/**
  * 添加记录
  *
  * @param uri
  * @param values
  * @return
  */
 @Override
 public Uri insert(Uri uri, ContentValues values) {
   int code = uriMatcher.match(uri);
   if (code == SUCCESS) {
     StuDao dao = new StuDao(getContext());
     dao.insert(values);
   } else {
     throw new IllegalArgumentException("这儿不是你完的地方");
   }
   return null;
 }
 /**
  * 删除记录
  *
  * @param uri
  * @param selection
  * @param selectionArgs
  * @return
  */
 @Override
 public int delete(Uri uri, String selection, String[] selectionArgs) {
   int code = uriMatcher.match(uri);
   int count = 0;
   if (code == SUCCESS) {
     StuDao dao = new StuDao(getContext());
     count = dao.delete(selection, selectionArgs);
   } else {
     throw new IllegalArgumentException("这儿不是你完的地方");
   }
   return count;
 }
 /**
  * 查询数据库
  *
  * @param uri
  * @param projection
  * @param selection
  * @param selectionArgs
  * @param sortOrder
  * @return
  */
 @Override
 public Cursor query(
     Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
   int code = uriMatcher.match(uri);
   Cursor cursor = null;
   if (code == SUCCESS) {
     StuDao dao = new StuDao(getContext());
     cursor = dao.query(projection, selection, selectionArgs, null, null, sortOrder);
   } else {
     throw new IllegalArgumentException("这儿不是你完的地方");
   }
   return cursor;
 }