java.lang.NullPointerException: Attempt to invoke virtual method ‘void android.widget.ImageView.setImageResource(int)’ on a null object reference 今天在家练习ListView的时候,遇到一个java.lang....
棕豆兔&的博客java.lang.NullPointerException: Cannot invoke "com.example.forum.dao.UserMapper.selectByPrimaryKey(java.lang.Long)" because "this.userMapper" is null ,问题已解决!