android 重要知识点

1、Android开发在线几个重要的知识点2博客分类：Android11.Android JSON解析示例代码如果远程服务器使用json而不是XML提供数据，则使用Android平台中已内置的org.json包可以简化Android平台的JSON解析过程。为了帮助以下Android123开发人员了解HTTP通信、正则表达式、JSON解析和appWidget开发，我们一起分析了此示例：Public class word构件extends appwidgetprovider /app构件Overridepublic void on update(context context、appwidgetman

2、ager appwidgetmanager、Int appWidgetIds) context . start service(new intent(context，update service . class)；/因为您避免了ANR，所以小部件打开了服务public static class updateservice extends service OverridePublic void onstart (intent intent，int startid) /Build the widget update for todayremote views update views=build

3、update(this)；component name this widget=new component name(this，word widget . class)；appwidgetmanager=appwidgetmanager . getinstance(this)；Manager.updateappwidget (this构件，update views)；public remote views build update(context)/pick out month names from resourcesresources RES=context . get resources(

4、)；stringmonthnames=RES . getstring array(r . array . month _ names)；Time today=new Time()；today . setto now()；string pagename=RES . getstring(r . string . template _ wotd _ title，Month names today.month，today . month day)；RemoteViews updateViews=nullString pageContent=Try simplewikihelper . prepare

5、user agent(context)；page content=simple wiki helper . getpage content(page name，false)； catch (ApiException e) log . e(“word构件”，“couldnt contact API”，e)； catch (ParseException e) log . e(“word小部件”，“couldnt parse API响应”，e)；pattern= pile(simple wiki helper . word _ of _ day _ regex)；/正则表达式处

6、理，有关定义，请参阅下面的SimpleWikiHelper类matcher matcher=pattern . matcher(page content)；If (matcher.find ()update views=new remote views(context . get package name()r . layout . widget _ word)；string word title=matcher . group(1)；update views . settextviewtext(r . id . word _ title，word title)；update views .

7、settextviewtext(r . id . word _ type，matcher . group(2)；update views . settextviewtext(r . id . definition，matcher.group (3)。trim()；string define page=RES . getstring(r . string . template _ define _ URL，uri . encode(word title)；intent define intent=new intent(intent . action _ view，uri . parse(defi

8、ne page)；/其中相应的网页打开，因此Uri是http的URL，action是view。这意味着web浏览器打开pending intent pending intent=pending intent . get activity(context、0/* no request code */，define intent，0/* no flags */)；update views . setonclickpendingintent(r . id . widget，pending intent)；/单击小部件打开活动 elseupdate views=new remote views(con

9、text . get package name()r . layout . widget _ message)；char sequence error message=context . get text(r . string . widget _ error)；update views . settextviewtext(r . id . message，error message)；Return updateViewsOverridepublic I binder on bind(intent intent)/web dont need to bind to this serviceRet

10、urn null网络通信的实体类和某些常量定义为：如下所示Public class simplewikihelperprivate static final string tag= simplewikihelper ；public static final string word _ of _ day _ regex=(？S)wotd|(.) |(.) | (# |)。*？ “；private static final string wiktionary _ page=/w/api.php？action=query prop=revisions t

11、itles=% s RV prop=content format=JSON % s ；private static final string wiktionary _ expand _ templates=rvexpandtemplates=true ；private static final int http _ status _ ok=200；private static bytesbuffer=new byte512；private static string suser agent=null；public static class API exception extends excep

12、tion public API exception string detail messageSuper(detailMessage，throw able)；public API exception(string detail message)super(detail message)；public static class pars exception exception public parse exception(string detail message，throwdable throwdle)、Super(detailMessage，throw able)；public static

13、 void prepare user agent(context context)Try /read package name and version number from manifestpackager manager=context . getpackagermanager()；package info=manager . get packaging info(context . get package name()0)；suser agent=string . format(context . getstring(r . string . template _ user _ agen

14、t)，Info.package name，info.version name catch (namenotfoundexception)Log.e (tag， could nt find package information in package manager ，e)；public static string getpage content(string title，boolean expand templates)Throws API exception，parseexceptionstring encoded title=uri . encode(title)；string expand clause=expand templates？wik tionary _ expand _ tem