AutoFitTextView
A TextView that automatically fit its font and line count based on its available size and content
This code is heavily based on this StackOverflow thread.
The sample shows how the library can handle various parameters being changed on the TextView: width, height, number of lines allowed, and the content (text) itself. You can play with the various properties to see how the library handle them.
Note that even though the sample is of API 16, it should work fine on most cases for much older versions.
A nice example of how to use an EditText that has this functionality can be found 
Preview
Known issues
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API 12-15 (including) of Android might have issues as a cause of this known bug, but in most cases it should work fine there too.
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On very rare cases, the last character of a line goes to the next line. If you know how to fix it, please write down about it.