Is there a way a way to animate setting BackgroundColorSpan to SpannableString?

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The string in my TextView is divided into spans of three letters in each (Triplets) in runtime as I add more letters to this TextView. And I set four different background colors to those triplets cyclically:

void color(TextView textView) {
        String sequenceColored = textView.getText().toString();
        SpannableString ss = new SpannableString(sequenceColored);
        int iter = 0;
        if (textView.getId() == R.id.sequence) {
            for (int i = 0; i < sequenceColored.length(); i += 3, iter++) {
                if (iter == 0) {
                    ss.setSpan(new BackgroundColorSpan(Color.argb(123, 255, 136, 0)), i, i + 3, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } else if (iter == 1) {
                    ss.setSpan(new BackgroundColorSpan(Color.argb(123, 255, 187, 51)), i, i + 3, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } else if (iter == 2) {
                    ss.setSpan(new BackgroundColorSpan(Color.argb(123, 0, 153, 204)), i, i + 3, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } else if (iter == 3) {
                    ss.setSpan(new BackgroundColorSpan(Color.argb(123, 170, 102, 204)), i, i + 3, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                    iter = -1;
                }
            }
        }
    }

So, the question is: is it possible to animate this background color change, make it slowly and nicely appear from no background color?

SpannableString is not a View, so I can't animate it traditionally, right?

Update

I tried to set this animation up by executing the folowing code inside the first inner if:

ValueAnimator animation = ValueAnimator.ofInt(0, 123);

animation.start();
final int finalI = i;
animation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
        ss.setSpan(new BackgroundColorSpan(Color.argb((int)animation.getAnimatedValue(), 255, 136, 0)), finalI, finalI + 3, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    }
});

But it does not set background color to the span at all.

android-transitions spannablestring android-animation android
1 Answers

Finally I made something that @CommonsWare suggested.
First, I made a custom MutableBackgroundColorSpan:

public class MutableBackgroundColorSpan extends BackgroundColorSpan {

    private int mAlpha = 255;
    private int mBackgroundColor;

    public MutableBackgroundColorSpan(int alpha, int color) {
        super(color);
        mAlpha = alpha;
        mBackgroundColor = color;
    }

    public MutableBackgroundColorSpan(Parcel src) {
        super(src);
        mBackgroundColor = src.readInt();
        mAlpha = src.readInt();
    }

    public void writeToParcel(Parcel dest, int flags) {
        super.writeToParcel(dest, flags);
        dest.writeInt(mBackgroundColor);
        dest.writeFloat(mAlpha);
    }

    @Override
    public void updateDrawState(TextPaint ds) {
        ds.bgColor = getBackgroundColor();
    }

    /**
     * @param alpha from 0 to 255
     */
    public void setAlpha(int alpha) {
        mAlpha = alpha;
    }

    public void setBackgroundColor(int backgroundColor) {
        mBackgroundColor = backgroundColor;
    }

    public float getAlpha() {
        return mAlpha;
    }

    @Override
    public int getBackgroundColor() {
        return Color.argb(mAlpha, Color.red(mBackgroundColor), Color.green(mBackgroundColor), Color.blue(mBackgroundColor));
    }
}

Then, I i initialized a custom Property

private static final Property<MutableBackgroundColorSpan, Integer> MUTABLE_BACKGROUND_COLOR_SPAN_FC_PROPERTY =
            new Property<MutableBackgroundColorSpan, Integer>(Integer.class, "MUTABLE_BACKGROUND_COLOR_SPAN_FC_PROPERTY") {

                @Override
                public void set(MutableBackgroundColorSpan span, Integer value) {
                    span.setBackgroundColor(value);
                }

                @Override
                public Integer get(MutableBackgroundColorSpan span) {
                    return span.getBackgroundColor();
                }
            };

And the actual code that does its functions is:

MutableBackgroundColorSpan span = new MutableBackgroundColorSpan(123, Color.WHITE);
ss.setSpan(span,  i, i + 3, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
ObjectAnimator objectAnimator = ObjectAnimator.ofInt(span, MUTABLE_BACKGROUND_COLOR_SPAN_FC_PROPERTY, Color.WHITE, Color.rgb(r, g, b));
objectAnimator.setDuration(100);
objectAnimator.setEvaluator(new ArgbEvaluator());
objectAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
        //refresh
        textView.setText(ss);
    }
});
objectAnimator.start();
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