[英]JPanel: automatically paint at creation?
这一定是微不足道的和直接的,但我无法弄清楚。
这是我的JPanel外观,它被添加到JFrame中:
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一直都在重新绘制。 但是,当我不调整JFrame的大小时,即使我在构造函数中调用了repaint,似乎也未调用JPanel的paintComponent方法。
有什么建议吗? 谢谢。
更新:
更完整的代码(除绘图逻辑外的所有内容):
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);
}
}
}
您第一次正确的地方。 自定义绘画是通过paintComponent()方法而不是paint()方法完成的。
永远不要从paintComponent()方法中调用repaint(),因为那样会导致无限循环。
如果要对绘画进行动画处理,则应使用Swing计时器来安排动画。
您不应该使用use setSize()。 那是布局管理器的工作。 相反,您可以覆盖面板的getPreferredSize()方法(或使用setPreferredSize()),然后可以对框架进行包装(而不是设置其大小)。
在使框架可见之前,应将面板添加到框架,否则面板的大小为(0,0),这意味着没有要绘画的东西。
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repaint是个好主意。 组件可见后,它将重新绘制。
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