无法使用FirebaseUI从FirebaseDatabase Realtime调用值 [英] Unable to call values from FirebaseDatabase Realtime Using FirebaseUI
问题描述
以上只是FirebaseDatabase中文件夹结构的示例. 我的查询是我应该如何获取那些子节点值.
Above is just an example of the structure of the folder in FirebaseDatabase. My query is that how am I suppose to get those child node value.
下面是我尝试的代码:
//FirebaseDatabase Collecting all the Item List
ValueEventListener listener= new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()){
for (DataSnapshot ds: dataSnapshot.getChildren()){
arrayItemList.add(ds.getKey());
}
firebaseRecyclerViewItem(arrayItemList);
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Log.i(TAG, "onCancelled: Unable to fetch data");
}
};
lookUpDatabase.addValueEventListener(listener);
以下是方法firebaseRecyclerViewItem()的代码:
Here is code for the Method firebaseRecyclerViewItem():
public void firebaseRecyclerViewItem(final ArrayList<String> arrayItemList) {
DatabaseReference reference = null;
String referenceName = null;
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
//FirebaseDatabase 2'nd Reference Address
for (DataSnapshot ds : dataSnapshot.getChildren()) {
String key1 = ds.getKey();
Log.i(TAG, "onDataChange: " + key1);
String firebaseItemName = ds.child("DATA").getValue(String.class);
Log.i(TAG, "onDataChange: " + firebaseItemName);
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
};
for (int i = 0; i < arrayItemList.size(); i++) {
referenceName = arrayItemList.get(i);
reference = FirebaseDatabase.getInstance().getReference().child("DATA").child(referenceName);
reference.addValueEventListener(valueEventListener);
//Loading RecyclerView
RecyclerViewItemList(reference, referenceName);
}
}
不是我无法获得这些值，但是我能够获得它，但是在我附加的数据库图片中有三个FILE01，FILE02和FILE03.我只能获取最新的FILE03，即"01"值，我的意思是ValueEventListner跳过那里存在的所有其他文件，仅获取最新的更新或最新的文件.但我希望在那里显示的所有文件数据都可以在我的recyclerView上显示.
Is not that I am not able to get the values, I am able to get it however in the database pic which I have attached there are three FILE01, FILE02 and FILE03. I am only able to get the last FILE03, "01" value, I mean ValueEventListner skips all the other FILE present there only take the Last update or the last file. But I want all the files data present there to display it on my recyclerView.
我还尝试了另一种方法来获取DataSnaphot，并使用for()循环，其中使用了嵌套循环:
I have also tried a different approached where I get the DataSnaphot, and use the for() Loop, where I used nested loop:
//FirebaseDatabase Collecting all the Item List
ValueEventListener listener= new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()){
// here is where the changes which I have made, I tried to called the value which is impossible but still I tried to, but not result.
for (DataSnapshot ds: dataSnapshot.getChildren()){
String key= ds.getKey();
String firebaseItemName = ds.child("DATA").getValue(String.class);
Log.i(TAG, "onDataChange: " + firebaseItemName);
}
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Log.i(TAG, "onCancelled: Unable to fetch data");
}
};
lookUpDatabase.addValueEventListener(listener);
RecyclerViewItemList(lookUpDatabase);
有没有一种方法或方法可以用来调用值.
Is there a way or a method which I can use to call the values.
推荐答案
您应在 for循环中调用 notifyDataSetChanged().否则，您的引用和 referenceName 将被重写.
You should call notifyDataSetChanged() in for loop. Otherwise your reference and referenceName will be rewrited.
因此您的代码应为
for (int i = 0; i < arrayItemList.size(); i++){
//Add your data to arraylist
rvAdapter.notifyDataSetChanged();
}
修改:
这将显示您的Firebase数据.我只是改变了第二种方法.
This will show your firebase data. I just changed your second method.
/*I changed Here*/
private ArrayList<HashMap<String,String>> yourChildList = new ArrayList<>();
ValueEventListener listener= new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()){
for (DataSnapshot ds: dataSnapshot.getChildren()){
/*I changed Here*/
HashMap<String,String> dataMap = new HashMap<>();
String key= ds.getKey();
String firebaseItemName = ds.child("DATA").getValue(String.class);
Log.i(TAG, "onDataChange: " + firebaseItemName);
/*I changed Here*/
dataMap.put(key,firebaseItemName);
yourChildList.add(yourDataMap);
}
/*I changed Here
*
*I think this method is used to update data to your recyclerView
*if I'm right, you can replace it
*RecyclerViewItemList(lookUpDatabase);
*
*/
yourRecyclerAdapter = new RecyclerAdapter(yourChildList);
yourRecyclerAdapter.notifyDataSetChanged();
recyclerView.setAdapter(yourRecyclerAdapter);
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Log.i(TAG, "onCancelled: Unable to fetch data");
}
};
lookUpDatabase.addValueEventListener(listener);
注意:我不建议您使用嵌套的侦听器.您应避免使用嵌套的侦听器以获得更好的性能和可维护性.您应该使用观察者或 LiveData 来更新Recyclerview.
Note:I don't recommend you to use nested listeners. You should avoid nested listener for better performance and maintainability. You should use Observer or LiveData to update Recyclerview.
这篇关于无法使用FirebaseUI从FirebaseDatabase Realtime调用值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
