I am trying to implement bottom navigation with an Activity and use Kotlin. So I search in youtube and I seen a lot of content which uses Fragment for bottom navigation T_T
So I try to copy code from https://www.youtube.com/watch?v=JjfSjMs0ImQ because they use Activity not Fragment
But the problem is they use Java. So I try to convert the code to Kotlin. And then this happened (Logcat)
Caused by: java.lang.IllegalStateException: bottomNavigationView must not be null at com.example.smscandroid.Profile.onCreate(Profile.kt:18)
So I look in Profile.kt
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_profile)
//init
val bottomNavigationView =
findViewById<BottomNavigationView>(R.id.bottom_navigation)
//Set
bottomNavigationView.selectedItemId = R.id.profile
//Perform ItemSelectedListener
bottomNavigationView.setOnNavigationItemSelectedListener(BottomNavigationView.OnNavigationItemSelectedListener { menuItem ->
when (menuItem.itemId) {
R.id.medication -> {
startActivity(
Intent(
applicationContext
, Medication::class.java
)
)
overridePendingTransition(0, 0)
return@OnNavigationItemSelectedListener true
}
R.id.home -> {
startActivity(
Intent(
applicationContext
, MainActivity::class.java
)
)
overridePendingTransition(0, 0)
return@OnNavigationItemSelectedListener true
}
R.id.profile -> return@OnNavigationItemSelectedListener true
}
false
})
}
I think the error is at
//init
val bottomNavigationView =
findViewById<BottomNavigationView>(R.id.bottom_navigation)
//Set
bottomNavigationView.selectedItemId = R.id.profile
I think findViewById<BottomNavigationView>(R.id.bottom_navigation) might get null
then bottomNavigationView.selectedItemId = R.id.profile would cause an Exception
This is bottom_navigation.xml
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/medication"
android:title="medication"
android:icon="@drawable/ic_medication"/>
<item
android:id="@+id/home"
android:title="home"
android:icon="@drawable/ic_home"/>
<item
android:id="@+id/profile"
android:title="profile"
android:icon="@drawable/ic_profile"/>
</menu>
Why does findViewById<BottomNavigationView>(R.id.bottom_navigation) get null?
If I write something wrong, tell me, I will improve it.
You should have a file named activity_profile.xml in your res/layout that looks like this:
<SomeLayout
...
>
<BottomNavigationView
android:id="@+id/this_is_the_id_you_should_use"
.../>
</SomeLayout>
And then in your Profile.kt you should use
val bottomNavigationView = findViewById<BottomNavigationView>(R.id.this_is_the_id_you_should_use)