随时通过按键打破c ++ [英] c++ breaking out of loop by key press at any time

问题描述

我在这里有一个循环，该循环应该每500毫秒读取一台设备上的输出.这部分工作正常.但是，当我尝试引入cin.get来拾取被按下的"n"键来停止循环时，到目前为止，我得到的输出仅是按键数.如果我多次按任何键("n"除外)，然后按Enter，将获得更多输出.我需要的是循环保持循环，没有任何交互，直到我希望它停止为止.

What I have here is a loop that is supposed to read the output on a piece of equipment every 500 milliseconds. This part works fine. However, when I try to introduce cin.get to pick up the key "n" being pressed to stop the loop, I only get as many outputs as the number of key presses up to this point. If I press any keys (apart from 'n') several times followed by enter, I will get a few more outputs. What I need is the loop keep looping without any interaction until I want it to stop.

代码如下:

for(;;)
{
    count1++;
    Sleep(500);
    analogInput = ReadAnalogChannel(1) / 51.0;
    cout << count1*0.5 << "     " << analogInput << endl;
    outputFile << count1*0.5 << ", " << analogInput << endl;
    if (cin.get() == 'n') //PROBLEM STARTS WITH THIS INTRODUCED
        break;
};

除非我再按几个键，然后按回车键，否则输出如下(有2次按键进入程序的此阶段)

My output is as follows (there are 2 key presses to get to this stage in the program) unless I press a few more keys followed by enter:

0.5    0 // as expected
1      2 // as expected
should be more values until stopped

我对使用哪种循环类型没有特别的偏好，只要它可以工作即可.

I have no particular preference in which type of loop to use, as long as it works.

谢谢！

推荐答案

cin.get()是 synchronous 调用，该调用将暂停当前执行线程，直到获得输入字符(您按一个键).

cin.get() is a synchronous call, which suspends the current thread of execution until it gets an input character (you press a key).

您需要在单独的线程中运行循环并轮询原子布尔，您可以在cin.get()返回之后在主线程中更改该原子布尔.

You need to run your loop in a separate thread and poll the atomic boolean, which you change in main thread after cin.get() returns.

它可能看起来像这样:

std::atomic_boolean stop = false;

void loop() {
    while(!stop)
    {
        // your loop body here
    }
}

// ...

int main() {
    // ...
    boost::thread t(loop); // Separate thread for loop.
    t.start(); // This actually starts a thread.

    // Wait for input character (this will suspend the main thread, but the loop
    // thread will keep running).
    cin.get();

    // Set the atomic boolean to true. The loop thread will exit from 
    // loop and terminate.
    stop = true;

    // ... other actions ...

    return EXIT_SUCCESS; 
}

注意:上面的代码只是一个想法，它使用Boost库和标准C ++库的最新版本.这些可能对您不可用.如果是这样，请使用您环境中的替代方法.

Note: the above code is just to give an idea, it uses Boost library and a latest version of standard C++ library. Those may not be available to you. If so, use the alternatives from your environment.

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