Question: Actually I'm handling 3 languages in my app so I have:

`values/strings.xml`

`values-it/strings.xml`

`values-de/strings.xml`

When I install the app, it is properly installed in the current language of the device.
But if I change the language of the device, the language of the app doesn't switch. I have to reinstall it to switch the language.

I've seent that this happens also to other apps, but not to all. The "big" ones (whatsapp, viber, all google's, etc) change.

So the question is: how can an app follow the device's language change ?

Answer: 
If the file is not fixed length, you are out of luck. Some function will have to read the file. If the file is fixed length, you can open the file, use the function `file.seek(line*linesize)`. Then read the file from there.
If the file to read is big, and you don't want to read the whole file in memory at once:

```
fp = open("file")
for i, line in enumerate(fp):
    if i == 25:
        # 26th line
    elif i == 29:
        # 30th line
    elif i > 29:
        break
fp.close()

```

Note that `i == n-1` for the nth line.