I cannot use databinding with TextView in viewpager2, postValue() is invalid

Question

I encountered a problem when using databinding and viewpager2. I used viewpager2 in a fragment. FragmentA in viewpager2 wanted to share the viewmodel of the fragment.

1. A TextView attribute text is bound in fragmentA, but postValue in viewmodel cannot change the text of TextView
2. But fragmentA is bound to a click event (TextView has a click, triggering the sendCode() function), which can be triggered in the viewmodel

fragmentA：

class SignUpMainFragment(val vm:SignUpFragmentVM):Fragment() {
    private var mBinding:FragmentSignUpMainBinding?=null

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        mBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_sign_up_main,container,true)
        mBinding?.signUp = vm
        return mBinding?.root!!
    }
}

Layout of fragmentA：

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <variable
            name="signUp"
            type="com.xxx.SignUpFragmentVM" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <EditText
            android:id="@+id/et_email"
            android:layout_width="468dp"
            android:layout_height="94dp"
            android:layout_marginStart="40dp"
            android:hint="Email"
            android:text="@={signUp.txtEmail}"
            android:textSize="30sp"
            android:textColor="@color/color_aaa280"
            android:drawableStart="@mipmap/img_mail"
            android:paddingStart="26dp"
            android:drawablePadding="18dp"
            android:inputType="textEmailAddress"
            android:background="@drawable/shape_edit_bg_e7e7e7"
            app:layout_constraintTop_toTopOf="@id/et_name"
            app:layout_constraintStart_toEndOf="@id/et_name" />

        <TextView
            android:id="@+id/tv_send_code"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{signUp.txtSendEmail}"
            android:textSize="30.5sp"
            android:textColor="@color/color_71cbc0"
            android:onClick="@{signUp.click}"
            android:clickable="true"
            android:layout_marginStart="25dp"
            app:layout_constraintTop_toTopOf="@id/et_lock_psw"
            app:layout_constraintBottom_toBottomOf="@id/et_lock_psw"
            app:layout_constraintStart_toEndOf="@id/et_lock_psw"/>
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

SignUpFragmentVM:

class SignUpFragmentVM constructor():ViewModel() {
    val txtSendEmail = MutableLiveData("Get verified.")
    
    ....

    private fun sendCode(){
        viewModelScope.launch {
            ...
            //TODO：60s Countdown
            txtSendEmail.postValue("60")
        }
    }
}

Answer 1

You need more

mBinding?.signUp = vm
mBinding?.lifecycleOwner = this // => add