java - 方法减慢执行 paintComponent()

Question

我有一个小问题。在动画期间执行方法 paintComponent() 时，我必须不断更新变量 bgImage。但这需要很多时间，以至于动画变慢。

有问题的一段代码:

public class ProblemClass extends JComponent {
    private static final int FRAME_FREQUENCY = 30;
    private final Timer animationTimer;

    public ProblemClass() {
        this.animationTimer = new Timer(1000 / FRAME_FREQUENCY, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                repaint(); // When the animation started is often invoked repaint()
            }
        });
    }

    // Other code...

    /** 
     * Start animation from another class
     */
    public void startAnimation() {
        this.animationTimer.start();
    }

    @Override 
    protected void paintComponent(Graphics g) { 
        // GraphicsUtils.gaussianBlur(...) it's a long-time operation
        BufferedImage bgImage = GraphicsUtils.gaussianBlur(AnotherClass.getBgImage()); 
        g2.drawImage(bgImage, 0, 0, null); 

        // Other code...
    }
}

我在 Internet 上读到我需要在并行线程 (SwingWorker) 中运行长任务，但我不知道如何在我的情况下执行此操作。我该如何解决这个问题？

附言抱歉我的英语不好，这不是我的母语。

Answer 1

您要做的最好的事情是在 paint 方法之外更新图像，并且仅在新图像准备就绪时才重新绘制。采用您现有的代码，并添加对图像的持久引用，该图像被绘制到 JComponent 的每个绘制方法中。然后让您的动画计时器执行高斯模糊并更新您的图像。

public class ProblemClass extends JComponent {
    private static final int FRAME_FREQUENCY = 30;
    private final Timer animationTimer;

    //persistent reference to the image
    private BufferedImage bgImage;

    public ProblemClass() {
        this.animationTimer = new Timer(1000 / FRAME_FREQUENCY, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                //Update the image on each call before repainting
                bgImage = GraphicsUtils.gaussianBlur(AnotherClass.getBgImage());
                repaint();
            }
        });
    }

    /** 
     * Start animation from another class
     */
    public void startAnimation() {
        this.animationTimer.start();
    }

    @Override
    protected void paintComponent(Graphics g2) {
        g2.drawImage(bgImage, 0, 0, null);

        // Other code...
    }
}