com.facebook.litho.annotations

Annotation Type OnShouldCreateLayoutWithNewSizeSpec

@Retention(value=SOURCE)
public @interface OnShouldCreateLayoutWithNewSizeSpec

This indicates that the annotated method will be called when the component's checks if it can use the last cached layout returned from the Layout Spec with a new Size Spec. This is used in conjunction with OnCreateLayoutWithSizeSpec. The annotated method must have the following signature:

  static boolean onShouldCreateLayoutWithNewSizeSpec(
    ComponentContext c,
    int newWidthSpec,
    int newHeightSpec, ...)
 

The annotated method should return true iff the Layout Spec should create a new layout for this new size spec. If the method returns false then the Component will use the last cached layout.

For example:

 @LayoutSpec
 class MyComponentSpec {

   @OnCreateLayoutWithSizeSpec
   static Component onCreateLayoutWithSizeSpec(
       ComponentContext c,
       int widthSpec,
       int heightSpec) {

     final Component textComponent =
         Text.create(c).textSizeSp(16).text("Some text to measure.").build();

     // UNSPECIFIED sizeSpecs will measure the text as being one line only,
     // having unlimited width.
     final Size textOutputSize = new Size();
     textComponent.measure(
         c,
         SizeSpec.makeSizeSpec(0, UNSPECIFIED),
         SizeSpec.makeSizeSpec(0, UNSPECIFIED),
         textOutputSize);

     // Small component to use in case textComponent does not fit within the current layout.
     final Component imageComponent = Image.create(c).drawableRes(R.drawable.ic_launcher).build();

     // Assuming SizeSpec.getMode(widthSpec) == EXACTLY or AT_MOST.
     final int layoutWidth = SizeSpec.getSize(widthSpec);
     final boolean textFits = (textOutputSize.width <= layoutWidth);

     return textFits ? textComponent : imageComponent;
   }

   @OnShouldCreateLayoutWithNewSizeSpec
   static boolean onShouldCreateLayoutWithNewSizeSpec(
       ComponentContext c,
       int newWidthSpec,
       int newHeightSpec,
       @FromPreviousCreateLayout int textWidth,
       @FromPreviousCreateLayout boolean didItFit) {

     final int newLayoutWidth = SizeSpec.getSize(newWidthSpec);
     final boolean doesItStillFit = (textWidth <= newLayoutWidth);

     // false if it still fits or if still doesn't fit
     return doesItStillFit ^ didItFit;
   }
 }

See Also:

FromPreviousCreateLayout, OnCreateLayoutWithSizeSpec