Android KTX (HWSW free! 34)

A lightning talk showing off some of the syntax gains that Google’s Android KTX library offers.

Talk recording (Hungarian): https://www.youtube.com/watch?v=R-oIo4A02CU

Transcript

1. Smoother Android development with Kotlin
   Márton Braun • AutSoft • braun.marton@autsoft.hu
   

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2. Android APIs are sometimes hard to use
   Kotlin allows us to reshape existing API
   Extension functions and properties
   Named and default parameters
   Operator overloading
   Lambdas, higher order functions, and inline functions
   Everyone has their own collection of utilities…
   

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3. Google takes a stance, creates their own
   First appeared Feb 2, 2018
   Goals
   Only provide uniquely Kotlin APIs
   Don’t provide new implementation, just new syntax
   Minimize overhead, focus on zero overhead abstractions
   

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5. Extension properties
   view.setVisibility(View.VISIBLE)
   view.visibility = View.VISIBLE
   view.isVisible = true
   

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6. Default and named parameters
   view.setPadding(20, view.topPadding,
   20, view.bottomPadding)
   view.updatePadding(left = 20, right = 20)
   

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7. Operator overloading and extension functions
   linearLayout.addView(view)
   linearLayout += view
   linearLayout.removeView(view)
   linearLayout -= view
   

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8. Higher order, inline extension functions
   for (i in 0 until linearLayout.childCount) {
   val view = linearLayout.get(i)
   Timber.d(view.tag)
   }
   linearLayout.forEach { view ->
   Timber.d(view.tag)
   }
   

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9. Extension functions
   val bitmap = Bitmap.createBitmap(
   view.width, view.height, Bitmap.Config.ARGB_8888)
   view.draw(Canvas(bitmap))
   val bitmap = view.toBitmap()
   

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10. Operator overloading
    val color = bitmap.getPixel(100, 50)
    val color = bitmap[100, 50]
    bitmap.setPixel(100, 50, color)
    bitmap[100, 50] = color
    

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11. Extension functions, default parameters
    Toast.makeText(this, "Hello world", Toast.LENGTH_SHORT)
    .show()
    toast("Hello world")
    

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12. Extension functions, default parameters
    Toast.makeText(this, "Hello world", Toast.LENGTH_LONG)
    .show()
    toast("Hello world", duration = Toast.LENGTH_LONG)
    

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13. Higher order, inline extension functions
    sharedPreferences.edit()
    .putBoolean("drawerOpened", true)
    .apply()
    sharedPreferences.edit {
    putBoolean("drawerOpened", true)
    }
    

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14. Higher order, inline extension functions
    db.beginTransaction()
    db.insert("users", null, values)
    db.setTransactionSuccessful()
    db.endTransaction()
    db.transaction {
    insert("users", null, values)
    }
    

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15. inline fun SQLiteDatabase.transaction(...): T {
    beginTransaction()
    try {
    val result = body()
    setTransactionSuccessful()
    return result
    } finally {
    endTransaction()
    }
    }
    

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16. Destructuring
    val lat = location.latitude
    val lon = location.longitude
    val (lat, lon) = location
    

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17. Explore Android KTX yourself and use it in your projects
    https://github.com/android/android-ktx/
    https://android.github.io/android-ktx/core-ktx/
    Write your own extensions for APIs that don’t fit your needs
    If these are on Android, consider submitting a PR to Android KTX
    

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18. Questions?
    Márton Braun • AutSoft • braun.marton@autsoft.hu
    

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