DialogQueue-2

dq.kt

class DialogQueueImpl(
    private val context: Context,
    private val lifecycleOwner: LifecycleOwner,
    private val fragmentManager: FragmentManager,
): DialogQueue {

    private var showingElement: DialogQueueElement? = null

    companion object {
        private val queue = PriorityQueue<DialogQueueElement>()
        const val TAG = "DialogQueue"
    }

    init {
        lifecycleOwner.lifecycle.addObserver(object: LifecycleEventObserver {
            override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
                when (event) {
                    Lifecycle.Event.ON_RESUME -> flush()
                    Lifecycle.Event.ON_PAUSE -> {
                        addFirst(showingElement)
                        showingElement = null
                    }
                    else -> {}
                }
            }
        })
    }

    private fun addFirst(element: DialogQueueElement?) {
        if (element != null) {
            queue.offer(element.copy(priority = maxOf(element.priority, DialogQueue.Priority.MEDIUM)))
        }
    }

    override fun add(
        element: DialogQueueElement,
    ) {
        queue.offer(element)
        flush()
    }

    private fun flush() {
        try {
            check(queue.isNotEmpty())
            check(showingElement == null) {
                "dialog is already showing."
            }
            check(lifecycleOwner.lifecycle.currentState.isAtLeast(Lifecycle.State.RESUMED)) {
                "lifecycle must be resumed."
            }

            // show dialog
            val element = queue.poll()

            showingElement = element

            val dialog = element.dialogBuilder(context) { // on dismiss
                showingElement = null
                (fragmentManager.findFragmentByTag(element.tag) as? DialogFragment)?.dismiss()
                flush()
            }
            dialog.show(fragmentManager, element.tag)
        } catch (e: IllegalStateException) {
            Log.e(TAG, "failed to flush: $e")
        }
    }
}