org.vaadin.miki.superfields.lazyload

Class LazyLoad<C extends com.vaadin.flow.component.Component>

java.lang.Object

com.vaadin.flow.component.Component

com.vaadin.flow.component.Composite<LazyLoad.LazyLoadElement>

org.vaadin.miki.superfields.lazyload.LazyLoad<C>

Type Parameters:

C - Type of component that is lazy-loaded.

All Implemented Interfaces:

com.vaadin.flow.component.AttachNotifier, com.vaadin.flow.component.DetachNotifier, com.vaadin.flow.component.HasElement, com.vaadin.flow.component.HasStyle, Serializable, HasId, WithIdMixin<LazyLoad<C>>

public class LazyLoad<C extends com.vaadin.flow.component.Component>
extends com.vaadin.flow.component.Composite<LazyLoad.LazyLoadElement>
implements WithIdMixin<LazyLoad<C>>, com.vaadin.flow.component.HasStyle

A component that remains empty until it gets into view. After that it displays the lazy-loaded content. Note that by default the size of this component is 0px, as there is no styling to it. Be sure to apply styling. As a result and by default, if there are many of lazy load components one next to another, all of them will trigger.

Since:

2020-04-22

Author:

miki

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LazyLoad.LazyLoadElement This class exists so that LazyLoad can have a custom tag name.

Field Summary

Fields

Modifier and Type	Field and Description
static String	EMPTY_CLASS_NAME Style name when this component is empty (not showing anything).
static String	LOADED_CLASS_NAME Style name when this component has content.

Constructor Summary

Constructors

Constructor and Description
LazyLoad(C contents) Creates lazy load wrapper for given contents.
LazyLoad(C contents, boolean removeOnHide) Creates lazy load wrapper for given contents.
LazyLoad(C contents, com.vaadin.flow.function.SerializableSupplier<ComponentObserver> observerSupplier) Creates lazy load wrapper for given contents.
LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> supplier) Creates lazy load wrapper for given component supplier.
LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> supplier, boolean removeOnHide) Creates lazy load wrapper for given component supplier.
LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> contentSupplier, com.vaadin.flow.function.SerializableSupplier<ComponentObserver> observerSupplier) Creates lazy load wrapper for given component supplier.
LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> contentSupplier, com.vaadin.flow.function.SerializableSupplier<ComponentObserver> observerSupplier, boolean removeOnHide) Creates lazy load wrapper for given component supplier.

Method Summary

Modifier and Type	Method and Description
double	getContentHiddenVisibilityRange() Returns the current range for considering the lazy-loaded component hidden.
double	getContentShownVisibilityRange() Returns the current range for considering the lazy-loaded component visible.
Optional<C>	getLoadedContent() Gets the content if it was already loaded (isOnlyLoadedOnce() ()} is true) or if it is currently showing.
boolean	isLoaded() Checks if the content has been already loaded (isOnlyLoadedOnce() ()} is true) or is currently loaded.
boolean	isOnlyLoadedOnce() Returns if the lazy loading happens only on the first showing.
protected void	onNowHidden() Called when the content becomes hidden.
protected void	onNowVisible() Called when the content becomes visible.
void	setContentVisibilityRanges(double hiddenOnOrBelow, double visibleOnOrAbove) Defines visibility ranges.
LazyLoad<C>	withContentVisibilityRanges(double hiddenOnOrBelow, double visibleOnOrAbove) Chains setContentVisibilityRanges(double, double) and returns itself.

Methods inherited from class com.vaadin.flow.component.Composite

getChildren, getContent, getElement, initContent

Methods inherited from class com.vaadin.flow.component.Component

addListener, fireEvent, from, get, getEventBus, getId, getLocale, getParent, getTranslation, getTranslation, getTranslation, getTranslation, getUI, hasListener, isAttached, isTemplateMapped, isVisible, onAttach, onDetach, onEnabledStateChanged, set, setElement, setId, setVisible

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.vaadin.miki.markers.WithIdMixin

withId

Methods inherited from interface org.vaadin.miki.markers.HasId

getId, setId

Methods inherited from interface com.vaadin.flow.component.HasStyle

addClassName, addClassNames, getClassName, getClassNames, getStyle, hasClassName, removeClassName, removeClassNames, setClassName, setClassName

Methods inherited from interface com.vaadin.flow.component.HasElement

getElement

Methods inherited from interface com.vaadin.flow.component.AttachNotifier

addAttachListener

Methods inherited from interface com.vaadin.flow.component.DetachNotifier

addDetachListener

Field Detail

EMPTY_CLASS_NAME

public static final String EMPTY_CLASS_NAME

Style name when this component is empty (not showing anything).

See Also:

Constant Field Values

LOADED_CLASS_NAME

public static final String LOADED_CLASS_NAME

Style name when this component has content.

See Also:

Constant Field Values

Constructor Detail

LazyLoad

public LazyLoad(C contents)

Creates lazy load wrapper for given contents. It will be displayed the first time this component becomes shown on screen.

Parameters:

contents - Contents to wrap for lazy loading.

