Android devices are all about interactions. And interactions can come not only from touches and sensors, but also from audio input. Most Android devices provide a micro to record sound and allow an application such as the Android desktop search to offer vocal features to record queries.
If sound input is available, OpenSL ES gives access to the sound recorder natively. It collaborates with a buffer queue to take data from the input device and fill an output sound buffer from it. Setup is pretty similar to what has been done with the
AudioPlayer except that data source and data sink are permuted.
To discover how this works, next the challenge consists in recording a sound when an application starts and playing it when it has finished ...