Kotlin: How do I call a DialogFragment from within an Adapter class?

Question

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:

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")
    }
}

But I rather want to call a function inside a DialogFragment class instead of the deleteCategory(id) function, like this:

  // 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")
  }

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.

Where do you define the `showDeleteCategoryDialog()` function? Inside the adapter? — earthw0rmjim, Apr 10 '18 at 16:07
Yes, because I need to provide a value for categoryId, a String that I retrieve in the bind function of my CategoryHolder. The showDeleteCategoryDialog() function works fine when defined in MainActivity and provided with a 'fake' categoryId. — CEO tech4lifeapps, Apr 10 '18 at 16:26

score 8 · Accepted Answer · answered Apr 11 '18 at 06:21

You can not refer to your MainActivity like your code above. You have to cast the context of your ViewHolder as MainActivity before using it:

val activity =  itemView.context as? MainActivity
// then you can show your dialog with activity?.supportFragmentManager

Massita · Answer 2 · 2018-04-10T17:18:03.503

0

My recommendation is to create a callback to this action and implement this callback on your MainActivity and create the dialog direct on your activity.

interface ClickListener {
    fun onLongClickListener(categoryId: Int)
}

then

class CategoryHolder(val customView: View, var category: Category? = null, var mListener: ClickListener?)

...
customView.setOnLongClickListener({
      mListener?.onLongClickListener(categoryId)
      ...
}

and on your MainActivity:

 class MainActivity : AppCompatActivity, ClickListener {

    override fun onLongClickListener(categoryId: Int) {
     // Create your dialog
    }


    ...
        /* when creating your adapter you need to pass the listener to
         * adapter, so it can be used on your viewholder
         * mElements are the category elements, 'this' is the impl of
         * the adapter that was implemented here
        */
        mAdapter = CategoryAdapter(mElements, this)
 }

on your Adapter:

class CategoryAdapter(var mElements: List<Category>, var mListener: ClickListener) : RecyclerView.Adapter<> ...

     // When creating your viewHolder
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CategoryHolder {
        return CategoryHolder(LayoutInflater.from(parent.context) 
            .inflate(R.layout.category_row, parent, false), listener)
}

edited Apr 10 '18 at 17:18

answered Apr 10 '18 at 14:37

Massita

309
2
10

This gives me an error in my onCreateViewHolder function: "No value passed for parameter mListener" – CEO tech4lifeapps Apr 10 '18 at 15:29
After implementing this listener in the MainActivity, you need to pass the activity as a new parameter on the ViewHolder constructor... Now you need to create your ViewHolder like `val holder = CategoryHolder(customView, category, listener)` – Massita Apr 10 '18 at 16:38
Now you need to pass the listener when creating the viewholder... `override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CategoryHolder { return CategoryHolder(LayoutInflater.from(parent.context) .inflate(R.layout.category_row, parent, false), listener) } ` You can create this listener on your adapter and pass the listener to the ViewHolder when creating it – Massita Apr 10 '18 at 17:05
@CEOtech4lifeapps i've updated my answer, is it easier now? :D – Massita Apr 10 '18 at 17:18
I'm afraid, this does not help. My MainAdapter is of type FirebaseRecyclerAdapter that does not work on a list holding elements and categoryId is of type String, not Int. – CEO tech4lifeapps Apr 11 '18 at 04:06

score 0 · Answer 3 · answered Apr 11 '18 at 08:23

Here is, in detail, how this was solved:

In class CategoryHolder

customView.setOnLongClickListener(
    {
      showDeleteCategoryDialog(it, categoryId)
      true
    } 
)

In function showDeleteCategoryDialog

// Create an instance of a DeleteCategoryDialogFragment and show it
fun showDeleteCategoryDialog(view: View, categoryId: String) {
    val activity = itemView.context as? MainActivity
    val dialog = DeleteCategoryDialogFragment.newInstance(categoryId)
    dialog.show(activity?.supportFragmentManager, "DeleteCategoryDialog")
}

Kotlin: How do I call a DialogFragment from within an Adapter class?

3 Answers3