如何在TextView上侦听并在Android中对同一TextView进行更改

Question

我尝试了以下代码，但是android不允许我这样做，因为我进入了无限循环。

mEditText = (EditText) getActivity().findViewById(R.id.input_content);
mEditText.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) {
                   //I want to format the already existing text in s in a certain way as      the user is typing
                   mEditText.setText(s.toString() + " \n");
            }       
        });

请任何想法将非常有帮助。 谢谢

Answer 1

3种可能的解决方案：

1. 检查字符串中是否有回车符

像这样 ：

mEditText = (EditText) getActivity().findViewById(R.id.input_content);
mEditText.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)
    {
        //I want to format the already existing text in s in a certain way as      the user is typing
        if (s.toString().charAt(s.length() - 1 ) != '\n')
        {
            mEditText.setText(s.toString() + " \n");
        }
    }
});

根据您输入字符串中的内容，这不是最佳解决方案

2. 在beforeTextChanged中执行

像这样 ：

mEditText = (EditText) getActivity().findViewById(R.id.input_content);
mEditText.addTextChangedListener(new TextWatcher()
{
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after)
    {
        //I want to format the already existing text in s in a certain way as      the user is typing
        mEditText.setText(s.toString() + " \n");
    }

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

    @Override
    public void afterTextChanged(Editable s) {}
});

3. 暂时取消监听器

像这样 ：

final TextWatcher tw = 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)
    {
        //I want to format the already existing text in s in a certain way as      the user is typing
        mEditText.removeTextChangedListener(tw);
        mEditText.setText(s.toString() + " \n");
        mEditText.addTextChangedListener(tw);
    }
});

mEditText = (EditText) getActivity().findViewById(R.id.input_content);
mEditText.addTextChangedListener(tw);

Answer 2

您最有可能进入无限循环，因为您是在public void afterTextChanged(Editable s)中更改文本，这将导致再次调用该方法。
最好的解决方案是使用其他方法之一更改文本，或者在失去可编辑焦点的情况下。 有关更多详细信息，请参见View.OnFocusChangeListener 。

这是一个例子：

textView.setOnFocusChangeListener(new OnFocusChangeListener() {          
    public void onFocusChange(View v, boolean hasFocus) {
        if(!hasFocus) {
            textView.setText(s.toString() + " \n");
        }
    }
});