java我正在尝试给JPanel窗口背景上色。但我在执行后得到了一个没有任何颜色的JPanel窗口。代码中有什么错误？

Question

我正在给JPanel窗口的背景上色。但我在处决后得到了一个没有任何颜色的JPanel窗口。代码中有什么错误

package BrickBreaker;

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

import javax.swing.JPanel;
import javax.swing.Timer;

public class Gameplay extends JPanel {

    private boolean play = false;
    private int totalBrick = 28;
    private Timer time;
    private int delay = 8;
    private int ballPosX = 120;
    private int ballPosY = 350;
    private int ballXdir = -1;
    private int ballYdir = -2;
    private int playerX = 350;

    public Gameplay() {

    }

    public void paint(Graphics g) {
        g.setColor(Color.black);
        g.fillRect(1, 1, 692, 592);
    }

}

Answer 1

你应该这样做（我假设你有一个添加了面板的JFrame）

public class Gameplay extends JPanel {

    private boolean play = false;
    private int totalBrick = 28;
    private Timer time;
    private int delay = 8;
    private int ballPosX = 120;
    private int ballPosY = 350;
    private int ballXdir = -1;
    private int ballYdir = -2;
    private int playerX = 350;

    public Gameplay() {
        setBackground(Color.black);
    }

    // if your going to override this you need to call the parent's paintComponent.
    // otherwise the setBackground would not work.
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
       g = g.create();
       // g.setColor(Color.black);// you don't need this
       // g.fillRect(1, 1, 692, 592); // now you don't need this
       // But if you want to draw a red circle, you do need to change the color
       // for that
       g.setColor(Color.red);
       g.fillOval(100,100,50,50);
       g.dispose();
    }

}