Android custom combined spans for spannable strings

Question

How could I create custom Spans that combined different types of spans together e.g. TypefaceSpan + RelativeSizeSpan. I want to create logical spans like "Footnote" or "Header2" that would change the text font and size.

Answer 1

You can apply two different spans to same portions.

SpannableStringBuilder builder = new SpannableStringBuilder("Hello there");
builder.setSpan(new TypefaceSpan("arial"), 1, 3, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
builder.setSpan(new RelativeSizeSpan(1.5f), 1, 3, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

EDIT: You say you're looking for a way to create aggregated Spans that combine these spans together -- so that the actual styling (e.g. TypefaceSpan or RelativeSizeSpan) can be encapsulated within logical spans (e.g. FooterSpan)

Since both TypeFaceSpan and RelativeSizeSpan are children of MetricEffectingSpan, following could be a solution:

class FooterSpan extends MetricAffectingSpan {

        MetricAffectingSpan[] spans;

        public FooterSpan(MetricAffectingSpan... spans) {
            this.spans = spans;
        }
        @Override
        public void updateMeasureState(TextPaint p) {
            for(MetricAffectingSpan span : spans) {
                span.updateMeasureState(p);
            }
        }

        @Override
        public void updateDrawState(TextPaint tp) {
            for(MetricAffectingSpan span : spans) {
                span.updateDrawState(tp);
            }
        }
    }

example usage:

builder.setSpan(new FooterSpan(new TypefaceSpan("arial"), new RelativeSizeSpan(1.5f)), 1, 3, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

You can even write your FooterSpan in a more specialized way so that you can use it like this:

builder.setSpan(new FooterSpan("arial", 1.5f), 1, 3, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

I think it is trivial to adopt the FooterSpan to the second case.