EditText - How to set default text in android edittext

Question

I am working on an android application which people will enter their bills. I have an EditText which people enter the amount.

What I want to do is that for example If a person enters "2" it should be converted automatically to "0.02". Then if he/she wants to enter 22$ he should push 2, 2, 0 and 0 buttons. It will be like that "22.00". How can I manage to do that using EditText. Can you give me some ideas guys?

Here is the related code pieces :

            <EditText
            android:id="@+id/amount"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginBottom="20dip"
            android:layout_marginTop="5dip"
            android:inputType="number"
            android:hint="@string/enter_amount"
            android:singleLine="true" />



            EditText payment = (EditText) findViewById(R.id.amount);
            if (payment.getText().toString().length() > 0){
                total_amount =Integer.parseInt(payment.getText().toString()) ;
            }

Answer 1

EditText payment = (EditText) findViewById(R.id.amount);
payment.addTextChangedListener(new TextWatcher() {
        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

            // TODO Auto-generated method stub
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            // TODO Auto-generated method stub
        }

        @Override
        public void afterTextChanged(Editable s) {

             total_amount =Integer.parseInt(s) ;
               payment.setText(""+(total_amount/100));
        }
    });