無需重新繪制每個組件即可重新繪制

Question

我有一個包含jframe的應用程序，然后此jframe添加一個包含圖像的jpanel。 將jpanel顯示給定的時間，然后將其從jframe中刪除，然后添加另一個jpanel。

我想在圖像之間淡入淡出，並且我使用計時器完成了此操作

private void fadeOut() {
    ActionListener fadeOutAc = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            opacity += 10;
            if (opacity >= 255) {
                opacity = 255;
                fadeOutT.stop();

            }
            repaint();
        }
    };

    fadeOutT = new Timer(20, fadeOutAc);
    fadeOutT.start();
}

private void fadeIn() {
    ActionListener fadeInAc = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            opacity -= 10;
            if (opacity <= 0) {
                opacity = 0;
                fadeInT.stop();
            }
            repaint();

        }
    };
    fadeInT = new Timer(10, fadeInAc);
    fadeInT.setInitialDelay(200);
    fadeInT.start();

}

public void paint(Graphics g) {
    super.paintComponent(g);
    g.setColor(new Color(picColor.getRed(), picColor.getGreen(), picColor.getBlue(), opacity));
    g.fillRect(0, 0, presWin.getWidth(), presWin.getHeight());
}

我最近將淡入淡出從jpanel移到了jframe。 問題在於，在jpanel中，重新繪制僅需繪制圖像，現在它每次必須重新繪制整個jpanel。 有沒有一種方法可以在不繪制組件（僅矩形）的情況下調用重新繪制？

Answer 1

完全正常，將函數移至JFrame並調用repaint函數實際上會調用JFrame的repaint 。

我認為最好的解決方案是將面板作為您的fadeIn和fadeOut函數的參數fadeIn ，並調用其repaint方法，例如fadeIn：

private void fadeIn(JPanel panelParam) {
    ActionListener fadeInAc = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            opacity -= 10;
            if (opacity <= 0) {
                opacity = 0;
                fadeInT.stop();
            }
            panelParam.repaint(); // here call repaint of the panel.

        }
    };
    fadeInT = new Timer(10, fadeInAc);
    fadeInT.setInitialDelay(200);
    fadeInT.start();

}

這樣，您可以將效果應用到任何其他面板上。 希望能有所幫助。

Answer 2

對我來說，當您想要的是一個可以淡入和淡出其內容的容器時，將功能放入JFrame似乎有點可笑。 這樣，您可以將職責隔離到單個容器/類，可以按照您希望的任何方式放置或使用該容器/類，以隔離UI的其余部分。

基本上，此示例使用FadingPane （基於JPanel ）來控制淡入淡出過程，但我將放置實際圖像的JLabel放置在其上。

褪色是通過使用AlphaComposite來控制的，這意味着該面板實際上會物理地淡入和淡出，而不僅僅是改變填充顏色;）

還有一個FadingListener ，它提供有關衰落過程的其他通知，實際上只對fadeOutDidComplete感興趣，因此您可以切換圖像並使面板變淡，但您永遠不知道...

import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel label;
        private FadingPane fadingPane;

        private File[] pictures;
        private int index;

        public TestPane() {
            // Just for show 
            setBackground(Color.RED);
            fadingPane = new FadingPane(new FadeListener() {
                @Override
                public void fadeDidStart(FadingPane panel) {
                }

                @Override
                public void fadeDidStop(FadingPane panel) {
                }

                @Override
                public void fadeOutDidComplete(FadingPane panel) {
                    nextPicture();
                    fadingPane.fadeIn();
                }

                @Override
                public void fadeInDidComplete(FadingPane panel) {
                }
            });
            setLayout(new BorderLayout());
            fadingPane.setLayout(new BorderLayout());
            label = new JLabel();
            fadingPane.add(label);

            add(fadingPane);

            JButton next = new JButton("Next");
            add(next, BorderLayout.SOUTH);
            next.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    fadingPane.fadeOut();
                }
            });

            pictures = new File("/Volumes/Disk02/Dropbox/MegaTokyo/thumnails").listFiles(new FileFilter() {
                @Override
                public boolean accept(File pathname) {
                    String name = pathname.getName().toLowerCase();
                    return name.endsWith(".jpg") || name.endsWith(".png");
                }
            });
            nextPicture();
        }

        protected void nextPicture() {
            index++;
            if (index >= pictures.length) {
                index = 0;
            }
            try {
                BufferedImage img = ImageIO.read(pictures[index]);
                label.setIcon(new ImageIcon(img));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

    }

    public interface FadeListener {
        public void fadeDidStart(FadingPane panel);
        public void fadeDidStop(FadingPane panel);
        public void fadeOutDidComplete(FadingPane panel);
        public void fadeInDidComplete(FadingPane panel);
    }

    public class FadingPane extends JPanel {

        private float delta;
        private float alpha = 1f;
        private Timer timer;

        private FadeListener fadeListener;

        public FadingPane(FadeListener fadeListener) {
            this.fadeListener = fadeListener;
            // This is important, as we may not always be opaque
            // and we don't want to stuff up the painting process
            setOpaque(false);

            timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    float alpha = getAlpha() + delta;
                    if (alpha < 0.001f) {
                        alpha = 0f;
                        timer.stop();
                        fadeListener.fadeOutDidComplete(FadingPane.this);
                    } else if (alpha >= 1.0f) {
                        alpha = 1.0f;
                        timer.stop();
                        fadeListener.fadeInDidComplete(FadingPane.this);
                    }
                    setAlpha(alpha);
                }
            });
        }

        public float getAlpha() {
            return alpha;
        }

        public void setAlpha(float value) {
            if (alpha != value) {
                this.alpha = Math.min(1.0f, Math.max(0.0f, value));
                repaint();
            }
        }

        @Override
        public void paint(Graphics g) {
            // I don't normally recomamned overriding paint, but in this case,
            // I want to affect EVERYTHING that might be added to this panel
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setComposite(AlphaComposite.SrcOver.derive(getAlpha()));
            super.paint(g2d);
            g2d.dispose();
        }

        public void fadeIn() {
            timer.stop();
            fadeListener.fadeDidStop(FadingPane.this);
            delta = 0.05f;
            timer.restart();
            fadeListener.fadeDidStart(FadingPane.this);
        }

        public void fadeOut() {
            timer.stop();
            fadeListener.fadeDidStop(FadingPane.this);
            delta = -0.05f;
            timer.restart();
            fadeListener.fadeDidStart(FadingPane.this);
        }

    }

}