//新浪微博字数限制
private static final int WEIBO_CONTENT_LENGTH_LIMITED = 140;
//添加微博内容edittext
mInputEditText.addTextChangedListener(mTextWatcher);
private TextWatcher mTextWatcher = new TextWatcher() {
    private int editStart;
    private int editEnd;
    public void afterTextChanged(Editable s) {
      editStart = mInputEditText.getSelectionStart();
      editEnd = mInputEditText.getSelectionEnd();
      // 先去掉监听器，否则会出现栈溢出
      mInputEditText.removeTextChangedListener(mTextWatcher);
      while (mInputEditText.getText().toString().length() > WEIBO_CONTENT_LENGTH_LIMITED) {
        s.delete(editStart - 1, editEnd);
        editStart--;
        editEnd--;
      }
      mInputEditText.setText(s);
      mInputEditText.setSelection(editStart);
      mInputEditText.addTextChangedListener(mTextWatcher);
      setPromptContent();
    }
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }
    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }
};
/**
* refresh prompt content numbers
*/
private void setPromptContent() {
  int contentLength = mInputEditText.getText().toString().length();
  mInputEditText.setSelection(contentLength);
  int limitedLength = WEIBO_CONTENT_LENGTH_LIMITED - contentLength;
  String prefix = getResources().getString(R.string.weibo_content_numbers_prefix);
    String suffix = getResources().getString(R.string.weibo_content_numbers_suffix);
    String promptContentNumbers = prefix + limitedLength + suffix;
    SpannableStringBuilder style = new SpannableStringBuilder(promptContentNumbers);
    style.setSpan(new ForegroundColorSpan(Color.RED), prefix.length(), promptContentNumbers.length() - suffix.length(),
        Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    mPromptContentNumbers.setText(style);
}