我有滑块可以创建RGB值，然后使用它创建一个框并填充其颜色。当我初始化我的程序时，它不会立即绘制正方形。它将绘制正方形并在移动滑块后开始填充它。
用于绘制矩形并用颜色填充它的方法在构造函数中被调用但是没有做任何事情，没有错误，只是没有绘制正方形。滑块在状态更改时调用SAME方法，然后绘制正方形。这毫无意义。
我确信这是其他人可能因缺乏某些基础而经历的事情。
这是我的代码，您可以复制粘贴并在jGrasp中运行或者其他什么来查看我的意思。谢谢！
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class Colors extends javax.swing.JFrame {
public Colors() {
initComponents();
addSliderListeners();
addSliderLabels();
this.setTitle("Color Mixer");
sliderRed.setValue(150);
sliderGreen.setValue(125);
sliderBlue.setValue(215);
updateImage();
}
private void addSliderListeners(){
sliderRed.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
updateImage();
}
});
sliderGreen.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
updateImage();
}
});
sliderBlue.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
updateImage();
}
});
}
private void updateImage(){
lblRedDec.setText(""+sliderRed.getValue());
lblRedDec.setForeground(new Color(sliderRed.getValue(),0,0));
lblRedHex.setText(Integer.toHexString(sliderRed.getValue()));
lblRedHex.setForeground(lblRedDec.getForeground());
lblGreenDec.setText(""+sliderGreen.getValue());
lblGreenDec.setForeground(new Color(0,sliderGreen.getValue(),0));
lblGreenHex.setText(Integer.toHexString(sliderGreen.getValue()));
lblGreenHex.setForeground(lblGreenDec.getForeground());
lblBlueDec.setText(""+sliderBlue.getValue());
lblBlueHex.setText(Integer.toHexString(sliderBlue.getValue()));
lblBlueDec.setForeground(new Color(0,0,sliderBlue.getValue()));
lblBlueHex.setForeground(lblBlueDec.getForeground());
Graphics2D g2 = (Graphics2D)this.getGraphics();
g2.setColor(new Color(sliderRed.getValue(),sliderGreen.getValue(),sliderBlue.getValue()));
g2.fill(new Rectangle(25,125,250,250));
}
private void addSliderLabels() {
sliderRed.setPaintLabels(true);
sliderGreen.setPaintLabels(true);
sliderBlue.setPaintLabels(true);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
sliderRed = new javax.swing.JSlider();
lblRed = new javax.swing.JLabel();
lblRedHex = new javax.swing.JLabel();
lblRedDec = new javax.swing.JLabel();
sliderGreen = new javax.swing.JSlider();
lblGreen = new javax.swing.JLabel();
lblGreenHex = new javax.swing.JLabel();
lblGreenDec = new javax.swing.JLabel();
sliderBlue = new javax.swing.JSlider();
lblBlue = new javax.swing.JLabel();
lblBlueHex = new javax.swing.JLabel();
lblBlueDec = new javax.swing.JLabel();
lblTitle = new java.awt.Label();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setResizable(false);
sliderRed.setMajorTickSpacing(15);
sliderRed.setMaximum(255);
sliderRed.setMinorTickSpacing(5);
sliderRed.setOrientation(javax.swing.JSlider.VERTICAL);
sliderRed.setPaintTicks(true);
sliderRed.setValue(212);
sliderRed.setCursor(new java.awt.Cursor(java.awt.Cursor.DEFAULT_CURSOR));
sliderRed.setName(""); // NOI18N
lblRed.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
lblRed.setText("Red");
lblRedHex.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
lblRedHex.setText("hex");
lblRedDec.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
lblRedDec.setText("dec");
sliderGreen.setMajorTickSpacing(15);
sliderGreen.setMaximum(255);
sliderGreen.setMinorTickSpacing(5);
sliderGreen.setOrientation(javax.swing.JSlider.VERTICAL);
sliderGreen.setPaintTicks(true);
sliderGreen.setSnapToTicks(true);
sliderGreen.setValue(35);
sliderGreen.setCursor(new java.awt.Cursor(java.awt.Cursor.DEFAULT_CURSOR));
sliderGreen.setName(""); // NOI18N
lblGreen.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
lblGreen.setText("Green");
lblGreenHex.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
lblGreenHex.setText("hex");
lblGreenDec.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
lblGreenDec.setText("dec");
sliderBlue.setMajorTickSpacing(15);
sliderBlue.setMaximum(255);
sliderBlue.setMinorTickSpacing(5);
sliderBlue.setOrientation(javax.swing.JSlider.VERTICAL);
sliderBlue.setPaintTicks(true);
