How Cool is Kotlin?

Before you dive deeper into Kotlin’s features, go back to DetailActivityKotlin.kt and replace the contents of the file with the following:

  
package com.tejsumeru.android.omgandroid

import android.content.Intent
import android.os.Bundle
import android.support.v4.view.MenuItemCompat
import android.support.v7.app.AppCompatActivity
import android.view.Menu
import android.widget.ImageView
import android.support.v7.widget.ShareActionProvider
import com.squareup.picasso.Picasso

class DetailActivityKotlin : AppCompatActivity() {

  private val imageUrlBase = "http://covers.openlibrary.org/b/id/"
  private var imageURL = ""
  private var shareActionProvider: ShareActionProvider? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    setContentView(R.layout.activity_detail)

    actionBar?.setDisplayHomeAsUpEnabled(true)

    val imageView = findViewById<ImageView>(R.id.img_cover)

    val coverId = this.intent.extras.getString("coverID")

    val len = coverId?.length ?: 0

    if (len > 0) {
      imageURL = imageUrlBase + coverId + "-L.jpg"
      Picasso.with(this).load(imageURL).placeholder(R.drawable.img_books_loading).into(imageView)
    }
  }

  private fun setShareIntent() {

    val shareIntent = Intent(Intent.ACTION_SEND)
    shareIntent.type = "text/plain"
    shareIntent.putExtra(Intent.EXTRA_SUBJECT, "Book Recommendation!")
    shareIntent.putExtra(Intent.EXTRA_TEXT, imageURL)

    shareActionProvider?.setShareIntent(shareIntent)
  }

  override fun onCreateOptionsMenu(menu: Menu): Boolean {

    menuInflater.inflate(R.menu.main, menu)

    val shareItem = menu.findItem(R.id.menu_item_share)

    shareActionProvider = MenuItemCompat.getActionProvider(shareItem) as ShareActionProvider

    setShareIntent()

    return true
  }
}

On the surface, the code resembles Java, but there are some Kotlin language specifics that you’ll get into in the next section.

Build and run, select a book and see if you get a cover this time. Oh, look, you do!