我在尝试解析json以获取theguardian新闻时遇到错误，并且说结果没有价值。我是一个noobie，我不确定我的代码的哪一部分是问题所在。每当我运行应用程序时，它都会正常运行，但不会在Feed中显示任何新闻
这是我的代码
public class NewsActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<List<News>> {
private static final String LOG_TAG = NewsActivity.class.getName();
private static final String GUARDIAN_REQUEST_URL =
"http://content.guardianapis.com/search?section=games&order-by=newest&api-key=test";
private static final int NEWS_LOADER_ID = 1;
private NewsAdapter mAdapter;
private TextView mEmptyStateTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.news_activity);
ListView newsListView = (ListView) findViewById(R.id.list);
mEmptyStateTextView = (TextView) findViewById(R.id.empty_view);
newsListView.setEmptyView(mEmptyStateTextView);
mAdapter = new NewsAdapter(this, new ArrayList<News>());
newsListView.setAdapter(mAdapter);
newsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
News currentNews = mAdapter.getItem(position);
Uri newsUri = Uri.parse(currentNews.getUrl());
Intent websiteIntent = new Intent(Intent.ACTION_VIEW, newsUri);
startActivity(websiteIntent);
}
});
ConnectivityManager connMgr = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()) {
LoaderManager loaderManager = getLoaderManager();
loaderManager.initLoader(NEWS_LOADER_ID, null, this);
} else {
View loadingIndicator = findViewById(R.id.loading_indicator);
loadingIndicator.setVisibility(View.GONE);
mEmptyStateTextView.setText(R.string.no_internet_connection);
}
}
@Override
public Loader<List<News>> onCreateLoader(int i, Bundle bundle) {
return new NewsLoader(this, GUARDIAN_REQUEST_URL);
}
@Override
public void onLoadFinished(Loader<List<News>> loader, List<News> news) {
View loadingIndicator = findViewById(R.id.loading_indicator);
loadingIndicator.setVisibility(View.GONE);
mEmptyStateTextView.setText(R.string.no_news);
if (news != null && !news.isEmpty()) {
mAdapter.addAll(news);
updateUi(news);
}
}
private void updateUi(List<News> news) {
}
@Override
public void onLoaderReset(Loader<List<News>> loader) {
mAdapter.clear();
}
}
QueryUtils
public class QueryUtils {
private static final String LOG_TAG = QueryUtils.class.getSimpleName();
private QueryUtils() {
}
public static List<News> fetchNewsData(String requestUrl) {
// Create URL object
URL url = createUrl(requestUrl);
// Perform HTTP request to the URL and receive a JSON response back
String jsonResponse = null;
try {
jsonResponse = makeHttpRequest(url);
} catch (IOException e) {
Log.e(LOG_TAG, "Problem making the HTTP request.", e);
}
List<News> newss = extractResultFromJson(jsonResponse);
return newss;
}
private static URL createUrl(String stringUrl) {
URL url = null;
try {
url = new URL(stringUrl);
} catch (MalformedURLException e) {
Log.e(LOG_TAG, "Problem building the URL ", e);
}
return url;
}
private static String makeHttpRequest(URL url) throws IOException {
String jsonResponse = "";
// If the URL is null, then return early.
if (url == null) {
return jsonResponse;
}
HttpURLConnection urlConnection = null;
InputStream inputStream = null;
try {
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setReadTimeout(10000 /* milliseconds */);
urlConnection.setConnectTimeout(15000 /* milliseconds */);
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// If the request was successful (response code 200),
// then read the input stream and parse the response.
