Fix Kotlin Fragments Not Displaying Issue

If you’re building an Android app using Kotlin and encounter the issue of fragments not displaying properly, you’re not alone. This is a common hurdle faced by developers when working with the fragment lifecycle, fragment transactions, or layout-related misconfigurations. In this guide, we’ll explore why your Kotlin fragments might not be rendering as expected and how to fix it with a complete working example.

Some of the common causes include:

• Using the wrong container or not using FragmentContainerView
• Not committing fragment transactions properly
• Lifecycle issues between Activity and Fragment
• Improper use of FragmentManager

Let’s go step-by-step with a working Kotlin example to display a fragment correctly in an activity.

MainActivity.kt

package com.example.myapp

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.example.myapp.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)

        // Check if fragment already exists
        if (savedInstanceState == null) {
            val fragment = SampleFragment()
            supportFragmentManager.beginTransaction()
                .replace(R.id.fragment_container_view, fragment)
                .commit()
        }
    }
}

SampleFragment.kt

package com.example.myapp

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import com.example.myapp.databinding.FragmentSampleBinding

class SampleFragment : Fragment() {

    private var _binding: FragmentSampleBinding? = null
    private val binding get() = _binding!!

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        _binding = FragmentSampleBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onDestroyView() {
        super.onDestroyView()
        _binding = null
    }
}

activity_main.xml

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragment_container_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

fragment_sample.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">

    <TextView
        android:id="@+id/sample_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fragment Loaded Successfully!"
        android:textSize="18sp" />

</LinearLayout>

By using FragmentContainerView instead of a regular FrameLayout, and ensuring commit() is called without delay, the fragment will load correctly. For additional reference on fragment best practices, visit the official Android documentation.