Creating Android UI Programmatically

So far, in all my examples, I have been
using the declarative way of creating an Android UI using XML. However, there
could arise certain situations when you may have to create UI programmatically.
Sincere advice would be to avoid such a design since android has a wonderful
architecture where the UI and the program are well separated. However, for
those few exceptional cases where we may need too… here is how we do it.

Every single view or viewgroup
element has an equivalent java class in the SDK. The structure and naming of
the classes and methods is very similar to the XML vocabulary that we are used
to so far.

Let us start with a LinearLayout.
How would we declare it in an XML?

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

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

<TextView 

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="@string/hello"

    />

</LinearLayout>

This just contains a TextView
embedded in a LinearLayout.
A very trivial example. But serves the purpose intended. Let me show how almost
every single element here corresponds to a class or a method call in the class.
 So the equivalent code in the onCreate(…)  method of an activity would
be like this:

         super.onCreate(savedInstanceState);

      

        lLayout = new
LinearLayout(this);

        lLayout.setOrientation(LinearLayout.VERTICAL);

        //-1(LayoutParams.MATCH_PARENT)
is fill_parent or match_parent since API level 8

        //-2(LayoutParams.WRAP_CONTENT)
is wrap_content

        lLayout.setLayoutParams(new LayoutParams(

LayoutParams.MATCH_PARENT,

LayoutParams.MATCH_PARENT));

        tView = new
TextView(this);

        tView.setText("Hello, This is a view created
programmatically! " +

                  "You CANNOT change me that easily :-)");

        tView.setLayoutParams(new LayoutParams(

LayoutParams.MATCH_PARENT,

LayoutParams.WRAP_CONTENT));

        lLayout.addView(tView);

        setContentView(lLayout);

Like this any layout view can be created.
But from this small example you can notice two outstanding things – very
tedious to code for every attribute of the view. And any simple change in the
view, you need to change the code, compile, deploy and only then you see the
effect of the change – unlike in a layout editor. 

You can download the sample
code here.