Is it possible to write vertically in a textview in android?

You can set your textview as you would normally do

for example:

 <TextView android:id="@+id/txtview"
    android:layout_height="fill_parent"
    android:layout_width="wrap_content" />

and write a function in your activity to

• reverse the characters in your text
• insert \n after every characters

and then set the text to the TextView.

If you dont want to insert the \n, you will have to set the size of android:layout_width and play with font size not to have 2 characters fitting on the same line and no truncation

Edit
If I have understood you correctly, you can get what you want by using animation.

For example

Under res/anim/myanim.xml:

<rotate  xmlns:android="http://schemas.android.com/apk/res/android"
           android:fromDegrees="0" 
           android:toDegrees="-90"
           android:pivotX="50%"
           android:duration="0" />

You will have to play with this file to define where you want your text view to be placed.

In your activity:

  TextView t = (TextView)findViewById(R.id.txtview);
  String txt = "Stackoverflow";         
  t.setText(txt);

  RotateAnimation ranim = (RotateAnimation)AnimationUtils.loadAnimation(this, R.anim.myanim);
  ranim.setFillAfter(true); //For the textview to remain at the same place after the rotation
  t.setAnimation(ranim);