安卓学习34

今天学习了安卓的一些知识其中主要的是：

Android JSON解析示例代码

来自Google官方的有关Android平台的JSON解析示例，如果远程服务器使用了json而不是xml的数据提供，在Android平台上已经内置的org.json包可以很方便的实现手机客户端的解析处理。下面Android123一起分析下这个例子，帮助Android开发者需要有关HTTP通讯、正则表达式、JSON解析、appWidget开发的一些知识。

[java]view plaincopyprint?

1. public class WordWidget extends AppWidgetProvider { //appWidget

2. @Override

3. public void onUpdate(Context context, AppWidgetManager appWidg

etManager,

 int[] appWidgetIds) {

5. context.startService(new Intent(context, UpdateService.class)); //

避免ANR，所以Widget中开了个服务

6. } public static class UpdateService extends Service {

7. @Override

8. public void onStart(Intent intent, int startId) {

9. // Build the widget update for today

10. RemoteViews updateViews = buildUpdate(this); Compo

nentName thisWidget = new ComponentName(this, WordWidget.class );

11. AppWidgetManager manager = AppWidgetManager.getInstanc

e(this);

12. manager.updateAppWidget(thisWidget, updateViews);

13. } public RemoteViews buildUpdate(Context context) {

14. // Pick out month names from resources

15. Resources res = context.getResources();

16. String[] monthNames = res.getStringArray(R.array.month_nam

es); Time today = new Time();

17. today.setToNow(); String pageName = res.getString(R.s

tring.template_wotd_title,

18. monthNames[today.month], today.monthDay);

19. RemoteViews updateViews = null;

20. String pageContent = ""; try {

21. SimpleWikiHelper.prepareUserAgent(context);

22. pageContent = SimpleWikiHelper.getPageContent(pageNam

e, false);

23. } catch (ApiException e) {

24. Log.e("WordWidget", "Couldn't contact API", e);

25. } catch (ParseException e) {

26. Log.e("WordWidget", "Couldn't parse API response", e);

27. } Pattern pattern = http://www.doczj.com/doc/ca10c5fc6037ee06eff9aef8941ea76e58fa4a08.htmlpile(SimpleWikiHelper.W

ORD_OF_DAY_REGEX); //正则表达式处理，有关定义见下面的

SimpleWikiHelper类

28. Matcher matcher = pattern.matcher(pageContent);

29. if (matcher.find()) {

30. updateViews = new RemoteViews(context.getPackageName

(), http://www.doczj.com/doc/ca10c5fc6037ee06eff9aef8941ea76e58fa4a08.htmlyout.widget_word); String wordTitle = matcher.group(

1);

31. updateViews.setTextViewText(R.id.word_title, wordTitle);

32. updateViews.setTextViewText(R.id.word_type, matcher.grou

p(2));

33. updateViews.setTextViewText(R.id.definition, matcher.group

(3).trim()); String definePage = res.getString(R.string.templat

e_define_url,

34. Uri.encode(wordTitle));

35. Intent defineIntent = new Intent(Intent.ACTION_VIEW, Uri.pa

rse(definePage)); //这里是打开相应的网页，所以Uri是http的url，action 是view即打开web浏览器

36. PendingIntent pendingIntent = PendingIntent.getActivity(cont

ext,

37. 0 /* no requestCode */, defineIntent, 0 /* no flags */);

38. updateViews.setOnClickPendingIntent(R.id.widget, pendingI

ntent); //单击Widget打开Activity } else {

39. updateViews = new RemoteViews(context.getPackageName

(), http://www.doczj.com/doc/ca10c5fc6037ee06eff9aef8941ea76e58fa4a08.htmlyout.widget_message);

40. CharSequence errorMessage = context.getText(R.string.wid

get_error);

41. updateViews.setTextViewText(R.id.message, errorMessage)

;

42. }

43. return updateViews;

44. } @Override

45. public IBinder onBind(Intent intent) {

46. // We don't need to bind to this service

47. return null;

