(FrameLayout) findViewById - returns null?

Question

Why do I always (FrameLayout) findViewById always returns null? The file exists. Working with Google Maps. I read the related topics. Powered by: Project-Clean. Delete folder gen.

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.travel_map_activity);
    mapView = (MapView) findViewById(R.id.travelMapView);

    FrameLayout mainLayout = (FrameLayout) findViewById(R.id.mapFrame);//null

}

What's the problem?

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

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/mapFrame"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

<TextView
    android:id="@+id/tvTop"
    android:layout_width="fill_parent"
    android:layout_height="20dip"
    android:background="#FFFFFF"
    android:gravity="top|center_horizontal"
    android:text="FLOATING VIEW - TOP"
    android:textColor="#000000"
    android:textStyle="bold" />

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/lvMain"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />
</LinearLayout></FrameLayout>

travel_map_activity.xml

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<com.google.android.maps.MapView
    android:id="@+id/travelMapView"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:apiKey="key" />

</LinearLayout>

thanks

Is that `travel_map_activity.xml`? I feel like it's not, due to referencing `R.id.travelMapView` on the line above. — Cat, Dec 27 '12 at 00:17

Sergi Juanola · Answer 1 · 2012-12-27T00:48:05.887

Are those two Views you are finding (travelMapView and mapFrame) in the same layout travel_map_activity. Because the layout you provided isn't holding travelMapView at all, yet you don't get a NullPointerException there.

EDIT: As you show right now, mapFrame is not in the same view, so there is no way to get to that...

Well, there is one, but it won't be useful, as setContentView only shows up one single layout at a time. Anyway, you could still access mapFrame with an inflated layout, without it being actually used (and that's because it is completely useless):

LayoutInflater inflater = (LayoutInflater) context.getSystemService( Context.LAYOUT_INFLATER_SERVICE );
View view = inflater.inflate( R.layout.your_other_layout_with_framelayout, null );
FrameLayout mainLayout = (FrameLayout) view.findViewById(R.id.mapFrame);

Using this will let you escape from that null, but again, there's no chance you can use that FrameLayout if it isn't in your current view.

I have not shown all the code that pops up only when NullPointerException FrameLayout. — JDev, Dec 27 '12 at 00:25
Check Eric's answer and my edit. And please, please, read **carefully** both answers — Sergi Juanola, Dec 27 '12 at 00:49

score 0 · Answer 2 · edited May 23 '17 at 11:58

0

You're inflating the layout from travel_map_activity.xml, which only contains one ID: R.id.travelMapView. You cannot select items from other layouts (with a few small exceptions that are more like abuses of the system).

You either need to set the content view to whichever layout it is that contains R.id.mapFrame, or you need to find another way to pass that data in (probably using a Bundle packaged with the Intent with .putExtra() and .getIntExtra(), for example; there are other questions and blogs that cover this kind of thing).

edited May 23 '17 at 11:58

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answered Dec 27 '12 at 00:35

Cat

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you aren't giving a nice answer – Dec 27 '12 at 01:27

(FrameLayout) findViewById - returns null?

2 Answers2