【導(dǎo)讀】所以說，下一代的平臺(tái)能否提供一個(gè)綜合性強(qiáng)的，可行性高的安全系統(tǒng)是非常重要的。盡管androidSDK自2021年就發(fā)布了，但是第一部android. “G1”手機(jī)卻在2021年10月才誕生。從這時(shí)，安卓才開啟了屬于自己的時(shí)代：T-MobileG1. 的制造商HTC估算G1的發(fā)貨量在2021年底已經(jīng)超過100萬部。的銷量將會(huì)在2021年繼續(xù)保持。在不久的將來其他許多手機(jī)供應(yīng)商都要計(jì)劃支持這個(gè)系統(tǒng)。Android的一個(gè)主要賣點(diǎn)是它能使開發(fā)人員無縫地把在線服務(wù)擴(kuò)展到手機(jī)。提供一個(gè)安全保護(hù)軟件。Android沒有停止為其他平臺(tái)提供應(yīng)用支持：應(yīng)用的執(zhí)行依賴于頂。應(yīng)用部署到Android就必須使用其自定義的用戶界面環(huán)境。此外，安卓通過運(yùn)行應(yīng)用時(shí)將其。進(jìn)行身份驗(yàn)證將各應(yīng)用相互調(diào)用限制在“API協(xié)作”上。我們一些有經(jīng)驗(yàn)的開發(fā)android應(yīng)用的人士透露，設(shè)計(jì)安全應(yīng)用程序并不總是直線前進(jìn)的。Android的安全的復(fù)雜性進(jìn)行講解，并注意一些可能的發(fā)展缺陷以及應(yīng)用程序的安全。接組件接口的服務(wù)。

　　

【正文】 ication with another. For simplicity, we call this interponent munication (ICC). In many ways, ICC is analogous to interprocess munication (IPC) in Unixbased systems. To the developer, ICC functions identically regardless of whether the target is in the same or different application, with the exception of the security rules defined later in this available ICC actions depend on the target ponent. Each ponent type supports interaction specifc to its type for example, when FriendViewer starts FriendMap, the FriendMap activity appears on the screen. Service ponents support start, stop, and bind actions, so the FriendTrackerControl activity, for instance, can start and stop the FriendTracker service that runs in the background. The bind action establishes a connection between ponents, allowing the initiator to execute RPCs defined by the service. In our example, FriendTracker binds to the location manager 15 in the system server. Android beginning XMLBased Layouts While it is technically possible to create and attach widgets to our activity purely through Java code, the way we did in Chapter 4, the more mon approach is to use an XMLbased layout file. Dynamic instantiation of widgets is reserved for more plicated scenarios, where the widgets are not known at piletime (e g., populating a column of radio buttons based on data retrieved off the Inter).With that in mind, it’s time to break out the XML and learn how to lay out Android activities that way. What Is an XMLBased Layout? As the name suggests, an XMLbased layout is a specification of widgets’ relationships to each other—and to their containers (more on this in Chapter7—encoded in XML format. Specifically, Android considers XMLbased layouts to be resources, and as such layout files are stored in the res/layout directory inside your Android project. Each XML file contains a tree of elements specifying a layout of widgets and their containers that make up one view hierarchy. The attributes of the XML elements are properties, describing how a widget should look or how a container should behave. For example, if a Button element has an attribute value of android: text Style = bold,that means that the text appearing on the face of the button should be rendered in a boldface font style. Android’s SDK ships with a tool (aapt) which uses the layouts. This tool should be automatically invoked by your Android tool chain (., Eclipse, Ant’s ).Of particular importance to you as a developer is that aapt generates the source file within your project, allowing you to access layouts and widgets within those layouts directly from your Java code. Use XMLBased Layouts? Most everything you do using XML layout files can be achieved through Java code. For example, you could use setTypeface() to have a button render its text in bold, instead of using a property in an XML layout. Since XML layouts are yet another file for you to keep 16 track of, we need good reasons for using such files. Perhaps the biggest reason is to assist in the creation of tools for view definition, such as a GUI builder in an IDE like Eclipse or a dedicated Android GUI designer like DroidDraw1. Such GUI builders could, in principle, generate Java code instead of XML. The challenge is rereading the UI definition to support edits—that is far simpler if the data is in a structured format like XML than in a programming language. Moreover, keeping generated XML definitions separated from handwritten Java code makes it less likely that somebody’s customcrafted source will get clobbered by accident when the generated bits get regenerated. XML forms a nice middle ground between something that is easy for toolwriters to use and easy for programmers to work with by hand as needed. Also, XML as a GUI definition format is being more monplace. Microsoft’s XAML2, Adobe’s Flex3, and Mozilla’s XUL4 all take a similar approach to that of Android: put layout details in an XML file and put programming smarts in source files (., JavaScript for XUL). Many lesswellknown GUI frameworks, such as ZK5, also use XML for view definition. While “following the herd” is not necessarily the best policy, it does have the advantage of helping to ease the transition into Android from any other XMLcentered view description language. layout file, found in the Layouts/NowRedux sample project. This code sample along with all others in this chapter can be found in the Source Code area of ?xml version= encoding=utf8? Button xmlns:android= android:id=@+id/button android:text= android:layout_width=fill_parent android:layout_height=fill_parent/