Service discovery failed exception using Bluetooth on Android

I'm currently working on an Android application that connects to an instrument via Bluetooth and need to write string commands and receive string responses back. Currently I have the connect/read/write working for TCP/IP over Wi-Fi and now trying to implement Bluetooth. But I am running into some roadblocks. I have been searching the web trying to find examples of something similar and hav

在Android上使用蓝牙的服务发现失败例外

我目前正在研究一种通过蓝牙连接到乐器的Android应用程序,需要编写字符串命令并接收字符串响应。 目前,我有通过Wi-Fi连接/读取/写入TCP / IP的工作,现在正在尝试实现蓝牙。 但我遇到了一些障碍。 我一直在寻找网络,试图找到类似的例子,并没有任何运气。 我一直在使用Android开发人员资源示例:蓝牙聊天作为我的主要参考点。 我目前的代码似乎工作..然后它会在连接点引发服务发现失败异常。 我正在使用DeviceListActi

Rotating quaternions based on mouse movement (OpenGL and Java)

I'm writing a game in Java using OpenGL (the LWJGL binding, to be specific). Each entity, including the camera, has a quaternion that represents it's rotation. I've figured out how to apply the quaternion to the current OpenGL matrix and everything rotates just fine. The issue I'm having is getting the camera to rotate with the mouse. Right now, every frame, the game grabs th

基于鼠标移动的旋转四元数(OpenGL和Java)

我正在使用OpenGL编写游戏(LWJGL绑定,具体而言)。 包括相机在内的每个实体都有一个代表其旋转的四元数。 我已经想出了如何将四元数应用于当前的OpenGL矩阵,并且一切都很好。 我遇到的问题是让相机随鼠标旋转。 现在,每一帧,游戏都会抓住鼠标在一个轴上移动的数量,然后将该数量应用于四元数以便相机旋转。 这里是旋转四元数的代码,我会发布它,因为我认为这是问题所在(虽然我总是对这类东西错误): public vo

How slow are Java exceptions?

Question: Is exception handling in Java actually slow? Conventional wisdom, as well as a lot of Google results, says that exceptional logic shouldn't be used for normal program flow in Java. Two reasons are usually given, its really slow - even an order of magnitude slower than regular code (the reasons given vary), and its messy because people expect only errors to be handled in exc

Java异常有多慢?

问题:Java中的异常处理实际上很慢吗? 传统观点以及大量的Google结果都表明,特殊的逻辑不应该用于Java中的正常程序流程。 通常有两个原因, 它真的很慢 - 甚至比普通代码慢一个数量级(原因各不相同), 和 它很混乱,因为人们只希望在特殊代码中处理错误。 这个问题是关于#1的。 举例来说,这个页面将Java异常处理描述为“非常慢”,并将慢速与创建异常消息字符串联系起来 - “然后将此字符串用于创建抛出的异常对

How do you assert that a certain exception is thrown in JUnit 4 tests?

How can I use JUnit4 idiomatically to test that some code throws an exception? While I can certainly do something like this: @Test public void testFooThrowsIndexOutOfBoundsException() { boolean thrown = false; try { foo.doStuff(); } catch (IndexOutOfBoundsException e) { thrown = true; } assertTrue(thrown); } I recall that there is an annotation or an Assert.xyz or somethin

你如何断言在JUnit 4测试中引发了某种异常?

我如何通过惯用方式使用JUnit4来测试某些代码是否会抛出异常? 虽然我当然可以做这样的事情: @Test public void testFooThrowsIndexOutOfBoundsException() { boolean thrown = false; try { foo.doStuff(); } catch (IndexOutOfBoundsException e) { thrown = true; } assertTrue(thrown); } 我记得有一个注释或一个Assert.xyz或者其他一些远远不够灵活的东西,而且在这种情况下JUnit的精神远不止于此

track down allocations of int[]

When viewing my remote application in JVisualVM over JMX, I see a saw-tooth of memory usage while idle: Taking a heap dump and analysing it with JVisualVM, I see a large chunk of memory is in a few big int[] arrays which have no references and by comparing heap dumps I can see that it seems to be these that are taking the memory and being reclaimed by a GC periodically. I am curious to track

追踪int []的分配

当通过JMX查看JVisualVM中的远程应用程序时,在空闲时看到了内存使用的锯齿: 拿堆转储和使用JVisualVM分析它,我看到一大块内存在一些没有引用的大型int[]数组中,并且通过比较堆转储,我可以看到它似乎是这些内存和由GC定期回收。 我很好奇跟踪这些,因为它激起我的兴趣,我自己的代码永远不会故意分配任何int[]数组。 我确实使用了很多像netty这样的库,所以罪魁祸首可能在别处。 我确实有其他服务器具有相同的框架组

How to increment a java String through all the possibilities?

