Creating Android UI Programmatically

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);