android-fhir

Use QuestionnaireFragment

QuestionnaireFragment is the main interface for displaying FHIR Questionnaires and getting user responses as FHIR QuestionnareResponses. In this section, we will discuss how to use QuestionnaireFragment in more detail. To use QuestionnaireFragment effectively, you should also be familiar with using Fragments in Android.

Display a Questionnaire in your application

Place a QuestionnaireFragment in your activity or fragment whenever you want to display a questionnaire. First, add a FragmentContainerView to your activity’s layout to contain the rendered Questionnaire, as shown in the following example:

<androidx.fragment.app.FragmentContainerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_container_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Next, define the content of the FHIR Questionnaire to render. The Questionnaire must be JSON-encoded and can be provided as a String or a URI to a JSON file. These values are provided in QuestionnaireFragment.Builder used to create a QuestionnaireFragment.

The following example reads a file in the assets/ directory to a String which will be passed to the QuestionnaireFragment.

val questionnaire: String =
    application.assets.open("questionnaire.json").bufferedReader().use { it.readText() }

Providing a String is only suitable for Questionnaires that are a few KBs in size, or you may get a TransactionTooLargeException exception. For larger FHIR Questionnaires, use the URI-based option below.

Alternatively, you may use a URI pointing to a JSON file containing the questionnaire. The example below creates a URI for a questionnaire file stored as a raw resource.

val questionnaire: Uri =
 Uri.parse("android.resource://" + this.packageName + "/" + R.raw.questionnaire)

How you get or create a URI for your questionnaire will depend on your data source. You cannot get a URI for a file in the assets/ directory. However, you can use the following code to create a temporary copy and get a URI for it.

/**
* Returns a [Uri] pointing to a temporary file containing the content of the asset file with
* [filename].
*/
private suspend fun createUri(filename: String) =
 withContext(backgroundContext) {
   val application = getApplication<Application>()
   val outputFile = File(application.externalCacheDir, filename)
   application.assets.open(filename).use { inputStream ->
     outputFile.outputStream().use { outputStream -> IOUtils.copy(inputStream, outputStream) }
   }
   Uri.fromFile(outputFile)
 }

Use QuestionnaireFragment.Builder to create the QuestionnaireFragment. You must call one of setQuestionnaire(questionnaireJson: String) or setQuestionnaire(questionnaireUri: Uri) in QuestionnaireFragment.Builder. If neither is provided, the system throws an IllegalStateException exception. If both are provided, setQuestionnaire(questionnaireUri: Uri) takes precedence and setQuestionnaire(questionnaireJson: String) is ignored.

In a real application, the FHIR Questionnaire JSON can be loaded from a file (like in the examples above), a database, the network, or even hardcoded, depending on your use case. If you are using any I/O operations to load the JSON, it should be done asynchronously such as by using coroutines.

Finally, use [FragmentManager](https://developer.android.com/guide/fragments/fragmentmanager) to programmatically set the fragment to the FragmentContainerView.

if (savedInstanceState == null) {
 supportFragmentManager.commit {
   setReorderingAllowed(true)
   add(
     R.id.fragment_container_view,
     QuestionnaireFragment.builder().setQuestionnaire(questionnaire).build(),
     QUESTIONNAIRE_FRAGMENT_TAG
   )
 }
}

This example shows the minimal code to add a fragment programmatically, but Android strongly recommends using the Navigation library to manage navigation in a real app.

Collect a Questionnaire response

Once the user has finished filling out the questionnaire, you can collect the questionnaire response. Typically you should use FragmentManager to find your questionnaire fragment and then call getQuestionnaireResponse().

val fragment: QuestionnaireFragment =
 supportFragmentManager.findFragmentById(R.id.fragment_container_view) as QuestionnaireFragment
val questionnaireResponse = fragment.getQuestionnaireResponse()

The form answers are structured as a FHIR QuestionnaireResponse, which is a structured set of answers to the questions in the corresponding FHIR Questionnaire. More specifically, it an instance of [org.hl7.fhir.r4.model.QuestionnaireResponse](https://hapifhir.io/hapi-fhir/apidocs/hapi-fhir-structures-r4/org/hl7/fhir/r4/model/QuestionnaireResponse.html), a class in the HAPI FHIR Structures library which is used as the in-memory data model for FHIR resources in the SDK. This provides a relatively convenient interface to work with the data:

// Get the first answer for the first item
val questionnaireResponseFirstAnswer =
 questionnaireResponse.item[0].answer[0].value.asStringValue()

// Convert the whole response to a JSON string and send to log
val jsonParser = FhirContext.forCached(FhirVersionEnum.R4).newJsonParser()
val questionnaireResponseString = jsonParser.encodeResourceToString(questionnaireResponse)
Log.d( "response", questionnaireResponseString)

Learn more about working with HAPI FHIR resources.

What you do with the questionnaire response depends on your use case:

Pre-fill a questionnaire with existing answers

If you want your questionnaire to start with some answers already filled, include a questionnaire response in your arguments bundle for your QuestionnaireFragment.

val questionnaireFragment =
 QuestionnaireFragment.builder()
   .setQuestionnaire(questionnaire)
   .setQuestionnaireResponse(questionnaireResponse)
   .build()

This may be useful if, for example, you allow a user to edit a form they have previously submitted, or to pre-fill certain fields where you already know the value based on another source.

Provide one of setQuestionnaire(questionnaireJson: String) or setQuestionnaire(questionnaireUri: Uri) in the QuestionnaireFragment.Builder. If both are provided, setQuestionnaire(questionnaireUri: Uri) takes precedence and setQuestionnaire(questionnaireJson: String) is ignored.

Similar to questionnaires, do not pass questionnaire responses over a few KBs in size as a String in setQuestionnaireResponse(questionnaireResponseJson: String), but instead provide a URI using setQuestionnaireResponse(questionnaireResponseUri: Uri).

Further reading

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