Java 透明度渲染错误

Question

我目前正在开发一个信息亭风格的 Java 程序来显示天气、时间、预报等。这是程序应该的样子（更新时间之前的屏幕截图）

各个部分被创建为 JPanel，并覆盖了 paintComponent() 方法。他们绘制渐变标题和半透明背景。但是，当我更改其中一个面板的内容时，之前的内容会被留下，而不是被删除。示例如下：

如你所见，当时间从11:51变为11:52时，数字重叠，背景变浅（因为半透明背景被重绘在上面）

图形错误

我应该怎么做才能防止这种重叠？最终，当单个面板更新其内容时，我宁愿不必重绘整个屏幕。我宁愿只重绘该特定部分。重绘背景很容易，然后是其中的所有组件。

更新

几个答案涉及清除要绘制的区域。无论我使用g.clear() 还是AlphaComposite.CLEAR，它都会删除背景图像。这可以在下图中看到。也许如果我可以在清除该区域之前复制背景，我可以重新绘制背景的那部分，然后适当地对其他图像进行分层。想法？

更新 2

提交了一个答案，其中显示了放置在透明面板和背景上的计时器的完整工作示例。这非常有用，但是，我不会手动绘制我的子组件。时间、天气图标和温度都是 JLabel 布局在半透明面板上。我宁愿不必手动绘制各个组件。

Answer 1

类似的问题

地址为here

还要注意，“Swing 程序应该覆盖paintComponent()，而不是覆盖paint()。”—Painting in AWT and Swing: The Paint Methods。

Answer 2

在进行绘画之前，请拨打g.clearRect(0,0,w,h) 电话。 这将删除指定区域中的所有内容，并且您不会在前一帧之上绘制。

您可能需要应用一些双缓冲技术，因为您的屏幕会因清除而轻微闪烁。

Answer 3

我很快就把它放在一起了，没什么特别的......

整个项目由一个 JFrame、一个 BackgroundImagePane 和 ClockPane 组成

ClockPane 看起来像这样（您可以重新创建其余部分；））

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.RoundRectangle2D;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.Timer;

public class ClockPane extends javax.swing.JPanel {

    private Timer tick;

    protected static final SimpleDateFormat SDF = new SimpleDateFormat("HH:mm.ss");

    public ClockPane() {

        setOpaque(false);

        tick = new Timer(500, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent ae) {

                repaint();

            }

        });

        tick.setCoalesce(true);
        tick.setRepeats(true);

        setPreferredSize(new Dimension(100, 100));
        setMinimumSize(new Dimension(100, 100));

    }

    @Override
    public void addNotify() {

        super.addNotify();

        tick.start();

    }

    @Override
    public void removeNotify() {

        tick.stop();

        super.removeNotify();

    }

    @Override
    protected void paintComponent(Graphics grphcs) {

        super.paintComponent(grphcs);

        Graphics2D g2d = (Graphics2D) grphcs;

        int width = getWidth() - 1;
        int height = getHeight() - 1;

        Color background = new Color(192, 192, 192, 128);
        Color border = new Color(128, 128, 128);
        RoundRectangle2D backing = new RoundRectangle2D.Float(0, 0, width, height, 20, 20);

        g2d.setPaint(background);
        g2d.fill(backing);
        g2d.setPaint(border);
        g2d.draw(backing);

        String text = SDF.format(new Date());
        FontMetrics fm = g2d.getFontMetrics();
        g2d.setPaint(Color.BLACK);

        int x = (width - fm.stringWidth(text)) / 2;
        int y = ((height - fm.getHeight()) / 2) + fm.getAscent();

        g2d.drawString(text, x, y);

    }

}

有了这个，时钟每半秒左右更新一次，我对重绘没有任何问题

我能想到的唯一有意义的是setOpaque(false);

更新

这个例子完全是用标签和面板完成的（背景面板是一个自定义的绘画工作，日期标签也有它的背景，但除此之外）

现在，我一起破解了我的，所以它不如你的好，但话说回来，我没有得到报酬；）

import core.ui.UIUtilities;
import core.ui.WindowUtilities;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.Timer;
import javax.swing.UIManager;

public class MainFrame extends javax.swing.JFrame {

    /**
     * Creates new form MainFrame
     */
    public MainFrame() {

        setUndecorated(true);
        WindowUtilities.setOpaque(this, false);

        initComponents();

        Timer timer = new Timer(500, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {

                lblTime.setText(new SimpleDateFormat("hh:MM:ss").format(new Date()));

            }
        });

        timer.setRepeats(true);
        timer.setCoalesce(true);
        timer.start();

        DateLabel label = new DateLabel();
        label.init();

        NewBackgroundPane backgroundPane = new NewBackgroundPane();
        backgroundPane.setLayout(new BorderLayout());
        backgroundPane.add(label, BorderLayout.NORTH);
        backgroundPane.add(pnlMain);

        add(backgroundPane, BorderLayout.CENTER);

        pack();

        setLocation(UIUtilities.centerOfDefaultScreen(this));

