java – JTextFields在JPanel上的活动绘图上,线程问题

有没有人试图使用Swing来构建一个适当的多缓冲渲染环境,其上可以添加Swing用户界面元素？

在这种情况下,我有一个动画的红色矩形绘制到背景上.背景不需要每帧更新,所以我将其渲染到BufferedImage并重绘仅清除矩形的以前位置所需的部分.请参阅下面的完整代码,这扩展了前一个线程here中@trashgod给出的示例.

到现在为止还挺好;平滑动画,低cpu使用,不闪烁.

然后我添加一个JTextField到Jpanel(通过点击屏幕上的任何位置),并通过点击文本框内的焦点.清除矩形的上一个位置现在在每个光标闪烁时都会失败,请参见下图.

如果有人知道为什么会发生这种情况,我很好奇(Swing不是线程安全的,图像被异步绘制),以及在什么方向寻找可能的解决方案.

这是在Mac OS 10.5,Java 1.6

JPanel redraw fail http://www.arttech.nl/javaredrawerror.png

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.Transparency;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;

public class NewTest extends JPanel implements 
    MouseListener,ActionListener,ComponentListener,Runnable 
{

JFrame f;
Insets insets;
private Timer t = new Timer(20,this);
BufferedImage buffer1;
boolean repaintBuffer1 = true;
int initWidth = 640;
int initHeight = 480;
Rectangle rect;

public static void main(String[] args) {
    EventQueue.invokelater(new Newtest());
}

@Override
public void run() {
    f = new JFrame("NewTest");
    f.addComponentListener(this);
    f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
    f.add(this);
    f.pack();
    f.setLocationRelativeto(null);
    f.setVisible(true);
    createBuffers();
    insets = f.getInsets();
    t.start();
}

public Newtest() {
    super(true);
    this.setPreferredSize(new Dimension(initWidth,initHeight));
    this.setLayout(null);
    this.addMouseListener(this);
}

void createBuffers() {
    int width = this.getWidth();
    int height = this.getHeight();

    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice gs = ge.getDefaultScreenDevice();
    GraphicsConfiguration gc = gs.getDefaultConfiguration();

    buffer1 = gc.createCompatibleImage(width,height,Transparency.OPAQUE);        

    repaintBuffer1 = true;
}

@Override
protected void paintComponent(Graphics g) {
    int width = this.getWidth();
    int height = this.getHeight();

    if (repaintBuffer1) {
        Graphics g1 = buffer1.getGraphics();
        g1.clearRect(0,width,height);
        g1.setColor(Color.green);
        g1.drawRect(0,width - 1,height - 1);
        g.drawImage(buffer1,null);
        repaintBuffer1 = false;
    }

    double time = 2* Math.PI * (System.currentTimeMillis() % 5000) / 5000.;
    g.setColor(Color.RED);
    if (rect != null) {
        g.drawImage(buffer1,rect.x,rect.y,rect.x + rect.width,rect.y + rect.height,this);
    }
    rect = new Rectangle((int)(Math.sin(time) * width/3 + width/2 - 20),(int)(Math.cos(time) * height/3 + height/2) - 20,40,40);
    g.fillRect(rect.x,rect.width,rect.height);
}

@Override
public void actionPerformed(ActionEvent e) {
    this.repaint();
}

@Override
public void componentHidden(ComponentEvent arg0) {
    // Todo Auto-generated method stub

}

@Override
public void componentMoved(ComponentEvent arg0) {
    // Todo Auto-generated method stub

}

@Override
public void componentResized(ComponentEvent e) {
    int width = e.getComponent().getWidth() - (insets.left + insets.right);
    int height = e.getComponent().getHeight() - (insets.top + insets.bottom);
    this.setSize(width,height);
    createBuffers();
}

@Override
public void componentShown(ComponentEvent arg0) {
    // Todo Auto-generated method stub

}

@Override
public void mouseClicked(MouseEvent e) {
    JTextField field = new JTextField("test");
    field.setBounds(new Rectangle(e.getX(),e.getY(),100,20));
    this.add(field);
    repaintBuffer1 = true;
}

@Override
public void mouseEntered(MouseEvent arg0) {
    // Todo Auto-generated method stub

}

@Override
public void mouseExited(MouseEvent arg0) {
    // Todo Auto-generated method stub

