Creating GUI for ROS

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You just need to write a Qt Program like normal using CMake for the build system. http://doc.qt.io/qt-5/cmake-manual.html

Now copy that stuff into a catkin package.

call ros::init somewhere in your code.

Then start a ros::asyncSpinner to receive ros packages (you can publish stuff and call service calls without it, but actionClient calls will never return and you get no callbacks)

Now do everything just like normal (as you did in your command-line version).

if you need callbacks, define the function you want to call as a qt slot, create a wrapper function that calls

QMetaObject::invokeMethod(yourObjectPointer, "functionName", Qt::QueuedConnection);

asyncSpinner will live in a new thread, if you call a Qt function directly from there, thing will go bad. Race conditions etc. Also your application might crash, because you are not allowed to call draw functions from other threads. QueuedConnections creates an Event that is processed later in the main thread.