com.google.gwt.user.client.ui.Widget Maven / Gradle / Ivy
/*
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.user.client.ui;
import com.google.gwt.dom.client.Element;
import com.google.gwt.event.dom.client.DomEvent;
import com.google.gwt.event.logical.shared.AttachEvent;
import com.google.gwt.event.logical.shared.AttachEvent.Handler;
import com.google.gwt.event.logical.shared.HasAttachHandlers;
import com.google.gwt.event.shared.EventHandler;
import com.google.gwt.event.shared.GwtEvent;
import com.google.gwt.event.shared.HandlerManager;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.EventListener;
/**
* The base class for the majority of user-interface objects. Widget adds
* support for receiving events from the browser and being added directly to
* {@link com.google.gwt.user.client.ui.Panel panels}.
*/
public class Widget extends UIObject implements EventListener, HasAttachHandlers,
IsWidget {
/**
* This convenience method makes a null-safe call to
* {@link IsWidget#asWidget()}.
*
* @return the widget aspect, or null if w is null
*/
public static Widget asWidgetOrNull(IsWidget w) {
return w == null ? null : w.asWidget();
}
/**
* A bit-map of the events that should be sunk when the widget is attached to
* the DOM. (We delay the sinking of events to improve startup performance.)
* When the widget is attached, this is set to -1
*
* Package protected to allow Composite to see it.
*/
int eventsToSink;
private boolean attached;
private HandlerManager handlerManager;
private Object layoutData;
private Widget parent;
public HandlerRegistration addAttachHandler(Handler handler) {
return addHandler(handler, AttachEvent.getType());
}
/**
* For browsers which do not leak, adds a native event handler to the widget.
* Note that, unlike the
* {@link #addDomHandler(EventHandler, com.google.gwt.event.dom.client.DomEvent.Type)}
* implementation, there is no need to attach the widget to the DOM in order
* to cause the event handlers to be attached.
*
* @param the type of handler to add
* @param type the event key
* @param handler the handler
* @return {@link HandlerRegistration} used to remove the handler
*/
public final HandlerRegistration addBitlessDomHandler(
final H handler, DomEvent.Type type) {
assert handler != null : "handler must not be null";
assert type != null : "type must not be null";
sinkBitlessEvent(type.getName());
return ensureHandlers().addHandler(type, handler);
}
/**
* Adds a native event handler to the widget and sinks the corresponding
* native event. If you do not want to sink the native event, use the generic
* addHandler method instead.
*
* @param the type of handler to add
* @param type the event key
* @param handler the handler
* @return {@link HandlerRegistration} used to remove the handler
*/
public final HandlerRegistration addDomHandler(
final H handler, DomEvent.Type type) {
assert handler != null : "handler must not be null";
assert type != null : "type must not be null";
int typeInt = Event.getTypeInt(type.getName());
if (typeInt == -1) {
sinkBitlessEvent(type.getName());
} else {
sinkEvents(typeInt);
}
return ensureHandlers().addHandler(type, handler);
}
/**
* Adds this handler to the widget.
*
* @param the type of handler to add
* @param type the event type
* @param handler the handler
* @return {@link HandlerRegistration} used to remove the handler
*/
public final HandlerRegistration addHandler(
final H handler, GwtEvent.Type type) {
return ensureHandlers().addHandler(type, handler);
}
public Widget asWidget() {
return this;
}
public void fireEvent(GwtEvent event) {
if (handlerManager != null) {
handlerManager.fireEvent(event);
}
}
/**
* Gets the panel-defined layout data associated with this widget.
*
* @return the widget's layout data
* @see #setLayoutData
*/
public Object getLayoutData() {
return layoutData;
}
/**
* Gets this widget's parent panel.
*
* @return the widget's parent panel
*/
public Widget getParent() {
return parent;
}
/**
* Determines whether this widget is currently attached to the browser's
* document (i.e., there is an unbroken chain of widgets between this widget
* and the underlying browser document).
*
* @return true if the widget is attached
*/
public boolean isAttached() {
return attached;
}
public void onBrowserEvent(Event event) {
switch (DOM.eventGetType(event)) {
case Event.ONMOUSEOVER:
// Only fire the mouse over event if it's coming from outside this
// widget.
case Event.ONMOUSEOUT:
// Only fire the mouse out event if it's leaving this
// widget.
