我需要帮助，我试图从USGS网站获取世界上不同位置的地震数据并将它们显示在listView上，但是在JSON链接上创建HttpRequest并从JSON链接获取数据后，我的应用程序无法提取数据并使屏幕空白，运行时没有任何崩溃消息。 这是JSON链接＆lt; http://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&orderby=time&minmag=5&limit=10＆gt;
请参阅我的代码以连接和获取数据
package com.example.android.quakereport;
import android.text.TextUtils;
import android.util.Log;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class QueryUtils {
//create tag for the log messages
public static final String LOG_TAG = EarthquakeActivity.class.getName();
//Create a private constructor because no one should ever create a {@link QueryUtils} object.
private QueryUtils() {
}
//Query the USGS data set to return an Earthquake object
public static List<Earthquake> fetchEarthquakeData(String requestUrl){
//create a url from the string url provided
URL url = createUrl(requestUrl);
//make Http request on the url created and receive json response back
String jsonResponse = null;
try{
jsonResponse = makeHttpRequest(url);
Log.e(LOG_TAG, "return Data " + jsonResponse );
}
catch (IOException e){
Log.e(LOG_TAG, "Error Closing input Stream");
}
return extractFeatureFromJSON(jsonResponse);
}
//create a url fro the given url string
private static URL createUrl(String StringUrl){
URL url = null;
try {
url = new URL(StringUrl);
}
catch (MalformedURLException e){
Log.e(LOG_TAG, "Malformed Url", e);
}
return url;
}
//make http request from the url created to return as a json string
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 /* im milliseconds*/);
urlConnection.setConnectTimeout(15000 /*in milliseconds*/);
urlConnection.setRequestMethod("GET");
urlConnection.connect();
//if the connection was successful i.e response code = 200
//then read the input stream and pass the response
if(urlConnection.getResponseCode() == 200){
inputStream = urlConnection.getInputStream();
jsonResponse = readFromStream(inputStream);
}
else{
Log.e(LOG_TAG, "Response Error Code: " + urlConnection.getResponseCode());
}
}
catch (IOException e){
Log.e(LOG_TAG, "Problem Retrieving the earthquake Json results");
}
finally {
if (urlConnection != null){
urlConnection.disconnect();
}
if (inputStream != null){
inputStream.close();
}
}
return jsonResponse;
}
//convert the input stream into a String which has the whole json response
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();
if(line != null){
line = reader.readLine();
output.append(line);
}
}
return output.toString();
}
//Return a list of {@link Earthquake} objects that has been built up from
private static List<Earthquake> extractFeatureFromJSON(String eartquakeJSON) {
//if the json string is empty or null, then return early
if (TextUtils.isEmpty(eartquakeJSON)){
return null;
}
// Create an empty ArrayList that we can start adding earthquakes to
ArrayList<Earthquake> earthquakes = new ArrayList<>();
// Try to parse the SAMPLE_JSON_RESPONSE. 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 the JSON object of the SAMPLE_JSON_RESPONSE
JSONObject EarthquakeObject = new JSONObject(eartquakeJSON);
//get the features JSON array
JSONArray featuresArray = EarthquakeObject.getJSONArray("features");
//loop through the features array
for (int i = 0; i < featuresArray.length(); i++) {
//get the JSON object at position i
JSONObject currentEarthquakeDetails = featuresArray.getJSONObject(i);
//get the JSON properties of the current object
JSONObject properties = currentEarthquakeDetails.getJSONObject("properties");
//get the magnitude of the current earthquate details
double magnitude = properties.getDouble("mag");
//get the location of the current earthquake details
String location = properties.getString("place");
//get the time of the current earthquake details
long time = properties.getLong("time");
Date dateObject = new Date(time);
SimpleDateFormat dateFormater = new SimpleDateFormat("MMM DD, yyyy HH:mm:ss");
String dateToDisplay = dateFormater.format(dateObject);
String url = properties.getString("url");
earthquakes.add(new Earthquake(magnitude, location, dateToDisplay, url));
}
// TODO: Parse the response given by the SAMPLE_JSON_RESPONSE string and
// build up a list of Earthquake objects with the corresponding data.
