Null Pointer Exception from PreferenceManager.getDefaultSharedPreferences

Question

this is the code for the application class that I made , I use it for keeping a default configuration for the realm database and keeping 2 static methods for dealing with SharedPreferences one of which I get a NullPointerException

public class BucketDropsApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        RealmConfiguration config=new RealmConfiguration.Builder(this).build();
        Realm.setDefaultConfiguration(config);
    }

    public static void save(Context context,int state){
        SharedPreferences mPrefs= PreferenceManager.getDefaultSharedPreferences(context);
        SharedPreferences.Editor mEditor=mPrefs.edit();
        mEditor.putInt("State",state);
        mEditor.apply();
    }

    public static int load(Context context){
        SharedPreferences mPrefs= PreferenceManager.getDefaultSharedPreferences(context);
        int stateType=mPrefs.getInt("State", StateType.NONE);
        return stateType;
    }

}

This is the class of the MainActivity :

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mToolbar = (Toolbar) findViewById(R.id.main_toolBar);
    setSupportActionBar(mToolbar);
    mBtnAdd = (Button) findViewById(R.id.btn_trigger_dialog);
    mBtnAdd.setOnClickListener(mBtnAddListener);
    mRealm = Realm.getDefaultInstance();
    int filterOption = BucketDropsApp.load(this);
    loadResults(filterOption);
    mEmptyView = findViewById(R.id.emptyScreen);
    mRecycler = (BucketDropRecycler) findViewById(R.id.rv_drops);
    mRecycler.addItemDecoration(new Divider(this, LinearLayoutManager.VERTICAL));
    mRecycler.hideIfEmpty(mToolbar);
    mRecycler.showIfEmpty(mEmptyView);
    mAdapter = new DropsAdapter(this, mResults,  mAddListener, mMarkListener,mRealm);
    mRecycler.setAdapter(mAdapter);
    CustomCallback callback = new CustomCallback(mAdapter);
    ItemTouchHelper helper = new ItemTouchHelper(callback);
    helper.attachToRecyclerView(mRecycler);
    initBackgroundImage();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    boolean handled = true;
    int filterOption = StateType.NONE;
    switch (id) {
        case R.id.menu_add:
            showDialogAdd();
            break;
        case R.id.menu_least:
            filterOption = StateType.LEAST_TIME_LEFT;
            break;
        case R.id.menu_most:
            filterOption = StateType.MOST_TIME_LEFT;
            break;
        case R.id.menu_complete:
            filterOption = StateType.COMPLETE;
            break;
        case R.id.menu_incomplete:
            filterOption = StateType.INCOMPLETE;
            break;
        default:
            handled = false;
            break;
    }
    loadResults(filterOption);
    BucketDropsApp.save(this, filterOption);
    return handled;
}

private void loadResults(int filterOption) {
    switch (filterOption) {
        case StateType.NONE:
            mResults = mRealm.where(Drop.class).findAllAsync();
            break;
        case StateType.LEAST_TIME_LEFT:
            mResults = mRealm.where(Drop.class).findAllSortedAsync("when");
            break;
        case StateType.MOST_TIME_LEFT:
            mResults = mRealm.where(Drop.class).findAllSortedAsync("when", Sort.DESCENDING);
            break;
        case StateType.COMPLETE:
            mResults = mRealm.where(Drop.class).equalTo("completed", true).findAllAsync();
            break;
        case StateType.INCOMPLETE:
            mResults = mRealm.where(Drop.class).equalTo("completed", false).findAllAsync();
            break;
    }
    mResults.addChangeListener(mChangeListener);
}

And this is what pops up in the logcat when I try to run the application

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.compassasu.bucketdrops/com.compassasu.bucketdrops.ActivityMain}: java.lang.NullPointerException
                                                                          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
                                                                          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
                                                                          at android.app.ActivityThread.access$800(ActivityThread.java:135)
                                                                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                          at android.os.Looper.loop(Looper.java:136)
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5001)
                                                                          at java.lang.reflect.Method.invokeNative(Native Method)
                                                                          at java.lang.reflect.Method.invoke(Method.java:515)
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
                                                                          at dalvik.system.NativeStart.main(Native Method)
                                                                       Caused by: java.lang.NullPointerException
                                                                          at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:374)
                                                                          at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:369)
                                                                          at com.compassasu.bucketdrops.BucketDropsApp.load(BucketDropsApp.java:33)
                                                                          at com.compassasu.bucketdrops.Recycler.DropsAdapter.update(DropsAdapter.java:64)
                                                                          at com.compassasu.bucketdrops.Recycler.DropsAdapter.<init>(DropsAdapter.java:51)
                                                                          at com.compassasu.bucketdrops.ActivityMain.onCreate(ActivityMain.java:105)
                                                                          at android.app.Activity.performCreate(Activity.java:5231)
                                                                          at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
                                                                          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
                                                                          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 
                                                                          at android.app.ActivityThread.access$800(ActivityThread.java:135) 
                                                                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
                                                                          at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                          at android.os.Looper.loop(Looper.java:136) 
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5001) 
                                                                          at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                          at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
                                                                          at dalvik.system.NativeStart.main(Native Method)

Maybe try initialising your preferences inside your application onCreate() using application context and keeping a reference to use in both save and load methods instead of getting shared prefs each time with the passed in context? The NullPointer probably comes from the Context (or the lack of it) — vkislicins, Jul 05 '16 at 15:38

score 0 · Answer 1 · edited May 23 '17 at 12:08

Is your activity extends android.app.Application?. If yes, then can you try to pass context as follows, i.e instead of this, pass getApplicationContext()

mAdapter = new DropsAdapter(getApplicationContext(), mResults,  mAddListener, mMarkListener,mRealm);

May want to refer below links:

Should I use getApplicationContext or Activity.this in a long running AsyncTask

Some notes about Android Context

Null Pointer Exception from PreferenceManager.getDefaultSharedPreferences

1 Answers1