Running app on Qt simulator gives an error 'Cannot open file myapp.exe'

[petrof]

Why doesn't Qt emulator close previous build automatically?. In order to run new build I have to click explicitly quit button on Application tab in Qt simulator. This is so tedious.

[axjensen]

You could add a custom build step for that, or simply hit the "stop" button.

[tobias.hunger]

Qt Creator does not stop running applications when clicking on the run button to allow users to test several apps working together. This is essential when e.g. working on a client/server project, or just to see how your app handles getting started repeatedly:-)