Java swing JFrame用repaint出现闪烁的问题解决

这几天用swing写登录页面背景动图的时候发现一直会有闪烁（我的类是继承JFrame），就来搜原因后发现好像是因为repaint会调用update()方法中的清屏操作导致闪烁。

我当时看的是这个文章

穆梓先生-java 双缓冲技术解决屏幕闪烁问题

于是按照他的方法重写了update方法，却发现问题没解决

public void paint(Graphics g) {
		g.drawImage(skyImag.getImage(), skyX, skyY, null);
		g.drawImage(groundImag, groundX, groundY, null);
		g.drawImage(dinosaurImag.getImage(), dinoX, dinoY, null);
	}
public void update(Graphics g) {
		System.out.println("==1==");//这个是我拿来测试会不会调用的输出信息
		if (groundImag == null) {
			System.out.println("==2==");
			//这句话从没输出过，说明了JFrame不会执行清屏操作，即groundImag ！= null，而Frame跟JPanel好像会执行清屏操作
			groundImag = this.createImage(500, 500); // 新建一个图像缓存空间,这里图像大小为800*600，为了使这句话没问题，我把我的对象从ImagIcon对象改成Imag对象
			}
			Graphics gImage = groundImag.getGraphics(); // 把它的画笔拿过来,给gImage保存着
			paint(gImage); // 将要画的东西画到图像缓存空间去
			g.drawImage(groundImag, 0, 0, null); // 然后一次性显示出来
		
	}

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于是我又继续查文章，我发现没什么人用JFrame出现闪烁现象（我上次写飞机大战都没闪烁的说！），所以我查文章的时候放大范围，只要是Java swing编程出现闪烁的文章我都看一遍过去，终于让我看到这个大佬的文章

ydcun-双缓冲原理在awt和swing中实现消除闪烁的方法

就是他做的测试，让我知道原来在JFrame中repaint()的时候update()方法就没被调用到，JFrame消除闪烁是在update()中“直接调用了paint()函数而没有clearRect()，也就是清屏的方法，这里他试图不通过清屏来阻止闪烁的发生。”

所以到底是哪一步出问题了。。paint()方法已经被我重写了是不会有清屏操作的，问题感觉只能出在repaint()上，看了repaint()的代码好像也没发现类似清屏的代码，我能力有限，还在学习中，有大佬知道咋回事就求赐教一下QWQ，为了方便大家找repaint()有没有问题我就把代码贴上来吧

public void repaint(long tm, int x, int y, int width, int height) {
        if (this.peer instanceof LightweightPeer) {
            // Needs to be translated to parent coordinates since
            // a parent native container provides the actual repaint
            // services.  Additionally, the request is restricted to
            // the bounds of the component.
            if (parent != null) {
                if (x < 0) {
                    width += x;
                    x = 0;
                }
                if (y < 0) {
                    height += y;
                    y = 0;
                }

                int pwidth = (width > this.width) ? this.width : width;
                int pheight = (height > this.height) ? this.height : height;

                if (pwidth <= 0 || pheight <= 0) {
                    return;
                }

                int px = this.x + x;
                int py = this.y + y;
                parent.repaint(tm, px, py, pwidth, pheight);
            }
        } else {
            if (isVisible() && (this.peer != null) &&
                (width > 0) && (height > 0)) {
                PaintEvent e = new PaintEvent(this, PaintEvent.UPDATE,
                                              new Rectangle(x, y, width, height));
                SunToolkit.postEvent(SunToolkit.targetToAppContext(this), e);
            }
        }
    }

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接下来我继续说说我是怎么解决这个问题的，在ydcun大佬那边是有讲他的解决方案的，我还没试过（因为凌晨3点了都！我写完立马睡觉！），我当时（凌晨2点）就想着既然不会去调用update()，那我手动调用不就好了？

于是

public void paint(Graphics g) {
		g.drawImage(skyImag.getImage(), skyX, skyY, null);
		g.drawImage(groundImag, groundX, groundY, null);
		g.drawImage(dinosaurImag.getImage(), dinoX, dinoY, null);
		update(getGraphics());//跟JPanel不同，JFrame的repaint方法不会自动调用update方法。所以我这边直接让它调用了。
		//而且参数不能用g得用getGraphics()

