使用文本字段和按鈕來初始化變量

Question

我有一塊這樣的，在這裏我想使用按鈕來訪問一個JTextField代碼...

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

public class NameGameFrame extends JFrame 
{ 
    public static void main(String[] args) 
    { 

     JFrame frame = new JFrame(); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setTitle("Name Game"); 
     frame.setLocation(500,400); 
     frame.setSize(500,500); 

     JPanel panel = new JPanel(new GridBagLayout()); 
     GridBagConstraints c = new GridBagConstraints(); 

     JLabel label = new JLabel("Enter the Name or Partial Name to search:"); 
     c.gridx = 0; 
     c.gridy = 0; 
     c.insets = new Insets(2,10,10,10); 

     panel.add(label,c); 

     JTextArea textarea = new JTextArea(5,30); 
     panel.add(textarea); 

     JTextField textfield = new JTextField(20); 

     JButton button = new JButton("Search"); 
     c.gridx = 1; 
     c.gridy = 1; 
     panel.add(button,c); 

     panel.add(textfield); 

     frame.getContentPane().add(panel, BorderLayout.NORTH); 
     frame.setVisible(true); 

    } 
    static class Action implements ActionListener 
    { 
     public void actionPerformed(ActionEvent e) 
     { 
      String name = textfield.getText(); 
      textarea.append(name); 
      textfield.selectAll(); 
     } 
    } 
} 

我收到以下錯誤在我的代碼中，我不明白爲什麼...

1. 錯誤找不到符號String name = textfield.getText（）;
2. 錯誤找不到符號textarea.append（name）;
3. 錯誤找不到符號textfield.selectAll（）;

Answer 1

我認爲這些錯誤的所有3的原因是相同的 - 你需要移動的變量出更高的水平，使這兩種方法都可以訪問他們...

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

public class NameGameFrame extends JFrame 
{ 

    // Moved these 2 variables to be class-level 
    static JTextField textfield = new JTextField(20); 
    static JTextArea textarea = new JTextArea(5,30); 

    public static void main(String[] args) 
    { 

     JFrame frame = new JFrame(); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setTitle("Name Game"); 
     frame.setLocation(500,400); 
     frame.setSize(500,500); 

     JPanel panel = new JPanel(new GridBagLayout()); 
     GridBagConstraints c = new GridBagConstraints(); 

     JLabel label = new JLabel("Enter the Name or Partial Name to search:"); 
     c.gridx = 0; 
     c.gridy = 0; 
     c.insets = new Insets(2,10,10,10); 

     panel.add(label,c); 

     panel.add(textarea); 

     JButton button = new JButton("Search"); 
     c.gridx = 1; 
     c.gridy = 1; 
     panel.add(button,c); 

     panel.add(textfield); 

     frame.getContentPane().add(panel, BorderLayout.NORTH); 
     frame.setVisible(true); 

    } 
    static class Action implements ActionListener 
    { 
     public void actionPerformed(ActionEvent e) 
     { 
      String name = textfield.getText(); 
      textarea.append(name); 
      textfield.selectAll(); 
     } 
    } 
} 

與Java和大多數其他語言，請確保在嘗試解決其他語言之前解決第一個錯誤 - 通常第一個錯誤可能會在以後導致其他錯誤。

Answer 2

該聲明和使用在不同的功能; 所以你不能訪問它。