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當沒有可用的互聯網連接時，我的應用程序崩潰，但通過WiFi或數據連接連接到互聯網時工作正常。當互聯網關閉時，Android應用程序崩潰
有人能告訴我如何添加一個異常以避免崩潰？
下面是代碼：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.List;
import org.json.JSONObject;
import android.app.Dialog;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MainActivity extends FragmentActivity implements LocationListener{
GoogleMap mGoogleMap;
Spinner mSprPlaceType;
String[] mPlaceType=null;
String[] mPlaceTypeName=null;
double mLatitude=0;
double mLongitude=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Array of place types
mPlaceType = getResources().getStringArray(R.array.place_type);
// Array of place type names
mPlaceTypeName = getResources().getStringArray(R.array.place_type_name);
// Creating an array adapter with an array of Place types
// to populate the spinner
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, mPlaceTypeName);
// Getting reference to the Spinner
mSprPlaceType = (Spinner) findViewById(R.id.spr_place_type);
// Setting adapter on Spinner to set place types
mSprPlaceType.setAdapter(adapter);
Button btnFind;
// Getting reference to Find Button
btnFind = (Button) findViewById(R.id.btn_find);
// Getting Google Play availability status
int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());
if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available
int requestCode = 10;
Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
dialog.show();
}else { // Google Play Services are available
// Getting reference to the SupportMapFragment
SupportMapFragment fragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
// Getting Google Map
mGoogleMap = fragment.getMap();
// Enabling MyLocation in Google Map
mGoogleMap.setMyLocationEnabled(true);
// Getting LocationManager object from System Service LOCATION_SERVICE
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
// Creating a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Getting the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Getting Current Location From GPS
Location location = locationManager.getLastKnownLocation(provider);
if(location!=null){
onLocationChanged(location);
}
locationManager.requestLocationUpdates(provider, 20000, 0, this);
// Setting click event lister for the find button
btnFind.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
int selectedPosition = mSprPlaceType.getSelectedItemPosition();
String type = mPlaceType[selectedPosition];
StringBuilder sb = new StringBuilder("https://maps.googleapis.com/maps/api/place/nearbysearch/json?");
sb.append("location="+mLatitude+","+mLongitude);
sb.append("&radius=5000");
sb.append("&types="+type);
sb.append("&sensor=true");
sb.append("&key=AIzaSyAuoLlC1LnlbneuG8cZEo3NCFHEstk0vpE");
// Creating a new non-ui thread task to download Google place json data
PlacesTask placesTask = new PlacesTask();
// Invokes the "doInBackground()" method of the class PlaceTask
placesTask.execute(sb.toString());
}
});
}
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while((line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
urlConnection.disconnect();
}
return data;
}
/** A class, to download Google Places */
private class PlacesTask extends AsyncTask<String, Integer, String>{
String data = null;
// Invoked by execute() method of this object
@Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
// Executed after the complete execution of doInBackground() method
@Override
protected void onPostExecute(String result){
ParserTask parserTask = new ParserTask();
// Start parsing the Google places in JSON format
// Invokes the "doInBackground()" method of the class ParseTask
parserTask.execute(result);
}
}
/** A class to parse the Google Places in JSON format */
private class ParserTask extends AsyncTask<String, Integer, List<HashMap<String,String>>>{
JSONObject jObject;
// Invoked by execute() method of this object
@Override
protected List<HashMap<String,String>> doInBackground(String... jsonData) {
List<HashMap<String, String>> places = null;
PlaceJSONParser placeJsonParser = new PlaceJSONParser();
try{
jObject = new JSONObject(jsonData[0]);
/** Getting the parsed data as a List construct */
places = placeJsonParser.parse(jObject);
}catch(Exception e){
Log.d("Exception",e.toString());
}
return places;
}
// Executed after the complete execution of doInBackground() method
@Override
protected void onPostExecute(List<HashMap<String,String>> list){
// Clears all the existing markers
mGoogleMap.clear();
for(int i=0;i<list.size();i++){
// Creating a marker
MarkerOptions markerOptions = new MarkerOptions();
// Getting a place from the places list
HashMap<String, String> hmPlace = list.get(i);
// Getting latitude of the place
double lat = Double.parseDouble(hmPlace.get("lat"));
// Getting longitude of the place
double lng = Double.parseDouble(hmPlace.get("lng"));
// Getting name
String name = hmPlace.get("place_name");
// Getting vicinity
String vicinity = hmPlace.get("vicinity");
LatLng latLng = new LatLng(lat, lng);
// Setting the position for the marker
markerOptions.position(latLng);
// Setting the title for the marker.
