How to generate the preview of a custom view that uses a ViewModelProvider?

Question

Android Studio stopped generating the preview of my layout. The problem is caused by the presence of custom views.

The error :

Render Problem

java.lang.NullPointerException   at

com.my.app.views.bars.TopBar$mainViewModel$2.invoke(TopBar.kt:26)   at com.my.app.views.bars.TopBar$mainViewModel$2.invoke(TopBar.kt:25)   at layoutlib.internal.kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)

The problem seems to come from the ViewModelProvider :

private val mainViewModel by lazy {
    ViewModelProvider(findViewTreeViewModelStoreOwner()!!).get<MainViewModel>()
}

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Custom View does not render in Design View in Android Studio?

Answer 1

Android Studio can't generate the preview of a custom view that uses a ViewModelProvider. However we can prevent it from crashing by checking if it is in "Edit Mode" before drawing the view.

override fun onDraw(canvas: Canvas) {
    if (isInEditMode) return
    ...
}

Please note that this must be done inside the "OnDraw" method.

Indeed, replacing the mainViewModel with NULL isn't an option, because it can and will lead to NullPointerExceptions.