android - 导致 stackOverflow 的 TextWatcher

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，如何不导致 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

您正在导致无限循环，因为您在文本已更改的监听器中再次设置文本。最简单的解决方法是使用 bool 标志来过滤掉不是由用户引起的事件。尝试这样的事情:

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方法。您可能需要在您的应用程序中使用更精细的解决方案。尽管如此，这个示例应该足以向您说明基础知识。