Alert Dialog box in android using Kotlin

A subclass of Dialog that can display one, two or three buttons. If you only want to display a String in this dialog box, use the setMessage() method.  Most frequently using part is creating alert dialog box during application development. Here we are going to develop alert dialog using kotlin.



Here is simle kotlin code:





and output looks like:

I hope you are enjoying simple code than java for making alert dialog box with take and give inputs.

full code: https://goo.gl/rJLyc7

#HappyCoding #ILoveKotlin #PrAndroid

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Solution: “Type inference failed” error by using "findViewById” in Kotlin

If you get any error when you are using kotlin and references views to kotlin, then most of time every developer faced  “Type inference failed” error  in Kotlin.

We have few option for such kind of error in kotlin,

var tvName = findViewById(R.id.txtName) as TextView

to

var tvName = findViewById<TextView>(R.id.txtName) 

You can use Kotlin Android Extensions too for that. Check the doc here.

Kotlin Android Extensions:

• In your app gradle.build add apply plugin: 'kotlin-android-extensions'
• In your class add import for import kotlinx.android.synthetic.main.<layout>.* where <layout> is the filename of your layout. for example activity_main
• That's it, you can call TextView directly in your code.

Sometimes its works like this:

var tvName:TextView = findViewById(R.id.txtName) as TextView

If you are using Anko, then you have to do this:

var tvName:TextView = find(R.id.txtName)

Where bind internally work like this:


fun <T : View> Activity.bind(@IdRes res : Int) : T {
    @Suppress("UNCHECKED_CAST")
    return findViewById(res) as T}

More info:
https://kotlinlang.org/docs/tutorials/android-plugin.html
https://blog.jetbrains.com/kotlin/2015/04/announcing-anko-for-android/
https://developer.android.com/sdk/api_diff/26/changes.html

#HappyCoding #ILoveKotlin #PrAndroid

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How to Install Crashlytics via Gradle in Android Studio and Kotlin

Crashlytics is the most powerful, yet lightest weight crash reporting solution.Spend less time finding and more time fixing crashes. Named the #1 performance SDK on both iOS and Android, Crashlytics provides deep and actionable insights, even the exact line of code your app crashed on.

First you have to signup in fabric.io.Then do following steps integrate crashlytics in android using kotlin.

1. Go To build.gradle(Project) and add following dependencies.


2. Go To build.gradle(App) and add following dependencies.


and click sync button on the top:

3. Now, Time to add some fabric key and give internet permission in manifest file



4. Then add following coding snippet in you code, where you want to be add crash.


Now you got email and click view, Then you will get following screen in fabric.io,

Want to know more about installation in android, please visit : fabric.io
#HappyCoding #ILoveKotlin #PrAndroid

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What is new in Android Oreo?

After more than a year of development and months of testing by developers and early adopters (thank you!), we're now ready to officially launch Android 8.0 Oreo to the world. Android 8.0 brings a ton

pic courtesy: developer.android.com

of great features such as picture-in-picture, autofill, integrated Instant Apps, Google Play Protect, faster boot time, and much more.

Make your apps compatible

Test your apps for compatibility with Android Oreo. Just download a device system image, install your current app, and test in areas where behavior changes may affect the app. 

Build for Android Oreo

Target Android Oreo (API 26) and extend your apps with the latest platform capabilities and APIs.      

         
The latest version of Android that’s smarter, faster, and more powerful. Android Oreo gives you many new ways to extend your app and develop more efficiently.

Picture-in-picture

Notification dots

Notification channels

Autofill framework

Autosizing TextView

Fonts in XML

Downloadable fonts

Adaptive icons

Shortcut pinning

Wide-gamut color

WebView features

Java 8 language APIs

Media features

Multidisplay support

More!

More about Oreo, Please visit official android developer website: https://developer.android.com/index.html

#HappyCoding #PrAndroid

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Splash screen in android using KOTLIN

Splash screen in android using kotlin just like java. Thread in java is same as kotlin, we have to make

 thread run certain time and go to next activity( or main activity) .

SpashScreen.Kt



You have to make your own layout as your requirement in activity_splash.xml.

It work just like java splash screen, it will be automatically redirect to MainActivity after 5 second.

#HappyCoding #ILoveKotlin #PrAndroid

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Kotlin 1.1.4-2 is released with new features

Kotlin 1.1.4-2 is just released with several important hotfixes, here are some change logs that kotlin changes in new released version.

