blocks|key|2452066|text|相反，repaint()正在被触发。您的问题是您在paintComponent方法中随机化，并且您永远不应该从这个方法更改类的状态，因为您不能完全控制应该或可以调用它的时间，甚至。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|2452067|相反，在actionPerformed方法中进行随机化，设置红色、蓝色和绿色实例字段，调用repaint，并在paintComponent方法中使用这些字段。|2452068|类似于：|2452069|private+int+red1,+green1,+blue1,+red2,+green2,+blue2;

@Override
public+void+actionPerfomed(ActionEvent+e)+{
++++red1+=+(int)+(Math.random()+*+256);
++++green1+=+(int)+(Math.random()+*+256);
++++blue1+=+(int)+(Math.random()+*+256);

++++red2+=+(int)+(Math.random()+*+256);
++++green2+=+(int)+(Math.random()+*+256);
++++blue2+=+(int)+(Math.random()+*+256);
++++repaint();
}

@Override
public+void+paintComponent(Graphics+g)+{
++++Graphics2D+g2d+=+(Graphics2D)+g;

++++Color+startColor+=+new+Color(red1,+green1,+blue1);
++++Color+endColor+=+new+Color(red2,+green2,+blue2);

++++GradientPaint+gradient+=+new+GradientPaint(70,70,startColor,+150,150,+endColor);
++++g2d.setPaint(gradient);
++++g2d.fillOval(70,70,100,100);
}|code-block|syntax|javascript|2452070|例如，|2452071|import+java.awt.BorderLayout;
import+java.awt.Color;
import+java.awt.Dimension;
import+java.awt.GradientPaint;
import+java.awt.Graphics;
import+java.awt.Graphics2D;
import+java.awt.RenderingHints;
import+java.awt.event.ActionEvent;
import+javax.swing.*;

public+class+SimpleGui3C+{

++++@SuppressWarnings("serial")
++++private+static+void+createAndShowGui()+{
++++++++final+MyDrawPanel+gui+=+new+MyDrawPanel();

++++++++JButton+drawButton+=+new+JButton(new+AbstractAction("Randomize")+{

++++++++++++@Override
++++++++++++public+void+actionPerformed(ActionEvent+arg0)+{
++++++++++++++++gui.randomizeColor();
++++++++++++}
++++++++});

++++++++JFrame+frame+=+new+JFrame("SimpleGui3C");
++++++++frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
++++++++frame.getContentPane().add(gui);
++++++++frame.getContentPane().add(drawButton,+BorderLayout.PAGE_END);
++++++++frame.pack();
++++++++frame.setLocationRelativeTo(null);
++++++++frame.setVisible(true);
++++}

++++public+static+void+main(String[]+args)+{
++++++++SwingUtilities.invokeLater(()+->+createAndShowGui());
++++}
}|2452072|​|2452073|@SuppressWarnings("serial")
class+MyDrawPanel+extends+JPanel+{
++++private+static+final+int+PREF_W+=+800;
++++private+static+final+int+PREF_H+=+650;
++++private+static+final+int+OVAL_X+=+70;
++++private+static+final+int+OVAL_W+=+100;
++++private+int+red1,+green1,+blue1,+red2,+green2,+blue2;

++++public+MyDrawPanel()+{
++++++++int+w+=+OVAL_W+%2B+2+*+OVAL_X;
++++++++setPreferredSize(new+Dimension(w,+w));
++++++++randomizeColor();
++++}

++++public+void+randomizeColor()+{
++++++++red1+=+(int)+(Math.random()+*+256);
++++++++green1+=+(int)+(Math.random()+*+256);
++++++++blue1+=+(int)+(Math.random()+*+256);

++++++++red2+=+(int)+(Math.random()+*+256);
++++++++green2+=+(int)+(Math.random()+*+256);
++++++++blue2+=+(int)+(Math.random()+*+256);
++++++++repaint();
++++}

