自定义LengthFilter

转载

 

字符判断若只判断中文可以考虑用位运算提高处理速度

public class CustomLengthFilter extends LengthFilter {

    private int max;// 字符串能输入的最大长度

    private onFullListener listener;

 

    /**

     * @param max

     *            字符串能输入的最大长度，半角字符算1，全角字符算2

     */

    public CustomLengthFilter(final int max) {

        super(max);

        this.max = max;

    }

 

    @Override

    public CharSequence filter(CharSequence source, int start, int end,

            Spanned dest, int dstart, int dend) {

// 修改字符串的长度

        int mlength = getLength(dest.subSequence(dstart, dend).toString());

// 已有字符串的长度

        int dlength = getLength(dest.toString());

// 要增加的字符串的长度

        int slength = getLength(source.subSequence(start, end).toString());

// 还差多少字符到最大长度

        int keep = this.max - (dlength - mlength);

        if (keep <= 0) {

            // 已经到达最大长度

            if (null != listener) {

                listener.isFull();

            }

            return "";

        } else if (keep >= slength) {

            // 还没到达最大长度

            return null;

        } else {

            // 超出最大长度

            int tmp = 0;

            int index;

            for (index = start; index <= end; index++) {

                if (isFullwidthCharacter(source.charAt(index))) {

                    tmp += 2;

                } else {

                    tmp += 1;

                }

                if (tmp > keep) {

                    break;

                }

            }

            if (null != listener) {

                listener.isFull();

            }

            return source.subSequence(start, index);

        }

    }

 

    public void setOnFullListener(onFullListener listener) {

        this.listener = listener;

    }

 

    public interface onFullListener {

 

        /**

         * 这个方法会在输入字符串超出极限时被调用

         */

        void isFull();

    }

 

    /**

     * 判断字符串是否为空或空串

     *

     * @param str

     *            待判断的字符串

     * @return true：字符串为空或空串

     */

    public static boolean isNull(final String str) {

        if (null == str || "".equals(str)) {

            return true;

        } else {

            return false;

        }

    }

 

    /**

     * 获取字符串长度（半角算1、全角算2）

     *

     * @param str

     *            字符串

     * @return 字符串长度

     */

    public static int getLength(final String str) {

        if (isNull(str)) {

            return 0;

        }

        int len = str.length();

        for (int i = 0; i < str.length(); i++) {

            if (isFullwidthCharacter(str.charAt(i))) {

                len = len + 1;

            }

        }

        return len;

    }

 

    /**

     * 获取字符串的全角字符数

     *

     * @param str

     *            待计算的字符串

     * @return 字符串的全角字符数

     */

    public static int getFwCharNum(final String str) {

        if (isNull(str)) {

            return 0;

        }

        int num = 0;

        for (int i = 0; i < str.length(); i++) {

            if (isFullwidthCharacter(str.charAt(i))) {

                num++;

            }

        }

        return num;

    }

 

    /**

     * 判断字符是否为全角字符

     *

     * @param ch

     *            待判断的字符

     * @return true：全角； false：半角

     */

    public static boolean isFullwidthCharacter(final char ch) {

        if (ch >= 32 && ch <= 127) {

            // 基本拉丁字母（即键盘上可见的，空格、数字、字母、符号）

            return false;

        } else if (ch >= 65377 && ch <= 65439) {

            // 日文半角片假名和符号

            return false;

        } else {

            return true;

        }

    }

 

}