Reading String from 2 different methods in same class fails, null pointer exception on HTC phones API 8

Question

I'm having a strange problem which only exhibits itself on certain manufacturers phones. Specifically HTC, this runs fine on my Samsumg S2.

I have 2 methods:

public void setPref(String key) {
    prefkey = key ;
    }

public String getPref() {
    return prefkey ;
    }

I'm using them to store a shared preference name before I start an intent for image selection and then read the value back in the onActivityResult so I can actually save the image path to the right preference.

The problem is the setPref() and getPref() methods only appear to work within the individual method only. so when I setPref(preference.getKey()) in onPreferenceTreeClick the set works fine and I've done a println to show that a getPref() works within the method, but when I run the getPref() in the onActivityResult method, it just returns null (only on HTC phones) hence the catlog output also attached. My Samsung S2 works fine returning the correct value. Am I doing something wrong in my java? (NOTE: I've not included some of the working code to make it look a bit easier to read)

public class Preferences extends PreferenceActivity implements SharedPreferences.OnSharedPreferenceChangeListener {

private static final int SELECT_PICTURE = 1;
private String selectedImagePath;
private String prefkey ;
private SharedPreferences preferences;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    addPreferencesFromResource(R.xml.pref);
    PreferenceManager.getDefaultSharedPreferences(this).registerOnSharedPreferenceChangeListener(this);
}

@Override
public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
    // TODO Auto-generated method stub


    if (preference.toString().substring(0,3).equals("Pho")) {
        setPref(preference.getKey());
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(Intent.createChooser(intent,"Select Picture"), SELECT_PICTURE);

    }

    return super.onPreferenceTreeClick(preferenceScreen, preference);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // TODO Auto-generated method stub

    if(resultCode != RESULT_CANCELED){
        if (resultCode == RESULT_OK) {

            if (requestCode == SELECT_PICTURE) {
                Uri selectedImageUri = data.getData();

                selectedImagePath = getPath(selectedImageUri);

                SharedPreferences mySharedPrefs = PreferenceManager.getDefaultSharedPreferences(getApplication());
                mySharedPrefs.edit().putString(getPref(),selectedImagePath).commit();

                super.onActivityResult(requestCode, resultCode, data);
            }

        }
    }
}

public void setPref(String key) {
        prefkey = key ;
    }

public String getPref() {
        return prefkey ;
    }
}

LogCat

    08-14 07:05:53.371 I/System.out(19175): OnSharedPref: arg0android.app.SharedPreferencesImpl@40d843b0 arg1 null
    08-14 07:05:53.371 D/AndroidRuntime(19175): Shutting down VM
    08-14 07:05:53.371 W/dalvikvm(19175): threadid=1: thread exiting with uncaught exception (group=0x40a97a08)
    08-14 07:05:53.381 E/EmbeddedLogger(  431): App crashed! Process: org.bazza.android.testlist
    08-14 07:05:53.381 E/EmbeddedLogger(  431): App crashed! Package: org.bazza.android.testlist v1 (1.0)
    08-14 07:05:53.381 E/EmbeddedLogger(  431): Application Label: testlist
    08-14 07:05:53.381 E/AndroidRuntime(19175): FATAL EXCEPTION: main
    08-14 07:05:53.381 E/AndroidRuntime(19175): java.lang.RuntimeException: Unable to resume activity {org.bazza.android.testlist/org.bazza.android.testlist.Preferences}: java.lang.RuntimeException: Failure
    delivering result ResultInfo{who=null, request=1, result=-1, data=Intent {
    dat=content://media/external/images/media/1297 typ=image/jpeg (has extras) }}
    to activity {org.bazza.android.testlist/org.bazza.android.testlist.Preferences}: java.lang.NullPointerException
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2823)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2862)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.access$600(ActivityThread.java:139)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1262)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.os.Handler.dispatchMessage(Handler.java:99)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.os.Looper.loop(Looper.java:154)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.main(ActivityThread.java:4977)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at java.lang.reflect.Method.invokeNative(Native Method)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at java.lang.reflect.Method.invoke(Method.java:511)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at dalvik.system.NativeStart.main(Native Method)
    08-14 07:05:53.381 E/AndroidRuntime(19175): Caused by: java.lang.RuntimeException: Failure
    delivering result ResultInfo{who=null, request=1, result=-1, data=Intent 
    {dat=content://media/external/images/media/1297 typ=image/jpeg (has extras) }} to
    activity {org.bazza.android.testlist/org.bazza.android.testlist.Preferences}: java.lang.NullPointerException
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3398)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2804)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     ... 12 more
    08-14 07:05:53.381 E/AndroidRuntime(19175): Caused by: java.lang.NullPointerException
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at org.bazza.android.testlist.Preferences.onSharedPreferenceChanged(Preferences.java:172)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.SharedPreferencesImpl$EditorImpl.notifyListeners(SharedPreferencesImpl.java:455)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.SharedPreferencesImpl$EditorImpl.commit(SharedPreferencesImpl.java:441)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at org.bazza.android.testlist.Preferences.onActivityResult(Preferences.java:136)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.Activity.dispatchActivityResult(Activity.java:4747)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3394)
    08-14 07:05:53.381 E/AndroidRuntime(19175):     ... 13 more
    08-14 07:05:53.381 W/ActivityManager(  431):   Force finishing activity org.bazza.android.testlist/.Preferences
    08-14 07:05:53.411 D/ViewRootImpl(  431): @@@- disable SystemServer HW acceleration

bazza2000 · Answer 1 · 2012-08-16T09:57:30.970

0

ok, think I may have found the answer, I wasn't using static vars or methods

i.e.

needed to be

private static String prefkey ;

and

public static void setPref(String key) {
    prefkey = key ;
}
public static String getPref() {
    return prefkey ;
}

This has resolved my issue.

Referencing some Android Docs below:

A public static field/method

An alternate way to make data accessible across Activities/Services is to use public static fields and/or methods. You can access these static fields from any other class in your application. To share an object, the activity which creates your object sets a static field to point to this object and any other activity that wants to use this object just accesses this static field.

edited Aug 16 '12 at 09:57

answered Aug 15 '12 at 17:07

bazza2000

131
1
12

I suspect the activity is being killed when the user leaves to select a photo, then recreated when they return. So any state not saved in onPause and restored in onCreate is getting lost. Note that the super methods do save UI controls with IDs at least. A static maintaining its value is probably due to just the activity getting killed, not the whole process, although technically Android is allowed to do both. You could test this by logging the onCreate on the HTC, or turning on the "don't keep activities" developer option on the Samsung (designed to let you test this situation repeatedly). – Lance Nanek Aug 17 '12 at 03:48

Reading String from 2 different methods in same class fails, null pointer exception on HTC phones API 8

1 Answers1