} 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;
}
}
另见我的主要活动代码
package com.example.android.quakereport;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
public class EarthquakeActivity extends AppCompatActivity {
/**
* Sample JSON response for a USGS query
*/
private static final String SAMPLE_JSON_RESPONSE = "http://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&orderby=time&minmag=5&limit=10";
private EarthquakeAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.earthquake_activity);
// Find a reference to the {@link ListView} in the layout
ListView earthquakeListView = (ListView) findViewById(R.id.list);
final ArrayList<Earthquake> earthquakes = new ArrayList<>();
// Create a new {@link ArrayAdapter} of earthquakes
adapter = new EarthquakeAdapter(this, earthquakes);
// Set the adapter on the {@link ListView}
// so the list can be populated in the user interface
earthquakeListView.setAdapter(adapter);
//set onclick listener to each item on the listView
earthquakeListView.setOnItemClickListener(new AdapterView.OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l){
//Get the current earthquake that was clicked
Earthquake currentEarthquake = earthquakes.get(position);
Intent browse = new Intent(Intent.ACTION_VIEW, Uri.parse(currentEarthquake.getUrl()));
startActivity(browse);
}
});
EarthquakeAsyncTask task = new EarthquakeAsyncTask();
task.execute(SAMPLE_JSON_RESPONSE);
}
private class EarthquakeAsyncTask extends AsyncTask<String, Void, List<Earthquake>> {
@Override
protected List<Earthquake> doInBackground(String... urls) {
//check if the url is empty
if (urls.length < 0 || urls[0] == null){
return null;
}
return QueryUtils.fetchEarthquakeData(urls[0]);
}
@Override
protected void onPostExecute(List<Earthquake> data){
//Clear the adapter of previous earthquake data
adapter.clear();
//if data is null then return empty
if(data != null && !data.isEmpty()){
adapter.addAll(data);
}
}
}
}
还有我的Log Cat
11-02 08：41：15.049 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：15.055 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：15.075 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：15.089 1710-1838 /？ E / UsimAccountType：AAS的[addDataKindEmail]。 11-02 08：41：15.089 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：15.092 1710-1838 /？ E / CsimAccountType：AAS的[addDataKindEmail]。 11-02 08：41：24.008 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：24.021 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：24.027 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：24.029 1710-1838 /？ E / UsimAccountType：AAS的[addDataKindEmail]。 11-02 08：41：24.030 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：41：24.033 1710-1838 /？ E / CsimAccountType：AAS的[addDataKindEmail]。 11-02 08：41：32.988 1665-1665 /？ E / InputEventModelImpl：onStartInput事件中止：com.touchtype.keyboard.c.ag：无法获取提取的文本（类com.touchtype.keyboard.c.ag） 11-02 08：41：33.977 898-898 /？ E / WifiTrafficPoller：ENABLE_TRAFFIC_STATS_POLL false令牌847 11-02 08：41：33.980 30524-30524 /？ E / hostapd：第0行：未知配置项'pno' 11-02 08：41：33.980 898-945 /？ E / WifiStateMachine：无法设置pno，现在想要假false 11-02 08：41：34.309 898-945 /？ E / WifiStateMachine：错误！未处理的消息{when = -2ms what = 131156 target = com.android.internal.util.StateMachine $ SmHandler} 11-02 08：42：26.243 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.249 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.253 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.256 1710-1838 /？ E / UsimAccountType：AAS的[addDataKindEmail]。 11-02 08：42：26.256 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.259 1710-1838 /？ E / CsimAccountType：AAS的[addDataKindEmail]。 11-02 08：42：26.346 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.349 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.353 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.357 1710-1838 /？ E / UsimAccountType：AAS的[addDataKindEmail]。 11-02 08：42：26.357 1710-1838 /？ E / MPlugin：不支持的类：com.mediatek.common.telephony.IOnlyOwnerSimSupport 11-02 08：42：26.360 1710-1838 /？ E / CsimAccountType：AAS的[addDataKindEmail]。 11-02 08：42：26.363 898-1757 /？ E / Sensors：handleToDriver句柄（0） 11-02 08：42：26.369 898-1757 /？ E / Sensors：handleToDriver句柄（0） 11-02 08：42：26.382 898-1757 /？ E / Sensors：新的setDelay句柄（0），ns（200000000）m，错误（0），索引（2）