Clash-of-clans – Does construction stop after a raid

The definite answer is no. Shields can only be acquired in specific ways. According to The Clash of Clans wiki of Shields, these are the ways you can get shields:

Beginning the game.

When you first begin playing Clash of Clans, you are given a 3-day shield. Once the shield expires, you will have to manually purchase shields.

Be a victim of a successful raid.

If your village is attacked by another user, you will gain one of the following:

• If your village is raided with 0-29% destruction and the player dropped at least 1/3 of his/her total current troop space, you will receive a village guard depending on your current league
• If your village is raided with 30-59% destruction, you will receive a 12-hour shield plus the equivalent village guard time (i.e. If you are in Gold League for example, your total "shielded time" is 12 hours and 30 minutes, with 12 shield hours and right after your shield expires, 30 minutes village guard time.)
• If your village is raided with 60-89% destruction, you will receive a 14-hour shield plus the equivalent village guard time
• If your village is raided with a 90% or more destruction, you will receive a 16-hour shield plus the equivalent village guard time

Purchase shields through the store.

Shields can be purchased through the store with Gems.

A 1-day shield costs 100 gems, and takes 5 days to cool down.

A 2-day shield costs 150 gems, and takes 10 days to cool down.

A week-long shield costs 250 gems, and takes 35 days to cool down.

So, the most probable answer is that your village was unsuccessfully raided but with a destruction amount above 29%. And in conclusion, shields cannot be activated automatically unless an event such as the ones mentioned above take place.

Yes this is possible. What your friend is going to need are at least two Google accounts linked to his phone.

First, from within Clash of Clans, go into settings and connect the current village to a Google+ account. This will allow him to restore his village from any device that he signs into his Google account from.

Then in Android,go to settings -> Apps -> Clash of Clans, and 'Clear Data'. This will wipe the village off the device, but it will still be linked to the Google+ account.

Now open Clash of Clans again and get past the intro tutorial. On your iOS device, open Clash of Clans, go to Settings -> Link a Device -> This is the old device. On the Android phone, open Clash of Clans, go to settings -> Link a Device -> This is the new device. Follow the steps to link the Android phone to your village. Now connect the new village to a second Google+ account (Must be different than the first one!)

Now any time he wants to switch between the two, he just simply needs to Clear Data as explained above. After loading Clash of Clans, he will be able to sign into a Google+ account (there's now an option to do so without doing the tutorial), and restore its respective village.

I just tried this entire procedure and verified it works.

For future reference, it appears that Android phones will soon be getting user profiles. So that like Android tablets, different user profiles store different sets of user data. When this feature comes out, it would be possible to setup each village on a different user profile and just simply switch between the profiles, no clearing user data needed. Though I would always recommend linking each village to a Google+ account for safety.