//This will be displayed on taping the marker
markerOptions.title(name + " : " + vicinity);
// Placing a marker on the touched position
mGoogleMap.addMarker(markerOptions);
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
@Override
public void onLocationChanged(Location location) {
mLatitude = location.getLatitude();
mLongitude = location.getLongitude();
LatLng latLng = new LatLng(mLatitude, mLongitude);
mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(12));
}
@Override
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
}
下面是logcat的日誌：
11-27 21:48:26.715: E/ActivityManager(242): ---wwd->startActivityLocked(14),packagename=in.wptrafficanalyzer.locationnearby,className=in.wptrafficanalyzer.locationnearby.MainActivity
11-27 21:48:26.831: E/FaceService(17156): -1--wwd->onReceive-action=com.android.tdc.stoppreview,packageName=in.wptrafficanalyzer.locationnearby,className=in.wptrafficanalyzer.locationnearby.MainActivity
11-27 21:48:26.912: E/FaceService(17156): -1--wwd->onReceive-action=com.android.tdc.stoppreview,packageName=in.wptrafficanalyzer.locationnearby,className=in.wptrafficanalyzer.locationnearby.MainActivity
11-27 21:48:27.633: E/samfan(17143): gestureActive=0
11-27 21:48:27.643: E/samfan(17143): gestureGallery=0
11-27 21:48:28.026: E/AndroidRuntime(17236): FATAL EXCEPTION: main
11-27 21:48:28.026: E/AndroidRuntime(17236): java.lang.RuntimeException: Unable to start activity ComponentInfo{in.wptrafficanalyzer.locationnearby/in.wptrafficanalyzer.locationnearby.MainActivity}: java.lang.SecurityException: ConnectivityService: Neither user 10089 nor current process has android.permission.ACCESS_NETWORK_STATE.
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2077)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2104)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.ActivityThread.access$600(ActivityThread.java:134)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.os.Handler.dispatchMessage(Handler.java:99)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.os.Looper.loop(Looper.java:154)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.ActivityThread.main(ActivityThread.java:4624)
11-27 21:48:28.026: E/AndroidRuntime(17236): at java.lang.reflect.Method.invokeNative(Native Method)
11-27 21:48:28.026: E/AndroidRuntime(17236): at java.lang.reflect.Method.invoke(Method.java:511)
11-27 21:48:28.026: E/AndroidRuntime(17236): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
11-27 21:48:28.026: E/AndroidRuntime(17236): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
11-27 21:48:28.026: E/AndroidRuntime(17236): at dalvik.system.NativeStart.main(Native Method)
11-27 21:48:28.026: E/AndroidRuntime(17236): Caused by: java.lang.SecurityException: ConnectivityService: Neither user 10089 nor current process has android.permission.ACCESS_NETWORK_STATE.
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.os.Parcel.readException(Parcel.java:1327)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.os.Parcel.readException(Parcel.java:1281)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.net.IConnectivityManager$Stub$Proxy.getActiveNetworkInfo(IConnectivityManager.java:663)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.net.ConnectivityManager.getActiveNetworkInfo(ConnectivityManager.java:420)
11-27 21:48:28.026: E/AndroidRuntime(17236): at in.wptrafficanalyzer.locationnearby.MainActivity.onCreate(MainActivity.java:66)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.Activity.performCreate(Activity.java:4546)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1050)
11-27 21:48:28.026: E/AndroidRuntime(17236): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2041)
11-27 21:48:28.026: E/AndroidRuntime(17236): ... 11 more
11-27 21:48:28.599: E/Launcher(8336): Error finding setting, default accessibility to not found: accessibility_enabled
11-27 21:48:28.603: E/Activity(8336): zbx The class is: com.android.phone
11-27 21:48:28.604: E/FaceService(17156): -1--wwd->onReceive-action=com.sec.android.intent.action.HOME_RESUME,packageName=in.wptrafficanalyzer.locationnearby,className=in.wptrafficanalyzer.locationnearby.MainActivity
能否請您發佈錯誤日誌和顯示錯誤的行號？ – JoelFernandes
@JoelFernandes我已經添加了logcat日誌。 – DevCon
你有沒有加入權限'android.permission.ACCESS_NETWORK_STATE'？ – Naddy