com.facebook.litho.sections.common

Class DataDiffSection<T>

java.lang.Object

com.facebook.litho.sections.SectionLifecycle

com.facebook.litho.sections.Section

com.facebook.litho.sections.common.DataDiffSection<T>

All Implemented Interfaces:

Equivalence<Section>, EventDispatcher, EventTriggerTarget, HasEventDispatcher, HasEventTrigger, Cloneable

public final class DataDiffSection<T>
extends Section

A DiffSectionSpec that creates a changeSet diffing a generic List of data. This Section emits the following events:

RenderEvent whenever it needs a Component to render a model T from the List<? extends T> data. Providing a handler for this OnEvent is mandatory.

OnCheckIsSameItemEvent whenever during a diffing it wants to check whether two items represent the same piece of data.

OnCheckIsSameContentEvent whenever during a diffing it wants to check whether two items that represent the same piece of data have exactly the same content.

Diffing happens when the new List<? extends T> data is provided. Changes in State alone will not trigger diffing.

• If OnCheckIsSameItemEvent returns false RenderEvent is triggered. Otherwise OnCheckIsSameContentEvent is called.
• If OnCheckIsSameContentEvent returns false RenderEvent is triggered.

If OnCheckIsSameItemEvent is not implemented, new List<? extends T> data is considered to be completely different and relayout will happen on every data update.

Example usage:

 '@'GroupSectionSpec
 public class MyGroupSectionSpec {
   '@'OnCreateChildren
   static Children onCreateChildren(
     SectionContext c,
     '@'Prop List modelList) {
     return Children.create()
         .child(
             DataDiffSection.create(c)
                 .data(modelList)
                 .renderEventHandler(MyGroupSection.onRender(c))
                 .onCheckIsSameItemEventHandler(MyGroupSection.onCheckIsSameItem(c))
                 .onCheckIsSameContentEventHandler(...))
        .build();
   }
   '@'OnEvent(OnCheckIsSameItemEvent.class)
   static boolean onCheckIsSameItem(SectionContext c, @FromEvent Model previousItem, @FromEvent Model nextItem) {
     return previousItem.getId() == nextItem.getId();
   }
   '@'OnEvent(RenderEvent.class)
   static RenderInfo onRender(SectionContext c, @FromEvent Model model) {
     return ComponentRenderInfo.create()
         .component(MyComponent.create(c).model(model).build())
         .build();
   }
 }
 

See Also:

com.facebook.litho.sections.common.DataDiffSectionSpec

Required Props

data

extends T>

Type:

java.util.List

Optional Props

alwaysDetectDuplicates

Type:

java.lang.Boolean

detectMoves

Type:

java.lang.Boolean

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DataDiffSection.Builder<T>

Method Summary

Modifier and Type	Method and Description
static <T> DataDiffSection.Builder<T>	create(SectionContext context)
protected void	generateChangeSet(SectionContext c, ChangeSet changeSet, Section _prevAbstractImpl, Section _nextAbstractImpl) This method will delegate to the DiffSectionSpec method annotated with OnDiff
static EventHandler	getOnCheckIsSameContentEventHandler(SectionContext context)
static EventHandler	getOnCheckIsSameItemEventHandler(SectionContext context)
static EventHandler	getRenderEventHandler(SectionContext context)
boolean	isDiffSectionSpec()
boolean	isEquivalentTo(Section other) Compares this section to a different one to check if they are the same

Methods inherited from class com.facebook.litho.sections.Section

generateUniqueGlobalKeyForChild, getChildren, getEventDispatcher, getGlobalKey, getHandle, getKey, getLogTag, getParent, getScopedContext, getSimpleName, getStateContainer, makeShallowCopy, makeShallowCopy, recordEventTrigger, setChildren, setCount, setGlobalKey, setKey, setScopedContext

Methods inherited from class com.facebook.litho.sections.SectionLifecycle

acceptTriggerEvent, bindService, createChildren, createInitialState, createService, dataBound, dataRendered, dispatchLoadingEvent, dispatchOnEvent, getEventTrigger, getEventTrigger, getLoadingEventHandler, getService, getTreePropsForChildren, isSectionIndexValid, newEventHandler, newEventHandler, newEventTrigger, populateTreeProps, refresh, requestFocus, requestFocus, requestFocus, requestFocusWithOffset, requestFocusWithOffset, requestFocusWithOffset, requestSmoothFocus, requestSmoothFocus, requestSmoothFocus, shouldUpdate, transferService, transferState, unbindService, viewportChanged

Methods inherited from class java.lang.Object

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

Method Detail

isEquivalentTo

public boolean isEquivalentTo(Section other)

Description copied from class: Section

Compares this section to a different one to check if they are the same

This is used to be able to skip rendering a section again. We avoid using the Object.equals(Object) so we can optimize the code better over time since we don't have to adhere to the contract required for a equals method.

Specified by:

isEquivalentTo in interface Equivalence<Section>

Overrides:

isEquivalentTo in class Section

Parameters:

other - the component to compare to

Returns:

true if the components are of the same type and have the same props

create

public static <T> DataDiffSection.Builder<T> create(SectionContext context)

getOnCheckIsSameContentEventHandler

public static EventHandler getOnCheckIsSameContentEventHandler(SectionContext context)

getOnCheckIsSameItemEventHandler

public static EventHandler getOnCheckIsSameItemEventHandler(SectionContext context)

getRenderEventHandler

public static EventHandler getRenderEventHandler(SectionContext context)

generateChangeSet

protected void generateChangeSet(SectionContext c,
                                 ChangeSet changeSet,
                                 Section _prevAbstractImpl,
                                 Section _nextAbstractImpl)

Description copied from class: SectionLifecycle

This method will delegate to the DiffSectionSpec method annotated with OnDiff

Overrides:

generateChangeSet in class SectionLifecycle

isDiffSectionSpec

public boolean isDiffSectionSpec()

Overrides:

isDiffSectionSpec in class SectionLifecycle

Returns:

true if this lifecycle will generate a changeSet. If false this lifecycle will instead implement createChildren.