    }

    /**
     * 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() {
        java.awt.GridBagConstraints gridBagConstraints;

        pnlMain = new javax.swing.JPanel();
        jPanel2 = new javax.swing.JPanel();
        lblTime = new javax.swing.JLabel();
        lblExtTime = new javax.swing.JLabel();
        jPanel3 = new javax.swing.JPanel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        jLabel6 = new javax.swing.JLabel();
        jPanel4 = new javax.swing.JPanel();
        jPanel5 = new javax.swing.JPanel();
        jLabel11 = new javax.swing.JLabel();
        jLabel12 = new javax.swing.JLabel();
        jLabel13 = new javax.swing.JLabel();
        jLabel14 = new javax.swing.JLabel();
        jPanel6 = new javax.swing.JPanel();
        jLabel15 = new javax.swing.JLabel();
        jLabel16 = new javax.swing.JLabel();
        jLabel17 = new javax.swing.JLabel();
        jLabel18 = new javax.swing.JLabel();
        jPanel7 = new javax.swing.JPanel();
        jLabel19 = new javax.swing.JLabel();
        jLabel20 = new javax.swing.JLabel();
        jLabel21 = new javax.swing.JLabel();
        jLabel22 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        pnlMain.setOpaque(false);
        pnlMain.setLayout(new java.awt.GridBagLayout());

        jPanel2.setOpaque(false);
        jPanel2.setLayout(new java.awt.GridBagLayout());

        lblTime.setFont(lblTime.getFont().deriveFont(lblTime.getFont().getStyle() | java.awt.Font.BOLD, lblTime.getFont().getSize()+18));
        lblTime.setForeground(new java.awt.Color(255, 255, 255));
        lblTime.setText("jLabel1");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        jPanel2.add(lblTime, gridBagConstraints);

        lblExtTime.setFont(lblExtTime.getFont().deriveFont(lblExtTime.getFont().getSize()+6f));
        lblExtTime.setForeground(new java.awt.Color(255, 255, 255));
        lblExtTime.setText("AM EDT");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel2.add(lblExtTime, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
        gridBagConstraints.weightx = 1.0;
        gridBagConstraints.insets = new java.awt.Insets(2, 2, 2, 2);
        pnlMain.add(jPanel2, gridBagConstraints);

        jPanel3.setOpaque(false);
        jPanel3.setLayout(new java.awt.GridBagLayout());

        jLabel3.setIcon(new javax.swing.ImageIcon(getClass().getResource("/transparentUpdate/Overcast.png"))); // NOI18N
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridheight = 2;
        jPanel3.add(jLabel3, gridBagConstraints);

        jLabel4.setFont(jLabel4.getFont().deriveFont(jLabel4.getFont().getSize()+6f));
        jLabel4.setForeground(new java.awt.Color(255, 255, 255));
        jLabel4.setText("<html>Currenctly<br>Overast</html>");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.FIRST_LINE_START;
        jPanel3.add(jLabel4, gridBagConstraints);

        jLabel5.setFont(jLabel5.getFont().deriveFont(jLabel5.getFont().getSize()+12f));
        jLabel5.setForeground(new java.awt.Color(255, 255, 255));
        jLabel5.setText("69");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.LAST_LINE_START;
        jPanel3.add(jLabel5, gridBagConstraints);

        jLabel6.setForeground(new java.awt.Color(255, 255, 255));
        jLabel6.setText("/65");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 2;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.LAST_LINE_START;
        jPanel3.add(jLabel6, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 2;
        gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
        gridBagConstraints.weightx = 1.0;
        gridBagConstraints.insets = new java.awt.Insets(2, 2, 2, 2);
        pnlMain.add(jPanel3, gridBagConstraints);

        jPanel4.setOpaque(false);
        jPanel4.setLayout(new java.awt.GridBagLayout());

        jPanel5.setOpaque(false);
        jPanel5.setLayout(new java.awt.GridBagLayout());

        jLabel11.setFont(jLabel11.getFont().deriveFont(jLabel11.getFont().getSize()+4f));
        jLabel11.setForeground(new java.awt.Color(255, 255, 255));
        jLabel11.setText("Today");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        jPanel5.add(jLabel11, gridBagConstraints);

        jLabel12.setForeground(new java.awt.Color(255, 255, 255));
        jLabel12.setIcon(new javax.swing.ImageIcon(getClass().getResource("/transparentUpdate/SmallOvercast.png"))); // NOI18N
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.gridheight = 2;
        jPanel5.add(jLabel12, gridBagConstraints);

        jLabel13.setFont(jLabel13.getFont().deriveFont(jLabel13.getFont().getSize()+4f));
        jLabel13.setForeground(new java.awt.Color(255, 255, 255));
        jLabel13.setText("83");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel5.add(jLabel13, gridBagConstraints);

        jLabel14.setForeground(new java.awt.Color(255, 255, 255));
        jLabel14.setText("65");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel5.add(jLabel14, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        gridBagConstraints.insets = new java.awt.Insets(2, 4, 2, 4);
        jPanel4.add(jPanel5, gridBagConstraints);

