If you want to do this Part of the Room Database Tutorial, beginn with the Branch Part_3 and do the tasks, given in the section below.

1. Create a simple Input Dialog with DialogFragment

   1.1) Modify the style.xml

   1.2) Create layout file - dialog_input.xml like the following example

   

   1.3) Create DialogFragment() - DialogInput.kt

   1.4) Save User Input to MainViewModel with fun insert(voc:Voc)

   1.5) Connect the FloatingActionButton @ MainActivity.kt with the DialogInput.kt

2. Register Observer on the VocList LiveData and Update VocListAdapter

   2.1) Create MainViewModel Instance

   2.2) Update VocListAdapter with method fun updateContent(..) and change ArrayList Type from String to Voc

   2.3) Override OnBindViewHolder(...) @ VocListAdapter.kt

   2.4) Implement Observer @ MainFragment.kt

To insert new vocabularies, we use a DialogFragment. To get a nice looking Dialog, with transparent Background, we have to create a new style for the DialogFragment.

<style name="FullScreenDialog" parent="AppTheme">
        <item name="windowNoTitle">true</item>
        <item name="android:layout_width">fill_parent</item>
        <item name="android:layout_height">fill_parent</item>
        <!-- No backgrounds, titles or window float -->
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:backgroundDimEnabled">true</item>
        <item name="android:backgroundDimAmount">0.7</item>
        <item name="android:windowIsFloating">false</item>
</style>

Please try it first on your own, before you take a look to the solution, given below: [dialog.input.xml]: https://github.com/ChrisRoh92/RoomDatabaseExample/blob/Part_4/app/src/main/res/layout/dialog_input.xml

A good way to show custom dialogs is to usw DialogFragment(). Below you see what you have to do, if you want to implement a DialogFragment: [InputDialog.kt]: https://github.com/ChrisRoh92/RoomDatabaseExample/blob/Part_4/app/src/main/java/com/example/roomdatabaseexample/main/DialogInput.kt

To use the new style FullscreenDialog you have to call the setStyle(...) method in onCreate(savedInstanceState: Bundle?):

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setStyle(
            STYLE_NO_FRAME,
            R.style.FullScreenDialog)

    }

To put new vocs into the Room Database, we have to create a method insert(voc:Voc). Please consider, that you have created an instance of MainViewModel in the onViewCreated(view: View, savedInstanceState: Bundle?) method:

private fun saveData()
    {
        if(!TextUtils.isEmpty(etForeign.editText?.text.toString()) && !TextUtils.isEmpty(etNative.editText?.text.toString()))
        {
            mainViewModel.insert(etNative.editText?.text.toString(),etForeign.editText?.text.toString())
            Toast.makeText(requireContext(),"Voc inserted in Database",Toast.LENGTH_SHORT).show()
            dismiss()
        }
        else
        {
            Toast.makeText(requireContext(),"Please insert data in both Fields!",Toast.LENGTH_SHORT).show()
        }
}

In the last step, to display the dialog, we have to create an OnClickListener for the FloatingActionButton in the MainActivity's onCreate(...)* method:

findViewById<FloatingActionButton>(R.id.fab).setOnClickListener { view ->
            val dialog = DialogInput()
            dialog.show(supportFragmentManager,"New Input")
        }

To create an instance of the MainViewModel use the following lines of code within the onViewCreated(...) method. Therefore create a global variable for the mainViewModel:

mainViewModel = ViewModelProvider(requireActivity(),MainViewModelFactory(requireActivity().application))
                    .get(MainViewModel::class.java)

If the Observer reports a detected change in the LiveData, we want to update the RecyclerView. Therefore, we need a method, which updates the content and notifies the Adapter, that the data has changed. Therefore we create the updateContent(...) method:

fun updateContent(content:ArrayList<Voc>)
{
    this.content = content
    notifyDataSetChanged()
}

Because we now want to use the Voc Object, we have to change the data type of the Arraylist content from String to Voc. Therefore, change the type of the Arraylist like in the following code snippet:

class VocListAdapter(var content:ArrayList<Voc>):RecyclerView.Adapter<VocListAdapter.ViewHolder>()

Now, we want to get the data of the vocs in the ArrayList "content". To display the informations, we have to override the OnBindViewHolder(...) method:

override fun onBindViewHolder(holder: VocListAdapter.ViewHolder, position: Int)
{
    val voc = content[position]
    holder.tvMain.text = voc.foreignWord
    holder.tvSub.text = voc.nativeWord
    holder.image.setImageResource(statusDrawables[voc.status])
}

In the onBindViewHolder method, we set the informations of each individual voc object, to the different views of the RecyclerView Item.

For the last step, we have to implement an Observer in the MainFragment, so we get informed, if there are any changes in the LiveData for the Voc List. Therefore, implement in the onViewCreated(...) method, the observer, right after the instantiation of the mainViewModel:

mainViewModel = ViewModelProvider(requireActivity(),MainViewModelFactory(requireActivity().application)).get(MainViewModel::class.java)
mainViewModel.getLiveVocList().observe(viewLifecycleOwner, Observer { items ->
    adapter.updateContent(ArrayList(items))
})

The first line, you should have already have from 2.1

Now you can start the Emulator, and test your App.