findViewByID returns null

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, 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: it didn't solve anything.

So what the heck am I doing wrong?

I'll appreciate any comments.

which returns null

Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.

Possibly, you are calling findViewById before calling setContentView? If that's the case, try calling findViewById AFTER calling setContentView

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.

FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.

This would be wrong

public CameraSurfaceView(Context context, AttributeSet attrs) {
        super(context);
}

This is correct

public CameraSurfaceView(Context context, AttributeSet attrs) {
        super(context,attrs);
}