TextUtils中能用到的方法

判断字符序列中   是否全部为数字

/** * Returns whether the given CharSequence contains only digits. */public static boolean isDigitsOnly(CharSequence str) {    final int len = str.length();    for (int i = 0; i < len; i++) {        if (!Character.isDigit(str.charAt(i))) {            return false;        }    }    return true;}

一个分割的字符串     分隔符      分割后是否包含 item                 返回是否包含这个 item

/** * Does a comma-delimited list 'delimitedString' contain a certain item? * (without allocating memory) * * @hide */public static boolean delimitedStringContains(        String delimitedString, char delimiter, String item) {    if (isEmpty(delimitedString) || isEmpty(item)) {        return false;    }    int pos = -1;    int length = delimitedString.length();    while ((pos = delimitedString.indexOf(item, pos + 1)) != -1) {        if (pos > 0 && delimitedString.charAt(pos - 1) != delimiter) {            continue;        }        int expectedDelimiterPos = pos + item.length();        if (expectedDelimiterPos == length) {            // Match at end of string.            return true;        }        if (delimitedString.charAt(expectedDelimiterPos) == delimiter) {            return true;        }    }    return false;}

合并多个字符串

/** * Returns a CharSequence concatenating the specified CharSequences, * retaining their spans if any. */public static CharSequence concat(CharSequence... text) {    if (text.length == 0) {        return "";    }    if (text.length == 1) {        return text[0];    }    boolean spanned = false;    for (int i = 0; i < text.length; i++) {        if (text[i] instanceof Spanned) {            spanned = true;            break;        }    }    StringBuilder sb = new StringBuilder();    for (int i = 0; i < text.length; i++) {        sb.append(text[i]);    }    if (!spanned) {        return sb.toString();    }    SpannableString ss = new SpannableString(sb);    int off = 0;    for (int i = 0; i < text.length; i++) {        int len = text[i].length();        if (text[i] instanceof Spanned) {            copySpansFrom((Spanned) text[i], 0, len, Object.class, ss, off);        }        off += len;    }    return new SpannedString(ss);}

对字符串进行 html 编码

/** * Html-encode the string. * @param s the string to be encoded * @return the encoded string */public static String htmlEncode(String s) {    StringBuilder sb = new StringBuilder();    char c;    for (int i = 0; i < s.length(); i++) {        c = s.charAt(i);        switch (c) {        case '<':            sb.append("&lt;"); //$NON-NLS-1$            break;        case '>':            sb.append("&gt;"); //$NON-NLS-1$            break;        case '&':            sb.append("&amp;"); //$NON-NLS-1$            break;        case '\'':            //http://www.w3.org/TR/xhtml1            // The named character reference &apos; (the apostrophe, U+0027) was introduced in            // XML 1.0 but does not appear in HTML. Authors should therefore use &#39; instead            // of &apos; to work as expected in HTML 4 user agents.            sb.append("&#39;"); //$NON-NLS-1$            break;        case '"':            sb.append("&quot;"); //$NON-NLS-1$            break;        default:            sb.append(c);        }    }    return sb.toString();}

用逗号分隔字符串

/** * Converts a CharSequence of the comma-separated form "Andy, Bob, * Charles, David" that is too wide to fit into the specified width * into one like "Andy, Bob, 2 more". * * @param text the text to truncate * @param p the Paint with which to measure the text * @param avail the horizontal width available for the text * @param oneMore the string for "1 more" in the current locale * @param more the string for "%d more" in the current locale */public static CharSequence commaEllipsize(CharSequence text,                                          TextPaint p, float avail,                                          String oneMore,                                          String more) {    return commaEllipsize(text, p, avail, oneMore, more,            TextDirectionHeuristics.FIRSTSTRONG_LTR);}

截断

/** * Returns the original text if it fits in the specified width * given the properties of the specified Paint, * or, if it does not fit, a truncated * copy with ellipsis character added at the specified edge or center. */public static CharSequence ellipsize(CharSequence text,                                     TextPaint p,                                     float avail, TruncateAt where) {    return ellipsize(text, p, avail, where, false, null);}

