如果时间戳字段，Firebase使用endAt
我有这个字段的记录：
age: 25
timestamp: 1484089199472
此记录由：
插入@Exclude
public Map<String, Object> toMap() {
HashMap<String, Object> result = new HashMap<>();
result.put("age", age);
result.put("timestamp", ServerValue.TIMESTAMP);
return result;
}
如果我使用endAt(24,"age")而不是其工作，则该项目是不可见的。
但是，如果我想在时间戳中使用endAt它不起作用。例如：
endAt(100000,"timestamp")并且该行保持可见。
为什么？
这是检查类型？
我该如何过滤它？
我什么都不知道！ :( 我希望有一个人可以帮助我！ 谢谢！
修改
查询获取实际日行
@Override
public Query getQuery(final DatabaseReference databaseReference) {
Date endTime = new Date();
endTime.setHours(23);
endTime.setMinutes(59);
endTime.setSeconds(59);
return databaseReference
.child("toplist")
.endAt(endTime.getTime(),"timestamp")
.orderByChild("point")
.limitToFirst(50);
}
数据
@IgnoreExtraProperties
public class Rank{
public int number;
public String username;
public int point;
// [START post_to_map]
@Exclude
public Map<String, Object> toMap() {
HashMap<String, Object> result = new HashMap<>();
result.put("number", number);
result.put("username", username);
result.put("point", point);
result.put("timestamp", ServerValue.TIMESTAMP);
return result;
}
}
添加新的随机项
private void writeNewRandomTopListItem() {
Random rnd = new Random();
Rank item = new Rank();
item.username = "Test " + rnd.nextInt(20000);
item.point = rnd.nextInt(2000000);
mDatabase.child("toplist").push().setValue(item.toMap());
}
适配器
Query postsQuery = getQuery(mDatabase);
mAdapter = new FirebaseRecyclerAdapter<Rank, PostViewHolder>(Rank.class, R.layout.item_post, PostViewHolder.class, postsQuery) {
@Override
protected void populateViewHolder(final PostViewHolder viewHolder, final Rank model, final int position) {
viewHolder.bindToPost(model,position);
}
};
mRecycler.setAdapter(mAdapter);
...
toplist
-Ka8m3hN-vRjPZhKH3Rt
number: 0
point: 1269424
timestamp: 148407253222471
username: "Test 19727"
-Ka8m3hWRIQKL7faNqUS
number: 0
point: 1398061
timestamp: 1484075322472
username: "Test 17679"
2 个答案:
答案 0 :(得分：4)
您应首先由points孩子订购您的节点，然后在客户端按@Override
public Query getQuery(final DatabaseReference databaseReference) {
Date endTime = new Date();
endTime.setHours(23);
endTime.setMinutes(59);
endTime.setSeconds(59);
return databaseReference.child("toplist").orderByChild("timestamp")
.endAt(endTime.getTime()).limitToFirst(50);
}
订购收到的商品。这被描述为here。
我建议您改用此查询：
timestamp通过这种方式，您可以告诉Firebase按其子节点之一对节点进行排序，在这种情况下，这些子节点将为RecyclerView。希望这会有所帮助。
接下来，您需要在客户端对数据进行排序。这样做的一个问题是，来自firebase的实时更改不会重新排序svg+xml内的项目。
我再次建议您通过this回答。
答案 1 :(得分：0)
经过几天的实验，我解决了这个问题。
重点是
我很惊讶地发现即使查询可以通过深度嵌套来排序 儿童，但仅对 ONE 级儿童有效！
在这种情况下，我尝试先将节点再下一层，并对其查询特定时间，然后它就可以工作了。
这是我在Firebase实时数据库上的数据树：
为读取存储在Firebase中的POJO模型，我设置了一个为我服务的助手类。
因此，我在运行FirebaseDatabaseHelper.getInstance().readCatalogFromDatabase(Card.class, listener, start, end);的同时用最新的数据库更新了UI。
关于我的FirebaseDatabaseHelper，有两种相对的方法可以很好地帮助我读取数据库reference（）上的模型，这是指父节点拥有很多模型，例如“ / Card / user_id”节点，其中有许多子代，这意味着卡片的详细信息在/ Card / user_id / card_id”。
/**
* attaches listener to obtain values at child locations of "catalog/" storing lots of models in JSON tree
* reads values created in a specific period and ordered by date
*
* catalog: "Card" for card
* "Comment" for comment
*
* It's surprised to found out even query can be ordered by deep nested children, but children ONE more level down only
