Lab 16

🖥 Lab 16: Using WorkManager for Background Tasks

Let's use WorkManager to upload a Note to a public GitHub repo.

• Work Manager is a library for defining persistent background work; that is work that should be completed across app restarts, configuration changes, or in the background.
• Work Manager supports 3 types of work:
  1. Immediate
  2. Persistent
  3. Deferrable

 

📝 Objectives

1. Add an "upload" Button to NoteDetailsFragment

   1. Add a Button element to fragment_note_details.xml
   2. When clicked, this button will eventually start our upload worker

2. Create a new package upload

3. Within the upload package, create a Worker to upload our Note to GitHub

   1. Create a NoteUploadWorker class that extends Worker
   2. Define a uploadFileData(context: Context, filename:String, content:String) method (see hints)
   3. Within uploadFileData(), use Volley to upload a Note as a .txt file to GitHub
      1. see notes for URL formatting
   4. Override doWork() to use uploadFileData() to upload your Note

4. Submit work request to WorkManager

   1. Within NoteDetailFragment.uploadNote() remove the call to start our upload service (if previously completed Lab 15)
   2. Construct a WorkRequest for NoteUploadWorker using OneTimeWorkRequestBuilder<NoteUploadWorker>().setInputData(NoteUploadWorker.buildInputData(note)).build() (see hints)
   3. Submit the request to WorkManager using WorkManager.getInstance(requireContext()).enqueue(uploadWorkRequest)

🖥 Lab 16 Hints: Using WorkManager for Background Tasks

 

💡 Helpful Resources

• WorkManager Basics

 

💡 What GitHub url should I use to upload my note file?

You should use a URL to any repo to which you can generate an access token.

The path to that repo should then be specified as https://api.github.com/repos/<username>/<repo>/contents/$filename

ex: https://api.github.com/repos/goobar-dev/workshop-sample-data/contents/$filename

 

💡 How do I pass my Note data to my Worker?

We can pass data to a Worker using the androidx.work.Data class. This class functions very similar to a Bundle.

Within NoteUploadWorker, create a companion object to help build and parse a Data object for passing the Note data.

companion object {
    private const val KEY_CONTENT = "key_content"
    private const val KEY_FILENAME = "filename"

    fun buildInputData(note: Note): Data = workDataOf(
      KEY_FILENAME to "uploaded-notes/${note.title}-${System.currentTimeMillis()}.txt",
      KEY_CONTENT to encodeNote(note)
    )

    fun parseInputData(data: Data): NoteUploadConfig {
      return NoteUploadConfig(data.getString(KEY_FILENAME)!!, data.getString(KEY_CONTENT)!!)
    }

    private fun encodeNote(note: Note): String {
      val noteContent = note.title + "\n" + note.category + "\n" + note.content
      return Base64.encodeToString(noteContent.toByteArray(), android.util.Base64.DEFAULT)
    }
  }

  data class NoteUploadConfig(val filename: String, val content: String)

 

💡 How to implement doWork()?

override fun doWork(): Result {

    // inputData is a property on [Worker]
    // it provides the input data specified by the work request
    val noteUploadConfig = parseInputData(inputData)

    uploadFileData(applicationContext, noteUploadConfig.filename, noteUploadConfig.content)

    // Indicate whether the work finished successfully with the Result
    return Result.success()
  }

 

💡 How do I submit an upload request to GitHub?

private fun uploadFileData(context: Context, filename: String, content: String) {
    val requestQueue = Volley.newRequestQueue(context)
    
    val body = JSONObject().apply {
      put("message", "Upload from app") // commit message of file upload to GitHub
      put("content", content) 
    }
    
    val request =  object : JsonObjectRequest(
      Method.PUT,
      "url to your repo",
      body,
      { 
          // handle success
          Toast.makeText(context, "Successfully uploaded note", Toast.LENGTH_SHORT).show()
      },
      {
          // handle error
          Toast.makeText(context, "Failed to upload note", Toast.LENGTH_SHORT).show()
      }
    ) {
      override fun getHeaders(): MutableMap<String, String> {
        return mutableMapOf(
          "Authorization" to "token <your repo access token>",
          "Accept" to "application/vnd.github.v3+json"
        )
      }
    }
    
    requestQueue.add(request)
}

 

💡 How do we submit a work request?

// within NoteDetailsFragment
private fun uploadNote() {
    lifecycleScope.launch(Dispatchers.IO) {
      val note = requireActivity().studyGuideApplication().database.noteDao().get(args.selectedNoteId)

      val uploadWorkRequest: WorkRequest =
        OneTimeWorkRequestBuilder<NoteUploadWorker>()
          .setInputData(NoteUploadWorker.buildInputData(note))
          .build()
      WorkManager.getInstance(requireContext()).enqueue(uploadWorkRequest)
    }
  }