Android如何把字符串中的数字变为红色？

直接上 工具类

public static SpannableStringBuilder setNumColor(String str) {
    SpannableStringBuilder style = new SpannableStringBuilder(str);
    for (int i = 0; i < str.length(); i++) {
        char a = str.charAt(i);
        if (a >= '0' && a <= '9') {
            style.setSpan(new ForegroundColorSpan(Color.RED), i, i + 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }
    return style;
}

用法   
tv.setText(
TextViewUtils.setNumColor("12341234asdfasdfasdf1243e12341")
);

则 tv 显示的字符串中数字变为红色.