SpannableString changes font color (limitation does not apply to list refresh, duplicate data will appear)

String str = "This is a test data";
SpannableString spanString = new SpannableString(str);
ForegroundColorSpan span = new ForegroundColorSpan(Color.BLUE);
spanString.setSpan(span, 0, str.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
btnLogin.append("Reply");
btnLogin.append(spanString);
btnLogin.append("This should be black");

/**
 * @Description change the local font color
* @Created by YCH on 2015/10/24.
 */
public class SpannableStringUtil {

/**
     * textView shows local font color change
* @param str
* @param color
* @param view
*/
public void convert(String str,int color,TextView view){
        SpannableString spanString = new SpannableString(str);
ForegroundColorSpan span = new ForegroundColorSpan(color);
spanString.setSpan(span, 0, str.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
view.append(spanString);
}

/**
     * button display local font color change
* @param str
* @param color
* @param view
*/
public void convert(String str,int color,Button view){
        SpannableString spanString = new SpannableString(str);
ForegroundColorSpan span = new ForegroundColorSpan(color);
spanString.setSpan(span, 0, str.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
view.append(spanString);
}

}