Java中的重绘() [英] repaint() in Java

问题描述

可能的重复:
Java GUI repaint() 问题?

我写了一段 Java 代码，但我遇到了 GUI 问题.当我将组件添加到 JFrame 对象中时，我调用 repaint() 方法以更新 GUI，但它不起作用.但是当我最小化或调整这个框架时，GUI 会更新.

I write a Java code, but I have a trouble with GUI problem. When I add a component into JFrame object, then I call repaint() method in order to update the GUI but it doesn't work. But when I minimize or resize this frame, the GUI is updated.

这是我的代码:

public static void main(String[] args)
{
    JFrame frame = new JFrame();

    frame.setSize(460, 500);
    frame.setTitle("Circles generator");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.setVisible(true);

    String input = JOptionPane.showInputDialog("Enter n:");
    int n = Integer.parseInt(input);

    CircleComponent component = new CircleComponent(n);
    frame.add(component);
    component.repaint();
}

推荐答案

如果你添加了 JComponent 到已经可见的 Container，那么你有调用

If you added JComponent to already visible Container, then you have call

frame.getContentPane().validate();
frame.getContentPane().repaint();

例如

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Main {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(460, 500);
        frame.setTitle("Circles generator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
              frame.setVisible(true);
           }
        });

        String input = JOptionPane.showInputDialog("Enter n:");
        CustomComponents0 component = new CustomComponents0();
        frame.add(component);
        frame.getContentPane().validate();
        frame.getContentPane().repaint();
    }

    static class CustomComponents0 extends JLabel {

        private static final long serialVersionUID = 1L;

        @Override
        public Dimension getMinimumSize() {
            return new Dimension(200, 100);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(300, 200);
        }

        @Override
        public void paintComponent(Graphics g) {
            int margin = 10;
            Dimension dim = getSize();
            super.paintComponent(g);
            g.setColor(Color.red);
            g.fillRect(margin, margin, dim.width - margin * 2, dim.height - margin * 2);
        }
    }
}

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