* Being such circumstance, go for node one more level down first and do query for a specific period on it
*/
public void readCatalogFromDatabase(final Class<?> clazz, final OnReadDatabaseChildEventListener child_listener, final long start, final long end) {
//Logger.d(">>> end at date before:" + (end/(1*24*60*60*1000) - start/(1*24*60*60*1000)));
Logger.d(">>> start:" + start + ", end:" + end);
DatabaseReference referenceCatalog;
OnReadDatabaseValueEventListener ids_listener;
String catalog;
if (clazz.getName().equals(Card.class.getName())) {
ids_listener = new OnReadDatabaseValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> ids = new LinkedList<>();
Logger.d("... user count:" + dataSnapshot.getChildrenCount());
/**
* $ROOT/catalog/user_id/CardId/CardId
* $ROOT/catalog/user_id/CardId/ProfilePhoto
* $ROOT/catalog/user_id/CardId/ProfileTitle
* $ROOT/catalog/user_id/CardId/ProfileName
* $ROOT/catalog/user_id/CardId/ProfileID
* $ROOT/catalog/user_id/CardId/ArticleTitle
* $ROOT/catalog/user_id/CardId/ArticleContent
* $ROOT/catalog/user_id/CardId/ArticleCount
* $ROOT/catalog/user_id/CardId/ArticlePhoto
* $ROOT/catalog/user_id/CardId/ArticlePhotoFileName
* $ROOT/catalog/user_id/CardId/Distance
* $ROOT/catalog/user_id/CardId/Date
* ^[key] :[value] -> initial
* ^[key] :[value] -> 1th for-loop
*/
for (DataSnapshot snapShotOfUserId : dataSnapshot.getChildren()) {
Logger.d("... user(" + snapShotOfUserId.getKey() + ") post count:" + snapShotOfUserId.getChildrenCount());
ids.add(snapShotOfUserId.getKey());
}
for (String id : ids) readListFromDatabase(clazz, id, child_listener, start, end);
FirebaseDatabaseHelper.getInstance().detachValueEventListener(this);
}
@Override
public void onCancelled(DatabaseError databaseError) {
child_listener.onCancelled(databaseError);
FirebaseDatabaseHelper.getInstance().detachValueEventListener(this);
}
};
catalog = Card.class.getSimpleName();
referenceCatalog = getDatabaseChild(catalog, null, null);
referenceCatalog.orderByKey().limitToLast(COUNT_ON_PAGE).addListenerForSingleValueEvent(ids_listener);
mValueEventListeners.put(ids_listener, referenceCatalog);
} else if (clazz.getName().equals(Comment.class.getName())) {
ids_listener = new OnReadDatabaseValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> ids = new LinkedList<>();
Logger.d("... card count:" + dataSnapshot.getChildrenCount());
/**
* $ROOT/catalog/card_id/CommentId/CardId
* $ROOT/catalog/card_id/CommentId/CommentId
* $ROOT/catalog/card_id/CommentId/ProfilePhoto
* $ROOT/catalog/card_id/CommentId/ProfileName
* $ROOT/catalog/card_id/CommentId/ProfileID
* $ROOT/catalog/card_id/CommentId/Comment
* $ROOT/catalog/card_id/CommentId/Distance
* $ROOT/catalog/card_id/CommentId/Date
* ^[key] :[value] -> initial
* ^[key] :[value] -> 1th for-loop
*/
for (DataSnapshot snapShotOfCardId : dataSnapshot.getChildren()) {
Logger.d("... card(" + snapShotOfCardId.getKey() + ") comment count:" + snapShotOfCardId.getChildrenCount());
ids.add(snapShotOfCardId.getKey());
}
for (String id : ids) readListFromDatabase(clazz, id, child_listener, start, end);
FirebaseDatabaseHelper.getInstance().detachValueEventListener(this);
}
@Override
public void onCancelled(DatabaseError databaseError) {
child_listener.onCancelled(databaseError);
FirebaseDatabaseHelper.getInstance().detachValueEventListener(this);
}
};