1.1.4-2

• KT-19679 CompilationException: Couldn't inline method call 'methodName' into...
• KT-19690 Lazy field in interface default method leads to ClassFormatError
• KT-19716 Quickdoc Ctrl+Q broken while browsing code completion list Ctrl-Space
• KT-19717 Library kind incorrectly detected for vertx-web in Kotlin project
• KT-19723 "Insufficient maximum stack size" during compilation

What feature do we have in kotlin 1.1.4

Android

New Features

• KT-11048 Android Extensions: cannot evaluate expression containing generated properties

Performance Improvements

• KT-10542 Android Extensions: No cache for Views
• KT-18250 Android Extensions: Allow to use SparseArray as a View cache

Fixes

• KT-11051 Android Extensions: completion of generated properties is unclear for ambiguous ids
• KT-14086 Android-extensions not generated using flavors dimension
• KT-14912 Lint: "Code contains STOPSHIP marker" ignores suppress annotation
• KT-15164 Kotlin Lint: problems in delegate expression are not reported
• KT-16934 Android Extensions fails to compile when importing synthetic properties for layouts in other modules
• KT-17641 Problem with Kotlin Android Extensions and Gradle syntax
• KT-17783 Kotlin Lint: quick fixes to add inapplicable @RequiresApi and @SuppressLint make code incompilable
• KT-17786 Kotlin Lint: "Surround with if()" quick fix is not suggested for single expression get()
• KT-17787 Kotlin Lint: "Add @TargetApi" quick fix is not suggested for top level property accessor
• KT-17788 Kotlin Lint: "Surround with if()" quick fix corrupts code in case of destructuring declaration
• KT-17890 [kotlin-android-extensions] Renaming layout file does not rename import
• KT-18012 Kotlin Android Extensions generates @NotNull properties for views present in a configuration and potentially missing in another
• KT-18545 Accessing to synthetic properties on smart casted Android components crashed compiler

Source form kotlin github page: https://github.com/JetBrains/kotlin/tree/1.1.4

#HappyCoding #ILoveKotlin

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Ad Mob Integration in Kotlin

Firebase is a mobile platform that helps you quickly develop high-quality apps, grow an engaged user base, and earn more money. Since AdMob is now a part of Firebase, we've made it simpler to use AdMob along with other Firebase services such as Analytics.

Here is the simplest way of how to integrate admob in android using kotlin and firebase is very easy.

1. Create a android project in android studio
2. go to tools->Firebase and go to bottom admob details and click first option connect your app to firebase and if you successfully connected then following green ok button appears.

Now click add a banner ad to you app

3. Now click 2nd option ad admob to your app then you got following dialog box and click accept for changes.

and 
4. To put a banner ad in your app, add the following code to your layout file, including the Android Ads schema.


5. Now, you have to load the ad in the activity
Add code to the onCreate() class of this activity to load the ad.

// appId, you can find through the ad mob

MobileAds.initialize(this, resources.getString(R.string.app_id));

// bannar addval adRequest = AdRequest.Builder().build()

adView.loadAd(adRequest)

don't forget to import:

import kotlinx.android.synthetic.main.activity_main.*

6. you have to create ad unit from admob.com and add on string.xml, that has name banner_ad_unit_id.


If you want to add Interstitial Ad, then do following steps,

First you have create Interstitial ad unit in admob and save  interstitial_ad_unit_id  string.xml.

Inside the MainActivity.

internal lateinit var mInterstitialAd: InterstitialAd
internal lateinit var adRequest : AdRequest

want the onCreate method:

mInterstitialAd =  InterstitialAd(this)
mInterstitialAd.setAdUnitId(getString(R.string.interstitial_ad_unit_id));
requestNewInterstitial()

Create function requestNewInterstitial(),

private fun requestNewInterstitial() {
     adRequest = AdRequest.Builder().build()
     mInterstitialAd.loadAd(adRequest)
}

Don't forget to internet permission, otherwise you ad will not displayed in your app.

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

Finally, Inside the button click

if (mInterstitialAd.isLoaded()) {
    mInterstitialAd.show();
} else {
    //go to second activity or do something
}

mInterstitialAd.adListener = object : AdListener() {
    override fun onAdClosed() {
        requestNewInterstitial()
         //go to second activity or do something
    }

    override fun onAdLoaded() {  
    }

    override fun onAdFailedToLoad(i: Int) {
        Log.w("AgeActivity", "onAdFailedToLoad:" + i)
    }
}

Now your both banner ad and  Interstitial Ad both will be displayed , just like screenshot below.

Download and fork project.

#HappyCoding!! and #ILoveKotlin

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Share Preferences in Kotlin

Interface for accessing and modifying preference data returned by getSharedPreferences(String, int).

You can create a new shared preference file or access an existing one by calling one of two methods:

• getSharedPreferences() — Use this if you need multiple shared preference files identified by name, which you specify with the first parameter. You can call this from any Context in your app.
• getPreferences() — Use this from an Activity if you need to use only one shared preference file for the activity. Because this retrieves a default shared preference file that belongs to the activity, you don't need to supply a name.

Lets to it in kotlin:

First attempt to defined the shared preference and editor then put values on editor and apply for use.

