Android Floating Action Button Using Kotlin With Example

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Hello Readers! In this post, we are going to learn about android floating action button using kotlin in any android application. We will also learn about different attributes of android floating action button that can be used to customise this widget.

Output

Tutorialwing Kotlin Floating Action Button Using Kotlin Tutorial With Example

Floating Action Button Using Kotlin Output

Getting Started

Android floating action button can be defined as below –

Floating action button is a circular button that floats above the UI and triggers primary action in android app’s user interface. It also have special motion behaviours related to morphing, launching and the transferring anchor point.

Android Floating Button comes into two sizes – (1) mini and (2) default.

Different Attributes of Android Floating Action Button Widget

Some of the popular attributes of android floating action button widget are –

Sr. XML Attributes Description
1. app:fabCustomSize It specifies the size of the button in pixels. If it is set to NO_CUSTOM_SIZE, custom size will not be used and size will be calculated based on the fabSize attribute.
2. app:fabSize It specifies the size of the button. There are three options available – mini, auto and normal. auto will choose size based on the screen size.
3. app:elevation Defines the elevation of the button.
4. app:rippleColor Sets the color of the ripple effect
5. app:useCompatPadding Sets inner padding of the button. It works on platform lollipop and after.



Example of Android Floating Action Button Using Kotlin

At first, we will create android application. Then, we will use Floating Action Button using kotlin in the application.

1. Creating New Project in Kotlin

Follow steps below to create new project. Please ignore the steps if you have already created the project.

Step Description
1. Open Android Studio.
2. Go to File => New => New Project. Write application name as FloatingActionButton. Then, check Include Kotlin Support and click next button.
3. Select minimum SDK you need. However, we have selected 17 as minimum SDK. Then, click next button
4. Then, select Empty Activity => click next => click finish.
5. You will get a newly created project successfully if you have followed steps properly.

Since we have a project now, we will modify xml and other files to use Floating Action Button using kotlin in the application.

2. Modify values folder

Open res/values/strings.xml file. Then, add below code into it.

<resources>
	<string name="app_name">FloatingActionButton</string>
	<string name="message">Click on Floating Action Button</string>
</resources>

Then, open res/values/styles.xml file and add below code into it.

<resources>

	<!-- Base application theme. -->
	<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
		<!-- Customize your theme here. -->
		<item name="colorPrimary">@color/colorPrimary</item>
		<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
		<item name="colorAccent">@color/colorAccent</item>
	</style>

	<style name="AppTheme.AppBarOverlay" parent="AppTheme">
	</style>

	<style name="AppTheme.PopupOverlay" parent="AppTheme">
	</style>

</resources>

3. Define Main Content xml file

Add an xml file , named content_main.xml , into main/res/layout folder. Then, add below code into
this newly created xml file.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
	xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:app="http://schemas.android.com/apk/res-auto"
	xmlns:tools="http://schemas.android.com/tools"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	app:layout_behavior="@string/appbar_scrolling_view_behavior"
	tools:showIn="@layout/activity_main">

	<TextView
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
		android:layout_centerInParent="true"
		android:text="@string/message"/>

</RelativeLayout>

This is the file where main UI content in the application is written.

Note – This is optional step. You may not need to add this file based on your application architecture.

4. Use Floating Action Button Widget in xml file

Open src/main/res/layout/activity_main.xml file and add below code into it.

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
	xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:app="http://schemas.android.com/apk/res-auto"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:fitsSystemWindows="true">

	<android.support.design.widget.AppBarLayout
		android:layout_width="match_parent"
		android:layout_height="wrap_content"
		android:theme="@style/AppTheme.AppBarOverlay">

		<android.support.v7.widget.Toolbar
			android:id="@+id/toolbar"
			android:layout_width="match_parent"
			android:layout_height="?android:attr/actionBarSize"
			android:background="@color/colorPrimary"
			app:popupTheme="@style/AppTheme.PopupOverlay"
			app:titleTextColor="@android:color/white"/>

	</android.support.design.widget.AppBarLayout>

	<include layout="@layout/content_main"/>

	<android.support.design.widget.FloatingActionButton
		android:id="@+id/fab"
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
		android:layout_gravity="bottom|end"
		android:layout_margin="16dp"
		android:src="@android:drawable/ic_dialog_email"/>

</android.support.design.widget.CoordinatorLayout>

5. Access Floating Action Button Widget in Kotlin file

Open src/main/java/com.tutorialwing.floatingactionbutton/MainActivity.kt file and add below code into it.

package com.tutorialwing.floatingactionbutton

import android.os.Bundle
import android.support.design.widget.FloatingActionButton
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.Toolbar
import android.widget.Toast

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val toolbar = findViewById<Toolbar>(R.id.toolbar)
        setSupportActionBar(toolbar)

        val fab = findViewById<FloatingActionButton>(R.id.fab)
        fab.setOnClickListener {
            // We are showing only toast message. However, you can do anything you need.
            Toast.makeText(applicationContext, "You clicked Floating Action Button", Toast.LENGTH_SHORT).show()
        }
    }
}

In this MainActivity.kt file, we have accessed floating action button and added a click listener to show a toast message whenever it is clicked. However, you can perform any action here.

Since AndroidManifest.xml file is very important in any android application, we are also going to see the content inside this file.

AndroidManifest.xml file

Code inside main/AndroidManifest.xml file is as below.

<?xml version="1.0" encoding="utf-8"?>
<manifest package="com.tutorialwing.floatingactionbutton"
		  xmlns:android="http://schemas.android.com/apk/res/android">

	<application
		android:allowBackup="true"
		android:icon="@mipmap/ic_launcher"
		android:label="@string/app_name"
		android:roundIcon="@mipmap/ic_launcher_round"
		android:supportsRtl="true"
		android:theme="@style/AppTheme">
		<activity android:name=".MainActivity">
			<intent-filter>
				<action android:name="android.intent.action.MAIN"/>

				<category android:name="android.intent.category.LAUNCHER"/>
			</intent-filter>
		</activity>
	</application>

</manifest>

When we run the program, we will get output as shown above.

That’s end of our tutorial on Android Floating Action Button using Kotlin.

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We have recently published 100+ articles on android tutorials with kotlin and java. If you need, you may visit Android Tutorial for beginners page. You can also check Kotlin Tutorial for beginners