	}

	public void update(Graphics g) {
//		System.out.println("==1==");
//		if (groundImag == null) {
//			//System.out.println("==2==");

//			groundImag = this.createImage(500, 500); }// 新建一个图像缓存空间,这里图像大小为800*600
			//Image对象在这边也会出问题
			//报getGraphics() not valid for images created with createImage(producer)
			//得改成BufferedImage，但是我懒得改，所以我直接全注释了
			
//			Graphics gImage = groundImag.getGraphics(); // 把它的画笔拿过来,给gImage保存着
//			paint(gImage); // 将要画的东西画到图像缓存空间去
//			g.drawImage(groundImag, 0, 0, null); // 然后一次性显示出来

	}
	//为了实现动画效果我写了个计时器来repaint()
	public void startTimeTask() {
		Timer timer = new Timer();
		TimerTask task = new TimerTask() {
			@Override
			public void run() {
				skyMove();
				groundMove();
				dinoMove();
				repaint();
			}
		};
		timer.schedule(task, 10, 20);
	}

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对，我调用了一个什么东西都没有的update()方法，就解决了闪烁的问题。。。但是如果我调用系统的update()

public void update(Graphics g) {
        paint(g);
    }

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就会更闪烁然后报错
Java HotSpot(TM) 64-Bit Server VM warning: Potentially dangerous stack overflow in ReservedStackAccess annotated method sun.java2d.d3d.D3DBlitLoops.IsoBlit(Lsun/java2d/SurfaceData;Lsun/java2d/SurfaceData;Ljava/awt/image/BufferedImage;Ljava/awt/image/BufferedImageOp;Ljava/awt/Composite;Lsun/java2d/pipe/Region;Ljava/awt/geom/AffineTransform;IIIIIDDDDZ)V [1] Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError at java.base/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:714) at java.base/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:937) at java.base/java.util.concurrent.locks.ReentrantLock$Sync.lock(ReentrantLock.java:153) at java.base/java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:322) at java.desktop/sun.awt.SunToolkit.awtLock(SunToolkit.java:195) at java.desktop/sun.java2d.pipe.RenderQueue.lock(RenderQueue.java:112) at java.desktop/sun.java2d.d3d.D3DBlitLoops.IsoBlit(D3DBlitLoops.java:313) at java.desktop/sun.java2d.d3d.D3DTextureToSurfaceScale.Scale(D3DBlitLoops.java:768) at java.desktop/sun.java2d.pipe.DrawImage.scaleSurfaceData(DrawImage.java:1001) at java.desktop/sun.java2d.pipe.DrawImage.renderImageScale(DrawImage.java:647) at java.desktop/sun.java2d.pipe.DrawImage.tryCopyOrScale(DrawImage.java:319) at java.desktop/sun.java2d.pipe.DrawImage.transformImage(DrawImage.java:258) at java.desktop/sun.java2d.pipe.DrawImage.copyImage(DrawImage.java:76) at java.desktop/sun.java2d.pipe.DrawImage.copyImage(DrawImage.java:1027) at java.desktop/sun.java2d.SunGraphics2D.drawImage(SunGraphics2D.java:3425) at java.desktop/sun.awt.image.ImageRepresentation.drawToBufImage(ImageRepresentation.java:813) at java.desktop/sun.java2d.pipe.DrawImage.copyImage(DrawImage.java:1034) at java.desktop/sun.java2d.pipe.ValidatePipe.copyImage(ValidatePipe.java:186) at java.desktop/sun.java2d.SunGraphics2D.drawImage(SunGraphics2D.java:3425) at java.desktop/sun.java2d.SunGraphics2D.drawImage(SunGraphics2D.java:3401) at cn.zhetech.BackImag.paint(UserLogin2.java:276) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283) at java.desktop/javax.swing.JFrame.update(JFrame.java:469) at cn.zhetech.BackImag.paint(UserLogin2.java:283)

窗口也关不掉，只能从控制台强制停止运行。。。

等日后有大佬评论教我了或者我自己学习到了再补充一下这个原因，碎觉，溜了||ヽ(￣▽￣)ノミ|Ю，狗命要紧

如果文章有帮到你或者给你提供了思路，那就送我个赞呗(◦˙▽˙◦)，不然我就默认每个浏览的都是想点然后忘了（自欺欺人，bushi）

原文章：https://blog.csdn.net/qq_38677092/article/details/112092928