【android:maxLength="50"  限制漢字50個】

AddLengthFilter.lengthFilter(this, et_explain, 100, "超出範圍");

/**

 * 長度監聽過濾
 * 
 * @version v1.0
 * EditText輸入中文和英文長度監聽，中文按兩個字元，英文按一個字元，監聽輸入的長度，在你需要呼叫的地方新增：
 * AddLengthFilter.lengthFilter(this, nameEt, 32, "提示資訊"));
 * @author
 */
public class AddLengthFilter implements InputFilter {


public CharSequence filter(CharSequence source, int start, int end,
Spanned dest, int dstart, int dend) {
return null;
}


// 長度監聽
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) {
// 獲取字元個數(一箇中文算2個字元)
int destLen = getCharacterNum(dest.toString());
int sourceLen = getCharacterNum(source.toString());


if (destLen + sourceLen > max_length) {
Toast.makeText(context, err_msg, Toast.LENGTH_SHORT).show();
return "";
}
return source;
}
};
editText.setFilters(filters);
}


/**
* @description 獲取一段字串的字元個數（包含中英文，一箇中文算2個字元）
* @param content
* @return
*/
public static int getCharacterNum(final String content) {
if (null == content || "".equals(content)) {
return 0;
} else {
return (content.length() + getChineseNum(content));
}
}


/**
* @description 返回字串裡中文字或者全形字元的個數
* @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;
}


}