Fix ViewModel Not Updating UI in Kotlin

When building Android apps using Kotlin and the MVVM architecture, a common issue developers encounter is that the ViewModel does not update the UI as expected. This article will walk you through the causes and solutions for this problem. We’ll also provide complete working code examples using Android Studio to help you debug and fix it effectively.

Common Reasons Why ViewModel Doesn’t Update UI

1. LiveData not observed properly
2. Observers bound to the wrong lifecycle
3. UI components not refreshed
4. Wrong usage of MutableLiveData
5. State updates not triggered

Example Case: LiveData Doesn’t Update UI

Let’s build a simple counter app using ViewModel and LiveData. We’ll demonstrate the issue and how to solve it.

1. ViewModel Class (Kotlin)

// CounterViewModel.kt
package com.example.viewmodelissue

import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel

class CounterViewModel : ViewModel() {

    private val _counter = MutableLiveData<Int>().apply { value = 0 }
    val counter: LiveData<Int> = _counter

    fun incrementCounter() {
        _counter.value = (_counter.value ?: 0) + 1
    }
}

2. Activity Code (Incorrect Usage Example)

// MainActivity.kt
package com.example.viewmodelissue

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.viewModels
import com.example.viewmodelissue.databinding.ActivityMainBinding

class MainActivity : ComponentActivity() {

    private lateinit var binding: ActivityMainBinding
    private val viewModel: CounterViewModel by viewModels()

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

        // Wrong: This doesn’t observe lifecycle properly
        viewModel.counter.observe(this) {
            binding.counterText.text = it.toString()
        }

        binding.incrementButton.setOnClickListener {
            viewModel.incrementCounter()
        }
    }
}

Fix: Observe With LifecycleOwner

Make sure you observe LiveData with the correct LifecycleOwner:

// Correct usage inside onCreate
viewModel.counter.observe(this@MainActivity) { count ->
    binding.counterText.text = count.toString()
}

Additional Tips:

• Always use observe(viewLifecycleOwner) if you’re using fragments.
• Avoid creating multiple observers unnecessarily.
• Use StateFlow for better lifecycle-aware reactive streams in complex apps.

Recommended Resource

For deeper understanding on ViewModel and LiveData best practices, refer to the official documentation on Android Developer Guide to LiveData.