sliderBlue.setSnapToTicks(true);
sliderBlue.setValue(218);
sliderBlue.setCursor(new java.awt.Cursor(java.awt.Cursor.DEFAULT_CURSOR));
sliderBlue.setName(""); // NOI18N
lblBlue.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
lblBlue.setText("Blue");
lblBlueHex.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
lblBlueHex.setText("hex");
lblBlueDec.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
lblBlueDec.setText("dec");
lblTitle.setFont(new java.awt.Font("Dialog", 0, 36)); // NOI18N
lblTitle.setText("Color Mixer");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap()
.addComponent(lblTitle, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 125, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
.addGroup(layout.createSequentialGroup()
.addGap(27, 27, 27)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(lblRedHex)
.addComponent(lblRed)
.addComponent(lblRedDec))
.addGap(25, 25, 25))
.addComponent(sliderRed, javax.swing.GroupLayout.PREFERRED_SIZE, 71, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(sliderGreen, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 71, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(lblGreenHex)
.addComponent(lblGreen)
.addComponent(lblGreenDec))
.addGap(25, 25, 25)))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(sliderBlue, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 71, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(lblBlueHex)
.addComponent(lblBlue)
.addComponent(lblBlueDec))
.addGap(25, 25, 25))))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(23, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
.addGroup(layout.createSequentialGroup()
.addComponent(lblBlueDec)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(lblBlueHex)
.addGap(18, 18, 18)
.addComponent(lblBlue)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(sliderBlue, javax.swing.GroupLayout.PREFERRED_SIZE, 285, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(lblGreenDec)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(lblGreenHex)
.addGap(18, 18, 18)
.addComponent(lblGreen)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(sliderGreen, javax.swing.GroupLayout.PREFERRED_SIZE, 285, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(lblRedDec)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(lblRedHex)
.addGap(16, 16, 16)
.addComponent(lblRed)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(sliderRed, javax.swing.GroupLayout.PREFERRED_SIZE, 285, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addComponent(lblTitle, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(38, 38, 38))
);
lblTitle.getAccessibleContext().setAccessibleName("");
lblTitle.getAccessibleContext().setAccessibleDescription("");
pack();
}// </editor-fold>
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Colors.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Colors.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Colors.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Colors.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Colors().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel lblBlue;
private javax.swing.JLabel lblBlueDec;
private javax.swing.JLabel lblBlueHex;
private javax.swing.JLabel lblGreen;
private javax.swing.JLabel lblGreenDec;
private javax.swing.JLabel lblGreenHex;
private javax.swing.JLabel lblRed;
private javax.swing.JLabel lblRedDec;
private javax.swing.JLabel lblRedHex;
private java.awt.Label lblTitle;
private javax.swing.JSlider sliderBlue;
private javax.swing.JSlider sliderGreen;
private javax.swing.JSlider sliderRed;
// End of variables declaration
}
答案 0 :(得分：2)
最初没有显示颜色方块的原因是GroupLayout导致其所有子组件的重绘，这有效地“涂抹”了正方形。
要让您的广场出现，您可以：
JComponent色方＆amp;添加到GroupLayout。JComponent并覆盖paintComponent方法，以便首先绘制所有GroupLayout组件。此选项允许您不要将颜色方块添加到GroupLayout。代码：
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
updateImage();
}