Develop Reference

query of json in flutter

I've got the following json response from spotify api:
{
"artists" : {
"href" : "https://api.spotify.com/v1/search?query=U2&type=artist&offset=0&limit=20",
"items" : [ {
"external_urls" : {
"spotify" : "https://open.spotify.com/artist/51Blml2LZPmy7TTiAg47vQ"
},
"followers" : {
"href" : null,
"total" : 3146466
},
"genres" : [ "irish rock", "permanent wave", "rock" ],
"href" : "https://api.spotify.com/v1/artists/51Blml2LZPmy7TTiAg47vQ",
"id" : "51Blml2LZPmy7TTiAg47vQ",
"images" : [ {
"height" : 640,
"url" : "https://i.scdn.co/image/e22d5c0c8139b8439440a69854ed66efae91112d",
"width" : 640
}, {
"height" : 160,
"url" : "https://i.scdn.co/image/7293d6752ae8a64e34adee5086858e408185b534",
"width" : 160
} ],
"name" : "U2",
"popularity" : 76,
"type" : "artist",
"uri" : "
I would like to get the id value, which in this case is
51Blml2LZPmy7TTiAg47vQ
but I can't figure out how to make a query in this json using dart.
I tried out as this answer but did not work.
Is there any way to make a query on json with flutter?

Try json.decode(string)['artists']['items'][0]['id']
json.decode decodes the string to a Map<dynamic, dynamic> containing nested Maps and Lists into which you can index. (Maps are indexed by key; Lists are indexed by integer.)

Firebase multiple where clauses using equalsTo

I have a list of all the keys I want to download from Firebase. For this I'm using this code:
Query newUidsQuery = FirebaseDatabaseHelper.getUsersReference();
newUidsQuery.orderByChild(DATABASE_NODE_USER_UID);
for (String uid : uidList) {
newUidsQuery.equalTo(uid);
}
newUidsQuery.addListenerForSingleValueEvent();
This is my current structure:
{
"users" : {
"5mvsiNKz2hO4rmcDDNskv855dkB3" : {
"contacts" : [ "GG8JeRNOIhb1qloZb4oCAb7Jd593", "gc0ci7Jgu2QpVYFbeiMJfVy1WHP2" ],
"contactsHash" : -224276455,
"email" : "lung.razvan#yahoo.com",
"name" : "Razvan Cristian Lung",
"photoUrl" : "https://lh5.googleusercontent.com/-bItm3-ieAtU/AAAAAAAAAAI/AAAAAAAALZo/mtPyAMohOvg/s96-c/photo.jpg",
"uid" : "5mvsiNKz2hO4rmcDDNskv855dkB3"
},
"GG8JeRNOIhb1qloZb4oCAb7Jd593" : {
"contactsHash" : 1,
"email" : "andralung#yahoo.com",
"name" : "Andra Florina Lung",
"photoUrl" : "https://lh4.googleusercontent.com/-po2yelyi3mY/AAAAAAAAAAI/AAAAAAAAQ5s/ROefxP6Q1oA/s96-c/photo.jpg",
"uid" : "GG8JeRNOIhb1qloZb4oCAb7Jd593"
},
"gc0ci7Jgu2QpVYFbeiMJfVy1WHP2" : {
"contactsHash" : 1,
"email" : "lung_razvan2100#yahoo.com",
"name" : "Lung Razvan",
"photoUrl" : "https://scontent.xx.fbcdn.net/v/t1.0-1/p100x100/15390976_1192204140865562_3397773349261436244_n.jpg?oh=d61795a8df67d3e9c5ddf60557e9e60c&oe=59270863",
"uid" : "gc0ci7Jgu2QpVYFbeiMJfVy1WHP2"
}
}
}
The problem is that when I try to get only the entries with the specific key I also get the other entries that have that key as a value in the "contacts" field.

When you call orderBy... or other methods, it returns a new query. So you're now creating a new query for each uid that you then don't use. To keep it, you'd need newUidsQuery = newUidsQuery.equalTo(uid).
But that won't solve the problem yet, because a query can only order/filter on a single property and value. See Query based on multiple where clauses in firebase.
Better news is that this doesn't matter much here, since you can just retrieve the items one at a time. Unlike what you might expect, that's not significantly slower than retrieving them in one go. See Speed up fetching posts for my social network app by using query instead of observing a single event repeatedly or watch this episode of #AskFirebase: https://youtu.be/66lDSYtyils?t=1m49s

