检索地震 JSON 结果时出现问题？

Question

Greeting! After I removed hardcoded JSON data and moved to request data from the URL. I am having an exception error. The code is pretty much the same as the final official git but I am getting the errors.

The code that I am extracting data from JSON is:

 private static final String USGS_REQUEST_URL =
            "http://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&orderby=time&minmag=5&limit=10";

//
  public static List<Earthquake> extractFeaturesfromJson(String earthquakeJSON) {
        /*if the json is null then return earlu*/
        if (TextUtils.isEmpty(earthquakeJSON)) {
            return null;
        }

        // Create an empty ArrayList that we can start adding earthquakes to
        List<Earthquake> earthquakes = new ArrayList<>();

        // Try to parse the JsonResponseString. If there's a problem with the way the JSON
        // is formatted, a JSONException exception object will be thrown.
        // Catch the exception so the app doesn't crash, and print the error message to the logs.
        try {
            // create an object form jsonString
            JSONObject root = new JSONObject(earthquakeJSON);
            JSONArray features = root.getJSONArray("features");

            for (int i = 0; i < features.length(); i++) {
                // Get a single earthquake at position i within the list of earthquakes
                JSONObject currentEarthquake = features.getJSONObject(i);
                // For a given earthquake, extract the JSONObject associated with the
                // key called "properties", which represents a list of all properties
                // for that earthquake.
                JSONObject properties = currentEarthquake.getJSONObject("properties");

                double mag = properties.getDouble("mag");
                String location = properties.getString("place");
                long time = properties.getLong("time");

                //extract the value of key url
                String url = properties.getString("url");
                //create new object with magnitude, location ane time and url from json response
                Earthquake earthquake = new Earthquake(mag, location, time, url);
                earthquakes.add(earthquake);


            }


        } catch (JSONException e) {
            // If an error is thrown when executing any of the above statements in the "try" block,
            // catch the exception here, so the app doesn't crash. Print a log message
            // with the message from the exception.
            Log.e("QueryUtils", "Problem parsing the earthquake JSON results", e);
        }

        // Return the list of earthquakes
        return earthquakes;
    }

The logcat shows:

09-26 14:49:23.628 2551-2584/com.example.android.quakereport E/com.example.android.quakereport.QueryUtils: Problem retrieving the earthquake JSON results.

Answer 1

The json data from your url is not formatted correctly. Compare what you are receiving from the url to the hardcoded data.

Answer 2

This method runs on the main UI thread after the background work has been completed. This method receives as input, the return value from the doInBackground() method.

First we clear out the adapter, to get rid of earthquake data from a previous query to USGS.

Then we update the adapter with the new list of earthquakes, which will trigger the ListView to re-populate its list items. But made mistake on populating data to adapter.

        @Override
        protected void onPostExecute(List<Earthquake> data) {
            //clear the adapter of previdous earthquake data
            mAdapter.clear();
            if (data != null && data.isEmpty()) { //====?????shourld be !data.isEmpty())
                mAdapter.addAll(data);
            }
        }

The real problem was onPostExecute method to populate data in mainthread after do in background method.

Answer 3

If you're taking the Udacity android course and encountering this error for the quakereport/DidUfeelIt app then change the URL and try with some other URL your problem will be solved. Eg:- The URL provided by during the course was " http://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&starttime=2012-01-01&endtime=2012-12-01&minmagnitude=6 "

Then I was getting the same error that is "problem parsing the JSON" So I tried different URL: https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/4.5_day.geojson

And it worked..!! Always try to get the latest URL's from the USGS website during the course.

Answer 4

Change your request URL to USGS_REQUEST_URL=" https://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&orderby=time&minmag=6&limit=10 "

The difference is in the use of https instead of http.

According to the API doc of the USGS website this website now uses the HyperText Transfer Protocol Secure (https) https://earthquake.usgs.gov/fdsnws/event/1/

Answer 5

Use Online Json Validator. http://jsonlint.com/ they will validate if the json has problems.