【发布时间】：2018-04-26 04:31:18
【问题描述】：
我正在 for 循环中从 firebase 数据库中检索数据，但问题是 firebase 函数没有同步执行，我知道 firebase 函数是异步的。有什么解决办法吗？
代码：-
registrationReference.child(userId).child("generated_links").addListenerForSingleValueEvent(new ValueEventListener()
{
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
peopleModelList.clear();
for(DataSnapshot snapshot : dataSnapshot.getChildren())
{
peopleModel = new PeopleModel();
peopleHashMap =(HashMap)snapshot.getValue();
peopleModel.setChatWith((String)peopleHashMap.get("chatWith"));
peopleModel.setNickname((String)peopleHashMap.get("nickname"));
peopleModel.setChatRoom(snapshot.getKey());
Log.d("kkkk","1st");
if(peopleModel.getChatWith()!=null && !("".equals(peopleModel.getChatWith())))
{
registrationReference.child(peopleModel.getChatWith()).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
peopleModel.setRefresh_token((String)dataSnapshot.child("refresh_token").getValue());
peopleModelList.add(peopleModel);
Log.d("kkkk","2nd");
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Log.d("kkkk","3rd");
}
iCallBackPeople.peopleAct(peopleModelList);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
输出：-
1st
3rd
2nd
但我想要这样的输出
1st
2nd
3rd
注意：- 我搜索了，但没有任何解决方案！
How to get data from Firebase Database in a loop?
Firebase addListenerForSingleValueEvent excute later in loop
我试过了，但对我不起作用，它用最后一项填满了我的清单！
public void listOfUsers(final ICallBackPeople iCallBackPeople) {
count=0;
//peopleModelList = new ArrayList<>();
sortedMap = new TreeMap<>();
// peopleModelList = new ArrayList<PeopleModel>(sortedMap.values());
registrationReference.child(userId).child("generated_links").addListenerForSingleValueEvent(new ValueEventListener()
{
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// peopleModelList.clear();
for(DataSnapshot snapshot : dataSnapshot.getChildren())
{
peopleModel = new PeopleModel();
peopleHashMap =(HashMap)snapshot.getValue();
peopleModel.setChatWith((String)peopleHashMap.get("chatWith"));
peopleModel.setNickname((String)peopleHashMap.get("nickname"));
peopleModel.setChatRoom(snapshot.getKey());
//Object chatRoom = snapshot.getKey();
Log.d("kkkk","1st");
if(peopleModel.getChatWith()!=null && !("".equals(peopleModel.getChatWith())))
{
addItem(count,iCallBackPeople);
count++;
}
Log.d("kkkk","3rd");
}
Log.d("kkkk","end");
//iCallBackPeople.peopleAct(peopleModelList);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void addItem(final int index, final ICallBackPeople iCallBackPeople) {
registrationReference.child(peopleModel.getChatWith()).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
peopleModel.setRefresh_token((String)dataSnapshot.child("refresh_token").getValue());
Log.d("kkkk","2nd");
sortedMap.put(index, peopleModel);
// sortedMap will sort your list by key (in this case, key is integer)
if(sortedMap.size()==2)
{
peopleModelList = new ArrayList<PeopleModel>(sortedMap.values());
iCallBackPeople.peopleAct(peopleModelList);
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
我试过了，但没有得到所有项目，只获取快照中最后一个项目的列表
public void listOfUsers(final ICallBackPeople iCallBackPeople) {
peopleModelList = new ArrayList<>();
registrationReference.child(userId).child("generated_links").addListenerForSingleValueEvent(new ValueEventListener()
{
PeopleModel peopleModel;
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
peopleModelList.clear();
for(final DataSnapshot snapshot : dataSnapshot.getChildren())
{
peopleModel = new PeopleModel();
peopleHashMap =(HashMap)snapshot.getValue();
peopleModel.setChatWith((String)peopleHashMap.get("chatWith"));
peopleModel.setNickname((String)peopleHashMap.get("nickname"));
peopleModel.setChatRoom(snapshot.getKey());
if(peopleModel.getChatWith()!=null && !("".equals(peopleModel.getChatWith())))
{
getToken(new CallBackGetToken() {
@Override
public void token(String token) {
peopleModel.setRefresh_token(token);
Toast.makeText(context, token, Toast.LENGTH_SHORT).show();
peopleModelList.add(peopleModel);
//here i am checking my peopleModelList size is equal or not to snapshot
if(peopleModelList.size()==2)
iCallBackPeople.peopleAct(peopleModelList);
}
},peopleModel);
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void getToken(final CallBackGetToken callBackGetToken ,PeopleModel peopleModel) {
registrationReference.child(peopleModel.getChatWith()).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
callBackGetToken.token((String)dataSnapshot.child("refresh_token").getValue());
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
【问题讨论】：
-
这并不意味着它不起作用。它有效，但它只显示最后一个对象的名称。为此，您应该将该语句从 for 循环中取出，因为每次迭代都会调用该语句，最终只有一项，最后一项，对吧？
-
是的，假设我有一个模型，其中有 3 个成员，所以我在调用回调函数之前获得 2 个数据成员值，在回调函数之后获得 1 个数据成员值然后放入列表！
-
请回复
@。同样在这种情况下，您需要等待数据。
标签： android firebase firebase-realtime-database