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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Introducing Kotlin in Google I/O 2017

Google introducing kotlin new programming language in Google I/O 2017 and Kotlin is now an officially supported language for Android. Simply Kotlin is a statically-typed programming language that runs on the Java Virtual Machine and also can be compiled to JavaScript source code or uses the LLVM compiler infrastructure[from wiki].

Here are some vidoe, that are presented on Google I/O 2017.

Getting Started with Kotlin

Introduction to Kotlin (Google I/O '17) 

  Life is Great and Everything Will Be Ok, Kotlin is Here (Google I/O '17) 

Would you learn more about kotlin, please visit:

All vedio source by official google Android Developers channels.

Happy Coding

#Kotlin #AndroidDeveloper #IO17 #GoogleIO17

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How to get Android O sdk in Android Studio

Android O introduces several new features and APIs, and includes changes that can affect the behavior of your app even if you change nothing.

1. Install Android Studio 2.4 Canary. Only Android Studio 2.4 includes support for all the new developer features available with Android O. So you need to get the canary version of Android Studio 2.4 to begin using the Android O SDK. But you can still keep your stable version of Android Studio installed.
   
2. Launch Android Studio 2.4 and open the SDK Manager by clicking Tools > Android > SDK Manager.
3. In the SDK Platforms tab, check Show Package Details. Below Android O Preview check the following:
   • Android SDK Platform O
   • Google APIs Intel x86 Atom System Image (only required for the emulator)
4. Switch to the SDK Tools tab and check all items that have updates available (click each checkbox that shows a dash ). This should include the following that are required:
   • Android SDK Build-Tools 26.0.0 (rc1 or higher)
   • Android SDK Platform-Tools 26.0.0 (rc1 or higher)
   • Android Emulator 26.0.0
   • Support Repository
5. Click OK to install all the selected SDK packages.

Now you're ready to starting developing with the Android O Developer Preview.

Update your build configuration

Update compileSdkVersion, buildToolsVersion, targetSdkVersion, and the Support Library version with the following versions:

android {
  compileSdkVersion 'android-O'
  buildToolsVersion '26.0.0-rc1'

  defaultConfig {
    targetSdkVersion 'O'
  }
  ...
}

dependencies {
  compile 'com.android.support:appcompat-v7:26.0.0-alpha1'
}

You cannot publish your app with this configuration. The "O" version is a provisional API level that is usable only for development and testing during the Android O Developer Preview. You must wait to publish your Android O changes until the final API level is released, and then update your configuration again at that time.

More about Android O: https://developer.android.com/index.html

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Interview Question: find the angle between hour hand and minute hand

Recently, I gave interview on the reputed company in silicon valley, I figure out the solution to that problem with solution in android.

Question: 
How do you find the angle between hour hand and minute hand with two input field, one is an hour and next one is minute and click the button find the angle, and calculate the angle between two input in textview.
Time: 30 Minute

Solution:
They given me, Hour: 6  and Minute: 30 and output will be 15

I took the base case for hour 12:00 (h = 12, m = 0) as a reference and followed these steps.

• Calculate the angle made by hour hand with respect to 12:00 in h hours and m minutes.
• Calculate the angle made by minute hand with respect to 12:00 in h hours and m minutes.
• The difference between two angles is the angle between two hands.

And I told them if I move minute hand  360 degree in 60 minute(or 6 degree in one minute) and move hour hand  360 degree in 12 hours(or 0.5 degree in 1 minute). 

In hour hours and minute minutes, 

#  minute hand would move to the (hour*60 + minute)*6 and 

# hour hand would move to the(h*60 + m)*0.5.

if you get the confuse above equation, please put the real hour and minute value check, it would be correct.

Now, I started to coding in android

Step 1: Layout

The layout is very easy, in relative layout, you can just put textview for label and editext for input for both hour and minute and the button for click and gives output, finally, I put one textview for display out.

Here is the Layout code, if you have any confusion:

Now, I am going to write, the actual code that I have present during interview session:

Here is the Acutal output of snapshot:

I am still waiting for response!!
Happy Coding !!!

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How to use Retrofit to get data from stackoverflow API and GitHub Demo in android studio

Retrofit is a type-safe REST client for Android developed by Square. The library provides a powerful framework for authenticating and interacting with APIs and sending network requests with OkHttp. See this guide to understand how OkHttp works.

