set Editview watchers only when the input from user?

Question

I have 2 fields: dollars and yen. When i change the dollars field i want to show the converted num in the yen field,and vice versa.

my problem is this:

If i have 2 fields with watchers like:

addTextChangedListener(new TextWatcher()...) 

and both doing things to each other the app crashes because when i do a small change on 1 num in the dollars the watcher on the dollars and the yen is working which cause the crash... my solution right now is bad, i remove the listener from the yen when i change the dollars (and when done put the listener back).

Is there any way to only watch for a change via input and not by the default TextWatcher? (if the field changes but not via input, don't do nothing)

Answer 1

You can still use TextWatcher#onTextChanged but add a hasFocus() check, so that you only modify the other field if this field has the focus (being updated by user).

    mDollarsText.addTextChangedListener(new TextWatcher() {
        ...
        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            if (mDollarsText.hasFocus()) {
                // show amount in yen
                if (s == null || s.length() == 0) {
                   mYenText.setText("0");
                } else { 
                   mYenText.setText(convertDollarsToYen(mDollarsText.getText().toString());
                }
            }
        }
        ...
    });

    mYenText.addTextChangedListener(new TextWatcher() {
        ...
        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            if (mYenText.hasFocus()) {
                // show amount in dollars
                if (s == null || s.length() == 0) {
                   mDollarsText.setText("0");
                } else { 
                   mDollarsText.setText(convertYenToDollars(mYenText.getText().toString());
                }
            }
        }
        ...
    });

I'm assuming here that you already have a convenience method for converting dollars<->yen.