catalog = Comment.class.getSimpleName();
referenceCatalog = getDatabaseChild(catalog, null, null);
referenceCatalog.orderByKey().limitToLast(COUNT_ON_PAGE).addListenerForSingleValueEvent(ids_listener);
mValueEventListeners.put(ids_listener, referenceCatalog);
}
然后转到
/**
* attaches listener to obtain values at child locations of "catalog/id/" storing list of models in JSON tree
* reads values created in a specific period and ordered by date
*
* id: user id for card
* card id for comment
*
* query can be ordered by deep nested ONE more level down children
*/
public void readListFromDatabase(Class<?> clazz, String id, OnReadDatabaseChildEventListener listener, long start, long end) {
//Logger.d(">>> end at date before:" + (end/(1*24*60*60*1000) - start/(1*24*60*60*1000)));
Logger.d(">>> start:" + start + ", end:" + end + ", id:" + id);
DatabaseReference referenceCatalog;
Query query;
String catalog;
if (clazz.getName().equals(Card.class.getName())) {
catalog = Card.class.getSimpleName();
referenceCatalog = getDatabaseChild(catalog, id, null);
query = referenceCatalog.orderByChild("Date").startAt(start).endAt(end).limitToLast(COUNT_ON_PAGE);
query.addChildEventListener(listener);
mChildEventListeners.put(listener, referenceCatalog);
} else if (clazz.getName().equals(Comment.class.getName())) {
catalog = Comment.class.getSimpleName();
referenceCatalog = getDatabaseChild(catalog, id, null);
query = referenceCatalog.orderByChild("Date").startAt(start).endAt(end).limitToLast(COUNT_ON_PAGE);
query.addChildEventListener(listener);
mChildEventListeners.put(listener, referenceCatalog);
}
}
关于数据库参考，
/**
* gets a database reference to location headed with "/catalog/", "/id/" and "/key/" as prefixes(to a child location in JSON tree)
*
* id: user id for card
* card id for comment
* key:
* card id for card
* comment id for comment
*/
private DatabaseReference getDatabaseChild(String catalog, String id, String key) {
Logger.d(">>>");
DatabaseReference reference;
if (catalog == null) {
if (id == null) {
if (key == null) {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference();
} else {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(key);
}
} else {
if (key == null) {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(id);
} else {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(id + "/" + key);
}
}
} else {
if (id == null) {
if (key == null) {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(catalog);
} else {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(catalog + "/" + key);
}
} else {
if (key == null) {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(catalog + "/" + id);
} else {
Logger.d("... catalog:" + catalog + ", id:" + id + ", key:" + key);
reference = FirebaseDatabase.getInstance().getReference(catalog + "/" + id + "/" + key);
}
}
}
return reference;
}
这就是我在特定时期查询的方式。
此外，我发现了一些有关人们应该致电的答案
addChildEventListener()之后的orderByChild()；但是，之后 我说进行实验
Query query;
query = referenceCatalog.orderByChild("Date").startAt(start).endAt(end).limitToLast(COUNT_ON_PAGE);
query.addChildEventListener(listener);
和
referenceCatalog.orderByChild("Date").startAt(start).endAt(end).limitToLast(COUNT_ON_PAGE).addChildEventListener(listener);
它们是相同的。
我认为它们的区别仅在于人们使用Java进行匿名编程的方式 是否上课。
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