原因：测试用的AI伴侣版本过旧（2.3版本，2015年的），使用最新版本的AI伴侣测试即可解决该问题。 参考英文社区：https://community.appinventor.mi ... nion3-screen1/60187

...试呗，试过才知道{:8_358:}。有任何新的发现也欢迎分享到社区哦{:8_357:}

...求解答 这个我晚些时候会看一下，但是有空的话也请为社区贡献一些力量，比如发帖分享一些自己的经验、心得等内容，感谢{:8_348:}

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... Logging libraries You could use logging libraries instead of re-inventing the wheel. Log4j for instance will provide methods for different messages like info(), warn() and error(). Homemade methods or simply make a println method of your own and call it: void println(Object line) { Sy...

...jQuery do it like all the other answers. Although this would work, it's re-inventing the wheel. – Peter Apr 4 '13 at 18:33 15 ...

... our stackOverflow account handle and we've made a whole bunch of money by inventing time travel, but that is beside the point. I just wanted to say, "Thanks", this little note helped me out. – isaacdre Oct 11 '18 at 0:54 ...

... you need to check a variable against undefined value, there is no need to invent any special method, since JavaScript has a typeof operator, which is simple, fast and cross-platform: if (typeof value === "undefined") { // ... } It returns a string indicating the type of the variable or other...

... I feel like this should be the accepted answer. Why re-invent the wheel? – Zack Aug 4 '14 at 16:54 2 ...

...ding, right disappearing. It's might not do exactly what you need but with inventive spirit you can make it work ;) share | improve this answer | follow | ...