48. }

49. }

50. }有关网络通讯的实体类，以及一些常量定义如

下: public class SimpleWikiHelper {

51. private static final String TAG = "SimpleWikiHelper"; public static fi

nal String WORD_OF_DAY_REGEX =

52. "(?s)\{\{wotd\|(.+?)\|(.+?)\|([^#\|]+).*?\}\}"; private static fin

al String WIKTIONARY_PAGE =

53. "http://www.doczj.com/doc/ca10c5fc6037ee06eff9aef8941ea76e58fa4a08.html/w/api.php?action=query&prop=revision

s&titles=%s&" +

54. "rvprop=content&format=json%s"; private static final String

WIKTIONARY_EXPAND_TEMPLATES =

55. "&rvexpandtemplates=true"; private static final int HTTP_ST

ATUS_OK = 200; private static byte[] sBuffer = new byte[512]; pri vate static String sUserAgent = null; public static class ApiExceptio n extends Exception {

56. public ApiException(String detailMessage, Throwable throwable) {

57. super(detailMessage, throwable);

58. } public ApiException(String detailMessage) {

59. super(detailMessage);

60. }

61. } public static class ParseException extends Exception {

62. public ParseException(String detailMessage, Throwable throwabl

e) {

63. super(detailMessage, throwable);

64. }

65. } public static void prepareUserAgent(Context context) {

66. try {

67. // Read package name and version number from manifest

68. PackageManager manager = context.getPackageManager();

69. PackageInfo info = manager.getPackageInfo(context.getPacka

geName(), 0);

70. sUserAgent = String.format(context.getString(R.string.template

_user_agent),

71. info.packageName, info.versionName); } catch(Name

NotFoundException e) {

72. Log.e(TAG, "Couldn't find package information in PackageMan

ager", e);

73. }

74. } public static String getPageContent(String title, boolean expandT

emplates)

75. throws ApiException, ParseException {

76. String encodedTitle = Uri.encode(title);

77. String expandClause = expandTemplates ? WIKTIONARY_EXPA

ND_TEMPLATES : ""; String content = getUrlContent(String.form at(WIKTIONARY_PAGE, encodedTitle, expandClause));

78. try {

79. JSONObject response = new JSONObject(content);

80. JSONObject query = response.getJSONObject("query");

81. JSONObject pages = query.getJSONObject("pages");

82. JSONObject page = pages.getJSONObject((String) pages.keys

().next());

83. JSONArray revisions = page.getJSONArray("revisions");

84. JSONObject revision = revisions.getJSONObject(0);

85. return revision.getString("*");

86. } catch (JSONException e) {

87. throw new ParseException("Problem parsing API response", e);

88. }

89. } protected static synchronized String getUrlContent(String url) thr

ows ApiException {

90. if (sUserAgent == null) {

91. throw new ApiException("User-Agent string must be prepared")

;

92. } HttpClient client = new DefaultHttpClient();

93. HttpGet request = new HttpGet(url);

94. request.setHeader("User-Agent", sUserAgent); //设置客户端标

识 try {

95. HttpResponse response = client.execute(request); Statu

sLine status = response.getStatusLine();

96. if (status.getStatusCode() != HTTP_STATUS_OK) {

97. throw new ApiException("Invalid response from server: " +

98. status.toString());

99. } HttpEntity entity = response.getEntity();

100. InputStream inputStream = entity.getContent(); //获取

HTTP返回的数据

流 ByteArrayOutputStream content = new ByteArrayOutputStre

am(); int readBytes = 0;

101. while ((readBytes = inputStream.read(sBuffer)) != -1) {

102. content.write(sBuffer, 0, readBytes); //转化为字节数组流

103. } return new String(content.toByteArray()); //从字节数组构建String

104. } catch (IOException e) {

105. throw new ApiException("Problem communicating with API ", e);

106. }

107. }

108. }

关整个每日维基的widget例子比较简单，主要是帮助大家积累常用代码，了解Android平台JSON的处理方式，毕竟很多Server还是Java的。