Package 

Interface FontFallbackStrategy

  • 
public interface FontFallbackStrategy

    Defines a strategy for providing fallback fonts with a specific weight when a character in a Rive file cannot be found using the current Rive font or if that font is not provided in the Rive file.

    This interface allows for custom implementations that can provide different sets of fallback fonts based on the specified font weight.

    • Within a given scope: You can implement the strategy in an activity or fragment as follows:

    class MyFontActivity : AppCompatActivity(), FontFallbackStrategy {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // Set the strategy
        FontFallbackStrategy.stylePicker = this
    }

    override fun getFont(weight: Fonts.Weight): List<FontBytes> {
        // Provide font bytes based on the weight
    }
}

    • At the global level: You can set the fallback strategy globally before loading a Rive file that needs fallback fonts:

    FontFallbackStrategy.stylePicker = object : FontFallbackStrategy {
    override fun getFont(weight: Fonts.Weight): List<ByteArray> {
        val myFonts = ...
        return listOf(myFonts)
    }
}

    The stylePicker is a WeakReference, which allows the Garbage Collector to automatically cleanup unused references to the FontFallbackStrategy. Once the referenced object is garbage collected, the WeakReference will return null, ensuring that memory is efficiently managed and released.

    • Implement getFont() to return a list of FontBytes for the specified font weight.

    • Use the companion object to manage the fallback strategy through stylePicker.

    • pickFont() is called statically from native C++ code when a missing character is detected, providing the fallback fonts as needed.

    • Method Summary

      Modifier and Type Method Description
      abstract List<ByteArray> getFont(Fonts.Weight weight) Returns a list of FontBytes (i.e.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Method Detail

      • getFont

         abstract List<ByteArray> getFont(Fonts.Weight weight)

        Returns a list of FontBytes (i.e. ByteArray) representing fonts that the runtime will use to try and match a missing character in the Rive file.

        The runtime attempts to match the character using the fonts in the list in a first-in, first-out (FIFO) order, starting with the font at index 0, then proceeding to index 1, and so on, until a font containing the required character is found or the list is exhausted.

        Caching Behavior: This function is invoked by the Rive runtime only when its internal native cache does not contain fallback font data for the requested weight. The returned list of FontBytes is immediately decoded into native font representations and cached internally, keyed by the weight. Subsequent requests for the same weight will use this cache, and this function will not be called again for that weight. The native cache associated with a particular FontFallbackStrategy instance is cleared only when a new strategy instance is configured for the Rive runtime (i.e. by setting a new stylePicker or equivalent configuration). Your implementation should return a complete and ordered list of fallback fonts for the requested weight during the initial call, as it represents the definitive set for that weight category weight category while this strategy instance is active.

        Parameters:
        weight - The weight of the font for which fallbacks are needed.