Java 调整对话框窗口大小时,PaintComponent()和getpreferredsize()如何工作?
下面是一个我不理解的Java代码。 我已经输出了程序调用getPreferredsize和paintComponent方法的时间。我发现,每次调整DialogWindow的大小时,它都会调用一次getPreferredsize方法和两次paintcomponent方法 为什么?Java 调整对话框窗口大小时,PaintComponent()和getpreferredsize()如何工作?,java,resize,paintcomponent,Java,Resize,Paintcomponent,下面是一个我不理解的Java代码。 我已经输出了程序调用getPreferredsize和paintComponent方法的时间。我发现,每次调整DialogWindow的大小时,它都会调用一次getPreferredsize方法和两次paintcomponent方法 为什么? 你的期望是什么?为什么担心?最好记住,您无法控制何时或是否调用这些方法,因此您必须确保没有程序逻辑,没有更改类状态的代码,我认为当我调整对话框WindowDot do g2d.drawLine0、panel.getHei
你的期望是什么?为什么担心?最好记住,您无法控制何时或是否调用这些方法,因此您必须确保没有程序逻辑,没有更改类状态的代码,我认为当我调整对话框WindowDot do g2d.drawLine0、panel.getHeight/2、panel.getWidth、panel.getHeight/2的大小时,应该调用一次getPreferred方法来了解窗口的实际大小,调用一次paintcomponent方法来重新绘制新窗口;当面板引用UI中的另一个组件时,该组件可能会在其外部绘制。getPreferredSize方法也是如此`
package examples;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.EtchedBorder;
import javax.swing.border.TitledBorder;
public class Bsp {
public static void main(String[] args) {
JFrame frame = new MyFrame();
}
}
class MyFrame extends JFrame {
JPanel panel=new JPanel(new GridBagLayout());
private class MyLine extends JLabel {
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
g2d.setColor(Color.BLACK);
g2d.setStroke(new BasicStroke(5));
System.out.println("PaintComponent: "+getWidth()+" "+getHeight());
g2d.drawLine(0, panel.getHeight()/2, panel.getWidth(), panel.getHeight()/2);
g2d.dispose();
}
@Override
public Dimension getPreferredSize() {
System.out.println("PreferredSize: "+panel.getWidth()+" "+panel.getHeight());
return new Dimension(panel.getWidth(),panel.getHeight());
}
}
public MyFrame() {
JLabel label=new MyLine();
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new GridLayout(3, 1));
panel.add(label);
add(new JButton("A"));
add(new JButton("B"));
add(panel);
pack();
centeringWindow();
setVisible(true);
}
public void borderingJPanel(JComponent panel, String jPanelname,
String fontStyle) {
Font font = new Font(fontStyle, Font.BOLD + Font.ITALIC, 12);
if (jPanelname != null) {
panel.setBorder(BorderFactory.createTitledBorder(BorderFactory
.createEtchedBorder(EtchedBorder.LOWERED, Color.GRAY,
Color.WHITE), jPanelname,
TitledBorder.DEFAULT_JUSTIFICATION,
TitledBorder.DEFAULT_POSITION, font));
} else if (jPanelname == null || fontStyle == null) {
panel.setBorder(BorderFactory.createTitledBorder(BorderFactory
.createEtchedBorder(EtchedBorder.LOWERED, Color.GRAY,
Color.WHITE)));
}
panel.setOpaque(false);
}
public void centeringWindow() {
Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
int x;
int y;
x = (int) (dimension.getWidth() - getWidth()) / 2;
y = (int) (dimension.getHeight() - getHeight()) / 2;
setLocation(x, y);
}
public BufferedImage getBufferedImage(){
BufferedImage buffImage=null;
try {
buffImage=ImageIO.read(MyFrame.class.getClassLoader().getResourceAsStream("examples/rightAnswerSign.png"));
} catch (IOException e) {
e.printStackTrace();
}
return buffImage;
}
}