Android JSON解析示例代码

有关 HTTP通讯、正则表达式、JSON解析、appWidget开发的一些知识。

public class WordWidget extends AppWidgetProvider { //appWidget @Override public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) { context.startService(new Intent(context, UpdateService.class)); //避免ANR，所以Widget中开了个服务 } public static class UpdateService extends Service { @Override public void onStart(Intent intent, int startId) { // Build the widget update for today RemoteViews updateViews = buildUpdate(this); ComponentName thisWidget = new ComponentName(this, WordWidget.class); AppWidgetManager manager = AppWidgetManager.getInstance(this); manager.updateAppWidget(thisWidget, updateViews); } public RemoteViews buildUpdate(Context context) { // Pick out month names from resources Resources res = context.getResources(); String[] monthNames = res.getStringArray(R.array.month_names); Time today = new Time(); today.setToNow(); String pageName = res.getString(R.string.template_wotd_title, monthNames[today.month], today.monthDay); RemoteViews updateViews = null; String pageContent = ""; try { SimpleWikiHelper.prepareUserAgent(context); pageContent = SimpleWikiHelper.getPageContent(pageName, false); } catch (ApiException e) { Log.e("WordWidget", "Couldn't contact API", e); } catch (ParseException e) { Log.e("WordWidget", "Couldn't parse API response", e); } Pattern pattern = Pattern.compile(SimpleWikiHelper.WORD_OF_DAY_REGEX); //正则表达式处理，有关定义见下面的SimpleWikiHelper类 Matcher matcher = pattern.matcher(pageContent); if (matcher.find()) { updateViews = new RemoteViews(context.getPackageName(), R.layout.widget_word); String wordTitle = matcher.group(1); updateViews.setTextViewText(R.id.word_title, wordTitle); updateViews.setTextViewText(R.id.word_type, matcher.group(2)); updateViews.setTextViewText(R.id.definition, matcher.group(3).trim()); String definePage = res.getString(R.string.template_define_url, Uri.encode(wordTitle)); Intent defineIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(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 PendingIntent pendingIntent = PendingIntent.getActivity(context, 0 /* no requestCode */, defineIntent, 0 /* no flags */); updateViews.setOnClickPendingIntent(R.id.widget, pendingIntent); //单击Widget打开Activity } else { updateViews = new RemoteViews(context.getPackageName(), R.layout.widget_message); CharSequence errorMessage = context.getText(R.string.widget_error); updateViews.setTextViewText(R.id.message, errorMessage); } return updateViews; } @Override public IBinder onBind(Intent intent) { // We don't need to bind to this service return null; } } }

有关网络通讯的实体类，以及一些常量定义如下:

public class SimpleWikiHelper { private static final String TAG = "SimpleWikiHelper"; public static final String WORD_OF_DAY_REGEX = "(?s)//{//{wotd//|(.+?)//|(.+?)//|([^#//|]+).*?//}//}"; private static final String WIKTIONARY_PAGE = "http://en.wiktionary.org/w/api.php?action=query&prop=revisions&titles=%s&" + "rvprop=content&format=json%s"; private static final String WIKTIONARY_EXPAND_TEMPLATES = "&rvexpandtemplates=true"; private static final int HTTP_STATUS_OK = 200; private static byte[] sBuffer = new byte[512]; private static String sUserAgent = null; public static class ApiException extends Exception { public ApiException(String detailMessage, Throwable throwable) { super(detailMessage, throwable); } public ApiException(String detailMessage) { super(detailMessage); } } public static class ParseException extends Exception { public ParseException(String detailMessage, Throwable throwable) { super(detailMessage, throwable); } } public static void prepareUserAgent(Context context) { try { // Read package name and version number from manifest PackageManager manager = context.getPackageManager(); PackageInfo info = manager.getPackageInfo(context.getPackageName(), 0); sUserAgent = String.format(context.getString(R.string.template_user_agent), info.packageName, info.versionName); } catch(NameNotFoundException e) { Log.e(TAG, "Couldn't find package information in PackageManager", e); } } public static String getPageContent(String title, boolean expandTemplates) throws ApiException, ParseException { String encodedTitle = Uri.encode(title); String expandClause = expandTemplates ? WIKTIONARY_EXPAND_TEMPLATES : ""; String content = getUrlContent(String.format(WIKTIONARY_PAGE, encodedTitle, expandClause)); try { JSONObject response = new JSONObject(content); JSONObject query = response.getJSONObject("query"); JSONObject pages = query.getJSONObject("pages"); JSONObject page = pages.getJSONObject((String) pages.keys().next()); JSONArray revisions = page.getJSONArray("revisions"); JSONObject revision = revisions.getJSONObject(0); return revision.getString("*"); } catch (JSONException e) { throw new ParseException("Problem parsing API response", e); } } protected static synchronized String getUrlContent(String url) throws ApiException { if (sUserAgent == null) { throw new ApiException("User-Agent string must be prepared"); } HttpClient client = new DefaultHttpClient(); HttpGet request = new HttpGet(url); request.setHeader("User-Agent", sUserAgent); //设置客户端标识 try { HttpResponse response = client.execute(request); StatusLine status = response.getStatusLine(); if (status.getStatusCode() != HTTP_STATUS_OK) { throw new ApiException("Invalid response from server: " + status.toString()); } HttpEntity entity = response.getEntity(); InputStream inputStream = entity.getContent(); //获取HTTP返回的数据流 ByteArrayOutputStream content = new ByteArrayOutputStream(); int readBytes = 0; while ((readBytes = inputStream.read(sBuffer)) != -1) { content.write(sBuffer, 0, readBytes); //转化为字节数组流 } return new String(content.toByteArray()); //从字节数组构建String } catch (IOException e) { throw new ApiException("Problem communicating with API", e); } } }

 

 

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