android應用架構(gòu)外文翻譯

1、<p>　　Android Application Architecture</p><p>　　author：Lars Vogel</p><p>　　1、AndroidManifest.xml </p><p>　　The components and settings of an Android application are described i

2、n the file AndroidManifest.xml. For example all Activities and Services of the application must be declared in this file. </p><p>　　It must also contain the required permissions for the application. For exam

3、ple if the application requires network access it must be specified here.</p><p>　　<?xml version="1.0" encoding="utf-8"?></p><p>　　<manifest xmlns:android="http

4、://schemas.android.com/apk/res/android"</p><p>　　package="de.vogella.android.temperature"</p><p>　　android:versionCode="1"</p><p>　　android:versionName=&quo

5、t;1.0"></p><p>　　<application android:icon="@drawable/icon" android:label="@string/app_name"></p><p>　　<activity android:name=".Convert"</p>

6、<p>　　android:label="@string/app_name"></p><p>　　<intent-filter></p><p>　　<action android:name="android.intent.action.MAIN" /></p><p>　　<

7、category android:name="android.intent.category.LAUNCHER" /></p><p>　　</intent-filter></p><p>　　</activity></p><p>　　</application></p><p>

8、;　　<uses-sdk android:minSdkVersion="9" /></p><p>　　</manifest></p><p>　　The package attribute defines the base package for the Java objects referred to in this file. If a J

9、ava object lies within a different package, it must be declared with the full qualified package name. </p><p>　　Google Play requires that every Android application uses its own unique package. Therefore it i

10、s a good habit to use your reverse domain name as package name. This will avoid collisions with other Android applications. </p><p>　　android:versionName and android:versionCode specify the version of your a

11、pplication. versionName is what the user sees and can be any String. </p><p>　　versionCode must be an integer. The Android Market determine based on the versionCode, if it should perform an update of the app

12、lications for the existing installations. You typically start with "1" and increase this value by one, if you roll-out a new version of your application. </p><p>　　The tag <activity> defines

13、an Activity, in this example pointing to the Convert class in the de.vogella.android.temperature package. An intent filter is registered for this class which defines that this Activity is started once the application sta

14、rts (action android:name="android.intent.action.MAIN"). The category definition category android:name="android.intent.category.LAUNCHER" defines that this application is added to the application dire

15、ctory on the Android device. </p><p>　　The @string/app_name value refers to resource files which contain the actual value of the application name. The usage of resource file makes it easy to provide differen

16、t resources, e.g. strings, colors, icons, for different devices and makes it easy to translate applications.</p><p>　　The "uses-sdk" part of the "AndroidManifest.xml" file defines the min

17、imal SDK version for which your application is valid. This will prevent your application being installed on devices with older SDK versions. </p><p>　　2、R.java and Resources </p><p>　　The "

18、 gen " directory in an Android project contains generated values. R.java is a generated class which contains references to certain resources of the project. </p><p>　　These resources must be defined in

19、the "res" directory and can be XML files, icons or pictures. You can for example define values, menus, layouts or animations via XML files. </p><p>　　If you create a new resource, the corresponding

20、 reference is automatically created in R.java via the Eclipse ADT tools. These references are static int values and define ID's for the resources. </p><p>　　The Android system provides methods to access

21、the corresponding resource via these ID's. </p><p>　　For example to access a String with the R.string.yourString ID, you would use the getString(R.string.yourString)) method. </p><p>　　R.jav

22、a is automatically created by the Eclipse development environment, manual changes are not necessary and will be overridden by the tooling. </p><p><b>　　3、Assets </b></p><p>　　While t

23、he res directory contains structured values which are known to the Android platform, the assets directory can be used to store any kind of data. You access this data via the AssetsManager which you can access the getAsse

24、ts() method. </p><p>　　AssetsManager allows to read an assets as InputStream with the open() method.</p><p>　　// Get the AssetManager</p><p>　　AssetManager manager = getAssets();<

25、;/p><p>　　// Read a Bitmap from Assets</p><p><b>　　try {</b></p><p>　　InputStream open = manager.open("logo.png");</p><p>　　Bitmap bitmap = BitmapFac

