first of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, i'm a little frustrated)
Most of them come with the advice to use "android:id" instead of just "id" in the xml file. I did.
From others, i learned, that View.findViewById works different than Activity.findViewById . I handled that, too.
in my location_layout.xml i use
<FrameLayout .... >
<some.package.MyCustomView ... />
<LinearLayout ... >
<TextView ...
android:id="@+id/txtLat" />
...
</LinearLayout>
</FrameLayout>
in my Activity i do
...
setContentView( R.layout.location_layout );
and in my custom view class:
...
TextView tv = (TextView) findViewById( R.id.txtLat );
which returns null. Doing this is my Activity works fine . So maybe it's because of the Activity.findViewById and View.findViewById differences. So i stored the context passed to the customs view constructor locally and tried
...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );
which also returned null.
then i changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: didn't solved anything.
So what the heck am i doing wrong ?
I'll appreciate any comments.
regards, Thomas ;)
Source: Tips4all, CCNA FINAL EXAM
which returns null
ReplyDeletePossibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.
Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.
ReplyDeletePossibly, you are calling findViewById before calling setContentView?
ReplyDeleteIf that's the case, try calling findViewById AFTER calling setContentView
A answer for those using ExpandableListView and run into this question based on it's title.
ReplyDeleteI had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.
You can use something like the following in your implementations of the getChildView() and getGroupView() methods.
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_layout, null);
}
I found this here.