c++ - Qt嵌入式Linux事件观察器

Question

我在 Qt 嵌入式应用程序 ( Cannot use keyboard within Qt app without sudo ) 中面临有关键盘输入读取的大问题。这个问题已经持续了很长时间，我认为它最终不会以正常方式得到解决。由于我的 Qt 应用程序看不到键盘事件(即 /dev/input/event1)，我想我被迫观看设备文件 mysalfe 并等待事件发生并手动解释它们。

在原始的 C++ 应用程序中，我会选择这样的东西:

/** BB-BONE-GPIO Test code to test the GPIO-KEYS interface.
* Written by Derek Molloy (www.derekmolloy.ie) for the book
* Exploring BeagleBone.
*
* This code is based on work in the document:
*    www.kernel.org/doc/Documentation/input/input.txt
*
* Written by Derek Molloy for the book "Exploring BeagleBone: Tools and 
* Techniques for Building with Embedded Linux" by John Wiley & Sons, 2014
* ISBN 9781118935125. Please see the file README.md in the repository root 
* directory for copyright and GNU GPLv3 license information.            */


#include<iostream>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<linux/input.h>
using namespace std;

#define KEY_PRESS 1
#define KEY_RELEASE 0

int main(){
   int fd, count=0;
   struct input_event event[64];
   if(getuid()!=0){
      cout << "You must run this program as root. Exiting." << endl;
      return -1;
   }
   cout << "Starting BB-BONE-GPIO Test (press 10 times to end):" << endl;
   if ((fd = open("/dev/input/event1", O_RDONLY)) < 0){
      perror("Failed to open event1 input device. Exiting.");
      return -1;
   }
   while(count < 20){  // Press and Release are one loop each
      int numbytes = (int)read(fd, event, sizeof(event));
      if (numbytes < (int)sizeof(struct input_event)){
         perror("The input read was invalid. Exiting.");
         return -1;
      }
      for (int i=0; i < numbytes/sizeof(struct input_event); i++){
         int type = event[i].type;
         int val  = event[i].value;
         int code = event[i].code;
         if (type == EV_KEY) {
            if (val == KEY_PRESS){
               cout << "Press  : Code "<< code <<" Value "<< val<< endl;
            }
            if (val == KEY_RELEASE){
               cout << "Release: Code "<< code <<" Value "<< val<< endl;
            }
         }
      }
      count++;
   }
   close(fd);
   return 0;
}

我想知道 Qt 库是否有任何更高级别的机制允许我做这样的事情？我一直在寻找一些，但我只找到了 QKeyPress 类。或者我需要用纯粹的 C 方式来做吗？我将感谢所有帮助!

编辑:在创建 MainWindow 对象之前，我刚刚在 Qt 应用程序的 main 中实现了上述代码。该代码有效，这意味着应用程序拥有读取输入所需的所有权限。为什么 Qt 不解释它呢？

Answer 1

您需要使用QKeyEvent类来获取键盘事件。您可以如下捕获键盘事件

void yourClass :: keyPressEvent(QKeyEvent *event)
{
    if (event->key() == Qt::Key_P)
        qDebug() << "Key P is Pressed";
}

如果您根本没有收到键盘事件，那么您检查 this link