What we have doing in MainActivity:

Now, get the value from shared preference in second activity using key.

Simple we can use for login section, where we can save username, password or remember password for any user.

Here is sample output screenshot:

Download full code and fork

#HappyCoding!!! and #IloveKotlin

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How to get different way of alphabetical letter in Kotlin

Using collection in kotlin is very easy to loop over the list. Here I am presenting way of getting alphabetically letter from A to Z in different way in kotlin.

Following output above code:
Print A to Z
ABCDEFGHIJKLMNOPQRSTUVWXYZ
-------------------------
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Print A to Z using With
-------------------------
Print A to Z using expression
ABCDEFGHIJKLMNOPQRSTUVWXYZ
-------------------------
print A to Z using apply
ABCDEFGHIJKLMNOPQRSTUVWXYZ
-------------------------
Print using buildString
ABCDEFGHIJKLMNOPQRSTUVWXYZ

 Happy Coding

#HappyCoding #ILoveKotlin #Android #KotlinLang #AndroidStudio

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First android app developed using Kotlin

I just started learning kotlin since google I/O air in 2017. I brought two books Kotlin in Action by Dmitry Jemerov and Svetlana Isakova and Kotlin for Android Developers by Antonio Leiva.


I developed small application "Tic Tac Toe" both 3x3 and 4x4 , which is published on google play store.


Here is the sample snapshots of Tic Tac Toe from google play store. Please checkout and expecting good suggestion.How do i improved the existing app.

Google Play: Download


#HappyCoding #IloveKotlin

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Override Equal, HashCode and ToString in Kotlin

We all know that override equal(), hashcode() and toString() in java, Here in Kotlin by default implementation, you don't have to need override them. However, if you want to override toString, equals and hashCode, you have to do this.

equals: 

open operator fun equals(other: Any?): Boolean

Indicates whether some other object is "equal to" this one. Implementations must fulfil the following requirements:

• Reflexive: for any non-null reference value x, x.equals(x) should return true.
• Symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• Transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true
• Consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.

Note that the == operator in Kotlin code is translated into a call to equals when objects on both sides of the operator are not null.

hashCode:

open fun hashCode(): Int

Returns a hash code value for the object. The general contract of hashCode is:

• - Whenever it is invoked on the same object more than once, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified.
• - If two objects are equal according to the equals() method, then calling the hashCode method on each of the two objects must produce the same integer result.

toString:

open fun toString(): String

Returns a string representation of the object.

------------------------------------------------------------

Here is the full implementation kotlin code:

Output looks like

without override equals , hashCode and toString method

false

false

euquals
false

false

toString
co.prandroid.firstkotlin.MainActivity$User@4c83bb6
hashCode
80231350

with override equals , hashCode and toString method

false

true

euquals
false

true

toString
Client(name=john, code=12345)

hashCode
101315726

Reference: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html

#HappyCoding #ILoveKotlin

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How to use RecyclerView in Android using Kotlin

Yes, we all love develop mobile application, but some case there is lots boilerplate, null safety problems in java, which is more concise using kotlin.

RecyclerView is a flexible view for providing a limited window into a large data set.It is a modernized version of the ListView and the GridView classes provided by the Android framework. Recycler view addresses several issues that the existing widgets have.

I assume, you have already download latest Android Studio 3.0 preview, If you have not download , please follow the download an install Android Studio 3.0 Preview, which includes Kotlin support out of the box.

RecyclerView allow to use different layout managers for positioning items. Such as LinearLayout, GridLayout and StaggerLayout. I have developing  all there layout and populate data on all the layouts.

Glide used for Image display.

1. First you have to add dependencies on app gradle, following dependencies.

implementation 'com.android.support:recyclerview-v7:25.4.0'
compile 'com.github.bumptech.glide:glide:3.5.2'

2. We must have to make add recyclerview on layout file .


3. Now we have to declear Pojo class in kotlin, which is more easy and simple


4. Create simple data using through object in kotlin.


5. Now, we have make MovieAdapter in Kotlin is simple, which is more complex in java.


6. Declear Recycler view and set layout depend you requirement, like Linear, Grid and Stagger.

7. If you want to make divider in your recycler view , then you using RecyclerView.ItemDecoration.
8. Finally, Application ready to run, and then we have get following snapshots.

To get full source code, please download and fork github repository. Download

#HappyCoding #ILoveKotlin

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Simple use of glide library for display images on android

We know all that memory to store images on mobile is limited, if we have display images using through the bitmap images, it will take lots of memory, which is followed by ultimately memory performance and finally application will be slow.

Yes, we have new image display library call glide. Glide is the perfect and best one to use compared to Picasso and Fresco.

