Typeface tfArial = Typeface.createFromAsset(getAssets(), "arial.ttf");
TextView tv = null;
// find the textview id from layout or create dynamically
tv.setTypeface(tfArial);

Typeface tf = Typeface.createFromAsset(getAssets(),"fonts/arial.ttf");
TextView tv = (TextView) findViewById(R.id.CustomFontText);
tv.setTypeface(tf);