I try to solve the above given problem.
1.Download the Malayalam font and store in the assets manager. then call like
Typeface typeNormal = Typeface.createFromAsset(getAssets(), "AnjaliOldLipi.ttf");
where 'AnjaliOldLipi.ttf' is one Malayalam font supported by android.
2.If we need to set the edit text box, which support Malayalam font. then
EditText mEt ;
mEt = (EditText) findViewById(R.id.xEt);
mEt.setTypeface(typeNormal);
3.If need to set any buttons in Malayalam font
Button mB;
mB = (Button) findViewById(R.id.x1);
mB.setTypeface(typeNormal);
mB.setText("അ");
mB.setTag("അ");
4.Go through this link- http://tutorials-android.blogspot.in/2011/06/create-your-own-custom-keyboard-for.html that will help you a lot to create custom keyboard in android