dissertation

This is available to programs, but no standard user interface is provided.3.3 SMS messagesAndroid has three standard content providers for accessing messages, dependingon which type of messages is desired. The SMS provider gives accessto SMS messages, the MMS 5 provider gives access to MMS messages, andthe MMS+SMS provider handles conversations consisting of both types ofmessages 6 .SMS messages can be stored on the SIM card as well as on the phone,but unlike SIM contacts there is no interface in Android for directly accessingSMS messages on the SIM card. Instead, the SMS provider itself isresponsible for copying messages from the SIM to the phone’s database.3.4 IntentsTo communicate between different processes, Android uses a framework calledBinder [85] to send messages called intents [2]. An intent can be directedto a specific receiver or broadcast, and carries information describing anaction to be performed or an event that has occurred. For example, wheneversomething happens to the phone’s USB connection, an intent calledACTION USB STATE is broadcast, containing e.g. whether the USB cable wasconnected or disconnected and which mode the phone is in, such as USB massstorage or USB debugging. Any application can register with the Binder systemto receive such broadcast messages.Non-broadcast intents can be either explicit (directed to a named applicationand component) or implicit (directed to a function). To receive animplicit intent, an application first registers with the Binder system that itwishes to implement a given function. For example, the content provider for5 Multimedia Messaging Service, a system for sending messages containing multiplemedia formats such as text, images, and sound.6 These are implemented in files in the directorypackages/providers/TelephonyProvider/src/com/android/providers/telephony/,named SmsProvider.java, MmsProvider.java, and MmsSmsProvider.java, respectively.14