获得偏移前面的 

public static int getOffsetBefore(CharSequence text, int offset) {    if (offset == 0)        return 0;    if (offset == 1)        return 0;    char c = text.charAt(offset - 1);    if (c >= '\uDC00' && c <= '\uDFFF') {        char c1 = text.charAt(offset - 2);        if (c1 >= '\uD800' && c1 <= '\uDBFF')            offset -= 2;        else            offset -= 1;    } else {        offset -= 1;    }    if (text instanceof Spanned) {        ReplacementSpan[] spans = ((Spanned) text).getSpans(offset, offset,                                                   ReplacementSpan.class);        for (int i = 0; i < spans.length; i++) {            int start = ((Spanned) text).getSpanStart(spans[i]);            int end = ((Spanned) text).getSpanEnd(spans[i]);            if (start < offset && end > offset)                offset = start;        }    }    return offset;}

偏移后面的public static int getOffsetAfter(CharSequence text, int offset) {    int len = text.length();    if (offset == len)        return len;    if (offset == len - 1)        return len;    char c = text.charAt(offset);    if (c >= '\uD800' && c <= '\uDBFF') {        char c1 = text.charAt(offset + 1);        if (c1 >= '\uDC00' && c1 <= '\uDFFF')            offset += 2;        else            offset += 1;    } else {        offset += 1;    }    if (text instanceof Spanned) {        ReplacementSpan[] spans = ((Spanned) text).getSpans(offset, offset,                                                   ReplacementSpan.class);        for (int i = 0; i < spans.length; i++) {            int start = ((Spanned) text).getSpanStart(spans[i]);            int end = ((Spanned) text).getSpanEnd(spans[i]);            if (start < offset && end > offset)                offset = end;        }    }    return offset;}

替换

/** * Return a new CharSequence in which each of the source strings is * replaced by the corresponding element of the destinations. */public static CharSequence replace(CharSequence template,                                   String[] sources,                                   CharSequence[] destinations) {    SpannableStringBuilder tb = new SpannableStringBuilder(template);    for (int i = 0; i < sources.length; i++) {        int where = indexOf(tb, sources[i]);        if (where >= 0)            tb.setSpan(sources[i], where, where + sources[i].length(),                       Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);    }    for (int i = 0; i < sources.length; i++) {        int start = tb.getSpanStart(sources[i]);        int end = tb.getSpanEnd(sources[i]);        if (start >= 0) {            tb.replace(start, end, destinations[i]);        }    }    return tb;}

反转

// XXX currently this only reverses chars, not spanspublic static CharSequence getReverse(CharSequence source,                                      int start, int end) {    return new Reverser(source, start, end);}

相等

/** * Returns true if a and b are equal, including if they are both null. * <p><i>Note: In platform versions 1.1 and earlier, this method only worked well if * both the arguments were instances of String.</i></p> * @param a first CharSequence to check * @param b second CharSequence to check * @return true if a and b are equal */public static boolean equals(CharSequence a, CharSequence b) {    if (a == b) return true;    int length;    if (a != null && b != null && (length = a.length()) == b.length()) {        if (a instanceof String && b instanceof String) {            return a.equals(b);        } else {            for (int i = 0; i < length; i++) {                if (a.charAt(i) != b.charAt(i)) return false;            }            return true;        }    }    return false;}

判空

/** * Returns true if the string is null or 0-length. * @param str the string to be examined * @return true if str is null or zero length */public static boolean isEmpty(@Nullable CharSequence str) {    if (str == null || str.length() == 0)        return true;    else        return false;}

切割

/** * String.split() returns [''] when the string to be split is empty. This returns []. This does * not remove any empty strings from the result. For example split("a,", ","  ) returns {"a", ""}. * * @param text the string to split * @param expression the regular expression to match * @return an array of strings. The array will be empty if text is empty * * @throws NullPointerException if expression or text is null */public static String[] split(String text, String expression) {    if (text.length() == 0) {        return EMPTY_STRING_ARRAY;    } else {        return text.split(expression, -1);    }}

截取字符串

/** * Create a new String object containing the given range of characters * from the source string.  This is different than simply calling * {@link CharSequence#subSequence(int, int) CharSequence.subSequence} * in that it does not preserve any style runs in the source sequence, * allowing a more efficient implementation. */public static String substring(CharSequence source, int start, int end) {    if (source instanceof String)        return ((String) source).substring(start, end);    if (source instanceof StringBuilder)        return ((StringBuilder) source).substring(start, end);    if (source instanceof StringBuffer)        return ((StringBuffer) source).substring(start, end);    char[] temp = obtain(end - start);    getChars(source, start, end, temp, 0);    String ret = new String(temp, 0, end - start);    recycle(temp);    return ret;}

字符串中 单个字符最后出现的角标

public static int lastIndexOf(CharSequence s, char ch) {    return lastIndexOf(s, ch, s.length() - 1);}