The best practice to pop up a common error dialog in any destination with navigation component

Question

I want to display an error dialog while receiving errors in any destination fragment's ViewModel.

Now, I created a BaseViewModel and a BaseFragment that does the stuff, and make all fragments and ViewModels extend it.
But it's hard to connect all destinations to the dialog's DialogFragment.

Should I leave the dialog out of the nav_graph.xml?

Answer 1

If you are using kotlin you can do it by using an extension function

inline fun Activity.alertDialog(
    title: CharSequence? = null,
    message: CharSequence? = null,
    func: AlertDialogHelper.() -> Unit
) {
    val dialogFragment = AlertDialogHelper(this, title, message).apply {
        func()
    }
    val fragmentTransaction = (this as AppCompatActivity).supportFragmentManager.beginTransaction()
    fragmentTransaction.let { dialogFragment.show(it, TAG) }
}

inline fun Fragment.alertDialog(
    title: CharSequence? = null,
    message: CharSequence? = null,
    func: AlertDialogHelper.() -> Unit
) {
    val dialogFragment = AlertDialogHelper(this.context!!, title, message).apply {
        func()
    }
    val fragmentTransaction = (this).childFragmentManager.beginTransaction()
    fragmentTransaction.let { dialogFragment.show(it, TAG) }
}

AlertDialogHelper is the same dialog class that is extended by DialogFragment

AlertDialogHelper

    class AlertDialogHelper(context: Context, title: CharSequence?, message: CharSequence?) :
    DialogFragment() {

    private val dialogView: View by lazyFast {
        LayoutInflater.from(context).inflate(R.layout.dialog_layout, null)
    }

    private val title: TextView by lazyFast {
        dialogView.findViewById(R.id.dialogInfoTitleTextView)
    }

    private val message: TextView by lazyFast {
        dialogView.findViewById(R.id.dialogInfoMessageTextView)
    }

    private val positiveButton: Button by lazyFast {
        dialogView.findViewById(R.id.dialogInfoPositiveButton)
    }

    private val negativeButton: Button by lazyFast {
        dialogView.findViewById(R.id.dialogInfoNegativeButton)
    }

    var cancelable: Boolean? = true

    init {
        this.title.text = title
        this.message.text = message
    }


    fun positiveButton(text: CharSequence, func: (() -> Unit)? = null) {
        with(positiveButton) {
            this.text = text
            setClickListenerToDialogButton(func)
        }
    }


    fun negativeButton(text: CharSequence, func: (() -> Unit)? = null) {
        with(negativeButton) {
            this.text = text
            setClickListenerToDialogButton(func)
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return dialogView
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        title.goneIfTextEmpty()
        message.goneIfTextEmpty()
        positiveButton.goneIfTextEmpty()
        negativeButton.goneIfTextEmpty()

        dialog?.window?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT))
        isCancelable = this.cancelable!!
    }

    override fun onDestroyView() {
        super.onDestroyView()
    }

    private fun TextView.goneIfTextEmpty() {
        visibility = if (text.isNullOrEmpty()) {
            View.GONE
        } else {
            View.VISIBLE
        }
    }

    private fun Button.setClickListenerToDialogButton(func: (() -> Unit)?) {
        setOnClickListener {
            func?.invoke()
            dialog?.dismiss()
        }
    }

    fun <T> lazyFast(operation: () -> T): Lazy<T> = lazy(LazyThreadSafetyMode.NONE) {
        operation()
    }
}