我添加這個MainPanel到我的框架。所以我的問題：在類MainPanel中我有refreshMe方法，我應該寫什麼來使我的GUI正常工作？謝謝。這裏是我的代碼：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

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

public class GuiTest { 

    public static void main(String[] args) { 
     JFrame f = new JFrame(); 
     MainPanel myPanel = new MainPanel(); 
     f.add(myPanel); 
     Button1 button1 = new Button1(); 
     Button2 button2 = new Button2(); 
     myPanel.add(button1); 
     myPanel.add(button2); 
     f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     f.pack(); 
     f.setVisible(true); 
    } 
} 

class MainPanel extends JPanel { 
    Panel1 p1 = new Panel1(); 
    Panel2 p2 = new Panel2(); 
    public int i = 1; //this is being changed later by clicking JButton 
    // I use this setter later in actionPerformed in order to change i 
    public void setI(int i) { 
     this.i = i; 
    } 

    MainPanel() { 
     if (i == 1) { 
      this.add(p1); 
     } 
     if (i == 2) { 
      this.add(p2); 
     } 
    } 

    public void refreshMe() { 
     // Need some help here: 
     // I don't know what should I write, how to make a repaint of myPanel? 
     System.out.println("just test, if the method refreshMe working by clicking some button"); 
    } 
} 

class Panel1 extends JPanel { 

    public Panel1() { 
     this.setBackground(Color.BLUE); 
     // a lot of drawing stuff going on here 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     return new Dimension(200, 200); 
    } 
} 

class Panel2 extends JPanel { 

    public Panel2() { 
     this.setBackground(Color.GREEN); 
     // a lot of drawing stuff going on here 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     return new Dimension(200, 200); 
    } 

} 

class Button1 extends JButton { 
    MainPanel someObj1 = new MainPanel(); 

    Button1() { 
     setText("Show Annimation A"); 
     addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       someObj1.setI(1); 
       System.out.println("The variable i is now: " + someObj1.i); 
       someObj1.refreshMe(); 

      } 
     }); 
    } 

} 

class Button2 extends JButton { 
    MainPanel someObj2 = new MainPanel(); 

    Button2() { 
     setText("Show Annimation B"); 
     addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       someObj2.setI(2); 
       System.out.println("The variable i is now: " + someObj2.i); 
       someObj2.refreshMe(); 
      } 
     }); 

    } 

} 

Answer 1

爲了反映添加/移除或調整一個組件，它是在添加/移除或調整所述部件後可見容器呼叫revalidate()和repaint()在容器實例之後的變化。

雖然這不會在你的代碼工作，主要的理由是一個JButton類中重新創建的MainPanel一個新實例，而實際上2 JButtons應該分享其正在使用的單個實例（你可以傳遞的mainPanel實例的JButton小號構造函數，但你真的不應該被延伸的JButton除非添加自定義功能）：

class Button2 extends JButton { 
    MainPanel someObj2 = new MainPanel();//you create an instance of MainPanel which isnt even showing and than do changes on that, this way you will never see any of the changes 

    Button2() { 
    } 
} 

幾個在你的代碼的其他建議：

• 不必擴展JButton類，只需創建JButton的實例，就像您使用JFrame所做的一樣，並調用JButton實例的方法。

• 不要忘記創建/操作Event Dispatch Thread上的Swing組件，通過SwingUtilities.invokeLater(..)塊，閱讀here瞭解更多信息。

這裏是你的代碼固定（以上建議ECT實現）：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.SwingUtilities; 

public class Test { 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       JFrame f = new JFrame(); 

       final MainPanel myPanel = new MainPanel(); 
       f.add(myPanel); 

       JButton button1 = new JButton("Show Animation A"); 
       JButton button2 = new JButton("Show Animation B"); 

       button1.addActionListener(new ActionListener() { 
        @Override 
        public void actionPerformed(ActionEvent e) { 
         myPanel.setI(1); 
         System.out.println("The variable i is now: " + myPanel.i); 
         myPanel.refreshMe(); 
        } 
       }); 
       button2.addActionListener(new ActionListener() { 
        @Override 
        public void actionPerformed(ActionEvent e) { 
         myPanel.setI(2); 
         System.out.println("The variable i is now: " + myPanel.i); 
         myPanel.refreshMe(); 
        } 
       }); 

       myPanel.add(button1); 
       myPanel.add(button2); 
       myPanel.checkPanel(); 

