How to use TextWatcher in android?
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I have a custom ListView which contains one TextView (Of numbers) and one EditText in a row. Outside the heading I have a TextView.

My Questing is that, when I am going to enter any number into any editText then on **heading textView** it should display the **multiplication of editText Value * textView Value of row of ListView.**

And after that if i enter any other number inside any other editText then the calculation will be same like previous one, say **multiplication of editText Value * textView Value of row of ListView + multiplication of editText Value * textView Value of row of ListView** and display this **new value on the heading textView**. And if change the value any editText then the previous value of **old position should be updated** on new value of **corrosponding position.** 
I know all this work is going to be happened in the textwatcher but don't know how??
Can you help me???