LazyPanel (GWT Javadoc)

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GWT 2.7.0

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com.google.gwt.user.client.ui
Class LazyPanel

java.lang.Object
  com.google.gwt.user.client.ui.UIObject
      com.google.gwt.user.client.ui.Widget
          com.google.gwt.user.client.ui.Panel
              com.google.gwt.user.client.ui.SimplePanel
                  com.google.gwt.user.client.ui.LazyPanel

All Implemented Interfaces:: HasAttachHandlers, HasHandlers, EventListener, AcceptsOneWidget, HasOneWidget, HasVisibility, HasWidgets, HasWidgets.ForIsWidget, IsWidget, java.lang.Iterable<Widget>

public abstract class LazyPanel
extends SimplePanel
extends SimplePanel

Convenience class to help lazy loading. The bulk of a LazyPanel is not instantiated until setVisible(boolean)(true) or ensureWidget() is called.

Example

public class LazyPanelExample implements EntryPoint {

  private static class HelloLazyPanel extends LazyPanel {
    @Override
    protected Widget createWidget() {
      return new Label("Well hello there!");
    }
  }

  public void onModuleLoad() {
    final Widget lazy = new HelloLazyPanel();
    
    // Not strictly necessary, but keeps the empty outer div
    // from effecting layout before it is of any use
    lazy.setVisible(false);

    PushButton b = new PushButton("Click me");    
    b.addClickHandler(new ClickHandler() {
      public void onClick(ClickEvent event) {
        lazy.setVisible(true);
      }
    });
    
    RootPanel root = RootPanel.get();
    root.add(b);
    root.add(lazy);
  }
}

Nested Class Summary

Nested classes/interfaces inherited from class com.google.gwt.user.client.ui.UIObject
`UIObject.DebugIdImpl, UIObject.DebugIdImplEnabled`

Nested classes/interfaces inherited from interface com.google.gwt.user.client.ui.HasWidgets
`HasWidgets.ForIsWidget`

Field Summary

Fields inherited from class com.google.gwt.user.client.ui.SimplePanel
`widget`

Fields inherited from class com.google.gwt.user.client.ui.Widget
`eventsToSink`

Fields inherited from class com.google.gwt.user.client.ui.UIObject
`DEBUG_ID_PREFIX, MISSING_ELEMENT_ERROR, SETELEMENT_TWICE_ERROR`

Constructor Summary
`LazyPanel()`

Method Summary
`protected abstract Widget`	`createWidget()` Create the widget contained within the `LazyPanel`.
`void`	`ensureWidget()` Ensures that the widget has been created by calling `createWidget()` if `SimplePanel.getWidget()` returns `null`.
`void`	`setVisible(boolean visible)` Sets whether this object is visible.

Methods inherited from class com.google.gwt.user.client.ui.SimplePanel
`add, getContainerElement, getWidget, iterator, remove, setWidget, setWidget`

Methods inherited from class com.google.gwt.user.client.ui.Panel
`add, adopt, clear, doAttachChildren, doDetachChildren, orphan, remove`

Methods inherited from class com.google.gwt.user.client.ui.Widget
`addAttachHandler, addBitlessDomHandler, addDomHandler, addHandler, asWidget, asWidgetOrNull, createHandlerManager, delegateEvent, ensureHandlers, fireEvent, getHandlerCount, getHandlerManager, getLayoutData, getParent, isAttached, isOrWasAttached, onAttach, onBrowserEvent, onDetach, onLoad, onUnload, removeFromParent, replaceElement, setLayoutData, setParent, sinkEvents, unsinkEvents`

Methods inherited from class com.google.gwt.user.client.ui.UIObject
addStyleDependentName, addStyleName, ensureDebugId, ensureDebugId, ensureDebugId, getAbsoluteLeft, getAbsoluteTop, getElement, getOffsetHeight, getOffsetWidth, getStyleElement, getStyleName, getStyleName, getStylePrimaryName, getStylePrimaryName, getTitle, isVisible, isVisible, onEnsureDebugId, removeStyleDependentName, removeStyleName, resolvePotentialElement, setElement, setElement, setHeight, setPixelSize, setSize, setStyleDependentName, setStyleName, setStyleName, setStyleName, setStyleName, setStylePrimaryName, setStylePrimaryName, setTitle, setVisible, setWidth, sinkBitlessEvent, toString

Methods inherited from class com.google.gwt.user.client.ui.UIObject

addStyleDependentName, addStyleName, ensureDebugId, ensureDebugId, ensureDebugId, getAbsoluteLeft, getAbsoluteTop, getElement, getOffsetHeight, getOffsetWidth, getStyleElement, getStyleName, getStyleName, getStylePrimaryName, getStylePrimaryName, getTitle, isVisible, isVisible, onEnsureDebugId, removeStyleDependentName, removeStyleName, resolvePotentialElement, setElement, setElement, setHeight, setPixelSize, setSize, setStyleDependentName, setStyleName, setStyleName, setStyleName, setStyleName, setStylePrimaryName, setStylePrimaryName, setTitle, setVisible, setWidth, sinkBitlessEvent, toString

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

LazyPanel

public LazyPanel()

Method Detail

createWidget

protected abstract Widget createWidget()

Create the widget contained within the LazyPanel.

Returns:: the lazy widget

ensureWidget

public void ensureWidget()

Ensures that the widget has been created by calling createWidget() if SimplePanel.getWidget() returns null. Typically it is not necessary to call this directly, as it is called as a side effect of a setVisible(true) call.

setVisible

public void setVisible(boolean visible)

Description copied from interface: HasVisibility

Sets whether this object is visible.

Specified by:: setVisible in interface HasVisibility
Overrides:: setVisible in class UIObject

Parameters:: visible - true to show the object, false to hide it