# java.lang.RuntimeException: Cannot create an instance of class com.example.MyViewModel. at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:221) ... Caused by: java.lang.InstantiationException: java.lang.Class<com.example.MyViewModel> has no zero argument constructor

- **ID:** `android/viewmodel-factory-required`
- **Domain:** android
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 88%

## Root Cause

ViewModelProvider.NewInstanceFactory is used but the ViewModel class has a parameterized constructor, requiring a custom ViewModelProvider.Factory or Hilt/AndroidViewModel.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| Lifecycle 2.5 - 2.7 | active | — | — |
| AndroidX Activity 1.7 - 1.8 | active | — | — |

## Workarounds

1. **Create a custom ViewModelProvider.Factory: 'class MyViewModelFactory(private val repository: Repository) : ViewModelProvider.Factory { override fun <T : ViewModel> create(modelClass: Class<T>): T { return MyViewModel(repository) as T } }' and pass it to viewModels(): 'val viewModel: MyViewModel by viewModels { MyViewModelFactory(repository) }'** (95% success)
   ```
   Create a custom ViewModelProvider.Factory: 'class MyViewModelFactory(private val repository: Repository) : ViewModelProvider.Factory { override fun <T : ViewModel> create(modelClass: Class<T>): T { return MyViewModel(repository) as T } }' and pass it to viewModels(): 'val viewModel: MyViewModel by viewModels { MyViewModelFactory(repository) }'
   ```
2. **Use AndroidViewModel if the ViewModel needs Application context: 'class MyViewModel(application: Application) : AndroidViewModel(application)' and use by viewModels() without factory.** (80% success)
   ```
   Use AndroidViewModel if the ViewModel needs Application context: 'class MyViewModel(application: Application) : AndroidViewModel(application)' and use by viewModels() without factory.
   ```

## Dead Ends

- **** — The ViewModel may have null fields, causing NullPointerExceptions when accessed; it's a workaround but not a proper fix. (50% fail)
- **** — The delegate uses NewInstanceFactory by default, which requires a no-arg constructor. (50% fail)