}

@Override
public void mousepressed(MouseEvent arg0) {
    // Todo Auto-generated method stub

}

@Override
public void mouseReleased(MouseEvent arg0) {
    // Todo Auto-generated method stub

}
}

解决方法

NewTest扩展了JPanel;但是因为每次调用paintComponent()时都不会绘制每个像素,所以您需要调用超类的方法并擦除旧图形：

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    int width = this.getWidth();
    int height = this.getHeight();
    g.setColor(Color.black);
    g.fillRect(0,height);
    ...
}

附录：如你所说,在构造函数中设置背景颜色排除了在paintComponent()中填充面板的需要,而super.paintComponent()允许文本字段正常运行.如您所见,拟议的解决方法是脆弱的.相反,简化代码并进行优化.例如,您可能不需要复杂的插件,额外的缓冲区和组件监听器.

附录2：请注意,super.paintComponent()调用UI委托的update()方法,“它将使用其背景颜色填充指定的组件(如果其opaque属性为true)”.您可以使用setopaque(false)来排除这一点.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsEnvironment;
import java.awt.Rectangle;
import java.awt.Transparency;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;

/** @see https://stackoverflow.com/questions/3256941 */
public class AnimationTest extends JPanel implements ActionListener {

    private static final int WIDE = 640;
    private static final int HIGH = 480;
    private static final int RADIUS = 25;
    private static final int FRAMES = 24;
    private final Timer timer = new Timer(20,this);
    private final Rectangle rect = new Rectangle();
    private BufferedImage background;
    private int index;
    private long totalTime;
    private long averageTime;
    private int frameCount;

    public static void main(String[] args) {
        EventQueue.invokelater(new Runnable() {

            @Override
            public void run() {
                new Animationtest().create();
            }
        });
    }

    private void create() {
        JFrame f = new JFrame("AnimationTest");
        f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocationRelativeto(null);
        f.setVisible(true);
        timer.start();
    }

    public Animationtest() {
        super(true);
        this.setopaque(false);
        this.setPreferredSize(new Dimension(WIDE,HIGH));
        this.addMouseListener(new MouseHandler());
        this.addComponentListener(new ComponentHandler());
    }

    @Override
    protected void paintComponent(Graphics g) {
        long start = System.nanoTime();
        super.paintComponent(g);
        int w = this.getWidth();
        int h = this.getHeight();
        g.drawImage(background,this);
        double theta = 2 * Math.PI * index++ / 64;
        g.setColor(Color.blue);
        rect.setRect(
            (int) (Math.sin(theta) * w / 3 + w / 2 - RADIUS),(int) (Math.cos(theta) * h / 3 + h / 2 - RADIUS),2 * RADIUS,2 * RADIUS);
        g.filloval(rect.x,rect.height);
        g.setColor(Color.white);
        if (frameCount == FRAMES) {
            averageTime = totalTime / FRAMES;
            totalTime = 0; frameCount = 0;
        } else {
            totalTime += System.nanoTime() - start;
            frameCount++;
        }
        String s = String.format("%1$5.3f",averageTime / 1000000d);
        g.drawString(s,5,16);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        this.repaint();
    }

    private class MouseHandler extends MouseAdapter {

        @Override
        public void mousepressed(MouseEvent e) {
            super.mousepressed(e);
            JTextField field = new JTextField("test");
            Dimension d = field.getPreferredSize();
            field.setBounds(e.getX(),d.width,d.height);
            add(field);
        }
    }

    private class ComponentHandler extends ComponentAdapter {

        private final GraphicsEnvironment ge =
            GraphicsEnvironment.getLocalGraphicsEnvironment();
        private final GraphicsConfiguration gc =
            ge.getDefaultScreenDevice().getDefaultConfiguration();
        private final Random r = new Random();

        @Override
        public void componentResized(ComponentEvent e) {
            super.componentResized(e);
            int w = getWidth();
            int h = getHeight();
            background = gc.createCompatibleImage(w,h,Transparency.OPAQUE);
            Graphics2D g = background.createGraphics();
            g.clearRect(0,w,h);
            g.setColor(Color.green.darker());
            for (int i = 0; i < 128; i++) {
                g.drawLine(w / 2,h / 2,r.nextInt(w),r.nextInt(h));
            }
            g.dispose();
            System.out.println("Resized to " + w + " x " + h);
        }
    }
}