Excel到CSV与UTF8编码(Excel to CSV with UTF8 encoding)

 您缺少orderByKey() 。 对于任何过滤查询，您必须使用排序功能。 请参阅文档 
 
 在你的onRefresh方法中，你需要设置限制： 
 
 public void onRefresh() {
     // Refresh items  
     ///HERE "oldestPostId" IS THE KEY WHICH I GET THE LAST RECORDS FROM THE FIREBASE
                mChatRef.orderByKey().startAt(oldestPostId).limitToFirst(10).addListenerForSingleValueEvent(new ValueEventListener() {
.....
 
 因此，在您获得前10条记录后，您检索的数据是仅有的10条新记录。 
 
 确保保存新检索数据的最旧密钥，以便在下一次刷新时仅检索此密钥的新数据。 
 
 建议：您可以使用值侦听器并获取大小的最后一个数据快照以获取最后一条记录的密钥，而不是添加子值侦听器来查找最后一个密钥。 

You are missing orderByKey(). For any filtering queries you must use the ordering functions. Refer to the documentation
 
In your onRefresh method you need to set the limit:
 
 public void onRefresh() {
     // Refresh items  
     ///HERE "oldestPostId" IS THE KEY WHICH I GET THE LAST RECORDS FROM THE FIREBASE
                mChatRef.orderByKey().startAt(oldestPostId).limitToFirst(10).addListenerForSingleValueEvent(new ValueEventListener() {
.....
 
So the data you retrieve is the only 10 new records after you got your first 10 records.
 
Make sure to save the oldest key of the newly retrieved data so that on next refresh new data from this key is only retrieved.
 
Suggestion: Instead of adding a child value listener to find the last key, you can just use the value listener and get the last data snapshot with the size to get the last record's key.