In this article, we will learn how to create android BottomAppBar programmatically in Kotlin. We will go through various steps that explains how to create BottomAppBar and add it in kotlin file, use different attributes to customise it etc. in any android application.

Learn to use Different Attributes of BottomAppBar in XML File to Customize it.

Output

Getting Started

We can define android BottomAppBar widget as below –

BottomAppBar is an extension of Toolbar supporting shaped background that cradles an attached FloatingActionButton. It means BottomAppBar provides an easy to navigation drawer and some primary actions including floating action buttons. Since it is placed at bottom of the screen, it’s easier to click on these primary actions button than when these buttons are placed at top of the screen in toolBar.

Now, how do we use BottomAppBar in android application ?

Before we move ahead, we need to setup for viewBinding to access BottomAppBar 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 BottomAppBar programmatically in Kotlin. Please follow the steps below.

Modify Values Folder

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

<resources>
    <string name="app_name">DynamicBottomAppBar</string>
    <string name="floating_action_button">Floating Action Button</string>
</resources>

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

Create Drawable Resources

We need some drawable resources for our application. So, follow our tutorial on Add Vector Image in Android Using Vector Asset Studio . You can also get drawable resources from source code .

Create menu for BottomAppBar

Follow steps below to create menu –

1. Create menu folder in main/res folder, if not created.
2. Now, create new xml file, bottom_app_bar_menu.xml, in res/menu folder. Then, add below code in it –

   <?xml version="1.0" encoding="utf-8"?>
   <menu xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:app="http://schemas.android.com/apk/res-auto">
   
       <item
           android:id="@+id/photos"
           android:icon="@drawable/ic_photo"
           android:title="Photos"
           app:showAsAction="ifRoom" />
   
       <item
           android:id="@+id/search"
           android:icon="@drawable/ic_search"
           android:title="Search"
           app:showAsAction="ifRoom" />
   
       <item
           android:id="@+id/option_1"
           android:title="Option 1"
           app:showAsAction="never" />
   
   </menu>
   

Modify Layout Folder

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

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/rootContainer"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

</androidx.coordinatorlayout.widget.CoordinatorLayout>

Note that CoordinatorLayout has id rootContainer. In Kotlin file, we will create BottomAppBar Dynamically and add it into this CoordinatorLayout having id rootContainer.

Create Android BottomAppBar programmatically in Kotlin

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

package com.tutorialwing.dynamicbottomappbar

import android.os.Bundle
import android.view.Gravity
import androidx.appcompat.app.AppCompatActivity
import androidx.coordinatorlayout.widget.CoordinatorLayout
import androidx.core.content.ContextCompat
import com.google.android.material.bottomappbar.BottomAppBar
import com.tutorialwing.dynamicbottomappbar.databinding.ActivityMainBinding


class MainActivity : AppCompatActivity() {

	private lateinit var binding: ActivityMainBinding

	override fun onCreate(savedInstanceState: Bundle?) {
		super.onCreate(savedInstanceState)

		binding = ActivityMainBinding.inflate(layoutInflater)
		setContentView(binding.root)

		setupBottomAppBar()
	}

	private fun setupBottomAppBar() {
		val bottomAppBar = BottomAppBar(this)
		val params = CoordinatorLayout.LayoutParams(
			CoordinatorLayout.LayoutParams.MATCH_PARENT,
			CoordinatorLayout.LayoutParams.WRAP_CONTENT
		)
		params.gravity = Gravity.BOTTOM
		bottomAppBar.layoutParams = params

		val menu = bottomAppBar.menu
		menuInflater.inflate(R.menu.bottom_app_bar_menu, menu)

		bottomAppBar.setNavigationIcon(R.drawable.ic_menu)

		bottomAppBar.setBackgroundColor(ContextCompat.getColor(this, R.color.purple_500))

		bottomAppBar.fabAlignmentMode = BottomAppBar.FAB_ALIGNMENT_MODE_CENTER
		bottomAppBar.fabCradleMargin = 0F
		bottomAppBar.fabCradleRoundedCornerRadius = 0F

		binding.rootContainer.addView(bottomAppBar)
	}
}

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

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

Set Id of BottomAppBar

Follow steps below to set id of BottomAppBar 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="bottomAppBar_ID" />
  </resources>
  

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

  bottomAppBar.id = R.id.bottomAppBar_ID  // BottomAppBar
  

  Here, we have set id of BottomAppBar using property access syntax – bottomAppBar.id

Learn to Set ID of BottomAppBar Using XML Attribute

Set Width and Height of BottomAppBar

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

bottomAppBar.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 BottomAppBar 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 BottomAppBar Using XML Attribute

Set Padding of BottomAppBar

Follow steps below to set padding of BottomAppBar 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 BottomAppBar dynamically, in MainActivity.kt file, as –

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

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

Learn to Set Padding of BottomAppBar Using XML Attribute

Set Margin of BottomAppBar

Follow steps below to set margin of BottomAppBar 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 BottomAppBar 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)
  bottomAppBar.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 BottomAppBar.

Learn to Set Margin of BottomAppBar Using XML Attribute

Set Background of BottomAppBar

Follow steps below to set background of BottomAppBar 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 BottomAppBar dynamically, in MainActivity.kt file, as –

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

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

Learn to Set Background of BottomAppBar Using XML Attribute

Set Visibility of BottomAppBar

We can set visibility of BottomAppBar programmatically as –

bottomAppBar.visibility = View.VISIBLE

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

That’s end of tutorial on Android BottomAppBar Programmatically in Kotlin With Example.