26、tory.decodeStream(open);</p><p>　　// Assign the bitmap to an ImageView in this layout</p><p>　　ImageView view = (ImageView) findViewById(R.id.imageView1);</p><p>　　view.setImageBitm

27、ap(bitmap);</p><p>　　} catch (IOException e) {</p><p>　　e.printStackTrace();</p><p><b>　　}</b></p><p>　　4、Activities and Layouts </p><p>　　The

28、user interface for Activities is defined via layouts. The layout defines the included Views (widgets) and their properties. </p><p>　　A layout can be defined via Java code or via XML. In most cases the layo

29、ut is defined as an XML file. </p><p>　　XML based layouts are defined via a resource file in the /res/layout folder. This file specifies the ViewGroups, Views, their relationship and their attributes for th

30、is specific layout. </p><p>　　If a View needs to be accessed via Java code, you have to give the View a unique ID via the android:id attribute. To assign a new ID to a View use @+id/yourvalue. The following

31、shows an example in which a Button gets the "button1" ID assigned. </p><p><b>　　<Button</b></p><p>　　android:id="@+id/button1"</p><p>　　android:la

32、yout_width="wrap_content"</p><p>　　android:layout_height="wrap_content"</p><p>　　android:text="Show Preferences" ></p><p><b>　　</Button>

33、</b></p><p>　　By conversion this will create and assign a new yourvalue ID to the corresponding View. In your Java code you can later access a View via the method findViewById(R.id.yourvalue). </p&g

34、t;<p>　　Defining layouts via XML is usually the preferred way as this separates the programming logic from the layout definition. It also allows the definition of different layouts for different devices. You can a

35、lso mix both approaches. </p><p>　　5、Reference to resources in XML files </p><p>　　In your XML files, for example your layout files, you can refer to other resources via the @ sign. </p>

36、<p>　　For example, if you want to refer to a color which is defined in a XML resource, you can refer to it via @color/your_id. Or if you defined a "hello" string in an XML resource, you could access it via

37、 @string/hello. </p><p>　　6、Activities and Lifecycle </p><p>　　The Android system controls the lifecycle of your application. At any time the Android system may stop or destroy your application,

38、 e.g. because of an incoming call. The Android system defines a lifecycle for Activities via predefined methods. The most important methods are: </p><p>　　onSaveInstanceState() - called if the Activity is st

39、opped. Used to save data so that the Activity can restore its states if re-started </p><p>　　onPause() - always called if the Activity ends, can be used to release resource or save data </p><p>

40、　　onResume() - called if the Activity is re-started, can be used to initialize fields </p><p>　　7、Configuration Change </p><p>　　An Activity will also be restarted, if a so called "configur

41、ation change" happens. A configuration change happens if an event is triggered which may be relevant for the application. For example if the user changes the orientation of the device (vertically or horizontally). A

42、ndroid assumes that an Activity might want to use different resources for these orientations and restarts the Activity. </p><p>　　In the emulator you can simulate the change of the orientation via CNTR+F11.

43、</p><p>　　You can avoid a restart of your application for certain configuration changes via the configChanges attribute on your Activity definition in your AndroidManifest.xml. The following Activity will no

44、t be restarted in case of orientation changes or position of the physical keyboard (hidden / visible). </p><p>　　<activity android:name=".ProgressTestActivity"</p><p>　　android:labe

45、l="@string/app_name"</p><p>　　android:configChanges="orientation|keyboardHidden|keyboard"></p><p>　　</activity></p><p>　　8、Context </p><p>

46、　　The class android.content.Context provides the connections to the Android system. It is the interface to global information about the application environment. Context also provides access to Android Services, e.g. the

47、Location Service. Activities and Services extend the Context class and can therefore be used as Context.</p><p>　　Android應用架構(gòu)</p><p>　　作者：Lars Vogel(拉爾斯·沃格爾)</p><p>　　1、Android

48、Manifest.xml </p><p>　　一個Android應用程序的組件和設置描述文件中的AndroidManifest.xml。例如，應用程序的所有活動和服務，必須在這個文件中聲明。它也必須包含應用程序所需的權(quán)限。例如，如果應用程序需要訪問網(wǎng)絡，它必須在這里指定。</p><p>　　<?xml version="1.0" encoding="

