Im not sure how to get the data from my text field

问题

I want to get the data from my textfield and set it to int h. and have that change the size of the rectangle im drawing, but im not sure how to go get the data from the textfield, I tired using e.getsource in actionperfomred but it cannot find my textfield. My code is below:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;
import java.net.*;
import java.sql.*;
import java.lang.Object;
import java.awt.Graphics;
import java.awt.Graphics2D;

/**
 * This class demonstrates how to load an Image from an external file
 */
public class test extends Component {

    int x=77, y=441, w=23, h=10;

    BufferedImage img =
  new BufferedImage(100, 50,
                    BufferedImage.TYPE_INT_ARGB);    
   // BufferedImage img;

    public void paint(Graphics g) {
        g.drawImage(img, 0, 0, null);
           // g.fillRect(10,10,10,10);
    }

    public test() {
       try {
           img = ImageIO.read(new File("sales-goal.png"));
       } catch (IOException e) {}


       Graphics2D g = img.createGraphics();
       Color myColor = Color.decode("#32004b");
       g.setColor(myColor);
       g.fillRect(x,y,w,h);
                //77,441,23,10
    }

    public Dimension getPreferredSize() {
        if (img == null) {
             return new Dimension(100,100);
        } else {
           //return new Dimension(img.getWidth(null), img.getHeight(null));
            return new Dimension(300,600);
       }
    }

    public static void main(String[] args) {

        JFrame f = new JFrame("Load Image Sample");
        JTextField textField=new JTextField();
        f.add(textField);
        textField.setBounds(10,10,40,30);
        textField.setVisible(true);

        f.addWindowListener(new WindowAdapter(){
                public void windowClosing(WindowEvent e) {
                    System.exit(0);
                }
            });

        f.add(new test());
        f.pack();
        f.setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
               // if (e.getSource() == textField) {}

    }
}

回答1:

The variable textField is local to main. If you want to access it from actionPerformed, you'll need to change it to an instance variable.

回答2:

Yeah. I agree with @jpm. You need to declare it as an instance variable. Do the following:-

  public class test extends Component {
       //Declare the variable here.
       private static JTextField textfield;

    public static void main(String[] args) {
       //Whenever you use the textfield use like this. Remove the keyword 'JTextField'.
       textfield = new JTextField();
  }
  }

来源：https://stackoverflow.com/questions/10145493/im-not-sure-how-to-get-the-data-from-my-text-field

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