Question

这一定是相当简单和直接的，但我无法弄明白。

这是我的JPanel的样子，它被添加到JFrame：

private class RadarPanel extends JPanel {       
        public RadarPanel() {
            super();
            this.repaint();
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            //painting logic here

            //repaint in 500 ms
            this.repaint(500);
        }
    }

现在，当我调整JFrame的大小时，这个JPanel会一直重新开始重绘。但是，当我没有调整JFrame的大小时，JPanel的paintComponent方法似乎没有被调用，即使我在构造函数中调用了repaint。

有什么建议吗？感谢。

更新：

更完整的代码（除了绘图逻辑之外的所有内容）：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;

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

public class PlayerRadar extends JFrame {
    private static final long serialVersionUID = 230324190;

    //settings
    private static final int windowWidth = 300;
    private static final int windowHeight = 300;
    private static final int maxDistance = 250;

    //components
    private PlayerRadar radarWindow;
    private JPanel radarPanel;

    public PlayerRadar(String title) {
        super(title);

        //set reference
        radarWindow = this;

        //create radar window
        Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
        this.setAlwaysOnTop(true);
        this.setBackground(new Color(0xFFFFFF));
        this.setBounds(screenSize.width - windowWidth, 0, windowWidth, windowHeight);
        this.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                radarWindow.setVisible(false);
            }
        });
        this.setVisible(true);

        //create a JPanel for drawing
        radarPanel = new RadarPanel();
        radarPanel.setBounds(0, 0, windowWidth, windowHeight);
        radarPanel.setBackground(new Color(0xFFFFFF));

        //add to frame
        this.getContentPane().add(radarPanel);
    }

    private class RadarPanel extends JPanel {
        private static final long serialVersionUID = 230324191;
        private static final int repaintInterval = 500;

        public RadarPanel() {
            super();
        }

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

        //draw player oval (center of the frame)
        g.setColor(Color.BLUE); //blue
        int ovalWidth = (int) Math.round(this.getWidth() / 30);
        int ovalHeight = (int) Math.round(this.getHeight() / 30);
        int playerLocalX = (int) Math.round(this.getWidth() / 2);
        int playerLocalY = (int) Math.round(this.getHeight() / 2);
        int ovalX = playerLocalX - ovalWidth / 2;
        int ovalY = playerLocalY - ovalHeight / 2;
        g.fillOval(ovalX, ovalY, ovalWidth, ovalHeight);
        g.setColor(Color.BLACK); //black
        g.drawOval(ovalX, ovalY, ovalWidth, ovalHeight);

        //get info of the player itself
        PlayerInfo thisPlayer = GameUtil.getPlayerInfo();
        float playerPosZ = thisPlayer.position[0];
        float playerPosX = thisPlayer.position[2];
        //float playerRotRad = thisPlayer.rotation;

        //set rectangle specs
        int rectWidth = this.getWidth() / 40;
        int rectHeight = this.getWidth() / 40;

        //only continue if we have information about our player
        if (thisPlayer != null) {
            //get nearby players
            ArrayList<PlayerInfo> playersInfo = GameUtil.getNearbyPlayers();

            //for each other player, draw a rectangle
            for (PlayerInfo playerInfo : playersInfo) {                 
                //get data
                float posZ = playerInfo.position[0];
                float posX = playerInfo.position[2];
                //float rotRad = playerInfo.rotation;

                //calculate relative x and y
                int rectX = playerLocalX + Math.round((posX - playerPosX) / maxDistance * this.getWidth() / 2) - rectWidth / 2;
                int rectY = playerLocalY + ovalHeight / 2 + Math.round((playerPosZ - posZ) / maxDistance * this.getHeight() / 2)  - rectHeight / 2;

                //draw rectangle
                g.setColor(Color.RED);
                g.fillRect(rectX, rectY, rectWidth, rectHeight);
                g.setColor(Color.BLACK);
                g.drawRect(rectX, rectY, rectWidth, rectHeight);
            }
        }

        //repaint soon
        this.repaint(repaintInterval);
    }
    }
}

Answer 1

你第一次纠正的地方。自定义绘制在paintComponent（）方法中完成，而不是paint（）方法。

你永远不应该在paintComponent（）方法中调用repaint（），因为这会导致无限循环。

如果你想为这幅画设置动画，那么你应该使用一个Swing Timer来安排动画。

您不应该使用use setSize（）。这是布局管理器的工作。相反，你可以覆盖面板的getPreferredSize（）方法（或使用setPreferredSize（）），然后你可以打包（）框架，而不是设置它的大小。

在框架可见之前，应将面板添加到框架中，否则其大小为（0,0），这意味着无需绘制任何内容。

Answer 2

在显示表单并初始化图形之前，它不会重新绘制。我不认为在构造函数中调用重绘是一个好主意。一旦组件可见，它将重新绘制。

JPanel：在创作时自动绘画？

2 个答案: