FragmentExtensions.kt

/**
 * Show fragment's view in a dialog, similar to [androidx.fragment.app.DialogFragment],
 * but without need to extend it. Should be called from [Fragment.onViewCreated].
 *
 * Add this Fragment without giving it a container view then call this from onViewCreated
 */
fun Fragment.showAsDialog(
    @StyleRes theme: Int = R.style.FullScreenDialog,
    widthDp: Int? = null,
    heightDp: Int? = null,
    cancelOnTouchOutside: Boolean = true,
    onCancel: (() -> Unit)? = null
): Dialog {
    val fragmentName = javaClass.simpleName
    Timber.i("Show $fragmentName as a dialog")
    val dialog = Dialog(requireContext(), theme)
    dialog.setContentView(view ?: error("fragment view must be present"))
    dialog.setOnKeyListener { _, keyCode, _ -> if (keyCode == KeyEvent.KEYCODE_BACK) true else false }

    var viewDestroyed = false
    dialog.setOnDismissListener {
        if (!viewDestroyed) {
            dismiss(allowStateLoss = true)
        }
    }
    dialog.setCanceledOnTouchOutside(cancelOnTouchOutside)
    dialog.setOnCancelListener { onCancel?.invoke() }
    if (widthDp != null || heightDp != null) {
        if (widthDp == null) throw IllegalArgumentException("You must specify a width if you specify a height.")
        if (heightDp == null) throw IllegalArgumentException("You must specify a height if you specify a width.")
        dialog.window?.setLayout(widthDp.dp.toInt(), heightDp.dp.toInt())
    }
    // This prevents the nav bar from flashing.
    // https://stackoverflow.com/a/23207365/715633
    dialog.window?.setFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE, WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE)
    dialog.window?.decorView?.setSystemUiVisibility(requireActivity().window.decorView.systemUiVisibility)

    dialog.setOnShowListener {
        if (viewDestroyed) {
            Timber.i("$fragmentName was dismissed before showing")
            return@setOnShowListener
        }
        // Clear the not focusable flag from the window.
        dialog.window?.clearFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE)

        // Update the WindowManager with the new attributes (no nicer way I know of to do this)..
        dialog.window?.windowManager?.updateViewLayout(dialog.window?.decorView, dialog.window?.getAttributes())
    }
    activity?.let { dialog.ownerActivity = it }
    viewLifecycleOwner.lifecycle.addObserver(LifecycleEventObserver { _, event ->
        when (event) {
            Lifecycle.Event.ON_START -> dialog.show()
            Lifecycle.Event.ON_STOP -> dialog.hide()
            Lifecycle.Event.ON_DESTROY -> {
                viewDestroyed = true
                dialog.dismiss()
            }
            else -> Unit
        }
    })
    return dialog
}