title: Kotlin: How do I call a DialogFragment from within an Adapter class?
body: <p>I have a MainAdapter.kt class that handles a RecyclerView. In its Holder class, I use a OnLongClickListener that calls a function deleteCategory(categoryId) to delete an entry in my Firebase database. This works perfectly: </p>
  
  <pre><code>class CategoryHolder(val customView: View, var category: Category? = null) : RecyclerView.ViewHolder(customView) {
      private val TAG = CategoryHolder::class.java.simpleName
  
      fun bind(category: Category) {
          with(category) {
              customView.textView_name?.text = category.name
              customView.textView_description?.text = category.description
  
              val categoryId = category.id
  
              customView.setOnClickListener {
                      // do something
              }
  
              customView.setOnLongClickListener(
                      {
                         deleteCategory(categoryId)
                         true
                      }
              )
          }
      }
  
      private fun deleteCategory(categoryId: String) {
          val database = FirebaseDatabase.getInstance()
  
          val myRef = database.getReference("categories").child(categoryId)
          myRef.removeValue()
          Log.d(TAG, "Category with id " + categoryId + " deleted")
      }
  }
  </code></pre>
  
  <p>But I rather want to call a function inside a DialogFragment class instead of the deleteCategory(id) function, like this:</p>
  
  <pre><code>  // Create an instance of a DeleteCategoryDialogFragment and show it
    fun showDeleteCategoryDialog(view: View, categoryId: String) {
        val dialog = DeleteCategoryDialogFragment.newInstance(categoryId)
        dialog.show(this@MainActivity.supportFragmentManager, 
        "DeleteCategoryDialog")
    }
  </code></pre>
  
  <p>This gives me a "Unresolved reference: @MainActivity" error.
  How can I solve this? Is there a way to get hold of categoryId (of type String) in my MainActivity? This would allow me to move the function showDeleteCategoryDialog to MainActivity and solve the problem. </p>