I changed the destructor code of RTLSClient to

RTLSClient::~RTLSClient() { workerThread.terminate(); if(!workerThread.wait(3000)) //Wait until it actually has terminated (max. 3 sec) { workerThread.terminate(); //Thread didn't exit in time, probably deadlocked, terminate it! workerThread.wait(); //We have to wait again here! } }

now app not showing ..QThread: Destroyed while thread is still running but it not responding when opening

@Christian-Ehrlicher @JonB Solved . By creating a seperate worker.cpp file and connected RTLSClient signal to worker slot, now data is inserting to mongodb very fast without freezing GUI.
Thanks ..

@jsulm @Christian-Ehrlicher signal/slot method working

connect(this,&MainWindow::starting,onethread,&myThread::recvNum); onethread->start(); for(int i=1;i<5;i++) { emit starting(i); }

As @Christian-Ehrlicher already said: the image gets deleted when the thread object is deleted. Do you delete the thread object?

Furthermore, I am not sure how you are trying to check if the memory is actually freed. The operating system might not be able to show you this. Your software will request memory from the OS when necessary, but can choose to keep it for later allocations when memory is freed. The only way you can test this is by repeatedly allocating and deallocating an image. If the memory usage does not grow then memory is correctly freed even if the OS does not show you this.

Yes, Thank you