我提供了一项服务来更新应用程序，它由广播接收器启动，该接收器从应用程序接收广播并启动系统。
java.lang.NullPointerException 发生。
java.lang.RuntimeException: Unable to instantiate service
com.ggservice.democracy.updateDemocracyService: java.lang.NullPointerException
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2237)
at android.app.ActivityThread.access$1600(ActivityThread.java:123)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1201)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4424)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.content.ContextWrapper.getSystemService(ContextWrapper.java:386)
at android.accounts.AccountManager.get(AccountManager.java:288)
at com.ggservice.democracy.updateDemocracyService.<init>(updateDemocracyService.java:33)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1319)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2234)
服务是这样的：
public class updateDemocracyService extends IntentService{
public updateDemocracyService() {
super("updateDemocracyService");
// TODO Auto-generated constructor stub
}
private pollDataSource datasource;
int mStartMode; // indicates how to behave if the service is killed
IBinder mBinder; // interface for clients that bind
boolean mAllowRebind; // indicates whether onRebind should be used
// url to make request
AccountManager am = AccountManager.get(this); // "this" references the current Context
//cerco un account per identificare l'utente.
Account[] accounts = am.getAccountsByType("com.google");
String nomeaccount = md5(accounts[0].name);
private static String url = "http://lnx.ggservice.com/democracy/domande.php?user=" ;
private static String risposteUrl = "http://lnx.ggservice.com/democracy/domande.php?useranswer=" ;
// JSON Node names
private static final String TAG_DOMANDE = "domande";
private static final String TAG_ID = "idWeb";
private static final String TAG_CATEGORIA = "categoria";
private static final String TAG_TESTODOMANDA = "testoDomanda";
private static final String TAG_QUANTERISPOSTE = "quanteRisposte";
private static final String TAG_TESTORISPOSTA = "testoRisposta";
private static final String TAG_OK = "ok";
// contacts JSONArray
JSONArray domanda = null;
JSONArray rispostescritte = null;
@SuppressWarnings("deprecation")
@Override
protected void onHandleIntent(Intent intent) {
datasource = new pollDataSource(this);
datasource.open();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url + nomeaccount);
try {
// Getting Array of Contacts
domanda = json.getJSONArray(TAG_DOMANDE);
// looping through All Contacts
for(int i = 0; i < domanda.length(); i++){
JSONObject c = domanda.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_ID);
String testoDomanda = c.getString(TAG_TESTODOMANDA);
String categoria = c.getString(TAG_CATEGORIA);
int quanteRisposte = c.getInt(TAG_QUANTERISPOSTE);
datasource.createCategoria(categoria);
//TEOTODO inserimento della categoria, se necessario
//TEOTODO inserimento della domanda
for(int ua = 0; ua < quanteRisposte; ua++){
//TEOTODO inserimento dei testi risposte.
}
//NOTIFICATION
NotificationManager notifManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
Notification note = new Notification(R.drawable.ic_launcher, "Democracy", System.currentTimeMillis());
PendingIntent intent1 = PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), 0);
note.setLatestEventInfo(this, "Nuovi sondaggi", "Ci sono nuovi sondaggi per te!!", intent1);
int NOTIF_ID = 1;
notifManager.notify(NOTIF_ID, note);
//NOTIFICATION
}
} catch (JSONException e) {
// e.printStackTrace();
}
//recupero tutte le risposte dal database, poi per ogni risposta:
//JSONObject json1 = jParser.getJSONFromUrl(risposteUrl + nomeaccount); //+idweb+risposta
// try {
// Getting Array of responses
// rispostescritte = json.getJSONArray(TAG_OK);
// } catch (JSONException e) {}
Intent i= new Intent();
i.setAction("AWESOME_TRIGGER_WORD"); //the name which we will specify in our receiver
i.putExtra("counter",234); PendingIntent pi = PendingIntent.getBroadcast(getApplicationContext(),
1111, i,PendingIntent.FLAG_CANCEL_CURRENT);
//getting current time and add 5 seconds in it
Calendar cal = Calendar.getInstance();
cal.add(Calendar.MINUTE, 10);
//registering our pending intent with alarmmanager
AlarmManager am = (AlarmManager) getSystemService(ALARM_SERVICE);
am.set(AlarmManager.RTC_WAKEUP,cal.getTimeInMillis(), pi);
}
public String md5(String s) {
try {
// Create MD5 Hash
MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
digest.update(s.getBytes());
byte messageDigest[] = digest.digest();
// Create Hex String
StringBuffer hexString = new StringBuffer();
for (int i=0; i<messageDigest.length; i++)
hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
return hexString.toString();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
return "";
}
}
为什么是 java.lang.NullPointerException ？ 这也是触发服务的调用：
public class BootCompletedReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Intent serviceIntent = new Intent(context, updateDemocracyService.class);
context.startService(serviceIntent);
}
}