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Android JSON解析示例代码 Android开发技术

Android JSON解析示例代码 Android开发技术

  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。

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);
        }
    }
}

 有关整个每日维基的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。

  

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