Fragments handling of TextView in an Android app-CodePudding

I am having a hard time dealing with fragments in an Android app of mine. Something seems weird and a look by somebody else might shed some light.

Here is the XML for the fragment:

<?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"
    android:id="@ id/theFragmentID"
    tools:context=".NiceFragment">

    <TextView
        android:id="@ id/labelOne"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:text="Place_Holder-One" />
    <TextView
        android:id="@ id/labelTwo"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:text="Place_Holder=Two" />
    <EditText
        android:id="@ id/inpNew"
        android:gravity="center"
        android:layout_width="match_parent"
        android:layout_height="60px" />
    .....
</FrameLayout>

Here is some Kotlin code I have somewhere in the app (namely in the onCreateView() method of the fragment):

val labelOne = fragHandle.findViewById<TextView>(R.id.labelOne)
labelOne.text = "Some interesting sentence"
val labelTwo = fragHandle.findViewById<TextView>(R.id.labelTwo)
labelTwo.text = "Some other very interesting sentence"

And finally this is the error I get on the last line of the code above:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
    at me.soft.myapp.NiceFragment.onCreateView(NiceFragment.kt:99)

The four lines of Kotlin code above may be better located in the onViewCreated() method of the fragment. But the point of my question is:

Why is there a problem on the 4th line while the 2nd works perfectly?

From my perspective labelOne and labelTwo are just two totally equivalent objects.

I also tried to put this chunk of code inside onViewCreated(), but the problem is still there.

What detail could I be missing?

CodePudding user response：

Please check the imported xml which is written in your kotlin class. Wrong XML file would be imported.

CodePudding user response：

While using kotlin there is a very good option while working with fragments. You should consider this too. Move your layout name to Fragment constructor and do as below code.

 class AccountFragment : Fragment(R.layout.fragment_account) {

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
    
        val labelOne = view.findViewById<TextView>(R.id.labelOne)
    
    }
}

Its always a good practice to use onViewCreated instead of onCreateView in fragments..

Happy Coding

CodePudding user response：

in my opinion, you can use viewBinding

add this in your gradle

viewBinding {
      enabled = true
}

and in your fragment can use the binding like this

private lateinit var binding: FragmentHomeNavBinding
override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View {
    binding = FragmentHomeNavBinding.inflate(LayoutInflater.from(requireContext()), container, false)
    return binding.root
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    binding.apply {
        myTextView.text = "some text"
    }
}

viewBinding replaces findViewById, and ViewBinding have null safety and type safety