Code for silence mode, normal mode and vibration mode in android Development

Silence Ringer
You can use the AudioManager to enable and disable silent mode.

AudioManager mAudio = (AudioManager) getSystemService(Activity.AUDIO_SERVICE);
mAudio.setRingerMode(AudioManager.RINGER_MODE_SILENT); // for silent mode
// or...
mAudio.setRingerMode(AudioManager.RINGER_MODE_NORMAL);// for normal mode

Here is the link for class AudioManager.