You can, but you are approaching it the wrong way!
You are now setting a textview as the only content in a ListActivity. Which is impossible since a listactivity requires a ListView with a special id.
If you want to use an activity extending ListActivity then at least add a ListView with the id "@android:id/list"
The easiest way doing this (in my opinion) is by creating your layout in XML and it must have at least the following attribute:
Using xml Syntax Highlighting
Parsed in 0.000 seconds, using GeSHi
You can also create your textviews in here and read/edit them in Java by finding them with findViewById.
Hope this helps!