Java Swing使用主机框架获取其他组件

Question

Here I have this code below which reverses a text.

TextFrame Class the main frame of my GUI

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;


public class TextFrame extends JFrame implements ActionListener{
    private Controls theControls;
    private ReverseText theReverseText;
    private InputOutputPanel theInputOutputPanel;

    public TextFrame(){

    this.getContentPane().setLayout(new BorderLayout());

    theInputOutputPanel = new InputOutputPanel();
    theReverseText = new ReverseText(this);
    theControls = new Controls(theReverseText);

    this.getContentPane().add(theInputOutputPanel, BorderLayout.NORTH);

    this.getContentPane().add(theControls, BorderLayout.SOUTH);
    this.pack();
    this.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }


    public Controls getControls(){
    return this.theControls;
    }

    public InputOutputPanel getInputOutPanel(){
        return this.theInputOutputPanel;

    }

    public static void main(String[] args) {
        // All we need to do is create the frame, as the constructor does everything required.
        TextFrame theFrame = new TextFrame();
//        theFrame.setSize(150, 150);
//        theFrame.setVisible(true);
    }

}

InputOutPut Class Panel which handles the input and output

import java.awt.GridLayout;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class InputOutputPanel extends JPanel {

    private JTextField input;
    private JTextField output;
    private JTextField situation;

    public InputOutputPanel() {

        this.setLayout(new GridLayout(2, 2));
         this.add(new JLabel("header"));
        this.add(situation = new JTextField("Situation"));
        this.add(input = new JTextField("input text here"));
        this.add(output = new JTextField());


    }

    public void setSituation(String sit){
        situation.setText(sit);

    }

    public void setOutPut(String s){
    output.setText(s);
    }

    public String getInput(){
        return input.getText();


    }
}

Controls class

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


public class Controls extends JPanel {
    private ReverseText reverseText; //the Event handler
    private TextFrame theTextFrame;  // the main frame to display the text

    public Controls(ReverseText reverseText){
    this.reverseText = reverseText;

    reverseText = new ReverseText(theTextFrame);

    JButton reversetheTextButton;       

    this.add(reversetheTextButton = new JButton("Text-Reverse"));
    reversetheTextButton.addActionListener(reverseText);   


    }

}

ReverseText Class which is my event handler

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

import java.awt.event.ActionListener;

public class ReverseText implements ActionListener {

    private TextFrame theTextFrame;
    private InputOutputPanel inputOutPanel;


    public ReverseText(TextFrame theTextFrame) {
        this.theTextFrame = theTextFrame;



    }

    @Override
    public void actionPerformed(ActionEvent event) {
    String buttonAction = event.getActionCommand();

    // trying to use the mainframe to get other components

    inputOutPanel = theTextFrame.getInputOutPanel(); // but this line complaining about null pointer error 

    String input = inputOutPanel.getInput();


    if (buttonAction.equals("Text-Reverse"))
        System.out.println("yes");
        inputOutPanel.setSituation(buttonAction);

        //Reverse The Text and send it to the Output
        String reversedText = new StringBuffer(input).reverse().toString();

        //
        inputOutPanel.setOutPut(reversedText);

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here

    }

}

I want to use the mainframe in my event handler class to call these components butthis is not working.

I have get and set methods in my main Frame called TextFrame.

My question is how do I use my event handler class using the main frame cato take input from the GUI and reverse this input.

Answer 1

You never set the Controls TextFrame field with any TextFrame instance. You need to pass it into the Controls constructor via a parameter, just as you do the model.

public class Controls extends JPanel {
    private ReverseText reverseText; //the Event handler
    private TextFrame theTextFrame;  // the main frame to display the text

    // **** note changes to constructor
    public Controls(ReverseText reverseText, TextFrame theTextFrame){
        this.reverseText = reverseText;
        this.theTextFrame = textFrame;  // ***** added

        reverseText = new ReverseText(theTextFrame);

Then change:

theControls = new Controls(theReverseText, this); // **** note change

Answer 2

after new JButton(...), call setActionCommand on the button. Otherwise you just set the label, and the listener won't get an ActionCommand of the button even when the listener is fired.