Rotating image. Animation list or animated rotate? (Android)

Question

Rotate drawable suggested by Praveen won’t give you control of frame count. Let’s assume you want to implement a custom loader which consists from 8 sections:

gif_icon

Using animation-list approach, you need to create 8 frames rotated by 45*frameNumber degrees manually. Alternatively, you can use 1st frame and set rotation animation to it:

progress_icon

File res/anim/progress_anim.xml:

<?xml version="1.0" encoding="utf-8"?>
<rotate
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:fromDegrees="0"
    android:toDegrees="360"
    android:pivotX="50%"
    android:pivotY="50%"
    android:repeatCount="infinite" />

File MainActivity.java

Animation a = AnimationUtils.loadAnimation(getContext(), R.anim.progress_anim);
a.setDuration(1000);
imageView.startAnimation(a);

This will give you smooth animation instead of 8-stepped. To fix this we need to implement custom interpolator:

a.setInterpolator(new Interpolator() {
    private final int frameCount = 8;

    @Override
    public float getInterpolation(float input) {
        return (float)Math.floor(input*frameCount)/frameCount;
    }
});

Also you can create a custom widget:

File res/values/attrs.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="ProgressView">
        <attr name="frameCount" format="integer"/>
        <attr name="duration" format="integer" />
    </declare-styleable>
</resources>

File ProgressView.java:

public class ProgressView extends ImageView {

    public ProgressView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        setAnimation(attrs);
    }

    public ProgressView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setAnimation(attrs);
    }

    public ProgressView(Context context) {
        super(context);
    }

    private void setAnimation(AttributeSet attrs) {
        TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.ProgressView);
        int frameCount = a.getInt(R.styleable.ProgressView_frameCount, 12);  
        int duration = a.getInt(R.styleable.ProgressView_duration, 1000);
        a.recycle();

        setAnimation(frameCount, duration);
    }

    public void setAnimation(final int frameCount, final int duration) {
        Animation a = AnimationUtils.loadAnimation(getContext(), R.anim.progress_anim);
        a.setDuration(duration);
        a.setInterpolator(new Interpolator() {

            @Override
            public float getInterpolation(float input) {
                return (float)Math.floor(input*frameCount)/frameCount;
            }
        });
        startAnimation(a);
    }
}

File activity_main.xml:

<com.example.widget.ProgressView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="https://stackoverflow.com/questions/3760381/@drawable/ic_progress" 
    app:frameCount="8"
    app:duration="1000"/>

File res/anim/progress_anim.xml: listed above

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