How to pass and get value from fragment and activity

Question

How to pass and get value from fragment and activity?

Answer 1

Here is the Android Studio proposed solution (= when you create a Blank-Fragment with File -> New -> Fragment -> Fragment(Blank) and you check "include fragment factory methods").

Put this in your Fragment:

class MyFragment: Fragment {  ...      companion object {              @JvmStatic             fun newInstance(isMyBoolean: Boolean) = MyFragment().apply {                 arguments = Bundle().apply {                     putBoolean("REPLACE WITH A STRING CONSTANT", isMyBoolean)                 }             }      } } 

.apply is a nice trick to set data when an object is created, or as they state here:

Calls the specified function [block] with this value as its receiver and returns this value.

Then in your Activity or Fragment do:

val fragment = MyFragment.newInstance(false) ... // transaction stuff happening here 

and read the Arguments in your Fragment such as:

private var isMyBoolean = false  override fun onAttach(context: Context?) {     super.onAttach(context)     arguments?.getBoolean("REPLACE WITH A STRING CONSTANT")?.let {         isMyBoolean = it     } } 

Enjoy the magic of Kotlin!

Answer 2

There is the companion object for that (https://kotlinlang.org/docs/reference/object-declarations.html#companion-objects )

Define your fragment as usual, and declare the companion that acts as the static newInstance() equivalent in Java :

class ViewStackListFragment : Fragment() {   companion object {         fun newInstance(position: Int): ViewStackListFragment {             val fragment = ViewStackListFragment()             val args = Bundle()             args.putInt("position", position)             fragment.setArguments(args)             return fragment         }     } } 

And simply call it like in Java :

val fragment = ViewStackListFragment.newInstance(4)