TextWatcher导致stackOverflow

Question

基本上，我有一个Editable (在本例中是一个TextView)，它有一个TextChangedListener (一个TextWatcher)，我的问题是当在TextWatcher的afterTextChanged回调中编辑它时，如何才能而不是导致stackOverflow

一些代码

private void writeNewMsg() {
    final EditText newMsgText = (EditText)findViewById(R.id.s4_et_message);
    newMsgText.addTextChangedListener(new TextWatcher() {

        @Override
        public void afterTextChanged(Editable editable) {
            newMsgText.setText(Smiley.getSmiledText(Messaging.this, newMsgText.getText().toString()));
            // The above line of code causes the stackOverflow
        }

        @Override
        public void beforeTextChanged(CharSequence charSequence, int arg1, int arg2, int arg3) {}

        @Override
        public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {}
    });
}

Answer 1

由于要在文本更改侦听器中再次设置文本，所以会导致无限循环。最简单的修复方法是使用布尔标志过滤出不是由用户引起的事件。试着做这样的事情：

private boolean userChange = true;

private void writeNewMsg() {
    final EditText newMsgText = (EditText)findViewById(R.id.s4_et_message);
    newMsgText.addTextChangedListener(new TextWatcher() {

        @Override
        public void afterTextChanged(Editable editable) {
            if (userChange) {
                // Event is invoked by the user, set flag to false to ignore the event caused by the following setText()
                userChange = false;

                // Save current selection so you can reapply it after setText()
                int selection = newMsgText.getSelectionStart();

                newMsgText.setText(Smiley.getSmiledText(Messaging.this, newMsgText.getText().toString()));

                // Reapply the previous selection
                newMsgText.setSelection(selection);
            } else {
                // Ignore this event, reset flag so next user interaction will not be ignored.
                userChange = true;
            }
        }

        @Override
        public void beforeTextChanged(CharSequence charSequence, int arg1, int arg2, int arg3) {

        }

        @Override
        public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {

        }
    });
}

当然，这只是一个快速的解决办法。您可能需要一个更精细的解决方案在您的应用程序。尽管如此，这个示例应该足以向您说明基本知识。