In this article, we will learn how to create android Floating Action Button programmatically in Kotlin. We will go through various steps that explains how to create Floating Action Button and add it in kotlin file, use different attributes to customise it etc. in any android application. For example, how to set text in Floating Action Button programmatically, how to set id of Floating Action Button, how to capitalise text of Floating Action Button dynamically etc. We will get answer to all such questions in this post.

Learn to use Different Attributes of Floating Action Button in XML File to Customize it.

Output

Dynamic Floating Action Button Output

Getting Started

We can define android Floating Action Button widget 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.

Now, how do we use Floating Action Button in android application ?

Before we move ahead, we need to setup for viewBinding to access Floating Action Button in Kotlin file without using findViewById() method.

Setup ViewBinding

Add viewBinding true in app/build.gradle file.

 
 android { 
 	// OTHER CODE... 
 	buildFeatures { 
 		viewBinding true 
 	} 
 } 
 

Now, set content in activity using view binding.
Open MainActivity.kt file and write below code in it.

 
 class MainActivity : AppCompatActivity() { 
 	
 	private lateinit var binding: ActivityMainBinding 
 	
 	override fun onCreate(savedInstanceState: Bundle?) { 
 		super.onCreate(savedInstanceState) 
 		binding = ActivityMainBinding.inflate(layoutInflater) 
 		val view = binding.root 
 		setContentView(view) 
 	} 
 } 
 

Now, we can access view in Kotlin file without using findViewById() method.

Since we have a new project, we will modify the xml and class file to use Floating Action Button programmatically in kotlin. Please follow the steps below.

2. Modify Values Folder

Open res/values/strings.xml file. Add below code into it.

<resources>
    <string name="app_name">DynamicFloatingActionButton</string>
    <string name="message">Floating Action Button has been created dynamically. Click on it to see Toast message.</string>
</resources>

Other values folders have not been changed. So, we are not going to mention it here.

3. Modify Layout Folder

Open res/layout/activity_main.xml file. Add below code into it.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="40dp"
        android:text="@string/message"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <LinearLayout
        android:id="@+id/rootContainer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent">

    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

Note that LinearLayout has id rootContainer. In Kotlin file, we will create Floating Action Button Dynamically and add it into this LinearLayout having id rootContainer.

4. Create Android Floating Action Button programmatically in Kotlin

Open src/main/java/com.tutorialwing.dynamicfloatingactionbutton/MainActivity.kt file. Then, add below code into it.

package com.tutorialwing.dynamicfloatingactionbutton

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.ViewGroup
import android.widget.LinearLayout
import android.widget.Toast
import com.google.android.material.floatingactionbutton.FloatingActionButton
import com.tutorialwing.dynamicfloatingactionbutton.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

	private lateinit var binding: ActivityMainBinding

	override fun onCreate(savedInstanceState: Bundle?) {
		super.onCreate(savedInstanceState)
		binding = ActivityMainBinding.inflate(layoutInflater)
		val view = binding.root
		setContentView(view)

		setupFloatingActionButton()
	}

	private fun setupFloatingActionButton() {
		val floatingActionButton = FloatingActionButton(this)

		val layoutParams = LinearLayout.LayoutParams(
			ViewGroup.LayoutParams.WRAP_CONTENT,
			ViewGroup.LayoutParams.WRAP_CONTENT
		)
		layoutParams.setMargins(32, 32, 32, 32)
		floatingActionButton.layoutParams = layoutParams
		floatingActionButton.setImageResource(android.R.drawable.ic_dialog_email)
		floatingActionButton.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()
		}
		binding.rootContainer.addView(floatingActionButton)
	}
}

Finally, when you run the application, you will get output as shown above.

