Android Mad - Development Guide for Mobile App Development

Introduction:

After the announcement of Google on Google I/O 2017, we have seen the series of tutorials in Kotlin. If you are new to Kotlin you can learn Kotlin from our previous articles. We had been crossed Basics of Kotlin and Hello World function, How to use ListView, RecyclerView in Kotlin and How to implement SQLite storage in Kotlin with CRUD operations.

In this article, we will learn how to make server call (i.e. HTTP Connection) from Kotlin powered application to web services.

Coding Part:

I have divided the coding part into 3 steps as shown in the following.

1. Creating new project.
2. Setting up the project with Fuel HTTP.
3. Implementing the Fuel HTTP Service Call.

Let’s start coding for Fuel HTTP.

Step 1: Creating new project:

1. Open Android Studio and Select Create new project.
2. Name the project as your wish and tick the Kotlin checkbox support.
3. Then Select your Activity type (For Example: Navigation Drawer Activity, Empty Activity, etc.).

4. Then Click “finish” button to create new project in Android Studio

Step 2: Setting up the project:

Now, we will setting up the project for Fuel HTTP.

1.      Open your app level build.gradle file and add the following line.

implementation 'com.github.kittinunf.fuel:fuel-android:1.6.0'

2.      If you are using Android Studio Version below 3.0, the add the following (Optional Step)

compile 'com.github.kittinunf.fuel:fuel-android:1.6.0'

3.       Then Click “Sync Now” to download the library and add to the project.

After this, you are ready to implement HTTP Service Call from your Application.
Step 3: Fuel HTTP implementation:

Now, we will setting up the project for Fuel HTTP.

1.      Open your AndroidManifest.xml and Add permission to access internet.

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

2.   Open your activity_main.xml file and create the User Interface as you wanted or Paste the following code.

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.androidmads.kotlinfuelhttpsample.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="GET Request's Response"
            android:textColor="#000000" />

        <TextView
            android:id="@+id/tvGetResponse"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
            android:background="#e1e1e1"
            android:padding="10dp"
            android:text="" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="10dp"
            android:background="@color/colorPrimary"
            android:onClick="httpGetJson"
            android:text="GET RESPONSE"
            android:textColor="#ffffff" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="POST Request's Response"
            android:textColor="#000000" />

        <TextView
            android:id="@+id/tvPostResponse"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
            android:background="#e1e1e1"
            android:padding="10dp"
            android:text="" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="10dp"
            android:background="@color/colorPrimary"
            android:onClick="httpPostJson"
            android:text="POST RESPONSE"
            android:textColor="#ffffff" />

    </LinearLayout>
</ScrollView>

Layout Preview

1.       Then Open your Activity file and here I am opening MainActivity.java file.

2.      Initialize the fuel library by the following code

FuelManager.instance.basePath = "http://demosmushtaq.16mb.com";

Here, you must specify the base address of your service. It will start or initialize the library.

GET REQUEST

We will use “Fuel.get()” to make server call with Get method. The following code shows how to implement this.

Fuel.get("<Service Link without base path>")
.responseJson { request, response, result ->
 Log.v(“response”, result.get().content)
}

POST REQUEST

We will use “Fuel.post()” to make server call with Post method. The following code shows how to implement this.

Fuel.post("<Service Link without base path>", listOf("<key>" to "<value>"))
.responseJson { request, response, result ->
 Log.v(“response”, result.get().content)
}

You can get the response as string or json by specify the response type “responseString” or “responseJson” respectively.You can pass the data to service using “listOf” method. It is an optional value. You can also access the without the parameters to be passed

You can get response from the result using “result.get().content” as mentioned in the code above.

Full Code of MainActivity:

You can find the full code implementation of MainActivty.kt in the following.

class MainActivity : AppCompatActivity() {

    var tvGetResponse: TextView? = null
    var tvPostResponse: TextView? = null
    var progress: ProgressDialog? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        initViewsAndWidgets()
        FuelManager.instance.basePath = "http://demosmushtaq.16mb.com";
    }

    private fun initViewsAndWidgets() {
        tvGetResponse = findViewById(R.id.tvGetResponse)
        tvPostResponse = findViewById(R.id.tvPostResponse)
        progress = ProgressDialog(this)
        progress!!.setTitle("Kotlin Fuel Http Sample")
        progress!!.setMessage("Loading...")
    }

    fun httpGetJson(view: View) {
        try {
            progress!!.show()
            Fuel.get("api/get_sample.php").responseJson { request, response, result ->
                tvGetResponse!!.text = result.get().content
            }
        } catch (e: Exception) {
            tvGetResponse!!.text = e.message
        } finally {
            progress!!.dismiss()
        }
    }

    fun httpPostJson(view: View) {
        try {
            progress!!.show()
            Fuel.post("api/post_sample.php", listOf("version_index" to "1")).responseJson { request, response, result ->
                tvPostResponse!!.text = result.get().content
            }
        } catch (e: Exception) {
            tvPostResponse!!.text = e.message
        } finally {
            progress!!.dismiss()
        }
    }
}

Download Code: 

You can download sample code from the following GitHub link.