Linking two EditText boxes for unit conversion

I'm trying to come up with a scalable way to link two edit text boxes together for unit开发者_JAVA百科 conversion. The user would enter a value in either of the boxes and the converted value would show up in the other.

I would normally just make it so when one EditText was edited, it would get the input, pass it through a method to convert the value and set the text of the other field.

The problem is I have a lot of these pairs and each pair is used to convert a different kind unit. If I used a TextWatcher for each box, you can see where that would start to get out of hand.

I thought about extending the TextWatcher so I could pass it the EditText View and its partner's view, but I'm not sure how to pass it what kind of conversion method needs to be used. I could assign an int to each kind of conversion and use a switch, but that doesn't seem like a good solution to me.

Is there a better way?

This is how I would do it. Create a class, say PartnerEditTextInfo ,which contains a reference number and a EditText obj. Attach this as a tag to every EditText in your app. Set the editText in the PartnerEditTextInfo to the partner editText and have a unique reference number. Thus every EditText can get a hold of its partner.

Extend the EditText class and over ride onTextChanged() method to call a common conversion method(This can be a static class static method) . You can get the partner editText by getting the tag object of the editText whose text has changed. Then ,based on which pairs of editText(based on reference number) is changed apply required conversion formula and do the setText on both the editTexts in the pair.

Caution- You need have a way to make sure you wont get into a infinite loop, have some sort of flag to differentiate changes to editText's text made by user and made by the conversion method.