查看文本观察器-https://developer.android.com/reference/android/text/TextWatcher

TextWatcher textWatcher = new TextWatcher() {
    @Override
    public void onTextChanged(CharSequence charSequence, int start, int before, int count) {
...
    }
...
};

textView.addTextChangedListener(textWatcher);

使用文本观察器和转换像这样

val codeValue = 'A'.code // 'A' dynamic
textView.setText(codeValue.toString())

使用文本监视器

youredittext.addTextChangedListener(new TextWatcher()
    {
        @Override
        public void afterTextChanged(Editable mEdit) 
        {
            text = mEdit.toString();
           textView.setText(text)
        }

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

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