I need to increment a String in java from "aaaaaaaa" to "aaaaaab" to "aaaaaac" up through the alphabet, then eventually to "aaaaaaba" to "aaaaaabb" etc. etc. Is there a trick for this? It's not much of a "trick", but this works for 4-char strings. Obviously it gets uglier for longer strings, but the idea is the same. char array

如何通过所有可能性增加一个Java String?

我需要通过字母表将Java中的字符串从“aaaaaaaa”增加到“aaaaaab”到“aaaaaac”,然后最终到“aaaaaaba”到“aaaaaabb”等。 这有什么窍门吗? 这不是什么“窍门”,但这适用于4字符串。 显然它对于更长的字符串来说更丑,但这个想法是相同的。 char array[] = new char[4]; for (char c0 = 'a'; c0 <= 'z'; c0++) { array[0] = c0; for (char c1 = 'a'; c1 <= 'z'; c1++) { array[1] = c1; for (char c2 = 'a'; c2

The difference between head & tail recursion

This question already has an answer here: What is tail recursion? 23 answers In head recursion , the recursive call, when it happens, comes before other processing in the function (think of it happening at the top, or head, of the function). In tail recursion , it's the opposite—the processing occurs before the recursive call. Choosing between the two recursive styles may seem arbitra

头尾递归的区别

这个问题在这里已经有了答案: 什么是尾递归? 23个答案 在head recursion ,当递归调用发生时,会在函数的其他处理(认为它发生在函数的顶部或头部)之前出现。 在tail recursion ,它的递归调用之前发生的相反的处理。 在两种递归风格之间进行选择可能看起来是任意的,但是选择可以使所有不同。 在路径开始处有一个具有单个递归调用路径的函数使用所谓的头递归。 先前展览的阶乘函数使用头部递归。 一旦它确定需要

What actually causes a Stack Overflow error?

This question already has an answer here: What is a StackOverflowError? 13 answers It seems you're thinking that a stackoverflow error is like a buffer overflow exception in native programs, when there is a risk of writing into memory that had not been allocated for the buffer, and thus to corrupt some other memory locations. It's not the case at all. JVM has a given memory alloca

什么实际上导致堆栈溢出错误?

这个问题在这里已经有了答案: 什么是StackOverflowError? 13个答案 看起来你认为一个stackoverflow错误就像本地程序中的缓冲区溢出异常,当存在写入未分配给缓冲区的内存的风险,从而破坏其他一些内存位置时。 事实并非如此。 JVM为每个线程的每个堆栈分配一个给定的内存,如果尝试调用某个方法来填充此内存,则JVM将引发错误。 就像它试图在长度为N的数组的索引N处写入一样。不会发生内存损坏。 堆栈不能写入堆中。

How to reduce heap usage impact from VisualVM?

I'm trying to optimize the memory usage of my application. Unfortunately, running my application with -Dcom.sun.management.jmxremote and connecting it via VisualVM has quite a big impact on the heap usage. At first I thought that it is my application problem, until I wrote a very simple program to confirm that it is indeed the JMX's overhead. Below is the image of the activity. After

如何减少来自VisualVM的堆使用影响?

我试图优化我的应用程序的内存使用情况。 不幸的是,使用-Dcom.sun.management.jmxremote运行我的应用程序并通过VisualVM连接它对堆的使用有相当大的影响。 起初我认为这是我的应用程序问题,直到我编写了一个非常简单的程序来确认它确实是JMX的开销。 以下是该活动的图像。 读完这些之后,我明白这是由于VisualVM通过连续轮询连接的应用程序来检索数据的方式。 我通过查看VisualVM的内存采样器来证实这一点。 RMI TCP连

how come Eclipse compiles this Java code but not Ant?

This compiles find using Eclipse: abstract class CollectionView implements Collection<Object> { ... public Object[] toArray(Object[] o) { if (fast) { return get(map).toArray(o); } else { synchronized (map) { return get(map).toArray(o); } } } ... } class KeySet exten

Eclipse如何编译这个Java代码,但不是Ant?

这编译使用Eclipse查找: abstract class CollectionView implements Collection<Object> { ... public Object[] toArray(Object[] o) { if (fast) { return get(map).toArray(o); } else { synchronized (map) { return get(map).toArray(o); } } } ... } class KeySet extends Collect