EditText最大值提醒

public class LengthFilter implements InputFilter {       public LengthFilter(int max) {           mMax = max;       }         @Override       public CharSequence filter(CharSequence source, int start, int end,               Spanned dest, int dstart, int dend) {           int keep = mMax - (dest.length() - (dend - dstart));             if (keep <= 0) {               if (mErrorToast == null) {                   mErrorToast = Toast.makeText(ShowDetailCommentActivity.this, R.string.comment_input_overflow,                           Toast.LENGTH_SHORT);               }               mErrorToast.show();               return "";           } else if (keep >= end - start) {               return null; // keep original           } else {               keep += start;               if (mErrorToast == null) {                   mErrorToast = Toast.makeText(ShowDetailCommentActivity.this, R.string.comment_input_overflow,                           Toast.LENGTH_SHORT);               }               mErrorToast.show();               if (Character.isHighSurrogate(source.charAt(keep - 1))) {                   --keep;                   if (keep == start) {                       return "";                   }               }               return source.subSequence(start, keep);           }       }         private int mMax;   }  

mEditText.setFilters(new InputFilter[] { new LengthFilter(mMaxTextNum) });