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

Question

I want to create a rotating progress image, and wonder what's the best way to proceed. I can make it work with an animation list with for example 12 images changing every 100ms. This works fine, but it's quite tedious to create 12 images or for every size and resolution:

<animation-list xmlns:android="http://schemas.android.com/apk/res/android" android:oneshot="false">
<item android:drawable="@drawable/ic_loading_grey_on_black_01" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_02" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_03" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_04" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_05" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_06" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_07" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_08" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_09" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_10" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_11" android:duration="100" />
<item android:drawable="@drawable/ic_loading_grey_on_black_12" android:duration="100" />

I suppose that an easier solution is to use one image per resolution, but rather rotate it for each frame. In the platform resources (android-sdk-windows/platforms...) I found something called animated-rotate in the file drawable/search_spinner.xml, but if I copy the code get a compiler error complaining about android:framesCount and android:frameDuration (Google APIs 2.2 in Eclipse):

<animated-rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:drawable="@drawable/spinner_black_20"
android:pivotX="50%"
android:pivotY="50%"
android:framesCount="12"
android:frameDuration="100" />

I have also tried using a repeating rotate animation (using in the anim resource folder), but I actually prefer the look of the animation list version.

What is the recommended way of solving this problem?

Answer 1

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:

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:

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="@drawable/ic_progress" 
    app:frameCount="8"
    app:duration="1000"/>

File res/anim/progress_anim.xml: listed above