This library makes downloading JSON or XML data from a web API fairly straightforward. Once the data is downloaded then it is parsed into a Plain Old Java Object (POJO) which must be defined for each "resource" in the response.

Setup

Must be defined on internet permission on AndroidManifest.xml .

Dependencies

Add following dependencies on app/build.gradle file:

Converter:

Here is the different type of  Gson converter, we can use them:

How to create retrofit instance, 

then we have to define, the userendpoint:

Now, create model class, user variables, In MainActivity.java, we have to create instance of APIClient and call the users.

Download Full code: https://github.com/dharmakshetri/Android-API-Demos

and you can find out Awesome Retrofit Article: Retrofit Tutorial With Example In Android Studio [Step by Step]

More details:

https://square.github.io/retrofit/
https://github.com/square/retrofit
https://guides.codepath.com/android/Consuming-APIs-with-Retrofit
https://realm.io/news/droidcon-jake-wharton-simple-http-retrofit-2/
http://www.vogella.com/tutorials/Retrofit/article.html


Happy Coding !!!

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What’s new – Material design (December 2016)

In the Material design in August 2016, three Notifications, Widgets and Confirmation and acknowledgement.

source:matrial.io

Now in December 2016, In Material design here is the latest added new section and significance updates.

New sections

• Platforms discusses when and how to adapt apps to Material Design, and when to adhere to platform conventions
• App shortcut icons contains specs on how to create app shortcut icons for the home screen
• Help and feedback describes how to indicate, craft, and place help content

Significant updates

• Bidirectionality has updated guidance on mirroring UI content and icons in right-to-left (RTL) languages
• Accessibility contains new guidance on sound, controls, labeling elements, and testing
• Selection includes detailed examples on item selection, toggling, and styling

Happy Coding !!!

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Firebase: Save, Delete and Retrieve data from firebase database in Android Studio

In Firebase Realtime Database we can store and sync data with our NoSQL cloud database. Data is synced across all clients in realtime, and remains available when your app goes offline.

The Firebase Realtime Database is a cloud-hosted database. Data is stored as JSON and synchronized in realtime to every connected client. When you build cross-platform apps with our iOS, Android, and JavaScript SDKs, all of your clients share one Realtime Database instance and automatically receive updates with the newest data.

Android Setup

Here is the one example how to store on firebase and retrieve data on your android device.

First step Create firebase project  from https://console.firebase.google.com.

Add the dependency for Firebase Realtime Database to your app-level build.gradle file:



Update the rules for your database to allow reads and writes from all users, as this demo will not cover Firebase Authentication.


Steps:
1. Create firebase database reference
2. Get data from your form
3. Add and push data on database
4. Update on your view using creating anonymous inner class ChildEventListener.
5. Check you firebase database

Here is the full code:





Update on recyclerview, which show in below git hub link.

Output Snapshots:

Clone the github java
$git clone https://github.com/dharmakshetri/FirebaseAddOrDeleteonDatabase.git

Happy Coding !!!

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RxAndroid Example to display data on RecyclerView in Android Studio

RxAndroid is simple in one term is reactive extension for android.
Android authorities defined, Observables and Observers in terms of RxAndrod, There are two basic and very important items in reactive programming, Observables and Observers. Observables publish values, while Observers subscribe to Observables, watching them and reacting when an Observable publishes a value.

In simpler terms:

    An Observable performs some action, and publishes the result.
    An Observer waits and watches the Observable, and reacts whenever the Observable publishes results.

There are three different changes that can occur on an Observable that the Observer reacts to. These are:

1.     Publishing a value
2.     Throwing an error
3.     Completed publishing all values

A class that implements the Observer interface must provide methods for each of the three changes above:

1.     An onNext() method that the Observable calls whenever it wishes to publish a new value
2.     An onError() method that’s called exactly once, when an error occurs on the Observable.
3.     An onCompleted() method that’s called exactly once, when the Observable completes execution.

Example: Display list of data using RxAndroid in to RecyclerView

First you have to import the dependencies  latest version of RxAndrod, RxJava and other like recyclerview, in to the build.gradle on app level inside the dependencies section.


Layout:
 RecyclerView is simply A flexible view for providing a limited window into a large data set.
activity_main.xml


and custom list item layout



Now, Obserable implement on MainActivity,



and Now implement RecyclerView Adapter



Output looks like:

Download full code from github: RxAndroid_RecyclerView_Example

Happy Coding!!!

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