49、utf-8"?></p><p>　　<manifest xmlns:android="http://schemas.android.com/apk/res/android"</p><p>　　package="de.vogella.android.temperature"</p><p>　　andr

50、oid:versionCode="1"</p><p>　　android:versionName="1.0"></p><p>　　<application android:icon="@drawable/icon" android:label="@string/app_name"><

51、/p><p>　　<activity android:name=".Convert"</p><p>　　android:label="@string/app_name"></p><p>　　<intent-filter></p><p>　　<action android:

52、name="android.intent.action.MAIN" /></p><p>　　<category android:name="android.intent.category.LAUNCHER" /></p><p>　　</intent-filter></p><p>　　<

53、/activity></p><p>　　</application></p><p>　　<uses-sdk android:minSdkVersion="9" /></p><p>　　</manifest></p><p>　　包屬性定義在這個文件中提到的Java 對象的基本

54、包。如果一個Java對象位于不同的包內(nèi)，這必須聲明的完整包名。Google Play 要求，每一個Android應用程序使用其唯一的包。因此，使用反向域名作為包名是推薦方式。這將避免與其他Android應用程序的沖突。Android:versionName和Android:versionCode指定的應用程序版本。 versionName是用戶看到的，可以是任何字符串。versionCode必須為整數(shù)。 Android Market的確

55、定根據(jù)上versionCode，是否應該對現(xiàn)有裝置的應用進行更新。你通常用“1”和增加這個值，如果轉(zhuǎn)出您的應用程序的新版本。</p><p>　　標簽<activity>定義活動，在此指向在de.vogella.android.temperature包Convert類的例子。意圖過濾器注冊這個類的定義，這個活動開始（action android:name="android.intent.a

56、ction.MAIN")自從應用程序開始時。這個類定義類別android:name="android.intent.category.LAUNCHER" 定義該應用程序被添加到Android設備上的應用程序目錄。</p><p>　　@string/ APP_NAME的值是指資源文件，其中包含應用程序的名稱的實際價值。使用資源文件，可以很容易地提供不同的資源，如字符串，顏色，圖標，為

57、不同的設備，可以很容易地轉(zhuǎn)化應用。</p><p>　　“AndroidManifest.xml”文件的“uses-SDK”部分定義了最小的SDK版本，為您的應用程序是有效的。這將防止您的應用程序被安裝在與舊的SDK版本的設備上。</p><p>　　2、R.java文件和資源</p><p>　　在一個Android項目中，“gen”目錄包含生成的值。 R.jav

58、a文件是一個自動生成的類，其中包含引用某些資源的項目。</p><p>　　這些資源必須定義在“res”目錄中，可以是XML文件，圖標或圖片。例如，通過XML文件，您可以定義值，菜單布局或動畫。</p><p>　　如果你創(chuàng)建一個新的資源，相應的參考會自動創(chuàng)建在R.java文件通過Eclipse ADT的工具。這些引用是靜態(tài)的int值和定義ID的資源。</p><p&g

59、t;　　Android系統(tǒng)提供的方法通過這些ID來訪問相應的資源。</p><p>　　例如訪問一個String與R.string.yourString ID，你會使用的getString（R.string.yourString）的方法。</p><p>　　R.java文件是Eclipse開發(fā)環(huán)境自動創(chuàng)建的，手動更改是沒有必要并且將通過工具重寫。</p><p>

60、<b>　　3、Assets </b></p><p>　　眾所周知Android平臺“res”目錄包含結(jié)構(gòu)化的值，這些資源目錄可以用來存儲??任何類型的數(shù)據(jù)。</p><p>　　您可以訪問這些數(shù)據(jù)通過AssetsManager類的getAssets（）方法訪問。</p><p>　　AssetsManager類允許讀取資源輸出流，通過ope

61、n（）方法。</p><p>　　// 得到 AssetManager</p><p>　　AssetManager manager = getAssets();</p><p>　　// 從資源中讀取一張位圖</p><p><b>　　try {</b></p><p>　　InputStre

