创建BufferStrategy时发生java.lang.IllegalStateException

当我尝试使用

createBufferStrategy（2）

创建用于双缓冲的缓冲策略时，出现以下错误：

Exception in thread "main" java.lang.IllegalStateException: Component must have a valid peer
    at java.awt.Component$FlipBufferStrategy.createBuffers(Unknown Source)
    at java.awt.Component$FlipBufferStrategy.<init>(Unknown Source)
    at java.awt.Component$FlipSubRegionBufferStrategy.<init>(Unknown Source)
    at java.awt.Component.createBufferStrategy(Unknown Source)
    at java.awt.Canvas.createBufferStrategy(Unknown Source)
    at java.awt.Component.createBufferStrategy(Unknown Source)
    at java.awt.Canvas.createBufferStrategy(Unknown Source)
    at SpritePractice.render(SpritePractice.java:87)
    at SpritePractice.run(SpritePractice.java:67)
    at SpritePractice.start(SpritePractice.java:100)
    at SpritePractice.init(SpritePractice.java:48)
    at SpritePractice.<init>(SpritePractice.java:41)
    at SpritePractice.main(SpritePractice.java:108)

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您必须将实例添加到框架中，因为如果不添加实例，画布将无法显示。有了这一点，它应该可以：

 frame.add(this);

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您的SpritePractice实例不可见。您尚未将其添加到正在创建的框架中

 frame.add(this);