Realm 错误

错误1：
Realm.getDefaultInstance()报错Class '类名' has been added.
https://ask.csdn.net/questions/703918

错误2：
Configurations cannot be different if used to open the same file. The most likely cause is that equals() and hashCode() are not overridden in the migration class
参考链接：https://www.thinbug.com/q/38684825
解决办法：
在自己写的CustomMigration中，添加：

public int hashCode() {
    return CustomMigration.class.hashCode();
}

public boolean equals(Object object) {
    if(object == null) {
        return false;
    }
    return object instanceof CustomMigration;
}