Rotate drawable has not effect - kotlin

Question

The starting point here is the need to periodically rotate a vector drawing, like for instance the hands of an analog clock.
I understand that a vectorDrawable resource does not directly support rotation attributes. I can put the drawable inside a group which can rotate the drawable, but that rotation won't be modifiable at run time.
I came across many posts explaining rotating views or canvases, as well as the rotate drawable. The latter seems to be appropriate for my purpose.
I created a new activity with the help of Android Studio 3.5 to achieve a simple rotation with the help of a rotate drawable.
java/com.example.myapplication/MainActivity:
package com.example.myapplication
import android.graphics.drawable.RotateDrawable
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.core.content.ContextCompat
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val activity = this#MainActivity
val context = activity.applicationContext
val drawable = ContextCompat.getDrawable(context, R.drawable.rotation)
val rotation = drawable as RotateDrawable
rotation.setLevel(180)
}
}
res/layout/activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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">
<ImageView
android:id="#+id/imageView2"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/rotation" />
</androidx.constraintlayout.widget.ConstraintLayout>
res/drawable/rotation.xml:
<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:pivotX="50%" android:pivotY="50%"
android:fromDegrees="0" android:toDegrees="360"
android:drawable="#drawable/ic_launcher_foreground"/>
I expect that the setLevel function can be used to rotate the drawable, but it has no effect.
Changing the fromDegrees attribute in the rotation.xml does the rotation as expected. I am not sure if the maximum level for <rotate> should be 360 or 10000, but that is not the issue.
What am I missing? Is it a detail, or is the rotateDrawable the wrong approach altogether?
Related questions:
Rotating a drawable in Android
Programmatically rotate drawable or view
Is it possible to rotate a drawable in the xml description?

Answer 1

Try using imageView2.setRotation(180) instead of rotation drawable.