如何实时更新Swing组件

Question

I am programming a multiplication app for very large integers, I need to update every sigle step of the multiplication in a Swing component ( I created a JPane extended class with a JTextArea in it, then add it to the JFrame inside a ScrollPane). The issue is that this Swing component only updates once the multiplication algorithm is done. I tried using a Thread that would call repaint method of the Pane every 10 ms, but it did not work. The next is a sample of the problem.

This is the main Frame class:

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

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

public class Frame extends JFrame implements ActionListener{
private Console console;
private JButton calculate;
private Calculator calculator;


public Frame(){
    console=new Console();
    calculate=new JButton("Calculate");
    calculate.addActionListener(this);
    calculate.setActionCommand("");
    calculator=new Calculator(this);
    this.setLayout(new BorderLayout());
    this.add(console,BorderLayout.CENTER);
    this.add(calculate, BorderLayout.NORTH);
    this.setTitle("Frame");
    this.setVisible(true);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setSize(new Dimension(500,500));
    this.setLocationRelativeTo(null);


}


public void writeOnConsole(String txt){
    console.write(txt);
}


@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    if(e.getActionCommand().equals("")){
        console.clear();
        calculator.calculate();
    }
}


public static void main(String[] args) {
    new Frame();
}
}

This is the Console Class

import java.awt.BorderLayout;

import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.border.TitledBorder;

public class Console extends JPanel{

    private JTextArea area;


    public Console(){
        this.setBorder(new TitledBorder("Console:"));
        area=new JTextArea();
        this.setLayout(new BorderLayout());
        JScrollPane scroll=new JScrollPane(area);
        this.add(scroll,BorderLayout.CENTER);
    }

    public void clear(){
        area.setText("");
    }
    public void write(String txt){
        area.append(txt+"\n");
    }
}

Finally, this is the Calculator class (the one responsible for calling the writing)

public class Calculator {


    private Frame parent;

    public Calculator(Frame f){
        parent=f;
    }

    public void calculate(){
        for (int i = 0; i <= 1000000; i++) {
            parent.writeOnConsole("Iteration "+i);
        }
    }
}

Note that if you run the program, the GUI will freeze until the Calculator class is done with the loop.

Answer 1

if you have a layout like a BorderLayout and you want to update it inside the JFrame do as bellow

JFrame frame = new JFrame();
BorderLayout layout = new BorderLayout();
layout.layoutContainer(frame.getContentPane());// use the frame as the border layout container

else you can use JFrame pack() method. The pack method packs the components within the window based on the component's preferred sizes. it's not for updating but it updates the JFrame which is kind of a trick

JFrame frame = new JFrame();
//change the components dynamically
frame.pack();

or use Container methdod validate(). Validating a container means laying out its subcomponents. Layout-related changes, such as setting the bounds of a component, or adding a component to the container.

JFrame frame = new JFrame();
Container container = frame.getContentPane();
container.validate();

or if you want to update an specific component use

Component component = new JPanel();
component.repaint();

If this component is a lightweight component, repaint() method causes a call to this component's paint method as soon as possible .

or if you want for example numerous changes happen one by one dynamically then you could use the code below which is completely different from the things i said above. for that you could use platform.runlater() inside another thread which deals with everything that is about to change in realtime

new Thread(new Runnable() 
    {
    @Override 
    public void run() 
    {

        Platform.runLater(new Runnable()//use platform.runlater if you are using javafx
        {
            @Override 
            public void run() 
            {
                try
                {Thread.sleep(50);}catch(Exception e){}//use it in for loop where changes happen
                //do some realtime change of components
            }
        });

}).start();

Answer 2

尝试使用update方法来调用paint方法以维护每个更改

Answer 3

your Console class would be

import java.awt.BorderLayout;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.border.TitledBorder;


public class Console extends JPanel{

    private JTextArea area;


    public Console(){
        this.setBorder(new TitledBorder("Console:"));
        area=new JTextArea();
        this.setLayout(new BorderLayout());
        JScrollPane scroll=new JScrollPane(area);
        this.add(scroll,BorderLayout.CENTER);
    }

    public void clear(){
        area.setText("");
    }
    public void write(String txt){

        area.append(txt+" "+"\n");

    }
  }

and the Calculator class is

public class Calculator {


    private Frame parent;

    public Calculator(Frame f){
        parent=f;
    }

    public void calculate(){
        new Thread(new Runnable() {
            @Override 
            public void run() 
            {

                for (int i = 0; i <= 100; i++) {
                    try
                    {
                        Thread.sleep(50);

                    }
                    catch(Exception e)
                    {
                        e.printStackTrace();
                    }

                    parent.writeOnConsole("Iteration "+i);
                }

            }   
        }).start();


    }
}

as you can see i used another thread to do the changes