The colors of button does not apply after migrate to view binding

Question

In this sample calculator app, I just migrate from old Kotlin synthetics "kotlin-android-extensions" to view binding, but I see the color of buttons app:backgroundTint didn't apply when I run I see the default button color

The supposed layout

after running

The xml of activity_main

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    android:background="@color/gray"
    >

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:background="@color/gray"
        android:gravity="end"
        android:paddingTop="50dp"
        android:paddingRight="5dp"
        android:paddingBottom="5dp"
        android:text="0"
        android:textColor="@color/white"
        android:textSize="50sp"
        android:layout_weight="1"
        android:paddingEnd="5dp"
        />

    <TableLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        >

        <TableRow
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            >

            <Button
                android:id="@+id/acButton"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:layout_weight="1"
                android:text="AC"
                android:onClick="buClear"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                />

            <Button
                android:id="@+id/buMinPlus"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:onClick="buNumberClick"
                android:text="+/-"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback" />

            <Button
                android:id="@+id/buPercent"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:layout_weight="1"
                android:text="%"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback" />

            <Button
                android:id="@+id/buDiv"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="/"
                android:onClick="buttonOp"
                android:textSize="25sp"
                app:backgroundTint="@color/orange" />
        </TableRow>

        <TableRow
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            >

            <Button
                android:id="@+id/bu7"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:text="7"
                android:onClick="buNumberClick"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback" />

            <Button
                android:id="@+id/bu8"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:text="8"
                android:onClick="buNumberClick"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                />

            <Button
                android:id="@+id/bu9"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:text="9"
                android:onClick="buNumberClick"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                />

            <Button
                android:id="@+id/buMul"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="*"
                android:textSize="25sp"
                android:onClick="buttonOp"
                app:backgroundTint="@color/orange"
                />
        </TableRow>

        <TableRow
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            >

            <Button
                android:id="@+id/bu4"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                android:onClick="buNumberClick"
                android:text="4" />

            <Button
                android:id="@+id/bu5"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                android:onClick="buNumberClick"
                android:text="5" />

            <Button
                android:id="@+id/bu6"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                android:onClick="buNumberClick"
                android:text="6" />

            <Button
                android:id="@+id/buMin"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:textSize="25sp"
                app:backgroundTint="@color/orange"
                android:onClick="buttonOp"
                android:text="-" />
        </TableRow>

        <TableRow
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            >

            <Button
                android:id="@+id/bu1"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                android:onClick="buNumberClick"
                android:text="1" />

            <Button
                android:id="@+id/bu2"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                android:onClick="buNumberClick"
                android:text="2" />

            <Button
                android:id="@+id/bu3"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:textColor="@color/gray"
                android:textSize="25sp"
                app:backgroundTint="@color/whiteback"
                android:layout_marginEnd="1dp"
                android:layout_marginRight="1dp"
                android:onClick="buNumberClick"
                android:text="3" />

            <Button
                android:id="@+id/buPlus"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:textSize="25sp"
                app:backgroundTint="@color/orange"
                android:onClick="buttonOp"
                android:text="+" />
        </TableRow>

    </TableLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0.20"
        android:orientation="horizontal">

        <Button
            android:id="@+id/bu0"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:layout_marginEnd="1dp"
            android:layout_marginRight="1dp"
            android:textColor="@color/gray"
            android:textSize="25sp"
            app:backgroundTint="@color/whiteback"
            android:onClick="buNumberClick"
            android:text="0" />

        <Button
            android:id="@+id/buDot"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:layout_marginEnd="1dp"
            android:layout_marginRight="1dp"
            android:textColor="@color/gray"
            android:textSize="25sp"
            app:backgroundTint="@color/whiteback"
            android:onClick="buNumberClick"
            android:text="." />

        <Button
            android:id="@+id/buEqual"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:textColor="@color/gray"
            android:textSize="25sp"
            app:backgroundTint="@color/orange"
            android:onClick="theResultOfOp"
            android:text="=" />
    </LinearLayout>
</LinearLayout>

build.gradle(app)

plugins {
    id 'com.android.application'
    id 'kotlin-android'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.example.calculator"
        minSdkVersion 16
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    buildFeatures {
        viewBinding true
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.2'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}