Take a look at some of the most useful kotlin tips for developing Android apps. Before reading this, it is required you have a good knowledge of kotlin, experience in working with Android SDK. The Android Application development service providers must also be familiar with the Kotlin plugin and using kotlin with Android studio.  

Best Kotlin tips for Android application development solutions

Without further ado lets jump to initial kotlin tips for Android 

Lazy loading 

Lazy loading is extremely useful as it results in faster startup time. When the user opens the app, it opens up immediately without the user having to wait.

For example when creating a shopping app, you can have the actual purchasing API be lazy loaded.

val purchasingApi: PurchasingApi by lazy {

    val retrofit: Retrofit = Retrofit.Builder()

            .baseUrl(API_URL)

            .addConverterFactory(MoshiConverterFactory.create())

            .build()

    retrofit.create(PurchasingApi::class.java)

}

It is also a good way to encapsulate initialization logic 

// bounds is created as soon as the first call to bounds is made 

val bounds: RectF by lazy {

    RectF(0f, 0f, width.toFloat(), height.toFloat())

}

Lambdas 

Lambas reduce the line of code in a source file. 

An on-click listener looks something like this

button.setOnClickListener { view ->

    startDetailActivity()

}

It even works with return values.  

toolbar.setOnLongClickListener {

    showContextMenu()

    true

}

Collection filtering  

One comes across collection filtering while working with API. The collection filtering in Kotlin adds more clarity and makes code more Succint. Something like this 

val users = api.getUsers() 

// we only want to show the active users in one list

val activeUsersNames = items.filter {

    it.active // the "it" variable is the parameter for single parameter lamdba functions

}

adapter.setUsers(activeUsers)

Custom Getters/setters 

By using custom Getters/setters, the access can be simplified.

Something like this

@ParseClassName("Book")

class Book : ParseObject() {

    // getString() and put() are methods that come from ParseObject

    var name: String

        get() = getString("name")

        set(value) = put("name", value)

    var author: String

        get() = getString("author")

        set(value) = put("author", value)

}

Global constants

When the scope needs to be global, kotlin provides best ways to do so without having to go through a constant class.

package com.savvyapps.example

import android.support.annotation.StringDef

// Note that this is not a class, or an object

const val PRESENTATION_MODE_PRESENTING = "presenting"

const val PRESENTATION_MODE_EDITING = "editing"

They can be used as constants anywhere in the project

import com.savvyapps.example.PRESENTATION_MODE_EDITING

val currentPresentationMode = PRESENTATION_MODE_EDITING

Leveraging let

Leveraging let allows Android App development providers execute a block if the value of the object is not null. For example this is how it looks like in Java.

if (currentUser != null) {

    text.setText(currentUser.name)

}

And in Kotlin, it looks something like this.

user?.let {

    println(it.name)

}

Extensions

Adding extensions is an intermediate kotlin tip. Using extensions, you can add to the functionality of a class without having to Inherit from it. With the extensions, you can accomplish this easily.

fun Activity.hideKeyboard(): Boolean {

    val view = currentFocus

    view?.let {

        val inputMethodManager = getSystemService(Context.INPUT_METHOD_SERVICE)

                as InputMethodManager

        return inputMethodManager.hideSoftInputFromWindow(view.windowToken,

                InputMethodManager.HIDE_NOT_ALWAYS)

    }

    return false

}

Data classes

Data classes simplify classes, adding copy(), equals(), and toString(),hashCode(),methods automatically.

For example, take a look at this data class.

data class User(val name: String, val age: Int)

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