Execute your first query

5. Execute your first query

Overview

Let's test out our query and validate that it can return data from our remote GraphQL server.

In this lesson we will:

Incorporate ApolloClient into our app
Add some temporary code to the LaunchListViewModel to show how to execute a GraphQL operation

Create an `ApolloClient`

Create a new file named Apollo.kt in the com.example.rocketreserver package and create an instance of ApolloClient in it:

app/src/main/kotlin/com/example/rocketreserver/Apollo.kt

import com.apollographql.apollo.ApolloClient

val apolloClient = ApolloClient.Builder()
    .serverUrl("https://apollo-fullstack-tutorial.herokuapp.com/graphql")
    .build()

Note: apolloClient is a top-level variable so that it can be reused from other parts of the app later on for better performance. Reusing the apolloClient allows you to reuse the underlying OkHttp instance and the associated threadpools and connections. In a production app, you would probably want to use a dependency injection framework to share the ApolloClient.

Creating ApolloClient is as simple as giving it the endpoint of your GraphQL backend. It is https://apollo-fullstack-tutorial.herokuapp.com/graphql in our case.

Execute the query

Open LaunchList.kt and update the contents of the LaunchList composable function. Use apolloClient and the generated LaunchListQuery to execute a new query:

app/src/main/kotlin/com/example/rocketreserver/LaunchList.kt

@Composable
fun LaunchList(onLaunchClick: (launchId: String) -> Unit) {
  LaunchedEffect(Unit) {
    val response = apolloClient.query(LaunchListQuery()).execute()
    Log.d("LaunchList", "Success ${response.data}")
  }
  LazyColumn(modifier = Modifier.fillMaxSize()) {
    // ...
  }
}

Thanks to Kotlin coroutines, the query will be executed in a background thread even if the code looks synchronous.

Note: for simplicity, we are executing the query in a LaunchedEffect block. In a real app, you may want to do this in a ViewModel and otherwise use a layered architecture.

Test your query

Hit run. You should see this in the logcat output:

(logcat)

Success Data(launches=Launches(cursor=1583556631, hasMore=true, launches=[Launch(id=110, site=KSC LC 39A), Launch(id=109, site=CCAFS SLC 40), Launch(id=108, site=VAFB SLC 4E), Launch(id=107, site=KSC LC 39A), Launch(id=106, site=CCAFS SLC 40), Launch(id=105, site=CCAFS SLC 40), Launch(id=104, site=KSC LC 39A), Launch(id=103, site=KSC LC 39A), Launch(id=102, site=KSC LC 39A), Launch(id=101, site=CCAFS SLC 40), Launch(id=100, site=CCAFS SLC 40), Launch(id=99, site=KSC LC 39A), Launch(id=98, site=CCAFS SLC 40), Launch(id=97, site=CCAFS SLC 40), Launch(id=96, site=CCAFS SLC 40), Launch(id=95, site=CCAFS SLC 40), Launch(id=94, site=KSC LC 39A), Launch(id=93, site=KSC LC 39A), Launch(id=92, site=KSC LC 39A), Launch(id=91, site=CCAFS SLC 40)]))

Android Studio with logcat output beginning with "Success Data"

This means the request was correctly executed and you now have a list of launch sites 🚀🚀🚀

Task!

I added the specified code and saw the correct output in logcat.

Up next

Next, let's connect this data to our UI 🚀

Share your questions and comments about this lesson

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beta

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