Kotlin使用TransitionDrawable实现颜色渐变效果流程讲解

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <array name="icons">
        <item>@drawable/idea1</item>
        <item>@drawable/idea2</item>
    </array>
</resources>

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="100dp"
    android:text="案例2：灯泡颜色渐变"
    android:textSize="20dp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/pushButton" />
<ImageView
    android:id="@+id/iv_light"
    android:layout_width="80dp"
    android:layout_height="80dp"
    android:src="@drawable/idea"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintHorizontal_bias="0.498"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textView2"
    app:layout_constraintVertical_bias="0.218" />
<Switch
    android:id="@+id/switchView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    android:layout_marginTop="20dp"
    android:showText="true"
    android:textOff="关"
    android:textOn="开"
    app:layout_constraintTop_toBottomOf="@+id/iv_light"
    tools:ignore="UseSwitchCompatOrMaterialXml" />

@SuppressLint("ClickableViewAccessibility", "ResourceType")
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    val resources: Resources = resources
    val icons: TypedArray = resources.obtainTypedArray(R.array.icons)
    val drawable = icons.getDrawable(0) // ending image
    val drawableTwo = icons.getDrawable(1) // starting image
    val iconDrawables = arrayOf(drawable,drawableTwo)
    var transitionDrawableIcon = TransitionDrawable(iconDrawables);
    val colorDrawables = arrayOf(ColorDrawable(Color.RED),ColorDrawable(Color.GREEN) )
    var transitionDrawable = TransitionDrawable(colorDrawables)
    switchView.setOnCheckedChangeListener { buttonView, isChecked ->
        iv_light.setImageDrawable(transitionDrawableIcon)
        transitionDrawableIcon.reverseTransition(
            2000
        )
        transitionDrawable.isCrossFadeEnabled = false
        val transitionDrawableTextView = TransitionDrawable(colorDrawables)
        textView2.background = transitionDrawableTextView
        transitionDrawableTextView.startTransition(1000)
    }
}