Element related = event.getRelatedEventTarget().cast();
if (related != null && getElement().isOrHasChild(related)) {
return;
}
break;
}
DomEvent.fireNativeEvent(event, this, this.getElement());
}
/**
* Removes this widget from its parent widget, if one exists.
*
*
* If it has no parent, this method does nothing. If it is a "root" widget
* (meaning it's been added to the detach list via
* {@link RootPanel#detachOnWindowClose(Widget)}), it will be removed from the
* detached immediately. This makes it possible for Composites and Panels to
* adopt root widgets.
*
*
* @throws IllegalStateException if this widget's parent does not support
* removal (e.g. {@link Composite})
*/
public void removeFromParent() {
if (parent == null) {
// If the widget had no parent, check to see if it was in the detach list
// and remove it if necessary.
if (RootPanel.isInDetachList(this)) {
RootPanel.detachNow(this);
}
} else if (parent instanceof HasWidgets) {
((HasWidgets) parent).remove(this);
} else if (parent != null) {
throw new IllegalStateException(
"This widget's parent does not implement HasWidgets");
}
}
/**
* Sets the panel-defined layout data associated with this widget. Only the
* panel that currently contains a widget should ever set this value. It
* serves as a place to store layout bookkeeping data associated with a
* widget.
*
* @param layoutData the widget's layout data
*/
public void setLayoutData(Object layoutData) {
this.layoutData = layoutData;
}
/**
* Overridden to defer the call to super.sinkEvents until the first time this
* widget is attached to the dom, as a performance enhancement. Subclasses
* wishing to customize sinkEvents can preserve this deferred sink behavior by
* putting their implementation behind a check of
* isOrWasAttached():
*
*
* {@literal @}Override
* public void sinkEvents(int eventBitsToAdd) {
* if (isOrWasAttached()) {
* /{@literal *} customized sink code goes here {@literal *}/
* } else {
* super.sinkEvents(eventBitsToAdd);
* }
*}
*/
@Override
public void sinkEvents(int eventBitsToAdd) {
if (isOrWasAttached()) {
super.sinkEvents(eventBitsToAdd);
} else {
eventsToSink |= eventBitsToAdd;
}
}
/**
* Creates the {@link HandlerManager} used by this Widget. You can override
* this method to create a custom {@link HandlerManager}.
*
* @return the {@link HandlerManager} you want to use
*/
protected HandlerManager createHandlerManager() {
return new HandlerManager(this);
}
/**
* Fires an event on a child widget. Used to delegate the handling of an event
* from one widget to another.
*
* @param event the event
* @param target fire the event on the given target
*/
protected void delegateEvent(Widget target, GwtEvent event) {
target.fireEvent(event);
}
/**
* If a widget contains one or more child widgets that are not in the logical
* widget hierarchy (the child is physically connected only on the DOM level),
* it must override this method and call {@link #onAttach()} for each of its
* child widgets.
*
* @see #onAttach()
*/
protected void doAttachChildren() {
}
/**
* If a widget contains one or more child widgets that are not in the logical
* widget hierarchy (the child is physically connected only on the DOM level),
* it must override this method and call {@link #onDetach()} for each of its
* child widgets.
*
* @see #onDetach()
*/
protected void doDetachChildren() {
}
/**
* Gets the number of handlers listening to the event type.
*
* @param type the event type
* @return the number of registered handlers
*/
protected int getHandlerCount(GwtEvent.Type type) {
return handlerManager == null ? 0 : handlerManager.getHandlerCount(type);
}
/**
* Has this widget ever been attached?
*
* @return true if this widget ever been attached to the DOM, false otherwise
*/
protected final boolean isOrWasAttached() {
return eventsToSink == -1;
}
/**
*
* This method is called when a widget is attached to the browser's document.
* To receive notification after a Widget has been added to the document,
* override the {@link #onLoad} method or use {@link #addAttachHandler}.
