JLayer和JPanel的绘画问题

Question

当用户输入无效时，我想要绘制一个图标。我找到了Oracle的一个例子，并为我的目的对它进行了修改。图标的绘制工作正常，但当我更改值以更正图标时，图标并不是完全不可见的:绘制在JPanel上的部分仍然显示。

这是我的代码：

import java.awt.AlphaComposite;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.text.NumberFormat;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayer;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.plaf.LayerUI;

public class FieldValidator extends JPanel {
    private static final int ICON_SIZE = 12;
    private static final Icon ICON = createResizedIcon((ImageIcon) UIManager.getIcon("OptionPane.errorIcon"));
    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createUI();
            }
        });
    }

    public static void createUI() {
        final JFrame f = new JFrame ("FieldValidator");

        final JComponent content = createContent();

        f.add (content);

        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo (null);
        f.setVisible (true);
    }

    private static JComponent createContent() {
        final LayerUI<JPanel> panelUI = new ValidationLayerUI();

        // Number field.
        final JLabel numberLabel = new JLabel("Number:");

        final NumberFormat numberFormat = NumberFormat.getInstance();
        final JFormattedTextField numberField = new JFormattedTextField(numberFormat) {
            /**
             * {@inheritDoc}
             */
            @Override
            public void replaceSelection(String content) {
                super.replaceSelection(content);
                getParent().repaint();
            }
        };
        numberField.setColumns(16);
        numberField.setFocusLostBehavior(JFormattedTextField.PERSIST);
        numberField.setValue(42);

        final int i = (ICON_SIZE / 2) + (ICON_SIZE % 2);
        final JPanel numberPanel = new JPanel();
        numberPanel.add(numberLabel);
        final JPanel panel = new JPanel(new GridBagLayout());
        final GridBagConstraints constr = new GridBagConstraints();
        constr.insets = new Insets(i, i, i, i);
        constr.weightx = 1;
        constr.weighty = 1;
        constr.fill = GridBagConstraints.BOTH;
        panel.add(numberField, constr);
        numberPanel.add(new JLayer<JPanel>(panel, panelUI));

        return numberPanel;
    }

    //Icon resized to 12x12
    private static Icon createResizedIcon(ImageIcon anIcon) {
        final BufferedImage result = new BufferedImage(ICON_SIZE, ICON_SIZE, BufferedImage.TYPE_INT_ARGB);
        final Graphics2D g = result.createGraphics();
        g.setComposite(AlphaComposite.Src);
        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                RenderingHints.VALUE_INTERPOLATION_BICUBIC);
        g.drawImage(anIcon.getImage(), 0, 0, ICON_SIZE, ICON_SIZE, null);
        g.dispose();
        return new ImageIcon(result);

    }
    static class ValidationLayerUI extends LayerUI<JPanel> {

        @Override
        public void paint (Graphics g, JComponent c) {
            super.paint (g, c);
            final JLayer jlayer = (JLayer) c;
            final JPanel panel = (JPanel) jlayer.getView();
            final JFormattedTextField ftf = (JFormattedTextField) panel.getComponent(0);
            if (!ftf.isEditValid()) {
                ICON.paintIcon(panel, g, 0, panel.getHeight() - ICON.getIconHeight());
            }
        }

    }
}

下面是屏幕:开头所有都是正确的

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当我画出无效图标时，一切都是正确的。

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但是，当值正确时，只有文本字段才会被重新绘制。

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我怎么能强迫JPanel重新油漆？

我已经在JLayeredPane中找到了一种正确的方法，但是我想知道我的代码中有什么问题吗？

Answer 1

使用DocumentListener怎么样？

numberField.getDocument().addDocumentListener(new DocumentListener() {
  @Override public void insertUpdate(DocumentEvent e) {
    //Container c = numberField.getParent();
    Container c = SwingUtilities.getUnwrappedParent(numberField);
    if (c != null) {
      c.repaint();
    }
  }
  @Override public void removeUpdate(DocumentEvent e) {
    insertUpdate(e);
  }
  @Override public void changedUpdate(DocumentEvent e) {}
});

编辑

引用此链接：AWT和Swing中的绘画

RepaintManager -- Swing的RepaintManager类的目的是在Swing容器层次结构上最大化重新绘制处理的效率，并实现Swing的‘重新验证’机制(后者将是另一篇文章的主题)。它通过拦截Swing组件上的所有重绘请求(因此它们不再由AWT处理)并在需要更新的内容(称为“脏区域”)上维护自己的状态来实现重绘机制。最后，它使用invokeLater()处理事件调度线程上的挂起请求，如“重新绘制处理”一节(选项B)所述。

在这种情况下，当父JPanel状态更改时，父isEditValid()并不是脏区域。所以剩下以前的Icon涂料。