Dynamic Floating Action Button Output

Now, Let’s check how to use different attributes of Floating Action Button to customize it dynamically –

Set Id of Floating Action Button

Follow steps below to set id of Floating Action Button programmatically –

• Create ids.xml file in res/values folder. Then, add below code into it –

  <?xml version="1.0" encoding="utf-8"?>
  <resources>
      <item type="id" name="floatingActionButton_ID" />
  </resources>
  

• Now, we can set id of Floating Action Button dynamically, in MainActivity.kt file, as –

  floatingActionButton.id = R.id.floatingActionButton_ID  // Floating Action Button
  

  Here, we have set id of Floating Action Button using property access syntax – floatingActionButton.id

Learn to Set ID of Floating Action Button Using XML Attribute

Set Width and Height of Floating Action Button

We use layoutParams to set width and height of any View programmatically. In this article, we have added Floating Action Button in LinearLayout. So, we will define LayoutParams as below –

floatingActionButton.layoutParams = LinearLayout.LayoutParams(
	ViewGroup.LayoutParams.WRAP_CONTENT,
	ViewGroup.LayoutParams.WRAP_CONTENT
)

Here, we have set width and height as WRAP_CONTENT. Some of possible values for width and height are –

• WRAP_CONTENT: Sets value of width or height depending on text inside it.
• MATCH_PARENT: Sets value of width of height depending on width or height of parent layout . i.e. width or height of Floating Action Button will be same as width or height of parent layout.
• Fixed Value: Sets width or height as per value provided.

Learn to Set Width or Height of Floating Action Button Using XML Attribute

Set Padding of Floating Action Button

Follow steps below to set padding of Floating Action Button Dynamically –

• If there is no dimens.xml file, create dimens.xml file in res/values folder. Then, add below code in it –

  <?xml version="1.0" encoding="utf-8"?>
  <resources>
      <dimen name="text_padding">16dp</dimen>
  </resources>
  

• Now, we can set padding of Floating Action Button dynamically, in MainActivity.kt file, as –

  val padding = resources.getDimension(R.dimen.text_padding).toInt()
  floatingActionButton.setPadding(padding, padding, padding, padding)
  

  Here, we have accessed dimension defined in dimens.xml using getDimension() method. Then, set padding of Floating Action Button using setPadding() method.

Learn to Set Padding of Floating Action Button Using XML Attribute

Set Margin of Floating Action Button

Follow steps below to set margin of Floating Action Button Dynamically –

• If there is no dimens.xml file, create dimens.xml file in res/values folder. Then, add below code in it –

  <?xml version="1.0" encoding="utf-8"?>
  <resources>
      <dimen name="text_margin">16dp</dimen>
  </resources>
  

• Now, we can set margin of Floating Action Button dynamically, in MainActivity.kt file, as –

  val margin = resources.getDimension(R.dimen.text_margin).toInt()
  val layoutParams = LinearLayout.LayoutParams(
  	ViewGroup.LayoutParams.WRAP_CONTENT,
  	ViewGroup.LayoutParams.WRAP_CONTENT
  )
  layoutParams.setMargins(margin, margin, margin, margin)
  floatingActionButton.layoutParams = layoutParams
  

  Here, we have accessed dimension defined in dimens.xml using getDimension() method. Then, we have defined layoutParams, set margin to layoutParams. After that, set layoutParams to Floating Action Button.

Learn to Set Margin of Floating Action Button Using XML Attribute

Set Background of Floating Action Button

Follow steps below to set background of Floating Action Button programmatically –

• If there is no colors.xml file, create colors.xml file in res/values folder. Then, add below code in it –

  <?xml version="1.0" encoding="utf-8"?>
  <resources>
      <color name="purple_200">#FFBB86FC</color>
  </resources>
  

• Now, we can set background of Floating Action Button dynamically, in MainActivity.kt file, as –

  val color = ContextCompat.getColor(this, R.color.purple_200)
  floatingActionButton.setBackgroundColor(color)
  

  Here, we used setBackgroundColor() method to set background color in floatingActionButton.

Learn to Set Background of Floating Action Button Using XML Attribute

Set Visibility of Floating Action Button

We can set visibility of Floating Action Button programmatically as –

floatingActionButton.visibility = View.VISIBLE

Here, we have set visibility of Floating Action Button using floatingActionButton.visibility attribute. Visibility can be of three types – gone, visible and invisible.
Learn to Set Visibility of Floating Action Button Using XML Attribute

That’s end of tutorial on Floating Action Button Programmatically in Kotlin With Example.