【導(dǎo)讀】站在高層來說，以用戶為中心來設(shè)。計良好的交互程序，對于應(yīng)用設(shè)計者或是開發(fā)者來說是非常重要的。務(wù)，activity重用，意圖和activity棧。這篇文檔也著重討論了一些設(shè)計決策，針對如。如果你使用Android手機試驗時，可能未提供本文檔中的某些例子。它們被捆綁在一起并。存放進.apk文件中，這就是Android應(yīng)用程序。Android中有著豐富的應(yīng)用程序，比如郵。Activity是Android應(yīng)用程序的主要組成部分，activity可以是你自己創(chuàng)建的，當然，它們都是在運行時綁定上的，以便于應(yīng)用程序擴展。當使用Android手機時，用戶在屏幕上一個接一個地滑動或是點擊圖標啟動activity，activity后面有activity，task后。Activity可以處理特定的數(shù)據(jù)類型和接受一相關(guān)的動作。正因為這個獨立性，activity可以以不同的方式被其它的activity. Activity是Android應(yīng)用中最為突出的組件，其余組件分別為：service、content. 那么其他activity都屬于當前任務(wù)的一部分。再次注意的是，這些activity可是任意應(yīng)。動activity一般有這么幾種方式，應(yīng)用程序發(fā)射器、桌面快捷方式、最近任務(wù)切換器。

　　

【正文】 hoice to the user. To give a specific example, Gallery enables a user to view and share pictures. When the user chooses Share from the menus, the system pares the Share request (an Intent object) to available activities (by looking at their intent filters) and displays choices to share. In this case, it matches Email, Gmail, Messaging and Picasa. If your activity can send a picture or upload it to a website, all it needs to do is make itself available for sharing (by setting its intent filter). Another activity can start your activity either with or without expecting a result back. o Start an activity expecting a result This approach is closed loop, where the activity being started must either return a valid result or be canceled. In the previous examples of sharing a photo from a Gallery, the user ends up back in the Gallery after pleting the send or upload procedure. These are examples of starting an activity external to the Gallery. (Such an activity is started with startActivityForResult().) o Start an activity not expecting a result This approach is openended. An example is choosing an house address in an message (or web page), where the Maps activity is started to map the location. No result from maps is expected to be returned to the message。 the user can return by pressing the BACK key. (Such an activity is started with startActivity().) Launch two or more main activities within a single application from separate icon at Home As we have defined it, all the code in a single .apk file is considered to be one application. You can write an application that contains two main activities launchable from Home. The application is a good example of an application that contains two independent main activities — Camera and Camcorder — that each have their own icons in application launcher, that can be launched separately, and so appear to the user as separate applications. They both share use of the same lens, and both store their images (still and moving) in the Gallery. In order for your application to contain two different, independent activities launchable from Home, you must define them to be associated with different tasks. (This means 東北大學 東軟信息學院畢業(yè)設(shè)計（論文） 譯文 13 setting the main activity for each task to a different task affinity — in this case, and .) Contacts and Dialer are another example of two main activities launchable from Home that reside in the same application. Making your application available as a widget An application can also display a portion of itself as an app widget, embedded in Home or another application, and receive periodic updates. Allow your activities to be added to the current task If your activities can be started from another application, allow them to be added to the current task (or an existing task it has an affinity with). Having activities added to a task enables the user to switch between a task that contains your activities and other tasks. Exceptions are your activities that have only one instance. For this behavior, your activity should have a launch mode of standard or singleTop rather than singleTask or singleInstance. These modes also enable multiple instances of your activity to be run. Use the notification system — don39。t use dialog boxes in place of notifications If your background service needs to notify a user, use the standard notification system — don39。t use a dialog or toast to notify them. A dialog or toast would immediately take focus and interrupt the user, taking focus away from what they were doing: the user could be in the middle of typing text the moment the dialog appears and could accidentally act on the dialog. Users are used to dealing with notifications and can pull down the notification shade at their convenience to respond to your message. Don39。t take over the BACK key unless you absolutely need to As a user navigates from one activity to the next, the system adds them to the activity stack. This forms a navigation history that is accessible with the BACK key. Most activities are relatively limited in scope, with just one set of data, such as viewing a list of contacts, posing an , or taking a photo. But what if your application is one big activity with several pages of content and needs finergrained control of the BACK key? Examples of such Google applications are the Browser, which can have several web pages open at once, and Maps, which can have several layers of geographic data to switch between. Both of these applications take control of the BACK key and maintain their own internal back stacks that operate only when these applications have focus. For example, Maps uses layers to present different information on a map to the user: displaying the location of a search result, displaying locations of friends, and 東北大學 東軟信息學院畢業(yè)設(shè)計（論文） 譯文 14 displaying a line for a street path providing direction between points. Maps stores these layers in its own history so the BACK key can return to a previous layer. Similarly, Browser uses browser windows to present different web pages to the user. Each window has its own navigation history, equivalent to tabs in a browser in a desktop operating system (such as Windows, Macintosh or Linux). For example, if you did a Google web search in one window of the Android Browser, clicking on a link in the search results displays a web page in that same window, and then pressing BACK would to the search results page. Pressing BACK goes to a previous window only if the current window was launched from that previous window. If the user keeps pressing back, they will eventually leave the browser activity and return Home.