Null Pointer Exception when assigned a View to an Activity?

Question

Hi there

I have built an activity to handle gestures in my Android game and want it to respond to a gesture anywhere on the screen but I am getting this error on the Log:

07-27 13:55:07.268: ERROR/AndroidRuntime(751): java.lang.NullPointerException
07-27 13:55:07.268: ERROR/AndroidRuntime(751):     at android.app.Activity.findViewById(Activity.java:1637)
07-27 13:55:07.268: ERROR/AndroidRuntime(751):     at com.darius.android.distractions.DistractionsView$DistractionsThread$GestureActivity.onCreate(DistractionsView.java:282)
07-27 13:55:07.268: ERROR/AndroidRuntime(751):     at com.darius.android.distractions.DistractionsView$DistractionsThread.doStart(DistractionsView.java:559)
07-27 13:55:07.268: ERROR/AndroidRuntime(751):     at com.darius.android.distractions.DistractionsView$DistractionsThread.doKeyDown(DistractionsView.java:829)
07-27 13:55:07.268: ERROR/AndroidRuntime(751):     at com.darius.android.distractions.DistractionsView.onKeyDown(DistractionsView.java:1278)

I understand I need to allocate a view to the activity and as you will see in my XML, a view called gestures will serve this purpose but I keep getting Inflation errors when trying to inflate the view. Before when this happened to me it was a misspelling of the view name in the XML but that's not it this time I don't think.

How would I properly assign the 'gesture' view to this activity to prevent the errors?

I do hope someone knows the answer and can help me!! Many thanks

I have defined my activity in my code like this:

public class GestureActivity extends Activity implements GestureOverlayView.OnGesturePerformedListener{

        public void onCreate(Bundle savedInstanceState){

        GestureOverlayView gestures = (GestureOverlayView) findViewById(R.id.gestures);

        gestures.addOnGesturePerformedListener(this);
            Log.w(getClass().getName(), "GESTURE ACTIVITY CREATED");
                // Load the gesture library
                Log.w(getClass().getName(), "LOADING GESTURE LIBRARY");
                mLibrary = GestureLibraries.fromRawResource(this, R.raw.gestures);
                if(!mLibrary.load()){
                    finish();
                }
            /*  
        GestureOverlayView gestures = (GestureOverlayView) findViewById(R.id.gestures);
        gestures.addOnGesturePerformedListener(this);
        Log.w(getClass().getName(), "GESTURE ACTIVITY CREATED");
        */
        }

        public void onStart(){
            //I replicated the code here from onCreate but will change this!!
GestureOverlayView gestures = (GestureOverlayView) findViewById   (R.id.gestures);
            gestures.addOnGesturePerformedListener(this);
            Log.w(getClass().getName(), "GESTURE ACTIVITY CREATED");
                // Load the gesture library
                Log.w(getClass().getName(), "LOADING GESTURE LIBRARY");
                mLibrary = GestureLibraries.fromRawResource(this, R.raw.gestures);
                if(!mLibrary.load()){
                    finish();
                }


        }




        public void onGesturePerformed(GestureOverlayView overlay, Gesture gesture){ ...}
 }

I have created the activity in the main thread in it's doStart() method by saying:

GestureActivity mGestureActivity = new GestureActivity();
mGestureActivity.onCreate(null);

And my XML layout looks like this:

<?xml version="1.0" encoding="utf-8"?>



<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
>


<com.darius.android.distractions.DistractionsView
  android:id="@+id/distractions_layout"
  android:layout_width="match_parent"
  android:layout_height="match_parent"/>

<android.gesture.GestureOverlayView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/gestures"
android:layout_width="match_parent"
android:layout_height="match_parent"

android:gestureStrokeType="multiple"
android:eventsInterceptionEnabled="true"/>


<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <TextView
      android:id="@+id/text"
              android:text="Hello"
              android:visibility="visible"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:gravity="center_horizontal"
      android:textColor="#88ffffff"
      android:textSize="24sp"/>
 <TextView  android:layout_height="wrap_content" 
            android:layout_width="wrap_content" 
            android:text="@string/concentration_bar"
            android:textColor = "#EB0000"
            android:textSize="10sp"
            android:id="@+id/conbartext" 
            android:visibility="visible"            

            ></TextView>
</RelativeLayout>

Answer 1

findViewById() requires either the use of setContentView() or to be called on a View. so I would advise you to, either called setContentView(R.layout.nameOfYourXmlfile) or inflate it with a Layout inflater.