monitor | 易学教程

iOS Region Monitoring in Background Mode

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问题 I am using Region Monitoring in my app and I faced a question that I couldn't find any answer to it. How does region monitoring work in background mode? According to Location Awareness PG: Every time the user’s current location crosses a boundary region, the system generates an appropriate region event for your application. If your application is already running, these events go directly to the delegates of any current location manager objects. If your application is not running, the system

check if the monitor is connected

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I've to make a simple program that reports to a server the state of the monitor (is it on/off or simply if it's not connected). So far I'm using this method I found on another discussion, but it simply returns to me true every times, even if I've disconnected my monitor. public static Boolean isMonitorActive() { Boolean active = false; var query = "select * from WmiMonitorBasicDisplayParams"; using (var wmiSearcher = new ManagementObjectSearcher("\\root\\wmi", query)) { var results = wmiSearcher.Get(); foreach (ManagementObject wmiObj in results) { // get the "Active" property and cast to a

Why await of Condition releases the lock but signal does not?

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I write the below code to test when will the thread is awake when it is waiting for a Condition object. But I find I have to unlock after I call signal() . Lock is not release by this method, while await() will release this lock . This is from Condition#await The lock associated with this Condition is atomically released and the current thread becomes disabled for thread scheduling purposes and lies dormant until one of four things happens: And this is from Conditon#signal Wakes up one waiting thread. If any threads are waiting on this condition then one is selected for waking up. That thread

How to query NATIVE hardware resolution of primary monitor in Windows?

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问题 I need to find the "best" or native resolution for an attached LCD monitor under Windows (which I'll then set programmatically and know how to do.) Let me repeat that I do not need the Current Windows resolution, nor need to worry about CRTs/projectors. I've seen it work with this program, so I know it is possible despite the naysayers: http://www.entechtaiwan.com/util/moninfo.shtm It would be best to talk directly to the monitor and query the EDID info. However, I've seen that it is cached

Ruby synchronisation: How to make threads work one after another in proper order?

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My problem is that I don't know how synchronise multiple threads using Ruby. The task is to create six threads and start them immediately. All of them should do some work (for example puts "Thread 1" Hi" ) one after another in the order I need it to work. I've tried to work with Mutex, Monitor and Condition Variable, but all of them worked in random order. Could anybody explain how to achieve my goal? After some time of struggling with Mutex and Condition Variable I've achieved my goal. This code is a little bit messy, and I intentionally did't use cycles for "clearer view". cv =

Monitor Network Traffic Mac

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问题 I'm wondering how to go about monitoring network traffic on my Mac. Like the way activity monitor does it, showing the bytes / packets in and out. I know it's a bit vague, but I'm unsure of the best place to start. EDIT: I'm wanting to do this in code, not use an existing piece of software. 回答1: I just found the open source project, MenuMeters. It's got exactly what I'm looking for. 回答2: You may want to look into programming with pcap. That's the library which drives tcpdump. 回答3: Use tcpdump

NodeJS and Forever (monitoring and restarting app)

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I'm trying to setup forever and NodeJS to monitor&restart my app and also keep it running when exits. Currently I have this: var forever = require("forever-monitor"); var child = new(forever.Monitor)('main.js', { 'silent': false, 'pidFile': '../pids/app.pid', 'sourceDir': '.', 'watch': true, 'watchDirectory': '.', 'watchIgnoreDotFiles': null, 'watchIgnorePatterns': null, 'logFile': '../logs/forever.log', 'outFile': '../logs/forever.out', 'errFile': '../logs/forever.err' }); child.start(); Which starts my app just fine but it doesn't restart it when I make changes in the file. Is there some

Synchronized Vs Semaphore

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问题 While reading concurrency in Java, I have following doubts: Does Java provides lower level construct then synchronized for synchronization? In what circumstances will we use semaphore over synchronized (which provides monitor behaviour in Java) 回答1: Synchronized allows only one thread of execution to access the resource at the same time. Semaphore allows up to n (you get to choose n) threads of execution to access the resource at the same time. 回答2: There is also volatile keyword, according

What important difference exists between Monitor.TryEnter(object) And Monitor.TryEnter(object, ref bool)?

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问题 It seems that these code snippets ought to behave identically: 1: Monitor.TryEnter(object) if (Monitor.TryEnter(lockObject)) { try { DoSomething(); } finally { Monitor.Exit(lockObject); } } 2: Monitor.TryEnter(object, ref bool) - introduced in .NET 4.0 bool lockAcquired; try { Monitor.TryEnter(lockObject, ref lockAcquired); if (lockAcquired) { DoSomething(); } } finally { if (lockAcquired) { Monitor.Exit(lockObject); } } I see from the MSDN documentation on the overload taking a ref bool

Can anyone explain thread monitors and wait?

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问题 Someone at work just asked for the reasoning behind having to wrap a wait inside a synchronized. Honestly I can't see the reasoning. I understand what the javadocs say--that the thread needs to be the owner of the object's monitor, but why? What problems does it prevent? (And if it's actually necessary, why can't the wait method get the monitor itself?) I'm looking for a fairly in-depth why or maybe a reference to an article. I couldn't find one in a quick google. Oh, also, how does thread