Kotlin Anko Commons

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Why Kotlin better than Java For Android Development
Why Kotlin better than Java For Android Development

Anko Commons is a “toolbox” for Kotlin Android developer. The library contains a lot of helpers for Android SDK, including, but not limited to:

1Using Anko Dialogs in your project

Dialog helpers are inside the anko-commons artifact. Add it as a dependency to your build.gradle:

dependencies {
    compile "org.jetbrains.anko:anko-commons:$anko_version"
}

2Toasts

Simply shows a Toast message.

toast("Hi there!")
toast(R.string.message)
longToast("Wow, such a duration")

3Alerts

A small DSL for showing alert dialogs.

alert("Hi, I'm Roy", "Have you tried turning it off and on again?") {
    yesButton { toast("Oh…") }
    noButton {}
}.show()

The code above will show the default Android alert dialog. If you want to switch to the appcompat implementation, use the Appcompat dialog factory:

alert(Appcompat, "Some text message").show()

4Selectors

selector() shows an alert dialog with a list of text items:

val countries = listOf("Russia", "USA", "Japan", "Australia")
selector("Where are you from?", countries) { i ->
    toast("So you're living in ${countries[i]}, right?")
}

5Progress dialogs

progressDialog() creates and shows a progress dialog.

val dialog = progressDialog(message = "Please wait a bit…", title = "Fetching data")

An indeterminate progress dialog is also available (see indeterminateProgressDialog()).

6Intent builder functions

In general, you have to write a couple of lines to start a new Activity. And it requires you to write an additional line for each value you pass as an extra. For example, this is a code for starting an Activity with extra ("id", 5) and a special flag:

val intent = Intent(this, SomeOtherActivity::class.java)
intent.putExtra("id", 5)
intent.setFlag(Intent.FLAG_ACTIVITY_SINGLE_TOP)
startActivity(intent)

Four lines is too much for this. Anko offers you an easier way:

startActivity(intentFor<SomeOtherActivity>("id" to 5).singleTop())

7Useful Intent callers

Anko has call wrappers for some widely used Intents:

Goal Solution
Make a call makeCall(number) without tel:
Send a text sendSMS(number, [text]) without sms:
Browse the web browse(url)
Share some text share(text, [subject])
Send a email email(email, [subject], [text])

Arguments in square brackets ([]) are optional. Methods return true if the intent was sent.

8Trait-like style

Android SDK provides android.util.Log class with some logging methods. Usage is pretty straightforward though the methods require you to pass a tag argument. You can eliminate this with using AnkoLogger trait-like interface:

class SomeActivity : Activity(), AnkoLogger {
    private fun someMethod() {
        info("London is the capital of Great Britain")
        debug(5) // .toString() method will be executed
        warn(null) // "null" will be printed
    }
}
android.util.Log AnkoLogger
v() verbose()
d() debug()
i() info()
w() warn()
e() error()
wtf() wtf()

The default tag name is a class name (SomeActivity in this case) but you can easily change it by overriding the loggerTag property.

Each method has two versions: plain and lazy (inlined):

info("String " + "concatenation")
info { "String " + "concatenation" }

9Colors

Two simple extension functions to make the code more readable.

Function Result
0xff0000.opaque non-transparent red
0x99.gray.opaque non-transparent #999999 gray

10Dimensions

You can specify dimension values in dip (density-independent pixels) or in sp (scale-independent pixels): dip(dipValue) or sp(spValue). Note that the textSize property already accepts sp (textSize = 16f). Use px2dip and px2sp to convert backwards.

11applyRecursively()

applyRecursively() applies the lambda expression to the passed View itself, and then recursively to every child of a View if it is a ViewGroup:

verticalLayout {
    editText {
        hint = "Name"
    }
    editText {
        hint = "Password"
    }
}.applyRecursively { view -> when(view) {
    is EditText -> view.textSize = 20f
}}

In next article we discuss about Anko Coroutines.

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