       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

       f.pack(); 
       f.setVisible(true); 
      } 
     }); 
    } 
} 

class MainPanel extends JPanel { 

    Panel1 p1 = new Panel1(); 
    Panel2 p2 = new Panel2(); 
    public int i = 1; //this is being changed later by clicking JButton 
    // I use this setter later in actionPerformed in order to change i 

    public void setI(int i) { 
     this.i = i; 
    } 

    public void refreshMe() { 
     checkPanel(); 

     revalidate(); 
     repaint(); 
     // Need some help here: 
     // I don't know what should I write, how to make a repaint of myPanel? 
     System.out.println("just test, if the method refreshMe working by clicking some button"); 
    } 

    public void checkPanel() { 
     if (i == 1) { 
      this.add(p1); 
      this.remove(p2);//or it will remain there as this is default flowlayout 
     } else if (i == 2) { 
      this.add(p2); 
      this.remove(p1); 
     } 
    } 
} 

class Panel1 extends JPanel { 

    public Panel1() { 
     this.setBackground(Color.BLUE); 
     // a lot of drawing stuff going on here 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     return new Dimension(200, 200); 
    } 
} 

class Panel2 extends JPanel { 

    public Panel2() { 
     this.setBackground(Color.GREEN); 
     // a lot of drawing stuff going on here 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     return new Dimension(200, 200); 
    } 
} 

但是標識表明簡單的東西，幸好你有2種選擇：

1）使用CardLayout這將允許你在單個JFrame /容器上的多個組件之間翻轉。

這裏是我做了一個例子：

import java.awt.BorderLayout; 
import java.awt.CardLayout; 
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; 
import javax.swing.SwingUtilities; 

public class Test { 

    private final static String PANEL1 = "panel 1"; 
    private final static String PANEL2 = "panel 2"; 

    public Test() { 
     initComponents(); 
    } 

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

    private void initComponents() { 
     JFrame frame = new JFrame(); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     JPanel panel1 = new JPanel(); 
     panel1.add(new JLabel("Panel 1")); 

     JPanel panel2 = new JPanel(); 
     panel2.add(new JLabel("Panel 2")); 

     //Create the panel that contains the "cards". 
     final JPanel cards = new JPanel(new CardLayout()); 
     cards.add(panel1, PANEL1); 
     cards.add(panel2, PANEL2); 

     //create button to allow chnage to next card 
     JButton buttonNext = new JButton(">"); 
     buttonNext.addActionListener(new ActionListener() { 
      @Override 
      public void actionPerformed(ActionEvent ae) { 
       CardLayout cl = (CardLayout) (cards.getLayout());//get cards 
       cl.next(cards); 
      } 
     }); 

     //create button to allow chnage to previous card 
     JButton buttonPrev = new JButton("<"); 
     buttonPrev.addActionListener(new ActionListener() { 
      @Override 
      public void actionPerformed(ActionEvent ae) { 
       CardLayout cl = (CardLayout) (cards.getLayout());//get cards 
       cl.previous(cards); 
      } 
     }); 

     //create panel to hold buttons which will allow switching between cards 
     JPanel buttonPanel = new JPanel(); 
     buttonPanel.add(buttonPrev); 
     buttonPanel.add(buttonNext); 


     frame.add(cards); 
     frame.add(buttonPanel, BorderLayout.SOUTH); 

     frame.pack(); 
     frame.setVisible(true); 
    } 
} 

2）使用removeAll()技術即呼叫frame.getContentPane().removeAll()將目前去除JFrame所有組件和不是增加新的內容，並呼籲revalidate()和repaint() （也可能需要在pack()中添加）在JFrame實例上以反映更改。雖然Id建議CardLayout。

Answer 2

我想你可以用CardLayout來實現你的功能。請參閱here