主View

<layout 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">

    <data>
        <variable
            name="layout"
            type="com.sh.wandroid.text.LoginViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        tools:context=".text.LoginActivity"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <include
            android:id="@+id/title1"
            layout="@layout/view_tile1"
            app:title = "@{layout.titleVm}"/>
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

include view

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <import type="android.text.TextUtils"/>
        <variable
            name="title"
            type="com.sh.wandroid.base.TitleVM" />
    </data>

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

        <TextView
            android:text="@{TextUtils.isEmpty(title.MTitle)?`null`:`not null`}"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

j结果显示 null

viewmodel

class LoginViewModel(app:Application):BaseViewModel(app) {

    val titleVm= TitleVM(
            title = "登录"
        )
}

123

TitleVM

class TitleVM(
    var leftText: String? = "",
    var leftDrawable: Drawable? = R.drawable.abc_vector_test.getDrawable(),
    var leftClick: (() -> Unit)? = null,
    var title: String? = "321",
    var rightText: String? = "",
    var rightDrawable: Drawable? = null,
    var rightClick: (() -> Unit)? = null,
    var background: Int = R.color.colorAccent.getResColor()
) : ViewModel() {
    init {
        println("title====$title")
    }
    val mTitle = ObservableField<String>(title)
    val mRightDrawable = ObservableField(rightDrawable)
}

绑定

private fun initVM() {
    val vm = getViewModel()
    val factory = ViewModelProvider.AndroidViewModelFactory(application)
    mViewModel = ViewModelProvider(this,factory)[vm::class.java]
    //每个布局都需要传入一个viewmodel
    binding.setVariable(BR.layout, mViewModel)
    //不添加 livedata观察不到数据变化
    binding.lifecycleOwner = this
}