Is there any difference between ViewStub and View? - performance

Question

I am new to Android Development.
I read about ViewStub from https://developer.android.com/training/improving-layouts/loading-ondemand.html
It mentions that it is cheap and less memory to use it.
I have the following:
MainLayout.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/Layout1"
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:background="#color/blue"
android:orientation="vertical" >
.....
.....
<Button android:id="#+id/ShowBackground"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
<Button android:id="#+id/ShowBackground2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="#string/title_close" />
<View
android:id="#+id/ShowView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#color/blue" />
<ViewStub
android:id="#+id/ShowViewStub"
android:layout="#layout/test"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:visibility="gone" />
</RelativeLayout>
test.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/ShowViewLayout"
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:background="#color/blue_dimmer"
android:orientation="vertical" >
</RelativeLayout>
MainActivity:
private ViewStub mViewStub;
private View mView;
private Button mBackground1;
private Button mBackground2
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.MainLayout);
mView = (ViewStub) findViewById(R.id.ShowView);
mViewStub = (ViewStub) findViewById(R.id.ShowViewStub);
mBackground1 = (Button)this.findViewById(R.id.ShowBackground);
mBackground1.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
mView.setVisibility(View.VISIBLE);
}
});
}
mBackground2 = (Button)this.findViewById(R.id. ShowBackground2);
mBackground2.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
mViewStub.setVisibility(View.VISIBLE);
}
});
}
Questions:
View and ViewStub are working fine in the MainActivity.
I do understand ViewStub is good for the view that is rarely used.
If ViewStub is called at least 1 time in the MainActivity, shouldn't it be more memory usage since the test.xml layout is added to the activity?
As I can see is that ViewStub is always visible unless it is called View.Gone....
Can someone please explain what the differences between the two?
I greatly appreciate for your help,
Thank you.

Answer 1

The < include /> will just include the xml contents in your base xml file as if the whole thing was just a single big file. It's a nice way to share layout parts between different layouts.
The < ViewStub /> is a bit different because it is not directly included, and will be loaded only when you actually use it/need it, ie, when you set its visibility to VISIBLE (actually visible) or INVISIBLE (still not visible, but its size isn't 0 anymore). This a nice optimization because you could have a complex layout with tons of small views or headers anywhere, and still have your Activity load up really fast. Once you use one of those views, it'll be loaded.