On Wednesday, October 30, 2013 7:44:17 PM UTC+2, Nobu Games wrote: > > I quickly peeked into the source code and well, this is the way how it is > programmed. When an exception occurs while the preferences data file gets > read, SharedPreferences sets internally an empty map so you start from > scratch. I even dug a bit deeper. The XML serializer just ignores NULL keys > and creates XML output that cannot be properly read anymore through the map > deserialization method which seems to expect an existing key value. > My question is really why was it allowed to insert a null key in the first place - why not throw a NPE immediately (and say so in the docs) ? If you read my links (point 3 here<http://stackoverflow.com/questions/19610569/android-sharedpreferences-null-keys-values-and-sets-corner-cases>) you will see that null keys are perfectly valid : - they fail only on loading the prefs - taking down everything with them They should either fix deserialization or prohibit null keys
> > As for why it has been programmed like that... I think the reasoning may > be that preferences are not deemed to be of so much importance that it > should make the app crash in case of failure. This error state is silently > discarded and you start over with the defaults. I think that's a reasonable > approach since any app should be able to start over with empty preferences. > Not* at all* - Shared Preferences is a documented<http://developer.android.com/guide/topics/data/data-storage.html#pref>persistence mechanism - it is as reasonable as deleting a database without even saying so > > In this particular case you may have discovered a tiny bug you may want to > report. But to be honest, using null keys is a pretty unusual thing to do. > Not so (either by mistake or not). See the discussions in the SO. Some more I suspect they *may *have to do with null keys : sharedpreferences - Android - Shared Preferences are lost sometimes - Stack Overflow http://stackoverflow.com/questions/7943573/android-shared-preferences-are-lost-sometimes android - Shared Preferences get lost after shutting down device or killing the app - Stack Overflow http://stackoverflow.com/questions/9803838/shared-preferences-get-lost-after-shutting-down-device-or-killing-the-app#comment12495021_9803838 > > On Wednesday, October 30, 2013 5:48:12 AM UTC-5, Palmer Eldritch wrote: >> >> The preferences are apparently *cleared *when one tries to load them >> when there is a null key which is bad ! Reproducer : >> >> public class XmlExceptionTest extends AndroidTestCase { >> /** Run it twice - on the second run the exception is thrown */ >> public void testXmlException() { >> Context ctx = getContext(); >> SharedPreferences prefs = PreferenceManager >> .getDefaultSharedPreferences(ctx); // exception thrown >> here (line 18) >> // and apparently it clears the prefs as the condition below >> is false >> if (prefs.contains("run_once")) { // false >> Log.w("XmlExceptionTest", >> "contains null key :" + prefs.contains(null)); >> } >> Editor e = prefs.edit(); >> e.putBoolean("run_once", true).commit(); >> e.putString(null, "I put a sting with null key").commit(); >> assertTrue("Contains null", prefs.contains(null)); >> PreferenceManager.getDefaultSharedPreferences(ctx); // >> exception >> // NOT thrown here - why ? - apparently there is a static >> factory >> // returning the instance it already constructed >> // e.clear().commit(); // this eliminates the exception >> } >> } >> >> exception : >> >> W/ApplicationContext(): getSharedPreferences >> W/ApplicationContext(): org.xmlpull.v1.XmlPullParserException: Map >> value without name attribute: string >> W/ApplicationContext(): at >> com.android.internal.util.XmlUtils.readThisMapXml(XmlUtils.java:521) >> W/ApplicationContext(): at >> com.android.internal.util.XmlUtils.readThisValueXml(XmlUtils.java:733) >> W/ApplicationContext(): at >> com.android.internal.util.XmlUtils.readValueXml(XmlUtils.java:667) >> W/ApplicationContext(): at >> com.android.internal.util.XmlUtils.readMapXml(XmlUtils.java:470) >> W/ApplicationContext(): at >> android.app.ContextImpl.getSharedPreferences(ContextImpl.java:361) >> W/ApplicationContext(): at >> android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:348) >> W/ApplicationContext(): at >> gr.uoa.di.android.helpers.test.XmlExceptionTest.testXmlException(XmlExceptionTest.java:18) >> W/ApplicationContext(): at >> java.lang.reflect.Method.invokeNative(Native Method) >> W/ApplicationContext(): at >> java.lang.reflect.Method.invoke(Method.java:521) >> W/ApplicationContext(): at >> junit.framework.TestCase.runTest(TestCase.java:154) >> W/ApplicationContext(): at >> junit.framework.TestCase.runBare(TestCase.java:127) >> W/ApplicationContext(): at >> junit.framework.TestResult$1.protect(TestResult.java:106) >> W/ApplicationContext(): at >> junit.framework.TestResult.runProtected(TestResult.java:124) >> W/ApplicationContext(): at >> junit.framework.TestResult.run(TestResult.java:109) >> W/ApplicationContext(): at >> junit.framework.TestCase.run(TestCase.java:118) >> W/ApplicationContext(): at >> android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:169) >> W/ApplicationContext(): at >> android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:154) >> W/ApplicationContext(): at >> android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:520) >> W/ApplicationContext(): at >> android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1447) >> >> Posted in SO >> here<http://stackoverflow.com/questions/19610569/android-sharedpreferences-null-keys-values-and-sets-corner-cases>and >> in the relevant thread >> here <http://stackoverflow.com/a/19621603/281545> - but still no answers >> >> Any ideas ? >> > -- You received this message because you are subscribed to the Google Groups "Android Developers" group. 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