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Circle-Animation project throws java.lang.NullPointerException. #1

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wingrez opened this issue Apr 12, 2020 · 0 comments
Open

Circle-Animation project throws java.lang.NullPointerException. #1

wingrez opened this issue Apr 12, 2020 · 0 comments

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@wingrez
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wingrez commented Apr 12, 2020

定位：02-Java-Swing-Basics\Chapter-02-Completed-Codes\Circle-Animation\src\AlgoFrame.java -> AlgoCanvas -> paintComponent
问题：在一些运行中，抛出Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
原因：paintComponent未经过render方法中的repaint方法自行调用，circles数组存在未定义的可能。
修复：一种简单的修复是在paintComponent中加入circles为null的检测。
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@wingrez