*
*
* It is strongly recommended that you override {@link #onLoad()} or
* {@link #doAttachChildren()} instead of this method to avoid inconsistencies
* between logical and physical attachment states.
*
*
* Subclasses that override this method must call
* super.onAttach() to ensure that the Widget has been attached
* to its underlying Element.
*
*
* @throws IllegalStateException if this widget is already attached
* @see #onLoad()
* @see #doAttachChildren()
*/
protected void onAttach() {
if (isAttached()) {
throw new IllegalStateException(
"Should only call onAttach when the widget is detached from the browser's document");
}
attached = true;
// Event hookup code
DOM.setEventListener(getElement(), this);
int bitsToAdd = eventsToSink;
eventsToSink = -1;
if (bitsToAdd > 0) {
sinkEvents(bitsToAdd);
}
doAttachChildren();
// onLoad() gets called only *after* all of the children are attached and
// the attached flag is set. This allows widgets to be notified when they
// are fully attached, and panels when all of their children are attached.
onLoad();
AttachEvent.fire(this, true);
}
/**
*
* This method is called when a widget is detached from the browser's
* document. To receive notification before a Widget is removed from the
* document, override the {@link #onUnload} method or use {@link #addAttachHandler}.
*
*
* It is strongly recommended that you override {@link #onUnload()} or
* {@link #doDetachChildren()} instead of this method to avoid inconsistencies
* between logical and physical attachment states.
*
*
* Subclasses that override this method must call
* super.onDetach() to ensure that the Widget has been detached
* from the underlying Element. Failure to do so will result in application
* memory leaks due to circular references between DOM Elements and JavaScript
* objects.
*
*
* @throws IllegalStateException if this widget is already detached
* @see #onUnload()
* @see #doDetachChildren()
*/
protected void onDetach() {
if (!isAttached()) {
throw new IllegalStateException(
"Should only call onDetach when the widget is attached to the browser's document");
}
try {
// onUnload() gets called *before* everything else (the opposite of
// onLoad()).
onUnload();
AttachEvent.fire(this, false);
} finally {
// Put this in a finally, just in case onUnload throws an exception.
try {
doDetachChildren();
} finally {
// Put this in a finally, in case doDetachChildren throws an exception.
DOM.setEventListener(getElement(), null);
attached = false;
}
}
}
/**
* This method is called immediately after a widget becomes attached to the
* browser's document.
*/
protected void onLoad() {
}
/**
* This method is called immediately before a widget will be detached from the
* browser's document.
*/
protected void onUnload() {
}
/**
* Ensures the existence of the handler manager.
*
* @return the handler manager
* */
HandlerManager ensureHandlers() {
return handlerManager == null ? handlerManager = createHandlerManager()
: handlerManager;
}
HandlerManager getHandlerManager() {
return handlerManager;
}
@Override
void replaceElement(com.google.gwt.dom.client.Element elem) {
if (isAttached()) {
// Remove old event listener to avoid leaking. onDetach will not do this
// for us, because it is only called when the widget itself is detached
// from the document.
DOM.setEventListener(getElement(), null);
}
super.replaceElement(elem);
if (isAttached()) {
// Hook the event listener back up on the new element. onAttach will not
// do this for us, because it is only called when the widget itself is
// attached to the document.
DOM.setEventListener(getElement(), this);
}
}
/**
* Sets this widget's parent. This method should only be called by
* {@link Panel} and {@link Composite}.
*
* @param parent the widget's new parent
* @throws IllegalStateException if parent is non-null and the
* widget already has a parent
*/
void setParent(Widget parent) {
Widget oldParent = this.parent;
if (parent == null) {
try {
if (oldParent != null && oldParent.isAttached()) {
onDetach();
assert !isAttached() : "Failure of " + this.getClass().getName()
+ " to call super.onDetach()";
}
} finally {
// Put this in a finally in case onDetach throws an exception.
this.parent = null;
}
} else {
if (oldParent != null) {
throw new IllegalStateException(
"Cannot set a new parent without first clearing the old parent");
}
this.parent = parent;
if (parent.isAttached()) {
onAttach();
assert isAttached() : "Failure of " + this.getClass().getName()
+ " to call super.onAttach()";
}
}
}
}