++++@Override
++++public+void+paintComponent(Graphics+g)+{
++++++++super.paintComponent(g);+//+*****+Don't+forget+this+*****
++++++++Graphics2D+g2d+=+(Graphics2D)+g;
++++++++g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,+RenderingHints.VALUE_ANTIALIAS_ON);

++++++++Color+startColor+=+new+Color(red1,+green1,+blue1);
++++++++Color+endColor+=+new+Color(red2,+green2,+blue2);

++++++++GradientPaint+gradient+=+new+GradientPaint(70,+70,+startColor,+150,+150,+endColor);
++++++++g2d.setPaint(gradient);
++++++++g2d.fillOval(OVAL_X,+OVAL_X,+OVAL_W,+OVAL_W);
++++}
}|2452074|此外，不要忘记在覆盖中调用super.paintComponent(g);+(参见上面的代码)|2452075|entityMap^0|3|9|2H|1|0|0|27|0|0|4|0|0|0|3|0|0|0|1|0|0|0|1B|D|O|0^^$0|@$1|2|3|4|5|6|7|11|8|@$9|12|A|13|B|C]|$9|14|A|15|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|16|8|@$9|17|A|18|B|D]]|E|@]|F|$]]|$1|I|3|J|5|6|7|19|8|@$9|1A|A|1B|B|D]]|E|@]|F|$]]|$1|K|3|L|5|M|7|1C|8|@]|E|@]|F|$N|O]]|$1|P|3|Q|5|6|7|1D|8|@$9|1E|A|1F|B|D]]|E|@]|F|$]]|$1|R|3|S|5|M|7|1G|8|@]|E|@]|F|$N|O]]|$1|T|3|U|5|6|7|1H|8|@$9|1I|A|1J|B|D]]|E|@]|F|$]]|$1|V|3|W|5|M|7|1K|8|@]|E|@]|F|$N|O]]|$1|X|3|Y|5|6|7|1L|8|@$9|1M|A|1N|B|D]|$9|1O|A|1P|B|C]]|E|@]|F|$]]|$1|Z|3|-4|5|6|7|1Q|8|@]|E|@]|F|$]]]|10|$]]

No, actionPerformed is most definitely not being triggered. Rather a <code>repaint()</code> is being triggered. Your problem is that you're randomizing within the paintComponent method, and you should never change the state of the class from this method since you do not have full control over when or even if it should or can be called.

Instead do your randomization within the actionPerformed method, set red, blue, and green instance fields, call repaint, and use those fields within the paintComponent method.

Something like:

<pre><code>private int red1, green1, blue1, red2, green2, blue2;

@Override
public void actionPerfomed(ActionEvent e) {
 red1 = (int) (Math.random() * 256);
 green1 = (int) (Math.random() * 256);
 blue1 = (int) (Math.random() * 256);

 red2 = (int) (Math.random() * 256);
 green2 = (int) (Math.random() * 256);
 blue2 = (int) (Math.random() * 256);
 repaint();
}

@Override
public void paintComponent(Graphics g) {
 Graphics2D g2d = (Graphics2D) g;

 Color startColor = new Color(red1, green1, blue1);
 Color endColor = new Color(red2, green2, blue2);

 GradientPaint gradient = new GradientPaint(70,70,startColor, 150,150, endColor);
 g2d.setPaint(gradient);
 g2d.fillOval(70,70,100,100);
}
</code></pre>

e.g.,

<pre><code>import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import javax.swing.*;

public class SimpleGui3C {

 @SuppressWarnings("serial")
 private static void createAndShowGui() {
 final MyDrawPanel gui = new MyDrawPanel();

 JButton drawButton = new JButton(new AbstractAction("Randomize") {

 @Override
 public void actionPerformed(ActionEvent arg0) {
 gui.randomizeColor();
 }
 });

