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App Inventor 2 MQTT拓展入门（保姆级教程） · App Inventor 2 中文网
...根据前缀进行过滤。
（2）订阅两个主题，一个专门用于接收，一个专门用于发布。
.aia 源码下载
mqtt_demo.aia
切换 目录 关注 我们 关注我，不迷路 ...
mqtt协议一般最大支持订阅几个主题？ - 创客硬件开发 - 清泛IT社区，为创新赋能！
...个通配符主题 /house/+/temperature。这样只需要一个订阅就能接收所有房间的温度消息。
+： 单层通配符，匹配一个层级。#： 多层通配符，匹配零个或多个层级（必须放在主题末尾）。
评估实际需求： 认真设计你的主题树结构。...
Process escape sequences in a string in Python
...ecs
ESCAPE_SEQUENCE_RE = re.compile(r'''
( \\U........ # 8-digit hex escapes
| \\u.... # 4-digit hex escapes
| \\x.. # 2-digit hex escapes
| \\[0-7]{1,3} # Octal escapes
| \\N\{[^}]+\} # Unicode characters by name
| \\[\\'"abfnrtv] # Single-...
MongoDB仿关系型数据库Group聚合例子 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
MongoDB仿关系型数据库Group聚合例子MongoDB Group,max仿关系型数据库例子，通过BsonJavaScript脚本实现。相当的SQL：select * from GroupDemo a right join (select userName,max(date) maxdate from GroupDemo group by userName) b on a date=b maxdate
namespace MongoGroupDemo
{
...
程序员之网络安全系列（四）：数据加密之非对称秘钥 - 更多技术 - 清泛网 -...
程序员之网络安全系列（四）：数据加密之非对称秘钥前文回顾假如，明明和丽丽相互不认识，明明想给丽丽写一封情书，让隔壁老王送去如何保证隔壁老王不能看到情书内容？（保密性)如何保证隔壁...前文回顾
假如，明明和...
how to check the jdk version used to compile a .class file [duplicate]
...
Alternatively, if you open the class file in a hex editor you can look at bytes 7 and 8. The number will map to the numbers given in the above answer. E.g. 00 2E -> JDK 1.2 = 46 (0x2E hex). Useful if you don't have access to javap. ref: en.wikipedia.org/wiki/Java_class...
How to create GUID / UUID?
...ion 4 compliant solution that solves that issue by offsetting the first 13 hex numbers by a hex portion of the timestamp, and once depleted offsets by a hex portion of the microseconds since pageload. That way, even if Math.random is on the same seed, both clients would have to generate the UUID th...
记一次MongoDB性能问题 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...能问题最近忙着把一个项目从MySQL迁移到MongoDB，在导入旧数据的过程中，遇到了些许波折，犯了不少错误，但同时也学到了不少知识，遂记录下来。公...最近忙着把一个项目从MySQL迁移到MongoDB，在导入旧数据的过程中，遇到了些...
What is the exact meaning of IFS=$'\n'?
...ne to three digits)
\xHH
the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
\uHHHH
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex digits)
\UHHHHHHHH
the Unicode (ISO/IEC 10646) character whose...
Android get color as string value
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Just for the sake of easy copypasta:
"#" + Integer.toHexString(ContextCompat.getColor(getActivity(), R.color.some_color));
Or if you want it without the transparency:
"#" + Integer.toHexString(ContextCompat.getColor(getActivity(), R.color.some_color) & 0x00ffffff);
...