LazyLoad

public LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> supplier)

Creates lazy load wrapper for given component supplier. It will be called exactly once, the first time this component becomes shown on screen.

Parameters:

supplier - Supplier that will be called when the component gets into view.

LazyLoad

public LazyLoad(C contents,
                boolean removeOnHide)

Creates lazy load wrapper for given contents.

Parameters:

contents - Contents to wrap for lazy loading.

removeOnHide - Whether to remove the component when this object gets hidden.

LazyLoad

public LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> supplier,
                boolean removeOnHide)

Creates lazy load wrapper for given component supplier.

Parameters:

supplier - Supplier that will be called when the component gets into view.

removeOnHide - Whether to remove the component when this object gets hidden.

LazyLoad

public LazyLoad(C contents,
                com.vaadin.flow.function.SerializableSupplier<ComponentObserver> observerSupplier)

Creates lazy load wrapper for given contents. It will be displayed the first time this component becomes shown on screen.

Parameters:

contents - Contents to wrap for lazy loading.

observerSupplier - a way to create a customised ComponentObserver that will be used by this component.

LazyLoad

public LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> contentSupplier,
                com.vaadin.flow.function.SerializableSupplier<ComponentObserver> observerSupplier)

Creates lazy load wrapper for given component supplier. It will be called exactly once, the first time this component becomes shown on screen.

Parameters:

contentSupplier - Supplier that will be called when the component gets into view.

observerSupplier - a way to create a customised ComponentObserver that will be used by this component.

LazyLoad

public LazyLoad(com.vaadin.flow.function.SerializableSupplier<C> contentSupplier,
                com.vaadin.flow.function.SerializableSupplier<ComponentObserver> observerSupplier,
                boolean removeOnHide)

Creates lazy load wrapper for given component supplier.

Parameters:

contentSupplier - Supplier that will be called when the component gets into view.

observerSupplier - a way to create a customised ComponentObserver that will be used by this component.

removeOnHide - Whether to remove the component when this object gets hidden.

Method Detail

getContentHiddenVisibilityRange

public double getContentHiddenVisibilityRange()

Returns the current range for considering the lazy-loaded component hidden.

Returns:

A number between 0 (inclusive) and getContentShownVisibilityRange() (inclusive).

See Also:

setContentVisibilityRanges(double, double)

getContentShownVisibilityRange

public double getContentShownVisibilityRange()

Returns the current range for considering the lazy-loaded component visible.

Returns:

A number between getContentHiddenVisibilityRange() (inclusive) and 1 (inclusive).

See Also:

setContentVisibilityRanges(double, double)

setContentVisibilityRanges

public void setContentVisibilityRanges(double hiddenOnOrBelow,
                                       double visibleOnOrAbove)

Defines visibility ranges. LazyLoad uses a ComponentObserver to decide if the content should be shown or not. By default, the component is lazy-loaded when LazyLoad is fully visible and hidden when it is fully invisible. Defining ranges allows for lazy-loading the contents when it becomes partially visible. Be sure to know what you are doing and why.

Parameters:

hiddenOnOrBelow - Visibility range at which or below which the component is considered hidden. Must be between 0 (inclusive) and the other parameter (inclusive).

visibleOnOrAbove - Visibility range at which or above which the component is considered visible. Must be between the other parameter (inclusive) and 1 (inclusive).

Throws:

IllegalArgumentException - when either range is below 0, above 1, or the first parameter is greater than the second

See Also:

issue 498

withContentVisibilityRanges

public LazyLoad<C> withContentVisibilityRanges(double hiddenOnOrBelow,
                                               double visibleOnOrAbove)

Chains setContentVisibilityRanges(double, double) and returns itself.

Parameters:

hiddenOnOrBelow - Visibility range at which or below which the component is considered hidden. Must be between 0 (inclusive) and the other parameter (inclusive).

visibleOnOrAbove - Visibility range at which or above which the component is considered visible. Must be between the other parameter (inclusive) and 1 (inclusive).

Returns:

This.

See Also:

setContentVisibilityRanges(double, double)

onNowHidden

protected void onNowHidden()

Called when the content becomes hidden.

onNowVisible

protected void onNowVisible()

Called when the content becomes visible.

isOnlyLoadedOnce

public boolean isOnlyLoadedOnce()

Returns if the lazy loading happens only on the first showing.

Returns:

true when the target component will be loaded only once, the first time this component is shown; otherwise false.

getLoadedContent

public Optional<C> getLoadedContent()

Gets the content if it was already loaded (isOnlyLoadedOnce() ()} is true) or if it is currently showing.

Returns:

A component that was lazy-loaded. If the component was not yet shown on-screen, returns Optional.empty().

See Also:

isLoaded(), isOnlyLoadedOnce()

isLoaded

public boolean isLoaded()

Checks if the content has been already loaded (isOnlyLoadedOnce() ()} is true) or is currently loaded.

Returns:

Whether the content has been loaded.

See Also:

getLoadedContent(), isOnlyLoadedOnce()