在我的代码中，当我在paintComponent()中添加代码时，所有的JLabel、文本字段和按钮都消失了——当我在程序运行时点击它们时，文本字段和按键会重新出现，但我仍然看不到任何JLabel。我希望是我注释掉了paintComponent()方法中的代码，导致了这个错误。
public class snowBoarding extends JFrame {
private JButton getReset() {
if (Reset == null) {
Reset = new JButton();
Reset.setBounds(new Rectangle(162, 411, 131, 39));
Reset.setFont(new Font("Dialog", Font.BOLD, 18));
Reset.setText("Reset");
Reset.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent e){
textField_1.setText("0");
textField_2.setText("0");
textField_3.setText("0");
textField_4.setText("0");
textField_5.setText("0");
textField_6.setText("0");
textField_7.setText("0");
textField_8.setText("0");
textField_9.setText("0");
textField_10.setText("0");
textField_11.setText("0");
textField.setText("0");
total_1.setText("0");
total_2.setText("0");
Overall.setText("0");
DrawPanel.clear(DrawPanel.getGraphics());
DrawPanel.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
}
});
}
return Reset;
}
public JButton getButton_calc_draw() {
if (Button_calc_draw == null) {
Button_calc_draw = new JButton();
Button_calc_draw.setBounds(303, 411, 131, 39);
Button_calc_draw.setFont(new Font ("Dialog", Font.BOLD, 18));
Button_calc_draw.setText("Draw");
Button_calc_draw.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent e) {
// Get values from the text fields
run_1[0] = Integer.parseInt(textField.getText());
run_1[1] = Integer.parseInt(textField_1.getText());
run_1[2] = Integer.parseInt(textField_2.getText());
run_1[3] = Integer.parseInt(textField_3.getText());
run_1[4] = Integer.parseInt(textField_4.getText());
run_1[5] = Integer.parseInt(textField_5.getText());
for (int i = 0; i < run_1.length; i++) {
temp[i] = run_1[i];
}
Arrays.sort(temp);
for (int i = 1; i < (temp.length -1) ; i++){
avg1+=temp[i];
}
avg1 = avg1/4;
run_2[0] = Integer.parseInt(textField_6.getText());
run_2[1] = Integer.parseInt(textField_7.getText());
run_2[2] = Integer.parseInt(textField_8.getText());
run_2[3] = Integer.parseInt(textField_9.getText());
run_2[4] = Integer.parseInt(textField_10.getText());
run_2[5] = Integer.parseInt(textField_11.getText());
for (int i = 0; i < run_2.length; i++) {
temp[i] = run_2[i];
}
Arrays.sort(temp);
for (int i = 1; i < (temp.length -1) ; i++){
avg2+=temp[i];
}
avg2 = avg2/4;
if (avg1 > avg2){
OverallScore = avg1;
}
else {
OverallScore = avg2;
}
total_1.setText(Integer.toString(avg1));
total_2.setText(Integer.toString(avg2));
Overall.setText(Integer.toString(OverallScore));
DrawPanel.repaint();
}
// Transfer the image from the BufferedImage to the JPanel to make it visible.
;
});
}
return Button_calc_draw;
}
}
});
}
return Reset;
}
private myJPanel getDrawPanel() {
if (DrawPanel == null) {
DrawPanel = new myJPanel();
DrawPanel.setLayout(new GridBagLayout());
DrawPanel.setBounds(new Rectangle(258, 39, 326, 361));
DrawPanel.setBackground(Color.white);
DrawPanel.setEnabled(true);
DrawPanel.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
//Instantiate the BufferedImage object and give it the same width
// and height as that of the drawing area JPanel
img = new BufferedImage(DrawPanel.getWidth(),
DrawPanel.getHeight(),
BufferedImage.TYPE_INT_RGB);
//Get its graphics context. A graphics context of a particular object allows us to draw on it.
g2dImg = (Graphics2D)img.getGraphics();
//Draw a filled white coloured rectangle on the entire area to clear it.
g2dImg.setPaint(Color.WHITE);
g2dImg.fill(new Rectangle2D.Double(0, 0, img.getWidth(), img.getHeight()));
}
return DrawPanel;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
snowBoarding thisClass = new snowBoarding();
thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
thisClass.setVisible(true);
}
});
}
public snowBoarding() {
super();
setResizable(false);
getContentPane().setLayout(null);
initialize();
}
private void initialize() {
this.setSize(600, 500);
this.setContentPane(getJContentPane());
this.setTitle("Snowboarding Score Calculator");
this.setResizable(false);
this.setVisible(true);
}
}
class myJPanel extends JPanel {
BufferedImage img;
Graphics2D g2dImg;
private static final long serialVersionUID = 1L;
private Rectangle2D.Double rectangle;
public void paintComponent(Graphics g) {
//Must be called to draw the JPanel control.
// As a side effect, it also clears it.
super.paintComponent(g);
Graphics2D g2D = (Graphics2D) g;
rectangle = new Rectangle2D.Double(0, 260-score[0] * 2, 25, score[0] * 2);
g2D.setPaint(Color.blue);
g2D.fill(rectangle);
g2D.draw(rectangle);
}
protected void clear(Graphics g) {
super.paintComponent(g);
// Also clear the BufferedImage object by drawing a white coloured filled rectangle all over.
g2dImg.setPaint(Color.WHITE);
g2dImg.fill(new Rectangle2D.Double(0, 0, img.getWidth(), img.getHeight()));
}
}
编辑：删除不必要的代码
在我单击draw和reset以将绘制的图像返回到白板之后，我需要重新绘制以使用run1和run2数组作为x或y值来绘制矩形。
绘制按钮-->绘制图形
重置按钮-->将删除图形，以便可以创建新的图形。
您不应在paintComponent()中使用g2dImg，而应使用g(方法paintComponent()接收的参数(。更确切地说，是((Grpahics2D)g)而不是g2dImg。
在这里发布的代码中，g2dImg似乎没有初始化，也许你已经在某个地方初始化了。。。
更一般地说，您应该始终使用在绘制方法中收到的Graphics实例(如果需要，将其转换为Graphics2D(。您不应尝试重用/共享/存储Graphics的实例。
这同样适用于clear()方法。
以下是如何重写此paintComponent()方法的示例：
private boolean shallPaint = false;
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (shallPaint) {
Graphics2D g2D = (Graphics2D) g;
rectangle = new Rectangle2D.Double(0, 260-score1 * 2, 25, score1 * 2);
g2D.setPaint(Color.blue);
g2D.fill(rectangle);
g2D.draw(rectangle);
}
}
public void setShallPaint(boolean pShallPaint) {
shallPaint = pShallPaint;
}
然后简单地调用myJPanel.repaint()来重新绘制它
您应在重置按钮中更换：
DrawPanel.clear(DrawPanel.getGraphics());
带有：
DrawPanel.setShallPaint(false);
DrawPanel.repaint();
在Button_calc_draw:中
DrawPanel.setShallPaint(true);
DrawPanel.repaint();