<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>

/**
 * 免提
 *
 * @param context
 */
private void toggleSpeaker(Context context)
{
    AudioManager am = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
    am.setMode(AudioManager.MODE_IN_CALL);
    am.setSpeakerphoneOn(!am.isSpeakerphoneOn());
}