Is there any way in which we can check the grammar of the sentence when a person types a sentence in a textbox?
There are several ways of doing that.
You can use any API that does it. There are many possibilities in Python however to do it using several kinds of libraries that can connect to API/Web.
You can try to list things down and follow the English Grammar rules to check the overall score.
You might be able to use a grammar api. Here are some examples, some free, some for subscription https://www.google.com/search?q=grammar+api&rlz=1C1CHBF_enUS887US887&oq=grammar+api&aqs=chrome..69i57.3711j0j7&sourceid=chrome&ie=UTF-8
Can they be used with App Inventor? ?? go ahead and try.
This May Help You
I am currently seeing this website, It can be usefull
Can I do it without using an API?
I think may be no
Theoretically you could use a set of grammar rules in a decision tree using conditional statements and check the text from your TextBox to see whether it follows the rules. Is this practical? No. Doing this is probably way to complex and would be very slow if you have lots of grammar 'rules' to scan.
Google docs has a grammar/spell checker. If you can export the TextBox text to google docs, you can check the grammar in that software possibly.
no but if somebody makes a extension based on the api it might be possible btw its grammar not grammer
The text field in appinventor has the auto correct flag turned on by default and underlines the words with errors in red.
Are you talking about grammarly.com extension?