Develop Reference

How to identify which layout xml is running currently?

I have to layout xml named activity_layout_1 and activity_layout_2 and one common Activity.
Based on different conditions, I set contentview of the two xml
In a case, I need to check which layout is currently set.
I can get the id as below:
View currentView = this.getWindow().getDecorView().findViewById(android.R.id.content);
int id = currentView.getId();
Is there a better way to get/identify current layout running?

That id is the id of android.R.id.content no the id of the current layout.
A better way of doing is with tags setTag() and getTag()
Like:
View view = inflater.inflate(R.layout.fragment, container, false);
view.setTag(R.layout.fragment)

RelativeLayout check runtime if is removed or not

In an activity I am changing one of the ViewGroup content runtime: buttons action, other events.
At a specific case I need to check if a child is in this layout or not ( in this case the child is another RelativeLayout, which hold other views)
How can I check runtime, programmatically if child_1_RelativeLayout is there or is already removed from view tree, his parent is parentRelativeLayout
The getParent() is usefully? - not much explanation how to use it, thanks.

In case you have stored your views you can use getParent() to check if view is a direct child for other view. After removing view its parent field will be cleared. For example:
ViewGroup parent = ...;
View child = ...;
assert(child.getParent() == parent); // <-- true
parent.removeView(child);
assert(child.getParent() == parent); // <-- false

Not really sure if I understand your question correctly, but:
when you add the relative layout, be sure to first give it an id (either in your layout.xml file, or from code)
to check existence of the relative layout within the ViewGroup, use ViewGroup's findViewById() method (inherited from View) and pass it the id you've given to the relative layout
if it returns null, the relative layout is not there, otherwise findViewById() will find it
So in short, findViewById() is not only defined for an Activity, but you can call this on any view you would like to use as a starting point for your search.

How to get element ids of inflated xml in listview?

I have a custom listview.In that I want to get ids of widgets used in particular row.Because I want to set the values on a textview click ,which is present in same xml.
How to get element ids of particular row
thanks

See answer at: How to get widget ids of selected row of listview
As you want to get hold of the textview in the same row, you can do the following.
with the textview that was clicked get its parent and then using the parentview you can search for your textview:
View parent = (View) textViewThatWasClicked.getParent();
if (parent != null) {
TextView textViewThatYouWantToChange = parent.findViewById(R.id.textViewThatYouWantToChange);
textViewThatYouWantToChange.setText(...);
}
you will need to change the id that you look for to the id you have for that other textview. If you need to set an id you can do this in the xml layout file you used.
I cant follow your code well enough to actually give you the code but this should be enough to get you in the right direction.

Duplicate layout IDs returning as -1 after view replacement

Short Story:
I have a layout "layout.xml", which gets replaced by another layout "success.xml" after a successful web request. Both layouts have an ImageView that provides the backgrounds to the layouts. These 2 backgrounds both need to be the same, and both are dependent on a user preference.
Longer Story: This all happens in a Fragmnet with an AsyncTask replacing the contentView with "success.xml" in onPostExecute after the web request. This happens as follows:
View view = getView();
view = null;
view = View.inflate(context, R.layout.success, null);
What I tried to do is give both ImageViews the following android:id="#+id/background_image" and then call
ImageView background = (ImageView)view.findViewById(R.id.background_image);
background.setImageResource(R.drawable.bg1);
This background-setting works for the initial view (layout.xml), but on trying to change to "success.xml", I get a NullPointException because background is null.
I've checked and the View's id is set to -1 while the original view's background_image id is set to something sensible and valid.
I've also tried setting the second view's background id like this: android:id="#id/background_image", i.e. without the '+', but still no luck.
The added complication is that it's not just 2 layouts, but about 5 that I need to do this for, so it would be really handy to recycle view id's.
Any help would be greatly appreciated.

Your code for replacing the fragment's view will not do what you want, the original view will remain the same as you change only a reference to that view and not the actual object.
To replace the view of the fragment with the new layout you could have another ViewGroup(for example a FrameLayout) in the basic layout (layout.xml) wrapping your current content(don't forget to give it an id) of layouts.xml(as I understand this is the basic layout). Then, when it's time to replace the layout you could simply do:
// remove the current content
((ViewGroup) getView().findViewById(R.id.yourWrapperLayout)).removeAllViews();
// add the new content
View.inflate(context, R.layout.success, ((ViewGroup) getView().findViewById(R.id.yourWrapperLayout)));
You could avoid adding an extra layout if, by any chance, all your five layouts have the same type for the root view(like a LinearLayout etc). In this case you would use the same code as above but you'll modify the other layouts file to use a merge tag. Also, you'll be looking for the id of the root in the layout.xml layout into which you'll add the content of the other files.
Then you could have the same ids, but you'll have to reinitialize any reference to the views(meaning that you'll have to search for the view again if you store a reference to the view(like a Button field in the fragment class)).

addFooterView for a ListView that is defined in the xml

I've got a ListView, which is fully defined in the xml file. Now I want to add a footer to thi s list so that the last element of the list became a button.
So firstly I do this: View v = getLayoutInflater().inflate(R.layout.add_new, null);, where add_new is the layout for my footer
Now I know that I need to do smth like this:
listViewInstance.addFooterView(v);
But i dont really have that instance as my ListView is defined in an xml file. So what do I write instead of listViewInstance? Is there a way to get its instance somehow from an xml?
Thanks in advance xxx

Use ListActivity.getListView() if you are using a ListActivity or Activity.findViewById() to get the reference to the list view otherwise.