Firebase whitelist and recyclerView

{
"Events" : {
"events" : {
"-KT5UMQAhDHs1bB8bKLc" : {
"activity" : "biking",
"address" : "54°05'45.8\"N 28°19'02.9\"E, просп. Мира 9, Жодино, Беларусь",
"category" : "sport",
"creatorID" : "m11EvlP19OSbEz8XYl2MsNCwGXX2",
"date" : 1475431200689,
"forFriends" : true,
"info" : "вттчтвт",
"name" : "ьаьатвтвтт",
"uid" : "-KT5UMQAhDHs1bB8bKLc"
},
"-KUSsl7RaL-dVoDCoSYT" : {
"activity" : "picnic",
"address" : "Узденский район, Узденский район, Беларусь",
"category" : "entertainment",
"creatorID" : "1RXDSJzSEXakxvNdM41Ae3nbHN72",
"date" : 1477328400000,
"forFriends" : false,
"info" : "45",
"name" : "Test of date",
"uid" : "-KUSsl7RaL-dVoDCoSYT"
}
},
"FriendsOF" : {
"NuKweeGv8zTgt1Vi9RcU3i1u86U2" : {
"1RXDSJzSEXakxvNdM41Ae3nbHN72" : true
},
"m11EvlP19OSbEz8XYl2MsNCwGXX2" : {
"1RXDSJzSEXakxvNdM41Ae3nbHN72" : true
}
},
"Users" : {
"1RXDSJzSEXakxvNdM41Ae3nbHN72" : {
"email" : "*#gmail.com",
"name" : "Алексей Гвоздицкий",
"picture" : "*.jpg"
},
"NuKweeGv8zTgt1Vi9RcU3i1u86U2" : {
"email" : "*#gmail.com",
"name" : "Ольга Гвоздицкая",
"picture" : "*.jpg"
},
"m11EvlP19OSbEz8XYl2MsNCwGXX2" : {
"email" : "*#gmail.com",
"name" : "Егор Александров",
"picture" : "*.jpg"
}
}
}
I have a list of "events". Every "event" can be "forFiends" only (only if current user is in event creators "FriendsOF" list, then he can see this event. FriendsOF it's a whitelist). All availiable for current user events i want to represent in RecyclerView.
I am stucked. I can get all data snapshot and then filter on client side it. But it is not way of Jedi, because i load tonns of unnecessary data. Another solution is to deny acces to event if user should not see it. But i don't understand how to do it. My ref is mEventsRef = FirebaseDatabase.getInstance().getReference().child("Events").child("events"); And rule i can make for
"events":{
"$eventId":{".read":....}
}
So according to this guide i'll get empty recyclerView because of "error callback triggered with PERMISSION_DENIED"
Help me to solve my problem please!

Firebase Android Database

I am making an app that should include chat. I would like to display conversations of the current user. I am not sure how to get only chats of the current user. This is my structure of database.
"chats" : {
"-KWYiJiFwE6miPNkKPe0" : {
"chatPartner1" : {
"id" : "rtg3ru7zNYQQp9LA484VIG5rItl1",
"name" : "ghjg",
"photo" : ""
},
"chatPartner2" : {
"id" : "rtg3ru7bzwwewNYQwwewetegb",
"name" : "petra",
"photo" : ""
},
"id" : "-KWYiJiFwE6miPNkKPe0",
"lastMessage" : "dhjcd",
"timestamp" : 1479141836276
}
This json represents storing message for specified chats according to its id.
"messages" : {
"-KWYiJiFwE6miPNkKPe0" : {
"-KWYiJiPWR3n_YcvokCm" : {
"senderId" : "rtg3ru7zNYQQp9LA484VIG5rItl1",
"text" : "dhjcd",
"timestamp" : 1479141836276
}
}
I would need to check if the chatPartner 1 or 2 contains id of the current user. Or do you know about better way to store chats?
Thanks

How to parse json data comming from drupal site to android app?

I am trying to send data from drupal website to android app in the form of json. i have created the link and now my link is returning data in this form.
i don't have any idea how to parse this formatted data to show in a list view in android app.
{
"nodes" : [
{
"node" : {
"title" : "Saksham Iron Store",
"Contact" : "09216630565",
"Category" : "Decoration & Hardware",
"City" : "Sangrur"
}
},
{
"node" : {
"title" : "Loaffer Hut Garments",
"Contact" : "8591697698",
"Category" : "Fashion & Garments",
"City" : "Sangrur"
}
},
{
"node" : {
"title" : "BCB English Academy and Visa Guidance",
"Contact" : "8699010091",
"Category" : "Education",
"City" : "Sangrur"
}
},
{
"node" : {
"title" : "Aggarwal Engineering Corporation",
"Contact" : "9417070197",
"Category" : "Decoration & Hardware",
"City" : "Sangrur"
}
},
{
"node" : {
"title" : "Inder Sain Paint and Decoration",
"Contact" : "9888821904",
"Category" : "Decoration & Hardware",
"City" : "Sangrur"
}
}
]
}
How can i parse it and show in listview in android app?

Assuming that the JSON syntax of your receiving data conforms to the standard model you can parse JSON in android with one of the libraries already present in the org.json package (eg. JSONArray for arrays).
I'd suggest you take a look at GSON library ( my personal preference, there are of course many others) for it makes it easier to focus on your business logic and not occupy yourself with parsing JSON.