Coroutine Samples

coroutines_sample.kt

// implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.2'
// for lifecycleScope:  implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.2.0-rc02'

class MyFragment : Fragment() {
  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val request = Request.Builder().get()
        .url("https://icanhazip.com")
        .build()

    // blocking style
    viewLifecycleOwner.lifecycleScope.launch {
      try {
        val result = exampleBlockingStyle(request)
        Log.e("result: $result", this)
      } catch (e: Exception) {
        e.printStackTrace()
      }
    }

    // listener style
    viewLifecycleOwner.lifecycleScope.launch {
      try {
        val result = exampleListenerStyle(request)
        Log.e("result: $result", this)
      } catch (e: Exception) {
        e.printStackTrace()
      }
    }
  }

  suspend fun exampleBlockingStyle(req: Request): String? {
    return withContext(Dispatchers.IO) {
      Log.d("execute on " + Thread.currentThread().name, this)
      val response = OkHttpClient().newCall(req).execute()
      Thread.sleep(3000)
      if (response.isSuccessful) {
        response.body()?.string()
      } else {
        throw IOException("HTTP error ${response.code()}")
      }
    }
  }

  suspend fun exampleListenerStyle(req: Request): String? {
    return suspendCoroutine { continuation ->
      OkHttpClient().newCall(req).enqueue(object : Callback {
        override fun onResponse(call: Call, response: Response) {
          val body = response.body()?.string()
          continuation.resume(body)
        }

        override fun onFailure(call: Call, e: IOException) {
          continuation.resumeWithException(e)
        }
      })
    }
  }
}