I have the following Activity:
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
with the following layout:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<fragment
android:id="@+id/navHostFragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/navigation_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
I also have two fragments: Fragment1 and Fragment2. Fragment1 is:
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.navigation.fragment.findNavController
class Fragment1 : Fragment() {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_1, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
findNavController().navigate(R.id.action_fragment1_to_fragment2)
}
}
and its layout is:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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=".Fragment1">
<TextView
android:id="@+id/toFragment2Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="Fragment 1" />
</FrameLayout>
Fragment2 is:
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
class Fragment2 : Fragment() {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_2, container, false)
}
}
with the following layout:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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=".Fragment2">
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Fragment 2" />
</FrameLayout>
and last but not least is the contents of navigation_graph.xml
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
app:startDestination="@id/fragment1">
<fragment
android:id="@+id/fragment1"
android:name="ir.fallahpoor.navigation.Fragment1"
android:label="fragment_1"
tools:layout="@layout/fragment_1">
<action
android:id="@+id/action_fragment1_to_fragment2"
app:destination="@id/fragment2" />
</fragment>
<fragment
android:id="@+id/fragment2"
android:name="ir.fallahpoor.navigation.Fragment2"
android:label="fragment_2"
tools:layout="@layout/fragment_2" />
</navigation>
As you can see there is nothing fancy here. The only thing that I'm doing is navigating to Fragment2 in onViewCreated
of Fragment1.
When I run the app Fragment2 is displayed as expected. When I press the back button I expect to return to Fragment1, but that doesn't happen. It is as if back button is disabled and pressing it doesn't do anything. I have to press the home button to exit the app.