        jPanel6.setOpaque(false);
        jPanel6.setLayout(new java.awt.GridBagLayout());

        jLabel15.setFont(jLabel15.getFont().deriveFont(jLabel15.getFont().getSize()+4f));
        jLabel15.setForeground(new java.awt.Color(255, 255, 255));
        jLabel15.setText("Sunday");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        jPanel6.add(jLabel15, gridBagConstraints);

        jLabel16.setForeground(new java.awt.Color(255, 255, 255));
        jLabel16.setIcon(new javax.swing.ImageIcon(getClass().getResource("/transparentUpdate/Sunny.png"))); // NOI18N
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.gridheight = 2;
        jPanel6.add(jLabel16, gridBagConstraints);

        jLabel17.setFont(jLabel17.getFont().deriveFont(jLabel17.getFont().getSize()+4f));
        jLabel17.setForeground(new java.awt.Color(255, 255, 255));
        jLabel17.setText("82");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel6.add(jLabel17, gridBagConstraints);

        jLabel18.setForeground(new java.awt.Color(255, 255, 255));
        jLabel18.setText("64");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel6.add(jLabel18, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        gridBagConstraints.insets = new java.awt.Insets(2, 4, 2, 4);
        jPanel4.add(jPanel6, gridBagConstraints);

        jPanel7.setOpaque(false);
        jPanel7.setLayout(new java.awt.GridBagLayout());

        jLabel19.setFont(jLabel19.getFont().deriveFont(jLabel19.getFont().getSize()+4f));
        jLabel19.setForeground(new java.awt.Color(255, 255, 255));
        jLabel19.setText("Monday");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        jPanel7.add(jLabel19, gridBagConstraints);

        jLabel20.setForeground(new java.awt.Color(255, 255, 255));
        jLabel20.setIcon(new javax.swing.ImageIcon(getClass().getResource("/transparentUpdate/Cloudy.png"))); // NOI18N
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.gridheight = 2;
        jPanel7.add(jLabel20, gridBagConstraints);

        jLabel21.setFont(jLabel21.getFont().deriveFont(jLabel21.getFont().getSize()+4f));
        jLabel21.setForeground(new java.awt.Color(255, 255, 255));
        jLabel21.setText("83");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 1;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel7.add(jLabel21, gridBagConstraints);

        jLabel22.setForeground(new java.awt.Color(255, 255, 255));
        jLabel22.setText("84");
        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 1;
        gridBagConstraints.gridy = 2;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        jPanel7.add(jLabel22, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 2;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.anchor = java.awt.GridBagConstraints.PAGE_START;
        gridBagConstraints.insets = new java.awt.Insets(2, 4, 2, 4);
        jPanel4.add(jPanel7, gridBagConstraints);

        gridBagConstraints = new java.awt.GridBagConstraints();
        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 3;
        gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
        gridBagConstraints.weightx = 1.0;
        gridBagConstraints.insets = new java.awt.Insets(2, 2, 2, 2);
        pnlMain.add(jPanel4, gridBagConstraints);

        getContentPane().add(pnlMain, java.awt.BorderLayout.CENTER);

        pack();
    }// </editor-fold>

    /**
     * @param args the command line arguments
     */
    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 {

            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainFrame.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 MainFrame().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JLabel jLabel11;
    private javax.swing.JLabel jLabel12;
    private javax.swing.JLabel jLabel13;
    private javax.swing.JLabel jLabel14;
    private javax.swing.JLabel jLabel15;
    private javax.swing.JLabel jLabel16;
    private javax.swing.JLabel jLabel17;
    private javax.swing.JLabel jLabel18;
    private javax.swing.JLabel jLabel19;
    private javax.swing.JLabel jLabel20;
    private javax.swing.JLabel jLabel21;
    private javax.swing.JLabel jLabel22;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JPanel jPanel4;
    private javax.swing.JPanel jPanel5;
    private javax.swing.JPanel jPanel6;
    private javax.swing.JPanel jPanel7;
    private javax.swing.JLabel lblExtTime;
    private javax.swing.JLabel lblTime;
    private javax.swing.JPanel pnlMain;
    // End of variables declaration
}

只是为了让生活更轻松，背景窗格

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;

public class NewBackgroundPane extends javax.swing.JPanel {

    /**
     * Creates new form NewBackgroundPane
     */
    public NewBackgroundPane() {
        initComponents();
    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g.create();

        int width = getWidth() - 1;
        int height = getHeight() - 1;

        g2d.setColor(Color.LIGHT_GRAY);
        g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f));
        g2d.fillRoundRect(0, 0, width, height, 20, 20);
    }

    /**
     * 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() {

        setOpaque(false);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );
    }// </editor-fold>
    // Variables declaration - do not modify
    // End of variables declaration
}

如果你仍然无法让它工作，我能想到的唯一其他问题可能与全屏独占模式有关，我还没有测试过：P