com.facebook.litho.annotations

Annotation Type FromPreviousCreateLayout

@Retention(value=RUNTIME)
public @interface FromPreviousCreateLayout

Annotates that the argument's value should be set to the named inter-stage output from the OnCreateLayoutWithSizeSpec lifecycle method. The name and type of the argument must match with the inter-stage output requested. This inter-stage output is different from the other because this OnShouldCreateLayoutWithNewSizeSpec is called in subsequent layout calculations when the framework has a cached layout to reuse.

This can be used in:

• OnShouldCreateLayoutWithNewSizeSpec

The annotation processor will validate this and other invariants in the API at build time.

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,  // Get the output value
       @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;
   }
 }