使用QT搭建ROS程序界面（C++）

mapp.cpp:
slider->setMinimum(0);
slider->setMaximum(100);
ui->ForBackSlider->setMinimum(0);
QObject::connect(ui->ForBackSlider,SIGNAL(valueChanged(int)),this,SLOT(set_speed_value(int));
void MAPP::set_speed_value(int slider_value)
{
   ForBackSpeed=slider_value;          
}

mapp.h:
 private slots:
     void set_speed_value(int s);
 private:
     float ForBackSpeed=0.0;

CMakeLists.txt:(为了支持C++11特性)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}  -std=c++11)

main_window.ui:
插入button，改名为roscore。

main_window.h:
private slots:
    void on_roscore_clicked();

main_window.cpp:
void  robomap::MainWindow::on_roscore_clicked()
{
    system("gnome -terminal -x bash -c ‘roscore‘ &");
}
如果想一个按钮启动多个命令，得分别写对应个数的system()，因为是新开终端。

$roslaunch usb_cam usb_cam_test.launch
参见https://github.com/ros-visualization/rqt_image_view
main_window.cpp:
void robomap::Maindow::on_camera_clicked()
{
　　system("gnome -terminal -x bash -c ‘source ~/catkin_ws/devel/setup.bash; rosrun usb_cam usb_cam_node‘&");
　　system("gnome -terminal -x bash -c ‘rqt_image_view‘&");
}

 直接参照原文改得话编译并不能通过，报错：QCamera:No such file or directory。确定问题是找不到外部库和头文件的问题。
在CMakeLists.txt:
include_directories(/usr/include/x86_64_linux-gnu/qt5/QtMultimedia)
添加后错误排除，但在link时有错误：undefined reference to ‘QCamera:: ‘
再添加：target_link_libraries(... Qt5::Multimedia），只剩下QCameraViewfinder没找到外部库。
再跑去学习CMakeLists.txt的资料，还是无法解决，倒是找到另一种方式specify the c++ standard: set(CMAKE_CXX_STANDARD 11)。

转而先实现QT界面中调用摄像头，先实现功能，不在ROS空间中完成：
step1:新建Qt widgets application 工程
step2:https://www.cnblogs.com/annt/p/ant_000.html
step3:运行时报错，安装必要的库。完成功能
cam.pro:
QT       += core gui multimedia multimediawidgets

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = cam
TEMPLATE = app
SOURCES += main.cpp\
        mainwindow.cpp
HEADERS  += mainwindow.h
FORMS    += mainwindow.ui
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QCamera>
#include <QCameraViewfinder>
#include <QCameraImageCapture>
#include <QFileDialog>



namespace Ui {
class MainWindow;
}

class QCamera;
class QCameraViewfinder;
class QCameraImageCapture;

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

private slots:
void captureImage();
void displayImage(int,QImage);
void saveImage();

private:
Ui::MainWindow *ui;

QCamera *camera;
QCameraViewfinder *viewfinder;
QCameraImageCapture *imageCapture;
};

#endif // MAINWINDOW_H
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

camera=new QCamera(this);
viewfinder=new QCameraViewfinder(this);
imageCapture=new QCameraImageCapture(camera);

ui->ImageView->addWidget(viewfinder);
ui->ImageCapture->setScaledContents(true);

camera->setViewfinder(viewfinder);
camera->start();

connect(imageCapture, SIGNAL(imageCaptured(int,QImage)), this, SLOT(displayImage(int,QImage)));

connect(ui->buttonCapture, SIGNAL(clicked()), this, SLOT(captureImage()));
connect(ui->buttonSave, SIGNAL(clicked()), this, SLOT(saveImage()));
connect(ui->buttonQuit, SIGNAL(clicked()), qApp, SLOT(quit()));
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::captureImage()
{
ui->statusBar->showMessage(tr("capturing..."), 1000);
imageCapture->capture();
}

void MainWindow::displayImage(int , QImage image)
{
ui->ImageCapture->setPixmap(QPixmap::fromImage(image));

ui->statusBar->showMessage(tr("capture OK!"), 5000);
}

void MainWindow::saveImage()
{
QString fileName=QFileDialog::getSaveFileName(this, tr("save file"), QDir::homePath(), tr("jpegfile(*.jpg)"));
if(fileName.isEmpty()) {
ui->statusBar->showMessage(tr("save cancel"), 5000);
return;
}
const QPixmap* pixmap=ui->ImageCapture->pixmap();
if(pixmap) {
pixmap->save(fileName);
ui->statusBar->showMessage(tr("save OK"), 5000);
}
}
功能可以实现。调用摄像头，截图，保存等。


接着在ROS空间中进行代码修改。（搜到一篇博客，是用CMAKE编译工程的，需要在CMakeLists文件添加qt库）（Ubuntu下Qt Multimedia 播放mp3文件注意事项）
CMakeLists.txt:
find_package(Qt5 REQUIRED Core Widgets SerialPort Multimedia)
set(QT_LIBRARIES Qt5::Widgets Qt5::SerialPort Qt5::Multimedia)
参照博客中的写法，加入MultimediaWidgets模块，编译成功


3.开启turtlebot仿真，验证程序。
sudo apt-get install ros-kinetic-turtlebot ros-kinetic-turtlebot-apps ro-kinetic-turtlebot-interactions ros-kinetic-turtlebot-sumulatio ros-kinetic-kobuki-ftdi
source /opt/ros/kinetic/setup.bash
roslaunch turtlebot_gazebo turtlebot_world.launch 需要等几分钟加载
roslaunch turtlebot_gazebo gmapping_demo.launch
roslaunch turtlebot_teleop keyboard_teleop.launch