 JFrame frame = new JFrame("SimpleGui3C");
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.getContentPane().add(gui);
 frame.getContentPane().add(drawButton, BorderLayout.PAGE_END);
 frame.pack();
 frame.setLocationRelativeTo(null);
 frame.setVisible(true);
 }

 public static void main(String[] args) {
 SwingUtilities.invokeLater(() -&gt; createAndShowGui());
 }
}
</code></pre>



<pre><code>@SuppressWarnings("serial")
class MyDrawPanel extends JPanel {
 private static final int PREF_W = 800;
 private static final int PREF_H = 650;
 private static final int OVAL_X = 70;
 private static final int OVAL_W = 100;
 private int red1, green1, blue1, red2, green2, blue2;

 public MyDrawPanel() {
 int w = OVAL_W + 2 * OVAL_X;
 setPreferredSize(new Dimension(w, w));
 randomizeColor();
 }

 public void randomizeColor() {
 red1 = (int) (Math.random() * 256);
 green1 = (int) (Math.random() * 256);
 blue1 = (int) (Math.random() * 256);

 red2 = (int) (Math.random() * 256);
 green2 = (int) (Math.random() * 256);
 blue2 = (int) (Math.random() * 256);
 repaint();
 }

 @Override
 public void paintComponent(Graphics g) {
 super.paintComponent(g); // ***** Don't forget this *****
 Graphics2D g2d = (Graphics2D) g;
 g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

 Color startColor = new Color(red1, green1, blue1);
 Color endColor = new Color(red2, green2, blue2);

 GradientPaint gradient = new GradientPaint(70, 70, startColor, 150, 150, endColor);
 g2d.setPaint(gradient);
 g2d.fillOval(OVAL_X, OVAL_X, OVAL_W, OVAL_W);
 }
}
</code></pre>

Also, don't forget to call the <code>super.paintComponent(g);</code> in your override (see code above)

I am trying to gain a better understanding of GUI programming in Java and some strange behavior has occurred. The program shows a circle with a gradient of random colors, and when you click the button the colors change. Very simple, except that I noticed when I accidentally expanded the window, the actionPerformed was triggered, and the button would constantly change colors as if I were spamming the button. My question is why this happened? I am using a Windows environment, if that matters. My code:

<pre><code>public class SimpleGui3C implements ActionListener {
JFrame frame;

public static void main (String[] args) {
 SimpleGui3C gui = new SimpleGui3C();
 gui.go();
}

public void go() {
 frame = new JFrame();
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 JButton button = new JButton("Change Colors");
 button.addActionListener(this);

 MyDrawPanel drawPanel = new MyDrawPanel();

 frame.getContentPane().add(BorderLayout.SOUTH, button);
 frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
 frame.setSize(300, 300);
 frame.setVisible(true);
}

public void actionPerformed(ActionEvent event) {
 frame.repaint();
}

}
</code></pre>

<hr>

MyDrawPanel

<pre><code>class MyDrawPanel extends JPanel {

@Override
public void paintComponent(Graphics g) {
 Graphics2D g2d = (Graphics2D) g;

 int red = (int) (Math.random() * 256);
 int green = (int) (Math.random() * 256);
 int blue = (int) (Math.random() * 256);
 Color startColor = new Color(red, green, blue);

 red = (int) (Math.random() * 256);
 green = (int) (Math.random() * 256);
 blue = (int) (Math.random() * 256);
 Color endColor = new Color(red, green, blue);

 GradientPaint gradient = new GradientPaint(70,70,startColor, 150,150, endColor);
 g2d.setPaint(gradient);
 g2d.fillOval(70,70,100,100);
}
}
</code></pre>

actionPerformed triggered when expanding window

Windows

Java

我试图更好地理解Java中的GUI编程，但出现了一些奇怪的行为。该程序显示一个具有随机颜色渐变的圆，当您单击按钮时，颜色会发生变化。非常简单，除了我注意到当我意外地扩展窗口时，actionPerformed被触发，并且按钮会不断地改变颜色，就像我在按下按钮一样。我的问题是为什么会发生这种情况？我正在使用Windows环...

问展开窗口时触发的actionPerformed
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