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【拍照图片处理】Attempt to invoke virtual method 'boolean android.grap...
在做图片识别App的时候，选择相册图片没有问题，拍照后图片就报错：
Attempt to invoke virtual method 'boolean android.graphics.Bitmap.compress(android.graphics.Bitmap$CompressFormat, int, java.io.OutputStream)' on a null object reference
图片大致的处理流程是...
Service and Characteristic are not published by the connected device -...
Service and Characteristic are not published by the connected device，报错如下：
问题原因：硬件/蓝牙芯片问题导致的，比如A硬件测试好的，换了B硬件没有修改uuid，就出现这个报错。
由于B硬件没有发布这些特征，就会报这个错误。
BLE（四）嗅探工具 - 创客硬件开发 - 清泛IT社区，为创新赋能！
...gle稳定，经常会抓不到后面数据通信的网络包，不过这一问题应该是可以通过优化算法得到解决的，但需要对官方的固件进行逆向或自己根据Nordic公司提供的BLE协议栈重写代码。。
优点：
价格便宜，USB Dongle淘宝价70...
ListCtrl 重绘（Custom Draw） - C/C++ - 清泛网 - 专注C/C++及内核技术
... DLL的版本必须至少是4.71。但随着IE4 的发布，这已经不是问题了。(IE会夹带着这个DLL一起发布)
Custom Draw 基础
我将会尽我所能把Custom Draw的处理描述清楚，而不是简单的引用MSDN的文档。这些例子都需要你的程序有一个ListCtrl在...
初窥InnoDB的Memcached插件 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...务器不仅浪费了内存，而且还必须自己维护数据的不一致问题，有了Memcached插件，这些问题都不存在了，而且借助MySQL本身的复制功能，我们可以说是变相的实现了Memcached的复制，这更是意外之喜。
安装
为了让文章更具完整性...
HashSet vs. List performance
... lot of people are saying that once you get to the size where speed is actually a concern that HashSet<T> will always beat List<T>, but that depends on what you are doing.
Let's say you have a List<T> that will only ever have on average 5 items in it. Over a large number of cycle...
Does Python support multithreading? Can it speed up execution time?
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The GIL does not prevent threading. All the GIL does is make sure only one thread is executing Python code at a time; control still switches between threads.
What the GIL prevents then, is making use of more than one CPU core or separate CPUs to run threads in...
UIView Infinite 360 degree rotation animation?
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This might help some one, [view.layer removeAllAnimations]; to stop animation when needed.
– arunit21
Aug 22 '14 at 13:57
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Algorithm for creating a school timetable
...ere are known solutions for algorithm of creating a school timetable. Basically, it's about optimizing "hour-dispersion" (both in teachers and classes case) for given class-subject-teacher associations. We can assume that we have sets of classes, lesson subjects and teachers associated with each ot...
Difference between java.util.Random and java.security.SecureRandom
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The standard Oracle JDK 7 implementation uses what's called a Linear Congruential Generator to produce random values in java.util.Random.
Taken from java.util.Random source code (JDK 7u2), from a comment on the method protected int next(int bits), which is the one that genera...