Android getWritableDatabase throws NullPointerException only sometimes

Question

I have a fragment where a function creates a DatabaseHandler and calls a function within the object:

final DatabaseHandler db = new DatabaseHandler(getActivity());
String teamName = db.getTeamName();

with the DatabaseHandler constructor being:

Context context;

public DatabaseHandler(Context contextPassed) {
    super(contextPassed, DATABASE_NAME, null, DATABASE_VERSION);  
    context = contextPassed;

}

Somewhere inside db.getTeamName() (via another function) I have:

SQLiteDatabase db = this.getWritableDatabase();//exception here!

This works fine 99% of the time. But if the app has been in the background for a while and I resume it, I get a NullPointerException. It's tough to replicate because the app needs to be in the background for ages before this happens. It makes me think of garbage collection? The process is started by a broadcast intent - not sure if this is relevant. I can't really debug it because I cant replicate it - but every morning when I wake up I test it and it crashes. Not a good way to start the day and it's driving me nuts! logcat:

threadid=1: thread exiting with uncaught exception (group=0x400259f8)
 FATAL EXCEPTION: main
 java.lang.RuntimeException: Error receiving broadcast Intent { act=updateSettingsTeamName } in com.gcm.goalpocket.MainActivity$4@4634a608
    at android.app.ActivityThread$PackageInfo$ReceiverDispatcher$Args.run(ActivityThread.java:938)
    at android.os.Handler.handleCallback(Handler.java:587)
    at android.os.Handler.dispatchMessage(Handler.java:92)
    at android.os.Looper.loop(Looper.java:144)
    at android.app.ActivityThread.main(ActivityThread.java:4937)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:521)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
    at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
    at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98)
    at com.gcm.goalpocket.DatabaseHandler.getUserID(DatabaseHandler.java:529)
    at com.gcm.goalpocket.DatabaseHandler.getTeamName(DatabaseHandler.java:563)
    at com.gcm.goalpocket.Settings.setTeamName(Settings.java:310)
    at com.gcm.goalpocket.MainActivity$4.onReceive(MainActivity.java:257)

if you required database for reading then use getReadableDatabse() only call getWritableDatabase(); when you required to write data. — Imtiyaz Khalani, Sep 13 '14 at 10:15
I'll try that now - shame there is no way for me to test until the morning! — Cem, Sep 13 '14 at 10:24

laalto · Accepted Answer · 2014-09-15T15:30:44.553

0

In a broadcast receiver as indicated by the onReceive() in your stacktrace, use the passed-in Context as your context you pass to the helper constructor.

There is no guarantee the activity is alive as a valid Context at the time your broadcast receiver runs.

edited Sep 15 '14 at 15:30

answered Sep 13 '14 at 10:32

laalto

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Thanks Laalto & Imtiyaz - woke up this morning with no error! – Cem Sep 15 '14 at 15:29

Android getWritableDatabase throws NullPointerException only sometimes

1 Answers1