62、am open = manager.open("logo.png");</p><p>　　Bitmap bitmap = BitmapFactory.decodeStream(open);</p><p>　　// 指定位圖到ImageView</p><p>　　ImageView view = (ImageView) findViewByI

63、d(R.id.imageView1);</p><p>　　view.setImageBitmap(bitmap);</p><p>　　} catch (IOException e) {</p><p>　　e.printStackTrace();</p><p><b>　　}</b></p><

64、p><b>　　4、活動和布局</b></p><p>　　用戶接口是通過布局定義的活動，布局定義所包含的意見（部件）及其屬性。</p><p>　　一個布局可以通過java代碼或是通過XML定義，在大多數(shù)案例中，布局被定義為一個XML文件。</p><p>　　基于XML布局被定義通過一個資源文件在/ RES/ layout文件夾中,這

65、個文件專門為了這個特別的布局的ViewsGroups、Views、他們的關(guān)系和屬性。</p><p>　　如果一個視圖需要通過Java代碼來訪問，你必須通過Android：id屬性得到視圖的唯一ID 。分配一個新的ID來查看使用@+ ID/ 值，下面顯示了一個例子，其中一個按鈕得到“button1”的ID分配。</p><p><b>　　<Button</b>

66、</p><p>　　android:id="@+id/button1"</p><p>　　android:layout_width="wrap_content"</p><p>　　android:layout_height="wrap_content"</p><p>　　an

67、droid:text="Show Preferences" ></p><p><b>　　</Button></b></p><p>　　通過轉(zhuǎn)換，這將創(chuàng)造和分配到相應的視圖的新你的ID值。在Java代碼中，你可以在以后通過查看方法findViewById（R.id.你的ID值）來訪問。</p><p>

68、　　通常是通過XML定義布局的首選方式，因為這分開的布局定義的編程邏輯。它也可以定義為不同的設備使用不同的布局。你也可以混合使用這兩種方法。</p><p>　　5、引用XML文件中的資源</p><p>　　在你的XML文件，例如你的布局文件，你可以參考其他資源，通過@符號。</p><p>　　例如，如果你想引用到這是在XML資源定義的顏色，你可以參考它通過@c

69、olor/ your_id?；蛘呷绻赬ML資源定義一個“hello”字符串，你可以訪問這通過@string/hello。</p><p><b>　　6、活動和生命周期</b></p><p>　　Android系統(tǒng)的控制您的應用程序的生命周期。在任何時候，Android系統(tǒng)可能會停止或破壞您的應用程序，例如因為一個來電。 Android系統(tǒng)的定義為通過預定義的方

70、法，活動的生命周期。最重要的方法是：</p><p>　　onSaveInstanceState（） - 如果停止活動。用于保存數(shù)據(jù)，如果重新啟動該活動可以恢復其狀態(tài) </p><p>　　onPause（）- 如果活動結(jié)束該方法總是被調(diào)用，可以用來釋放資源或保存數(shù)據(jù)</p><p>　　onResume（）- 如果活動被重新啟動,該方法被調(diào)用，可以用來初始化字段&

71、lt;/p><p><b>　　7、配置變化</b></p><p>　　一個活動也將被重新啟動，如果一個所謂的“配置變化”發(fā)生。如果事件被觸發(fā)，這可能是應用程序的相關(guān)配置發(fā)生變化。例如，如果用戶改變設備的方向（縱向或橫向）。 Android的假定活動可能要使用不同的資源，這些方向和重新啟動的活動。</p><p>　　你可以在模擬器模擬通過CNT

72、R+ F11鍵的方向轉(zhuǎn)變。</p><p>　　你能避免某些配置更改，通過configChanges活動的定義在你的AndroidManifest.xml屬性的重新啟動您的應用程序。下列活動將在取向的變化或物理鍵盤的位置（隱藏/可見）的情況下無法重新啟動。</p><p>　　<activity android:name=".ProgressTestActivity&quo

73、t;</p><p>　　android:label="@string/app_name" android:configChanges="orientation|keyboardHidden|keyboard"></p><p>　　</activity></p><p>　　8、上下文（Contex