So I've just downloaded project from udacity course.
(所以我刚刚从udacity课程下载了项目。)
Unfortunately I've received some kinds of error, that I can't fix.. I've already added Internet permision, what else could I do? (不幸的是，我收到了一些我无法解决的错误。.我已经添加了Internet渗透，我还能做什么？)
Here's the code from github https://github.com/udacity/ud843_Soonami
(这是来自github https://github.com/udacity/ud843_Soonami的代码)
And here's the error
(这是错误)
Problem parsing the earthquake JSON results
org.json.JSONException: End of input at character 0
MainActivity
(主要活动)
/**
* Displays information about a single earthquake.
*/
public class MainActivity extends AppCompatActivity {
/** Tag for the log messages */
public static final String LOG_TAG = MainActivity.class.getSimpleName();
/** URL to query the USGS dataset for earthquake information */
private static final String USGS_REQUEST_URL =
"http://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&starttime=2012-01-01&endtime=2012-12-01&minmagnitude=6";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Kick off an {@link AsyncTask} to perform the network request
TsunamiAsyncTask task = new TsunamiAsyncTask();
task.execute();
}
/**
* Update the screen to display information from the given {@link Event}.
*/
private void updateUi(Event earthquake) {
// Display the earthquake title in the UI
TextView titleTextView = (TextView) findViewById(R.id.title);
titleTextView.setText(earthquake.title);
// Display the earthquake date in the UI
TextView dateTextView = (TextView) findViewById(R.id.date);
dateTextView.setText(getDateString(earthquake.time));
// Display whether or not there was a tsunami alert in the UI
TextView tsunamiTextView = (TextView) findViewById(R.id.tsunami_alert);
tsunamiTextView.setText(getTsunamiAlertString(earthquake.tsunamiAlert));
}
/**
* Returns a formatted date and time string for when the earthquake happened.
*/
private String getDateString(long timeInMilliseconds) {
SimpleDateFormat formatter = new SimpleDateFormat("EEE, d MMM yyyy 'at' HH:mm:ss z");
return formatter.format(timeInMilliseconds);
}
/**
* Return the display string for whether or not there was a tsunami alert for an earthquake.
*/
private String getTsunamiAlertString(int tsunamiAlert) {
switch (tsunamiAlert) {
case 0:
return getString(R.string.alert_no);
case 1:
return getString(R.string.alert_yes);
default:
return getString(R.string.alert_not_available);
}
}
/**
* {@link AsyncTask} to perform the network request on a background thread, and then
* update the UI with the first earthquake in the response.
*/
private class TsunamiAsyncTask extends AsyncTask<URL, Void, Event> {
@Override
protected Event doInBackground(URL... urls) {
// Create URL object
URL url = createUrl(USGS_REQUEST_URL);
// Perform HTTP request to the URL and receive a JSON response back
String jsonResponse = "";
try {
jsonResponse = makeHttpRequest(url);
} catch (IOException e) {
// TODO Handle the IOException
}
// Extract relevant fields from the JSON response and create an {@link Event} object
Event earthquake = extractFeatureFromJson(jsonResponse);
// Return the {@link Event} object as the result fo the {@link TsunamiAsyncTask}
return earthquake;
}
/**
* Update the screen with the given earthquake (which was the result of the
* {@link TsunamiAsyncTask}).
*/
@Override
protected void onPostExecute(Event earthquake) {
if (earthquake == null) {
return;
}
updateUi(earthquake);
}
/**
* Returns new URL object from the given string URL.
*/
private URL createUrl(String stringUrl) {
URL url = null;
try {
url = new URL(stringUrl);
} catch (MalformedURLException exception) {
Log.e(LOG_TAG, "Error with creating URL", exception);
return null;
}
return url;
}
/**
* Make an HTTP request to the given URL and return a String as the response.
