How to change Fragment Kotlin

Question

I'm starting in Kotling and I don't know how to change between fragments, I have tried this code:

val manager = supportFragmentManager
    val transaction = manager.beginTransaction()
    transaction.add(R.layout.fragment_information.toInt(), ComplainFragment())
    transaction.commit()

R.layout.fragment_information.toInt()

But i have an error with this parameter because it doesn't find the fragment Id.

Solution 1

I usually use replace to change between fragments. Also change R.layout.fragment_information to R.id.fragment_layout_id only, so no need toInt()

transaction.replace(R.id.fragment_layout_id, fragment)

Here is my suggestion.

    var fragment: Fragment? = null

            when (itemId) {
                        R.id.fragment_information -> {
                            fragment = ComplainFragment()
                        }
            }

            if (fragment != null) {
                    val transaction = supportFragmentManager.beginTransaction()
                    transaction.replace(R.id.fragment_layout_id, fragment)
                    transaction.commit()
            }

Solution 2

This is an example for you to go to a fragment or activity by clicking a button inside another fragment:

class Fragment_One: Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_one, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        btn_goToActivity2.setOnClickListener {
            val intent = Intent(context, SecondActivity::class.java)
            startActivity(intent)
        }

        btn_goToFragment2.setOnClickListener {
            var fr = getFragmentManager()?.beginTransaction()
            fr?.replace(R.id.fragment, Fragment_Two())
            fr?.commit()
        }
    }
}

Solution 3

The other answers will work but still we can improve a lot by using extension functions in Kotlin.

Add an extension function to the FragmentManager class like below,

inline fun FragmentManager.doTransaction(func: FragmentTransaction.() -> 
FragmentTransaction) {
    beginTransaction().func().commit()
}

then create an extension function to the AppCompatActivity class,

fun AppCompatActivity.addFragment(frameId: Int, fragment: Fragment){
    supportFragmentManager.doTransaction { add(frameId, fragment) }
}


fun AppCompatActivity.replaceFragment(frameId: Int, fragment: Fragment) {
    supportFragmentManager.doTransaction{replace(frameId, fragment)}
}

fun AppCompatActivity.removeFragment(fragment: Fragment) {
    supportFragmentManager.doTransaction{remove(fragment)}
}

Now, to add and remove fragments from any activity, you just need to call like this,

addFragment(R.id.fragment_container, fragment)

replaceFragment(R.id.fragment_container, fragment)

please refer the below link for more info,

https://medium.com/thoughts-overflow/how-to-add-a-fragment-in-kotlin-way-73203c5a450b

Solution 4

When you add a fragment, you need to add it to an ID that exists in your Activity's layout, not an entire layout:

supportFragmentManager.beginTransaction().add(R.id.some_id_in_your_activity_layout, ComplainFragment()).commit()

Solution 5

In case anyone still needs a quick approach to this. I created a function than can be easily called whenever you need to change a fragment.

 private fun replaceFragment(fragment: Fragment) {
    val transaction = supportFragmentManager.beginTransaction()
    transaction.replace(R.id.frame, fragment)
    transaction.commit()
}

R.id.frame in this case is the id of my Framelayout in the activity that will hold my fragment. All you have to do now is call the function.

replaceFragment(HomeFragment())

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