Question

package Jai;

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


public class tuna extends JFrame{

    tuna(){
        super("Title");
        setLayout(new FlowLayout());

        getContentPane().setBackground(Color.white);
    }

    public void paint(Graphics g){
        super.paint(g);

        g.fillOval(50, 100, 100, 155);      
    }

    public static void main(String[] arg){
        JFrame.setDefaultLookAndFeelDecorated(true);
        tuna obj = new tuna();
        obj.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        obj.setSize(500,500);
        obj.setVisible(true);
    }
}

我有JFrame，我使用paint方法在框架上绘制椭圆。每当我尝试最大化或最小化窗口时，通过paint()方法绘制的椭圆消失。我希望绘制的图形即使在我最大化或最小化帧时也能保持不变。

Answer 1

您的问题是覆盖了错误对象的错误方法。您必须覆盖主面板的paintComponent方法。这是正确的代码：

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class tuna extends JFrame {
    tuna() {
        super("Title");
        // you need to override the method paintComponent for the main panel
        setContentPane(new JPanel(new FlowLayout()) {
            @Override
            public void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.fillOval(50, 100, 100, 155);
            }
        });
        getContentPane().setBackground(Color.white);
    }

    public static void main(String[] arg) {
        JFrame.setDefaultLookAndFeelDecorated(true);
        tuna obj = new tuna();
        obj.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        obj.setSize(500, 500);
        obj.setVisible(true);
    }
}

为什么paint类不能使用setDefaultLookAndFeelDecorated（true）

1 个答案: