App crashes on lock/sleep screen - NullPointerException

Using a device for testing - Whenever I lock the screen (or sleeps after 1 min idle), the app crashes and the `logcat` shows a `NullPointerException` always on an `imageView.setOnClickListener` in the `onResume()` method. Here's the small part of the code where I get the exception : ``` protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.critical_items_list); // instantiate member variables mExtras = getIntent().getExtras(); mItems_P1 = mExtras.getParcelableArrayList(EXTRA_ITEMS_P1); mItems_P2 = mExtras.getParcelableArrayList(EXTRA_ITEMS_P2); mItems_Engine = mExtras.getParcelableArrayList(EXTRA_ITEMS_ENGINE); } protected void onResume() { super.onResume(); ImageView imageAddToMultiple = (ImageView) findViewById(R.id.image_add_to_multiple); //This is where the I get the NullPointer imageAddToMultiple.setOnClickListener(listenerAddToMultipleItems); refreshLists(); ListView listP1 = (ListView) findViewById(R.id.list_p1); ListView listP2 = (ListView) findViewById(R.id.list_p2); ListView listEngine = (ListView) findViewById(R.id.list_engine); listP1.setAdapter(new MyAdapter(mList_P1)); listP2.setAdapter(new MyAdapter(mList_P2)); listEngine.setAdapter(new MyAdapter(mList_Engine)); } ``` The imageView itself lies in a `RelativeLayout`: ``` <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <LinearLayout android:layout_width="fill_parent" android:layout_height="@dimen/standard_bar_height" android:background="@color/green" android:baselineAligned="false" > <LinearLayout android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="1" android:gravity="center" > <TextView android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="center" android:text="@string/plant_1" android:textColor="@android:color/black" /> </LinearLayout> <LinearLayout android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="1" android:gravity="center" > <TextView android:layout_width="fill_parent" android:layout_height="match_parent" android:layout_gravity="center" android:gravity="center" android:text="@string/plant_2" android:textColor="@android:color/black" /> </LinearLayout> <RelativeLayout android:id="@+id/RelativeLayout1" android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="1" > <ImageView android:id="@+id/image_add_to_multiple" android:layout_width="@dimen/standard_bar_height" android:layout_height="@dimen/standard_bar_height" android:layout_alignParentRight="true" android:layout_centerHorizontal="true" android:contentDescription="@string/description_add_to_multiple_items" android:src="@android:drawable/ic_menu_add" /> <TextView android:id="@+id/TextView1" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_centerInParent="true" android:gravity="center" android:text="@string/engine" android:textColor="@android:color/black" /> </RelativeLayout> </LinearLayout> <LinearLayout android:id="@+id/linearLayout1" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <ListView android:id="@+id/list_p1" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" > </ListView> <View android:layout_width="2dp" android:layout_height="fill_parent" android:background="@color/green" /> <ListView android:id="@+id/list_p2" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" > </ListView> <View android:layout_width="2dp" android:layout_height="fill_parent" android:background="@color/green" /> <ListView android:id="@+id/list_engine" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" > </ListView> </LinearLayout> </LinearLayout> ``` I have no clue why I'm getting this `NullPointer`. FATAL EXCEPTION: main java.lang.RuntimeException: Unable to resume activity {nmw.nss/nmw.nss.CriticalList}: java.lang.NullPointerException at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2820) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2859) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2242) at android.app.ActivityThread.access$600(ActivityThread.java:139) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1262) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:4974) 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 nmw.nss.CriticalList.onResume(CriticalList.java:93) at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1236) at android.app.Activity.performResume(Activity.java:4620) at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2804) ... 12 more Thanks. EDIT : I've added the complete activity(sort of), the `xml`, and the `logcat`. Do I need to override any of `Activity` methods, perhaps the `onStop` or `onPause` to make this work?