Implementing an Expandable TextView with Topic and URL Span Handling in Android

The article explains how to create a custom ExpandableTextView in Android that can display topics and other rich text elements as clickable spans.

It introduces a method

replaceTopicSpan(List<RemoteTopicBean> topics, String content, OnTopicClickListener listener)

that iterates over topic data, finds start and end positions, and uses a SpanUtils helper to convert plain text into colored, clickable spans, returning the processed CharSequence.

The core click handling is implemented with a ClickableSpan that prevents rapid repeated clicks and invokes a callback when a topic is tapped.

For the expand/collapse functionality, the article describes using StaticLayout to measure line counts and determine where to truncate the text, then appends a "[More]" or "[Show Less]" label as a ButtonSpan. The setCloseText method calculates the required heights, creates the collapsed and expanded layouts, and sets the appropriate text and movement method.

Two approaches for toggling the view are presented: directly changing maxLines or animating the height change with a custom ExpandCollapseAnimation class that interpolates between the collapsed and expanded heights.

Additional utilities include replacing default URLSpan objects with a custom InterceptUrlSpan to handle link clicks inside the app, and configuring custom fonts via MyTypefaceSpan.

Finally, the article provides sample usage snippets and notes on integrating the component into a RecyclerView item, emphasizing the modularity of the solution.