if (urlConnection.getResponseCode() == 200) {
inputStream = urlConnection.getInputStream();
jsonResponse = readFromStream(inputStream);
} else {
Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
}
} catch (IOException e) {
Log.e(LOG_TAG, "Problem retrieving the news JSON results.", e);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (inputStream != null) {
inputStream.close();
}
}
return jsonResponse;
}
private static String readFromStream(InputStream inputStream) throws IOException {
StringBuilder output = new StringBuilder();
if (inputStream != null) {
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
BufferedReader reader = new BufferedReader(inputStreamReader);
String line = reader.readLine();
while (line != null) {
output.append(line);
line = reader.readLine();
}
}
return output.toString();
}
private static List<News> extractResultFromJson(String newsJSON) {
if (TextUtils.isEmpty(newsJSON)) {
return null;
}
List<News> newss = new ArrayList<>();
try {
JSONObject baseJsonResponse = new JSONObject(newsJSON);
JSONArray newsArray = baseJsonResponse.getJSONArray("results");
for (int i = 0; i < newsArray.length(); i++) {
JSONObject currentNews = newsArray.getJSONObject(i);
String title = currentNews.getString("webTitle");
long date = currentNews.getLong("webPublicationDate");
String url = currentNews.getString("webUrl");
News news = new News(title, date, url);
newss.add(news);
}
} catch (JSONException e) {
Log.e("QueryUtils", "Problem parsing the news JSON results", e);
}
return newss;
}
}
适配器
public class NewsAdapter extends ArrayAdapter<News> {
public NewsAdapter(Context context, List<News> news) {
super(context, 0, news);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View listItemView = convertView;
if (listItemView == null) {
listItemView = LayoutInflater.from(getContext()).inflate(
R.layout.news_list_item, parent, false);
}
News currentNews = getItem(position);
TextView titleView = (TextView) listItemView.findViewById(R.id.title);
String title = currentNews.getTitle();
titleView.setText(title);
TextView dateView = (TextView) listItemView.findViewById(R.id.date);
String dateToString = String.valueOf(currentNews.getDate());
String date = dateToString.substring(0, 10);
dateView.setText(date);
return listItemView;
}
} 清单
<?xml version="1.0" encoding="utf-8"?>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".NewsActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
错误消息
E/QueryUtils: Problem parsing the news JSON results
org.json.JSONException: No value for results
at org.json.JSONObject.get(JSONObject.java:392)
at org.json.JSONObject.getJSONArray(JSONObject.java:587)
at com.example.android.newsapp.QueryUtils.extractResultFromJson(QueryUtils.java:117)
at com.example.android.newsapp.QueryUtils.fetchNewsData(QueryUtils.java:40)
at com.example.android.newsapp.NewsLoader.loadInBackground(NewsLoader.java:30)
at com.example.android.newsapp.NewsLoader.loadInBackground(NewsLoader.java:8)
at android.content.AsyncTaskLoader.onLoadInBackground(AsyncTaskLoader.java:315)
at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:69)
at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:64)
at android.os.AsyncTask$2.call(AsyncTask.java:333)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
at java.lang.Thread.run(Thread.java:764)
感谢任何帮助或批评
答案 0 :(得分：0)
首先你需要获得“响应”对象，然后才能在那里寻找“结果”数组
JSONObject baseJsonResponse = new JSONObject(newsJSON).getJSONObject(“response”);
JSONArray newsArray = baseJsonResponse.getJSONArray("results");
仔细看看你的json
答案 1 :(得分：0)
将extractResultFromJson方法替换为以下代码
private static List<News> extractResultFromJson(String newsJSON) {
if (TextUtils.isEmpty(newsJSON)) {
return null;
}
List<News> newss = new ArrayList<>();
try {
JSONObject baseJsonResponse = new JSONObject(newsJSON);
JSONObject mainResponse = baseJsonResponse.getJSONObject("response");
JSONArray newsArray = mainResponse.getJSONArray("results");
for (int i = 0; i < newsArray.length(); i++) {
JSONObject currentNews = newsArray.getJSONObject(i);
String title = currentNews.getString("webTitle");
long date = currentNews.getLong("webPublicationDate");
String url = currentNews.getString("webUrl");
News news = new News(title, date, url);
newss.add(news);
}
} catch (JSONException e) {
Log.e("QueryUtils", "Problem parsing the news JSON results", e);
}
return newss;
}
在获得Feed的结果后，请在适配器上调用notifyDataSetChange（）