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。
