EditText addTextChangedListener循环

Question

I have two Edit Texts, each one have text watcher that change the second edittext text when the first edittext text is changed, it seems the code create a loop, is there something i can do to make the text watcher only listen to user input and not by changing the text by code?

et1.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        @Override
        public void afterTextChanged(Editable s) {

            double x = Double.valueOf(et1.getText().toString());
            et2.setText(String.valueOf((x*2)));
        }
    });

    et2.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        @Override
        public void afterTextChanged(Editable s) {

           double x = Double.valueOf(et2.getText().toString());
            et1.setText(String.valueOf((x/2)));
        }
    });

Answer 1

You can keep a reference on the TextWatcher to remove them when needed before an operation and later put them back.

private TextWatcher tv1;
private TextWatcher tv2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final EditText et1 = (EditText) findViewById(R.id.editText);
    final EditText et2 = (EditText) findViewById(R.id.editText1);

    tv1 = new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {}

        @Override
        public void afterTextChanged(Editable s) {
            double x = Double.valueOf(et1.getText().toString());
            et2.removeTextChangedListener(tv2); // "disable" the watcher
            et2.setText(String.valueOf((x*2)));
            et2.addTextChangedListener(tv2);    // "enable" the watcher
        }
    };

    tv2 = new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {}

        @Override
        public void afterTextChanged(Editable s) {
            double x = Double.valueOf(et2.getText().toString());
            et1.removeTextChangedListener(tv1); // "disable" the watcher
            et1.setText(String.valueOf((x/2)));
            et1.addTextChangedListener(tv1);    // "enable" the watcher
        }
    };

    et1.addTextChangedListener(tv1);
    et2.addTextChangedListener(tv2);
}