android edittext 输入长度限制并提示

public static void lengthFilter(final Context context, final EditText editText, final int max_length, final String err_msg) {

InputFilter[] filters = new InputFilter[1];

filters[0] = new InputFilter.LengthFilter(max_length) {
@Override
public CharSequence filter(CharSequence source, int start, int end,
Spanned dest, int dstart, int dend) {
int destLen = StringUtils.getCharacterNum(dest.toString()); //获取字符个数(一个中文算2个字符)
int sourceLen =  StringUtils.getCharacterNum(source.toString()); 
if (destLen + sourceLen > max_length) {
Toast.makeText(context, err_msg,Toast.LENGTH_SHORT).show();
return "";
}
return source;
}
};
editText.setFilters(filters);

}

附加方法：

/**
 * @description 获取一段字符串的字符个数（包含中英文，一个中文算2个字符）
 * @param content
 * @return
 */
public static int getCharacterNum(final String content) {
if (null == content || "".equals(content)) {
return 0;
}else {
return (content.length() + getChineseNum(content));
}
}

/**
* @description 返回字符串里中文字或者全角字符的个数
* @param s 
* @return
*/
public static int getChineseNum(String s) {

int num = 0;
char[] myChar = s.toCharArray();
for (int i = 0; i < myChar.length; i++) {
if ((char)(byte)myChar[i] != myChar[i]) {
num++;
}
}
return num;
}