Gridview/CursorAdapter nullPointerException

Question

I can't seem to figure out what's wrong with this code. The last Log.d message that I receive is "We're in getView". Afterwards comes an error, which is below. Am I using getView, newView and bindView correctly?

Error:

02-28 15:22:54.063: E/AndroidRuntime(10855): FATAL EXCEPTION: main
02-28 15:22:54.063: E/AndroidRuntime(10855): Process: com.example.wwwww_testi, PID: 10855
02-28 15:22:54.063: E/AndroidRuntime(10855): java.lang.NullPointerException
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.widget.AbsListView.obtainView(AbsListView.java:2265)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.widget.GridView.onMeasure(GridView.java:1044)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.View.measure(View.java:16497)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.View.measure(View.java:16497)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.View.measure(View.java:16497)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.View.measure(View.java:16497)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.Choreographer.doCallbacks(Choreographer.java:574)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.Choreographer.doFrame(Choreographer.java:544)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.os.Handler.handleCallback(Handler.java:733)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.os.Handler.dispatchMessage(Handler.java:95)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.os.Looper.loop(Looper.java:136)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at android.app.ActivityThread.main(ActivityThread.java:5017)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at java.lang.reflect.Method.invokeNative(Native Method)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at java.lang.reflect.Method.invoke(Method.java:515)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-28 15:22:54.063: E/AndroidRuntime(10855):    at dalvik.system.NativeStart.main(Native Method)

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/gridView1"
    android:numColumns="auto_fit"
    android:gravity="center"
    android:columnWidth="50dp"
    android:stretchMode="columnWidth"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

</GridView>

grid_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativelayout"
    android:layout_width="match_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/header"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_gravity="bottom"
        android:textColor="#FEFCFF"
        android:textSize="16sp"/>

</RelativeLayout>

Gridadapter.java

public class GridAdapter extends CursorAdapter {

    private Context mContext;
    private LayoutInflater mInflater;
    private final String LOG_TAG = "GridAdapter";
    private ViewHolder holder;

    public GridAdapter(Context context, Cursor c, boolean autoRequery) {
        super(context, c, autoRequery);
        this.mContext = context;
        mInflater = LayoutInflater.from(context);
        Log.d(LOG_TAG, "We're in constructor");
    }

    public static class ViewHolder {
        public TextView txtView;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Log.d(LOG_TAG, "We're in getView");
        return null;
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        Log.d(LOG_TAG, "We're in bindView");
        holder = (ViewHolder) view.getTag();
        int headerIndex = cursor.getColumnIndex(ArticleTable.MAIN_HEADER);
        String header = cursor.getString(headerIndex);
        holder.txtView.setText(header);
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        Log.d(LOG_TAG, "We're in newView");
        View view = mInflater.inflate(R.layout.grid_item, parent, false);

        holder = new ViewHolder();
        holder.txtView = (TextView) view.findViewById(R.id.header);
        view.setTag(holder);
        return view;
    }
}

EDIT: This solved the issue for me:

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    Log.d(LOG_TAG, "We're in getView");
    View v;
    if (convertView == null) {
        v = newView(mContext, cursor, parent);
    } else {
        v = convertView;
    }
    bindView(v, mContext, cursor);
    return v;
}

Answer 1

getView can not return null, otherwise Android can not measure the amount of space it needs to draw the element. You can avoid to override that method.