Query about BREAK statement in Appinventor

[Mayank Rathore]

How to break out of current while loop in AI2? Please help!

[Tim Carter]

Just like you would in any coding situation, set an if/then clause where the loop meets a certain condition

see here:

https://groups.google.com/forum/#!searchin/mitappinventortest/break%7Csort:relevance/mitappinventortest/5Oq5TQFjts8/Kw5Kio7ayO8J

[SteveJG]

You  cannot use a Button.Click or other method to break out of a loop .  To interrupt the loop (terminating the looping before it self terminates) must be done programmably, as AI doesn't have a built in loop break.  See Tim's post   and here https://code.google.com/archive/p/app-inventor-for-android/issues/474 .    And endless loop will result in a run time error.  The model of event processing in App Inventor by  Lyn  

 Depending on how you are iterating,, instead of a simple loop you could try using a Clock as suggested by Taifun  The 'Do something' example .  You did not provide an example of the 'looping' activity, so that is a guess.

Issue 474 (to provide a Break function) has been on MIT's 'to do' list since late 2010 ... almost seven years.  This is probably insolvable because AI executes asynchronously.

A runaway activity within a loop will crash your app.   What to do?  Certainly avoid long loops (and perhaps loops in general). Never use a loop without a way to escape.

Regards,

Steve

[Taifun]

@SteveJG: Scott found a solution, see the link Tim posted...

Taifun

[SteveJG]

@Thanks Taifun,.  Scott's examples  work to 'terminate a loop early' if the loop is  processing a List.  The methods would not terminate  Math activity.   But, good to know.

Can something similar be done with 

to terminate before the counter reaches 1000 using perhaps a button click?  The only solution I can find other than providing an if statement within the loop..say if counter= 200 then counter =1001  which is a software 'termination'    is to use something once suggested by ABG using a Clock  and that 'works sometimes".

--Steve

[Abraham Getzler]

This is an example of forced breaks in sieve based prime number search ...

http://ai2.appinventor.mit.edu/?galleryId=6477875229491200

ABG