無法從靜態上下文錯誤中引用按鈕變量

Question

如何防止我的當前代碼發生此錯誤？我很抱歉我的邏輯非常業餘。

public class jButExmp {  
JFrame exmpFrame; 
JButton Button1, Button2, Button3;  
public jButExmp() { 
    exmpFrame.setLayout(new FlowLayout()); 
    exmpFrame.setSize(250,150); 
    exmpFrame.setVisible(true); 
    exmpFrame.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE); 
    exmpFrame.add(Button1); 
    exmpFrame.add(Button2); 
    exmpFrame.add(Button3); 
} 
public static void main(String[] args) { 
exmpFrame = new JFrame ("Example Frame"); 
Button1 = new JButton ("1"); 
Button2 = new JButton ("2"); 
Button3 = new JButton ("3"); 

Button1.setSize(80, 30); //set size of button 
Button1.setLocation(0,0); 
Button1.setEnabled(true); 

Button2.setSize(80,30); 
Button2.setLocation(90, 0); 
Button2.setEnabled(false); 

} 
} 

Answer 1

在你的代碼中，你正試圖訪問靜態主方法中的靜態變量，所以會產生編譯錯誤。

試試這個

import java.awt.FlowLayout; 

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

public class jButExmp { 
    JFrame exmpFrame = new JFrame("Example Frame"); 
    JButton button1, button2, button3; 

    public JButton getButton1() { 
     return button1; 
    } 

    public void setButton1(JButton button1) { 
     this.button1 = button1; 
    } 

    public JButton getButton2() { 
     return button2; 
    } 

    public void setButton2(JButton button2) { 
     this.button2 = button2; 
    } 

    public JButton getButton3() { 
     return button3; 
    } 

    public void setButton3(JButton button3) { 
     this.button3 = button3; 
    } 

    public jButExmp() { 
     exmpFrame = new JFrame("Example Frame"); 
     exmpFrame.setLayout(new FlowLayout()); 
     exmpFrame.setSize(250, 150); 
     exmpFrame.setVisible(true); 
     button1 = new JButton("1"); 
     button2 = new JButton("2"); 
     button3 = new JButton("3"); 
     exmpFrame.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE); 
     exmpFrame.add(button1); 
     exmpFrame.add(button2); 
     exmpFrame.add(button3); 
    } 

    public static void main(String[] args) { 
     jButExmp jButExmpRef = new jButExmp(); 

     jButExmpRef.getButton1().setSize(80, 30); // set size of button 
     jButExmpRef.getButton1().setLocation(0, 0); 
     jButExmpRef.getButton1().setEnabled(true); 

     jButExmpRef.getButton2().setSize(80, 30); 
     jButExmpRef.getButton2().setLocation(90, 0); 
     jButExmpRef.getButton2().setEnabled(false); 

    } 
} 

Answer 2

這woud是做的更地道的方式，但這種代碼有一些其他的問題，包括事實，你不設立BUTTON3你與按鈕1的方式， button2，以及您在使用默認FlowLayout（不支持設置位置）時設置按鈕位置的事實。

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


    public class JButExmp extends JFrame { 

    JButton button1; 
    JButton button2; 
    JButton button3; 

    public JButExmp (String title) { 

     super(title); 

     button1 = new JButton("1"); 
     button2 = new JButton("2"); 
     button3 = new JButton("3"); 

     add(button1); 
     add(button2); 
     add(button3); 

     button1.setSize(80, 30); //set size of button 
     button1.setLocation(0,0); 
     button1.setEnabled(true); 

     button2.setSize(80,30); 
     button2.setLocation(90, 0); 
     button2.setEnabled(false); 

     setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE); 
     setLayout(new FlowLayout()); 
     setSize(250,150); 
     setVisible(true); 
    } 

    public static void main(String[] args) { 
     JButExmp jButExmp = new JButExmp("Example Frame"); 
    } 
} 

Answer 3

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

public class ExmpFile { 

    JFrame exmpFrame; 
    JButton Button1, Button2, Button3; 

    public ExmpFile() { 
     exmpFrame = new JFrame ("Example Frame"); 
     Button1 = new JButton ("1"); 
     Button2 = new JButton ("2"); 
     Button3 = new JButton ("3"); 

     Button2.setEnabled(false); 

     exmpFrame.setLayout(new FlowLayout(FlowLayout.CENTER)); 

     // better to pack() to the size of content.. BNI 
     exmpFrame.setSize(250,150); 
     exmpFrame.setVisible(true); 
     exmpFrame.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE); 
     exmpFrame.add(Button1); 
     exmpFrame.add(Button2); 
     exmpFrame.add(Button3); 

     exmpFrame.setVisible(true); 
    } 

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