【導讀】目前隨著移動設備越來越普及以及移動設備的硬件的提升，移動設備的功能越來越完善，他的系統(tǒng)平臺也日漸火熱起來。Phone以及當下正在逐步興起的Android。目前為止國內已經(jīng)有很多Android系統(tǒng)的用戶。場占有率也在20%左右。發(fā)在國內仍然屬于起步和探索階段。急需要大量的相關技術和人員的投入。下面首先介紹一下Android系統(tǒng)。Android是基于Linux內核的軟件平臺和操作系統(tǒng)，是。Google在2021年11月5日公布的手機系統(tǒng)平臺，早期由Google開發(fā)，后由（OpenHandset. 低層以Linux核心工作為基礎，只提供基本功能；其他的應用軟件則由各公司自行開發(fā)，以Java作為編寫程式的一部分[1]。手機游戲作為Android系統(tǒng)平臺的一個重要組成部分，正在被越來越多的人所重視。在使用的移動電話已經(jīng)超過10億部，而且這個數(shù)字每天都在不斷增加。在除美國之外的各個。系統(tǒng)進行深入細致的研究。在國內Android相關領域屬于較早研究的一批，經(jīng)過老師和同學一。還沒有自主研發(fā)并商品化的手機操作系統(tǒng)。在2021年8月，由中國移動所主導開發(fā)OPhone平臺面世。

　　

【正文】 larity and Applications The Android application framework forces a structure on developers. It doesn’t have a main() function or single entry point for execution—instead, developers must design applications in terms of ponents. Example Application. We developed a pair of applications to help describe how Android applications operate. Interested readers can download the source code from our web Let’s consider a locationsensitive social working application for mobile phones in which users can discover their friends’locations. We split the functionality into two applications: one for tracking friends and one for viewing them. As Figure 1 shows, the FriendTracker application consists of ponents specifc to tracking friend locations (for example, via a Web service), storing geographic coordinates, and sharing those coordinates with other applications. The user then uses the FriendViewer application to retrieve the stored geographic coordinates and view friends on a applications contain multiple ponents for performing their respective tasks。 the ponents themselves are classifed by their ponent types. An Android developer chooses from predefned ponent types depending on the ponent’s purpose (such as interfacing with a user or storing data).Component TypesAndroid defnes four ponent types:Activity? ponents defne an application’s user interface. Typically, an application developer defnes one activity per “screen.” Activities start each other, possibly passing and returning values. Only one activity on the system has keyboard and ocessing focus at a time。 all others are ponents perform background processing. When an activity needs to perform some operation that must continue after the user interface disappears (such as download a fle or play music), it monly starts a service specifcally designed for that action. The developer can also use services as applicationspecifc daemons, possibly starting on boot. 26 Services often define an interface for Remote Procedure Call (RPC) that other system ponents can use to send mands and retrieve data, as well as register callbacks. Content provider ? ponents store and share data using a relational database interface. Each content provider has an associated “authority” describing the content it contains. Other ponents use the authority name as a handle to perform SQL queries (such as SELECT, INSERT, or DELETE) to read and write content. Although content providers typically store values in database records, data retrieval is implementationspecifc—for example, fles are also shared through content provider receiver? ponents act as mailboxes for messages from other applications. Commonly, application code broadcasts messages to an implicit destination. Broadcast receivers thus subscribe to such destinations to receive the messages sent to it. Application code can also address a broadcast receiver explicitly by including the namespace assigned to its containing application. Figure 1 shows the FriendTracker and FriendViewer applications containing the diferent ponent types. The developer specifes ponents using a manifest fle (also used to defne policy as described later). There are no restrictions on the number of ponents an application defnes for each type, but as a convention, one ponent has the same name as the application. Frequently, this is an activity, as in the FriendViewer application. This activity usually indicates the primary activity that the system application launcher uses to start the user interface。 however, the specifc activity chosen on launch is marked by meta information in the manifest. In the FriendTracker application, for example, the FriendTrackerControl activity is marked as the main user interface entry point. In this case, we reserved the name “FriendTracker” for the service ponent performing the core application FriendTracker application contains each of the four ponent types. The FriendTracker service polls an external service to discover friends’ locations. In our example code, we generate locaFriendTracker application BootReceiver Broadcast receiver ActivityFriendTracker FriendProvider Content provider Service FriendTracker control FriendViewer application FriendReceiver Broadcast receiver Activity FriendTracker Activity FriendViewer Figure 1. Example Android application. The FriendTracker and FriendViewer applications consist of multiple ponents of different types, each of which provides a different set of functionalities. Activities provide a user interface, services execute background processing, 27 content providers are data storage facilities, and broadcast receivers act as mailboxes for messages from other randomly, but extending the ponent to interface with a Web service is straightforward. The FriendProvider content provider maintains the most recent geographic coordinates for friends, the FriendTrackerControl activity defnes a user interface for starting and stopping the tracking functionality, and the BootReceiver broadcast receiver obtains a notifcation from the system once it boots (the application uses this to utomatically start the FriendTracker service).The FriendViewer application bis primarily concerned with showing information about friends’ locations. The FriendViewer activity lists all friends and their geographic coordinates, and the FriendMap activity displays them on a map. The FriendReceiver broadcast receiver waits for messages that indicate the physical phone is near a particular friend and displays a message to the user upon such an event. Although we could have placed these ponents within the FriendTracker application, we created a separate application to demonstrate crossapplication munication. dditionally, by separating the tracking and user interface logic, we can c