*/
private String makeHttpRequest(URL url) throws IOException {
String jsonResponse = "";
HttpURLConnection urlConnection = null;
InputStream inputStream = null;
try {
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setReadTimeout(10000 /* milliseconds */);
urlConnection.setConnectTimeout(15000 /* milliseconds */);
urlConnection.connect();
inputStream = urlConnection.getInputStream();
jsonResponse = readFromStream(inputStream);
} catch (IOException e) {
// TODO: Handle the exception
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (inputStream != null) {
// function must handle java.io.IOException here
inputStream.close();
}
}
return jsonResponse;
}
/**
* Convert the {@link InputStream} into a String which contains the
* whole JSON response from the server.
*/
private 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();
}
/**
* Return an {@link Event} object by parsing out information
* about the first earthquake from the input earthquakeJSON string.
*/
private Event extractFeatureFromJson(String earthquakeJSON) {
try {
JSONObject baseJsonResponse = new JSONObject(earthquakeJSON);
JSONArray featureArray = baseJsonResponse.getJSONArray("features");
// If there are results in the features array
if (featureArray.length() > 0) {
// Extract out the first feature (which is an earthquake)
JSONObject firstFeature = featureArray.getJSONObject(0);
JSONObject properties = firstFeature.getJSONObject("properties");
// Extract out the title, time, and tsunami values
String title = properties.getString("title");
long time = properties.getLong("time");
int tsunamiAlert = properties.getInt("tsunami");
// Create a new {@link Event} object
return new Event(title, time, tsunamiAlert);
}
} catch (JSONException e) {
Log.e(LOG_TAG, "Problem parsing the earthquake JSON results", e);
}
return null;
}
}
}
Event (pojo)
(活动（pojo）)
public class Event {
/** Title of the earthquake event */
public final String title;
/** Time that the earthquake happened (in milliseconds) */
public final long time;
/** Whether or not a tsunami alert was issued (1 if it was issued, 0 if no alert was issued) */
public final int tsunamiAlert;
/**
* Constructs a new {@link Event}.
*
* @param eventTitle is the title of the earthquake event
* @param eventTime is the time the earhtquake happened
* @param eventTsunamiAlert is whether or not a tsunami alert was issued
*/
public Event(String eventTitle, long eventTime, int eventTsunamiAlert) {
title = eventTitle;
time = eventTime;
tsunamiAlert = eventTsunamiAlert;
}
}
JSON response
(JSON回应)
{
"type": "FeatureCollection",
"metadata": {
"generated": 1575220865000,
"url": "https://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&starttime=2012-01-01&endtime=2012-12-01&minmagnitude=6",
"title": "USGS Earthquakes",
"status": 200,
"api": "1.8.1",
"count": 122
},
"features": [
{
"type": "Feature",
"properties": {
"mag": 6.7999999999999998,
"place": "Izu Islands, Japan region",
"time": 1325395675980,
"updated": 1435683543922,
"tz": null,
"url": "https://earthquake.usgs.gov/earthquakes/eventpage/usp000jcws",
"detail": "https://earthquake.usgs.gov/fdsnws/event/1/query?eventid=usp000jcws&format=geojson",
"felt": 300,
"cdi": 5.0999999999999996,
"mmi": null,
"alert": null,
"status": "reviewed",
"tsunami": 0,
"sig": 864,
"net": "us",
"code": "p000jcws",
"ids": ",usp000jcws,usc0007fbh,choy20120101052756,duputel201201010527a,",
"sources": ",us,us,choy,duputel,",
"types": ",associate,dyfi,focal-mechanism,impact-text,moment-tensor,origin,phase-data,",
"nst": 628,
"dmin": null,
"rms": 0.83999999999999997,
"gap": 10.800000000000001,
"magType": "mww",
"type": "earthquake",
"title": "M 6.8 - Izu Islands, Japan region"
},
"geometry": {
"type": "Point",
"coordinates": [
138.072,
31.456,
365.30000000000001
]
},
"id": "usp000jcws"
}
],
"bbox": [
-178.295,
-60.948,
6.3,
178.52,
72.96,
586.9
]
}
ask by Aws translate from so 
