Add Warning Reminder to Simple Draw to warn user to save if user try exiting without saving work

Components

Simple Draw is an open source app that enable the user to freely draw or sketch on their mobile devices. it is designed in such a way that users can select any color of choice, can save there drawings and even share such drawing.this app can be downloaded from this link https://f-droid.org/packages/com.simplemobiletools.draw/ . while using this app, i mistakenly press my phone exit button and the app closed without prompting me to save, and so, i lost my fine drawing and have to start again. this lost would have been averted if i was warned. on that bases i propose the bellow

Proposal

i want to propose that the feature that will make the app prompt a warning when a user want to exit without saving his or her work/drawing be added to this great app.(Warning Reminder to warn/promt user to save if user try exiting with saving work) for example if a user due to imperfection, mistakenly press the exit button, instead of the app just exiting, there should be a popup dialog box reminding the user that his work/drawing is not saved yet. and should have an option of further action he would want to take(either to save,don't save or cancel the exit ) .

HOW THIS FEATURE CAN BE ADDED

the project owner should design a popup dialog box that will have the following massages " Your Work has not been saved! complete action using one of the following: SAVE, DON'T SAVE, CANCEL. (please see the picture to see how it should look)and code it in such a way that ones a user tap/click the exit button without saving his work first, this popup dialog box will popup on the screen reminding the user the actions to take in order to complete his/her action.

Mockups / Examples

the drawing before the exit button is clicked

how it should be when exit button is clicked

Benefits

unnecessary loss of work will be eliminated as the app will prompt the user to select what action he or she wants to take as a result of clicking the phone exit key. thus making the time spent on such a project not to be a wasted time and effort. and above , the app will stand out among similar apps that performs such service.