Java中的事件处理未按预期工作
我无法让下面链接的代码完全执行我希望它执行的操作Java中的事件处理未按预期工作,java,swing,event-handling,Java,Swing,Event Handling,我无法让下面链接的代码完全执行我希望它执行的操作 import javax.swing.*; import java.awt.*; import java.awt.event.*; public class Gui { static JFrame frame; static JLabel label; public static void main (String[] args) { Gui gui = new Gui(); gui.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Gui {
static JFrame frame;
static JLabel label;
public static void main (String[] args) {
Gui gui = new Gui();
gui.go();
}
public void go () {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400,300);
frame.setVisible(true);
MyDrawPanel panel = new MyDrawPanel();
frame.getContentPane().add(BorderLayout.CENTER, panel);
label = new JLabel("I'm a label");
frame.getContentPane().add(BorderLayout.WEST, label);
JButton colorButton = new JButton("Change Colors");
ColorButtonListener colorButtonListener = new ColorButtonListener();
colorButton.addActionListener(colorButtonListener);
frame.getContentPane().add(BorderLayout.SOUTH, colorButton);
JButton labelButton = new JButton("Change Label");
LabelButtonListener labelButtonListener = new LabelButtonListener();
labelButton.addActionListener(labelButtonListener);
frame.getContentPane().add(BorderLayout.EAST, labelButton);
}
}
class ColorButtonListener implements ActionListener {
JFrame frame = Gui.frame;
public void actionPerformed (ActionEvent event) {
frame.repaint();
}
}
class LabelButtonListener implements ActionListener {
JLabel label = Gui.label;
public void actionPerformed (ActionEvent event) {
if (label.getText() == "That hurt") {
label.setText("I'm a label");
} else {
label.setText("That hurt");
}
}
}
class MyDrawPanel extends JPanel {
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(0, 0, this.getWidth(), this.getHeight());
}
}
有一个用于绘制圆的面板类,然后将面板定位在框架的中心区域
标签位于框架的西部区域,两个按钮colorButton(位于南部)和labelButton(位于东部)应分别控制圆圈和标签。ColorButtonListener和LabelButtonListener两个类实现了ActionListener接口,分别注册到colorButton和labelButton。单击“颜色”按钮时,应使用随机颜色绘制一个圆圈,单击“标签”按钮时,应在文本“我是标签”和“那伤害”之间切换
现在,我遇到的问题是标签按钮。单击它时,它不仅会更改文本(如预期的那样),还会重新绘制圆。此按钮不应重新绘制圆。“颜色”按钮按预期工作 这是因为如果新文本与旧文本不同,则
setText()
方法在内部调用repaint()
。这是因为如果新文本与旧文本不同,则setText()
方法会在内部调用repaint()
。因此,每当您单击该按钮时,也会导致颜色变化。问题在于您无法控制重新绘制的时间。例如,不要每次调用paintComponent
时都更改颜色(这是您无法控制的),而应仅在需要时更改颜色,并从paintComponent
方法中进行引用
class MyDrawPanel extends JPanel {
private Color startColor;
private Color endColor;
// And setters or some other way
// to randomise the colors
public void paintComponent (Graphics g) {
Graphics2D g2d = (Graphics2D) g;
GradientPaint gradient = new GradientPaint(70, 70, startColor, 150, 150, endColor);
g2d.setPaint(gradient);
g2d.fillOval(0, 0, this.getWidth(), this.getHeight());
}
}
查看更多详细信息问题在于您无法控制重新绘制的时间。例如,不要每次调用
paintComponent
时都更改颜色(这是您无法控制的),而应仅在需要时更改颜色,并从paintComponent
方法中进行引用
class MyDrawPanel extends JPanel {
private Color startColor;
private Color endColor;
// And setters or some other way
// to randomise the colors
public void paintComponent (Graphics g) {
Graphics2D g2d = (Graphics2D) g;
GradientPaint gradient = new GradientPaint(70, 70, startColor, 150, 150, endColor);
g2d.setPaint(gradient);
g2d.fillOval(0, 0, this.getWidth(), this.getHeight());
}
}
查看更多详细信息SetText-On并不能保证其他组件需要重新绘制(是的,标签需要重新绘制),真正的罪魁祸首很可能是标签大小的变化,这会导致容器层次结构的级联失效,这将导致其他容器重新绘制其中的内容…但您的语句较短;)SetText-On并不能保证其他组件将需要重新绘制(是的,标签将需要重新绘制),真正的罪魁祸首可能是标签大小的变化,这将导致容器层次结构的级联失效,这将导致其他容器重新绘制其中的内容……但您的语句较短;)