java - 如何逐部分绘制图像？

Question

class DrawIma extends JPanel{
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);
        for (int i=0;i<20;i++){
            for (int j=0;j<20;j++) {    
                g.drawImage(BuArr[i*20+j], 20*i, 20*j, 20, 20, null);
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

在这部分中，BuArr是从BufferedImage中划分出的400个 block ，现在我希望它们被一一绘制，但是该方法无法单独绘制 block ，我该怎么做？

Answer 1

Swing 是单线程的，并且不是线程安全的。

这意味着您不应在 IU 线程(事件调度线程)内执行任何长时间运行或阻塞 ( Thread.sleep ) 操作。这还意味着您无法在 EDT 上下文之外更新、修改或创建 UI 元素。

相反，使用 Swing Timer以指定的时间间隔生成重复的回调并将图像的部分渲染为类似 BufferedImage 的内容，您可以通过其 paintComponent 将其绘制到组件上方法...

参见Concurrency in Swing和 How to use Swing Timers了解更多详情

因为这是一个很好的消磨时间

这会生成 List的Rectangles代表我想要绘制的各个 block ，然后我随机化 List并运行 Timer ，挑选最上面的Rectangle关闭List并使用 BufferedImage#getSubImage将其从主控绘制到缓冲区，缓冲区被绘制到屏幕上...

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestImage {

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

    public TestImage() {
        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 BufferedImage master;
        private BufferedImage copy;

        private List<Rectangle> blocks;

        public TestPane() {
            setBackground(Color.BLACK);
            try {
                master = ImageIO.read(new File("..."));
                copy = new BufferedImage(master.getWidth(), master.getHeight(), BufferedImage.TYPE_INT_ARGB);
                Graphics2D g2d = copy.createGraphics();
                AlphaComposite composite = AlphaComposite.getInstance(AlphaComposite.CLEAR, 0.0f);
                g2d.setComposite(composite);
                g2d.setColor(new Color(0, 0, 0, 0));
                g2d.fillRect(0, 0, master.getWidth(), master.getHeight());
                g2d.dispose();

                int blockSize = 40;

                int width = master.getWidth();
                int height = master.getHeight();

                float aspect = Math.min(width, height) / (float) Math.max(width, height);

                int blockHeight = blockSize;
                blocks = new ArrayList<>(blockSize * 2);
                for (int y = 0; y < master.getHeight(); y += blockHeight) {
                    if (y + blockHeight > master.getHeight()) {
                        blockHeight = master.getHeight() - y;
                    }
                    int blockWidth = blockSize;
                    for (int x = 0; x < master.getWidth(); x += blockWidth) {
                        if (x + blockWidth > master.getWidth()) {
                            blockWidth = master.getWidth() - x;
                        }
                        Rectangle block = new Rectangle(x, y, blockWidth, blockHeight);
                        blocks.add(block);
                    }
                }
                Collections.shuffle(blocks);
                Timer timer = new Timer(40, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        if (blocks.isEmpty()) {
                            ((Timer) e.getSource()).stop();
                        } else {
                            Graphics2D g2d = copy.createGraphics();
                            Rectangle block = blocks.remove(0);
                            g2d.drawImage(master.getSubimage(block.x, block.y, block.width, block.height), block.x, block.y, TestPane.this);
                            g2d.dispose();
                            repaint();
                        }
                    }
                });

                timer.start();

            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return master == null ? new Dimension(200, 200) : new Dimension(master.getWidth(), master.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            if (copy != null) {
                int x = (getWidth() - copy.getWidth()) / 2;
                int y = (getHeight() - copy.getHeight()) / 2;
                g2d.drawImage(copy, x, y, this);
            }
            g2d.dispose();
        }

    }

}