Here's some of the interesting Andriod apps for teens/ adult learners.
“Learn
by constructing words and phrases out of mandarin characters. As each word is
constructed, the meaning and Mandarin pronunciation are appended. You are first
instructed on how to construct the words and phrases, then your recall of them
is tested.”
Includes 29 lessons, with Pinyin, English
translation and Chinese audio.
Chinese notecards
“This
Chinese Notecard app lets you choose whether to start on the characters and
practice your pronunciation and reading or you can start with the definitions
to test if you know how to write the characters.” The vocabulary lists are
taken from Integrated Chinese, Chinese Link, and Advanced Placement.
Vocabulary list from HSK exam, includes pinyin and meaning in English.
Contains sentences, grouped according to themes. Pinyin and translation in English available. Audio provided free for a few themes.
Learn writing through games.