Reasons of using Glide:

1. Recommended by Google and has been used in many Google open source projects.
2. Picasso loads the full-size image (1920x1080 pixels) into the memory and let GPU does the real-time resizing when drawn. While Glide loads the exact ImageView-size (768x432 pixels) into the memory which is a best practice.
3. Glide cache both the full-size image and the resized one. Picasso will cache only single size of image, the full-size one. Glide acts differently, caches separate file for each size of ImageView.
4. GIF (animated image) support.
5. In addition, it also helps preventing an app from popular OutOfMemoryError.

Fresco has huge size of library and cache also. Moreover, app freezes while loading big images from internet into ListView.

While Glide has small size of both library and cache.(Source: Quora)

Here is the pictorial difference between Glide vs Picasso vs Fresco.

Now, How to use Glide to display images on Android, Here is the simple steps,

First you have to introduces dependencies on gradle.

compile 'com.github.bumptech.glide:glide:3.5.2'

and 

On your imageview, please provide this code for display images.

image is image view , depend you requirement, 

In kotlin:

val image = currentView.findViewById(R.id.image) as ImageView

In Java

ImageView image= (ImageView) findViewById(R.id.image)

Now, render the image url on our imageview.

Glide.with(context)

.load(currentVolume.imageUrl)

.into(image)

#HappyCoding #ILoveKotlin

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Hello World and Button Click Event fire in Kotlin (Android) .

We are going to series of kotlin tutorials for android. JetBrains software company introduce new android studio 3.0 in build kotlin plugin, we don't have to add any plugin.
First you have to download Android Studio 3.0 Canary 4 is now available on developer.android.com and learn kotlin from the basic , there is a official documentation of kotlin.
https://kotlinlang.org/.

Let start kotlin

We are going to print simply hello world, then we will moving series of kotlin for android developer.

After finish download android studio, then follow the follow the following steps.


1. Open Android studio 3.0

2. Click File -> New -> New Project.

3. The give the name of Project and you have see by default kotlin plugin checked on android studio.Then click Next.

4. Then choose target Minimum SDK for the application.

5.  Now choose the Activity to mobile, by default there is empty activity, choose this and click next.

6. Finally, when you click finish, then it take few seconds for loading gradles, libraries and other necessary files for mobile application.

Now, your project is created, initially, you can see different then tradition java code because it is kotlin. you simple run the project you have to see, hello world.

I am going to simple change the App, We give the input from EditText and click show Button and display on TextView.

Let start to do this,

Here is the simple layout file:



Here is the simple kotlin code, which is more less and more clear to understand then java code.




Here is the simple output of above program:

I love kotlin and please follow the next tutorials.

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Kotlin For Android Apps

Kotlin is an Android-compatible language that is concise, expressive, and designed to be type- and null-safe. It works with the Java language seamlessly, so it makes it easy for developers who love the Java language to keep using it but also incrementally add Kotlin code and leverage Kotlin libraries. Also, many Android developers have already found that Kotlin makes development faster and more fun, so we want to better support these Kotlin users.

Kotlin is a great fit for developing Android applications, bringing all of the advantages of a modern language to the Android platform without introducing any new restrictions:

• Compatibility: Kotlin is fully compatible with JDK 6, ensuring that Kotlin applications can run on older Android devices with no issues. The Kotlin tooling is fully supported in Android Studio and compatible with the Android build system.
• Performance: A Kotlin application runs as fast as an equivalent Java one, thanks to very similar bytecode structure. With Kotlin's support for inline functions, code using lambdas often runs even faster than the same code written in Java.
• Interoperability: Kotlin is 100% interoperable with Java, allowing to use all existing Android libraries in a Kotlin application. This includes annotation processing, so databinding and Dagger work too.
• Footprint: Kotlin has a very compact runtime library, which can be further reduced through the use of ProGuard. In a real application, the Kotlin runtime adds only a few hundred methods and less than 100K to the size of the .apk file.
• Compilation Time: Kotlin supports efficient incremental compilation, so while there's some additional overhead for clean builds, incremental builds are usually as fast or faster than with Java.
• Learning Curve: For a Java developer, getting started with Kotlin is very easy. The automated Java to Kotlin converter included in the Kotlin plugin helps with the first steps. Kotlin Koans offer a guide through the key features of the language with a series of interactive exercises. 

If want to learn kotlin, today now, please follow the following links

• Download an install Android Studio 3.0 Preview, which includes Kotlin support out of the box.
• Follow the Getting Started with Android and Kotlin tutorial to create your first Kotlin application.
• For a more in-depth introduction, check out the reference documentation on this site and Kotlin Koans.
• Another great resource is Kotlin for Android Developers, a book that guides you step by step through the process of creating a real Android application in Kotlin.
• Check out Google's sample projects written in Kotlin. Source content(KotlinLang)

I am going to write some kotlin tutorials for android and java, based on official website, and other books like kotlin in Action, kotlin for android developer. please follow thing updated my tutorials.

#HaveANiceKotlin #HappyCoding

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