How to Communicate Between Fragments in Android?
Last Updated : 08 Aug, 2024
Nowadays most apps have so many features so for that they use multiple fragments in a single app and communication is one of the important parts of apps for sharing data from one fragment to another because two fragments can't communicate directly. A Fragment represents a portion of any user interface. There can be a number of fragments within one activity. They have their own life cycle.
Approach
There are multiple ways in which we can communicate within apps:
- We can communicate within fragments using the ViewModel.
- We can also communicate between fragments using an Interface.
In this article, we are going to explain how to communicate between fragments using the Interface using Kotlin.
Step-by-Step Implementation
Step 1: Create a New Project in your android studio
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Kotlin as the programming language.
Step 2: Create two blank fragments
Navigate to your Project file where MainActivity.kt exists. Right-click on that folder and click on the new package and name it fragments. Now inside this newly created folder create two blank fragments and name them Fragment1 & Fragment2.
Step 3: Working with XML files
Navigate to the app > res > layout > fragment1.xml and add the below code to that file. Below is the code for the fragment1.xml file.
XML <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".fragments.Fragment1"> <!-- Text View for showing Fragment1 text --> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Fragment 1" android:textSize="40sp" android:layout_centerHorizontal="true" android:gravity="center" android:layout_marginTop="20dp" android:textColor="@color/black"/> <!-- Edit Text for taking user input --> <EditText android:id="@+id/messageInput" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Enter text to Pass" android:layout_marginTop="200dp" android:gravity="center" android:layout_marginLeft="30dp" android:layout_marginRight="30dp" android:textSize="30sp"/> <!-- Button for submit user response --> <Button android:id="@+id/sendBtn" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/etText" android:text="Submit" android:backgroundTint="#0F9D58" android:textSize="20sp" android:textAllCaps="false" android:layout_marginLeft="30dp" android:layout_marginRight="30dp" android:layout_marginTop="20dp" /> </RelativeLayout>
Navigate to the app > res > layout > fragment2.xml and add the below code to that file. Below is the code for the fragment2.xml file.
XML <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".fragments.Fragment2"> <!-- Text View for showing Fragment2 text --> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Fragment 2" android:textSize="40sp" android:layout_centerHorizontal="true" android:gravity="center" android:layout_marginTop="20dp" android:textColor="@color/black"/> <!-- Frame Layout which will replaced by data from Fragment1 --> <FrameLayout android:id="@+id/frameLayout" android:layout_width="match_parent" android:layout_height="wrap_content"> <TextView android:id="@+id/displayMessage" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Text" android:textSize="30sp" android:layout_centerHorizontal="true" android:gravity="center" android:layout_marginTop="300dp" android:textColor="@color/black"/> </FrameLayout> </RelativeLayout>
Step 4: Create Interface
Again navigate to your Project folder where MainActivity.kt exists and right-click on that folder -> new -> Kotlin class/file -> Interface them name it as Communicator.
Kotlin package com.mrtechy.gfg interface Communicator { fun passData(editTextInput:String) }
Step 5: Working With the MainActivity.kt
Kotlin package com.mrtechy.gfg import androidx.appcompat.app.AppCompatActivity import android.os.Bundle import com.mrtechy.gfg.fragments.Fragment1 import com.mrtechy.gfg.fragments.Fragment2 class MainActivity : AppCompatActivity(), Communicator { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) // created instance of Fragment1 val fragment1 = Fragment1() // Frame manager called to replace Fragment2 frame layout with Fragment1 data supportFragmentManager.beginTransaction().replace(R.id.frameLayout,fragment1).commit() } // Override function which we // have created in our interface override fun passData(editTextInput: String) { val bundle = Bundle() bundle.putString("message", editTextInput) val transaction = this.supportFragmentManager.beginTransaction() // Created instance of fragment2 val fragment2 = Fragment2() fragment2.arguments = bundle transaction.replace(R.id.frameLayout,fragment2) transaction.commit() } }
Step 6: Working With Fragment1 & Fragment file
Below is the code for the Fragment1.kt and Fragment2.kt files respectively.
Kotlin package com.mrtechy.gfg.fragments import android.os.Bundle import androidx.fragment.app.Fragment import android.view.LayoutInflater import android.view.View import android.view.ViewGroup import android.widget.Button import android.widget.EditText import com.mrtechy.gfg.Communicator import com.mrtechy.gfg.R class Fragment1 : Fragment() { private lateinit var communicator: Communicator override fun onCreateView( inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle? ): View? { // Inflate the layout for this fragment val view = inflater.inflate(R.layout.fragment_1, container, false) communicator = activity as Communicator // there are button and edittext id which we have saved val button:Button = view.findViewById(R.id.sendBtn) val textMessage:EditText = view.findViewById(R.id.messageInput) // pass data to our interface while // button clicked using setOnClickListener button.setOnClickListener { communicator.passData(textMessage.text.toString()) } return view } } package com.mrtechy.gfg.fragments import android.os.Bundle import androidx.fragment.app.Fragment import android.view.LayoutInflater import android.view.View import android.view.ViewGroup import android.widget.TextView import com.mrtechy.gfg.R class Fragment2 : Fragment() { // initialised a empty string variable var displayMessage:String? ="" override fun onCreateView( inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle? ): View? { // Inflate the layout for this fragment val view = inflater.inflate(R.layout.fragment_2, container, false) val displayM:TextView = view.findViewById(R.id.displayMessage) // get text from interface and send // to textView present in Fragment2 displayMessage = arguments?.getString("message") displayM.text = displayMessage return view } } Output: