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/*
 * Copyright 2009 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.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.Style.Unit;
import com.google.gwt.layout.client.Layout;
import com.google.gwt.layout.client.Layout.Alignment;
import com.google.gwt.layout.client.Layout.AnimationCallback;
import com.google.gwt.layout.client.Layout.Layer;

/**
 * A panel that lays its children out in arbitrary
 * {@link com.google.gwt.layout.client.Layout.Layer layers} using the
 * {@link Layout} class.
 * 
 * 

* This widget will only work in standards mode, which requires that * the HTML page in which it is run have an explicit <!DOCTYPE> * declaration. *

* *

*

Example

* {@example com.google.gwt.examples.LayoutPanelExample} *

* *

Use in UiBinder Templates

*

* LayoutPanel elements in {@link com.google.gwt.uibinder.client.UiBinder * UiBinder} templates lay out their children with arbitrary constraints, using * <g:layer> elements. Each layer may have any of the following constraint * attributes specified as CSS length attributes: left, * top, right, bottom, width * , and height. * *

* Precisely zero or two constraints are required for each axis (horizontal and * vertical). Specifying no constraints implies that the child should fill that * axis completely. * *

* The valid sets of horizontal constraints are: *

*
(none) *
Fill the parent's horizontal axis *
left, width *
Fixed width, positioned from parent's left edge *
right, width *
Fixed width, positioned from parent's right edge *
left, right *
Width implied by fixed distance from parent's left and right edges *
* *

* The valid sets of vertical constraints are: *

*
(none) *
Fill the parent's vertical axis *
top, height *
Fixed height, positioned from parent's top edge *
bottom, height *
Fixed height, positioned from parent's bottom edge *
top, bottom *
Height implied by fixed distance from parent's top and bottom edges *
* *

* The values of constraint attributes can be any valid CSS length, * such as 1px, 3em, or 0 (zero lengths require no * units). * *

* For example: * *

 * <g:LayoutPanel>
 *   <!-- No constraints causes the layer to fill the parent -->
 *   <g:layer>
 *     <g:Label>Lorem ipsum...</g:Label>
 *   </g:layer>
 *   <!-- Position horizontally 25% from each edge;
 *        Vertically 4px from the top and 10em tall. -->
 *   <g:layer left='25%' right='25%' top='4px' height='10em'>
 *     <g:Label>Header</g:Label>
 *   </g:layer>
 * </g:LayoutPanel>
 * 
*/ public class LayoutPanel extends ComplexPanel implements AnimatedLayout, RequiresResize, ProvidesResize { private final Layout layout; private final LayoutCommand layoutCmd; /** * Creates an empty layout panel. */ public LayoutPanel() { setElement(Document.get().createDivElement()); layout = new Layout(getElement()); layoutCmd = new LayoutCommand(layout); } /** * Adds a widget to this panel. * *

* By default, each child will fill the panel. To build more interesting * layouts, set child widgets' layout constraints using * {@link #setWidgetLeftRight(Widget, double, Style.Unit, double, Style.Unit)} * and related methods. *

* * @param widget the widget to be added */ @Override public void add(Widget widget) { insert(widget, getWidgetCount()); } @Override public void animate(int duration) { animate(duration, null); } @Override public void animate(final int duration, final AnimationCallback callback) { layoutCmd.schedule(duration, callback); } @Override public void forceLayout() { layoutCmd.cancel(); layout.layout(); onResize(); } /** * Gets the container element wrapping the given child widget. * * @param child * @return the widget's container element */ public Element getWidgetContainerElement(Widget child) { assertIsChild(child); return getLayer(child).getContainerElement(); } /** * Inserts a widget before the specified index. * *

* By default, each child will fill the panel. To build more interesting * layouts, set child widgets' layout constraints using * {@link #setWidgetLeftRight(Widget, double, Style.Unit, double, Style.Unit)} * and related methods. *

* *

* Inserting a widget in this way has no effect on the DOM structure, but can * be useful for other panels that wrap LayoutPanel to maintain insertion * order. *

* * @param widget the widget to be inserted * @param beforeIndex the index before which it will be inserted * @throws IndexOutOfBoundsException if beforeIndex is out of * range */ public void insert(Widget widget, int beforeIndex) { // Detach new child. widget.removeFromParent(); // Logical attach. getChildren().insert(widget, beforeIndex); // Physical attach. Layer layer = layout.attachChild(widget.getElement(), widget); widget.setLayoutData(layer); // Adopt. adopt(widget); animate(0); } @Override public void onResize() { for (Widget child : getChildren()) { if (child instanceof RequiresResize) { ((RequiresResize) child).onResize(); } } } @Override public boolean remove(Widget w) { boolean removed = super.remove(w); if (removed) { layout.removeChild((Layer) w.getLayoutData()); } return removed; } /** * Sets the child widget's bottom and height values. * * @param child * @param bottom * @param bottomUnit * @param height * @param heightUnit */ public void setWidgetBottomHeight(Widget child, double bottom, Unit bottomUnit, double height, Unit heightUnit) { assertIsChild(child); getLayer(child).setBottomHeight(bottom, bottomUnit, height, heightUnit); animate(0); } /** * Overloaded version for IsWidget. * * @see #setWidgetBottomHeight(Widget,double, Style.Unit, double, Style.Unit) */ public void setWidgetBottomHeight(IsWidget child, double bottom, Unit bottomUnit, double height, Unit heightUnit) { this.setWidgetBottomHeight(child.asWidget(), bottom, bottomUnit, height, heightUnit); } /** * Sets the child widget's horizontal position within its layer. * * @param child * @param position */ public void setWidgetHorizontalPosition(Widget child, Alignment position) { assertIsChild(child); getLayer(child).setChildHorizontalPosition(position); animate(0); } /** * Sets the child widget's left and right values. * * @param child * @param left * @param leftUnit * @param right * @param rightUnit */ public void setWidgetLeftRight(Widget child, double left, Unit leftUnit, double right, Unit rightUnit) { assertIsChild(child); getLayer(child).setLeftRight(left, leftUnit, right, rightUnit); animate(0); } /** * Overloaded version for IsWidget. * * @see #setWidgetLeftRight(Widget,double, Style.Unit, double, Style.Unit) */ public void setWidgetLeftRight(IsWidget child, double left, Unit leftUnit, double right, Unit rightUnit) { this.setWidgetLeftRight(child.asWidget(), left, leftUnit, right, rightUnit); } /** * Sets the child widget's left and width values. * * @param child * @param left * @param leftUnit * @param width * @param widthUnit */ public void setWidgetLeftWidth(Widget child, double left, Unit leftUnit, double width, Unit widthUnit) { assertIsChild(child); getLayer(child).setLeftWidth(left, leftUnit, width, widthUnit); animate(0); } /** * Overloaded version for IsWidget. * * @see #setWidgetLeftWidth(Widget,double, Style.Unit, double, Style.Unit) */ public void setWidgetLeftWidth(IsWidget child, double left, Unit leftUnit, double width, Unit widthUnit) { this.setWidgetLeftWidth(child.asWidget(), left, leftUnit, width, widthUnit); } /** * Sets the child widget's right and width values. * * @param child * @param right * @param rightUnit * @param width * @param widthUnit */ public void setWidgetRightWidth(Widget child, double right, Unit rightUnit, double width, Unit widthUnit) { assertIsChild(child); getLayer(child).setRightWidth(right, rightUnit, width, widthUnit); animate(0); } /** * Overloaded version for IsWidget. * * @see #setWidgetRightWidth(Widget,double, Style.Unit, double, Style.Unit) */ public void setWidgetRightWidth(IsWidget child, double right, Unit rightUnit, double width, Unit widthUnit) { this.setWidgetRightWidth(child.asWidget(), right, rightUnit, width, widthUnit); } /** * Sets the child widget's top and bottom values. * * @param child * @param top * @param topUnit * @param bottom * @param bottomUnit */ public void setWidgetTopBottom(Widget child, double top, Unit topUnit, double bottom, Unit bottomUnit) { assertIsChild(child); getLayer(child).setTopBottom(top, topUnit, bottom, bottomUnit); animate(0); } /** * Overloaded version for IsWidget. * * @see #setWidgetTopBottom(Widget,double, Style.Unit, double, Style.Unit) */ public void setWidgetTopBottom(IsWidget child, double top, Unit topUnit, double bottom, Unit bottomUnit) { this.setWidgetTopBottom(child.asWidget(), top, topUnit, bottom, bottomUnit); } /** * Sets the child widget's top and height values. * * @param child * @param top * @param topUnit * @param height * @param heightUnit */ public void setWidgetTopHeight(Widget child, double top, Unit topUnit, double height, Unit heightUnit) { assertIsChild(child); getLayer(child).setTopHeight(top, topUnit, height, heightUnit); animate(0); } /** * Overloaded version for IsWidget. * * @see #setWidgetTopHeight(Widget,double, Style.Unit, double, Style.Unit) */ public void setWidgetTopHeight(IsWidget child, double top, Unit topUnit, double height, Unit heightUnit) { this.setWidgetTopHeight(child.asWidget(), top, topUnit, height, heightUnit); } /** * Sets the child widget's vertical position within its layer. * * @param child * @param position */ public void setWidgetVerticalPosition(Widget child, Alignment position) { assertIsChild(child); getLayer(child).setChildVerticalPosition(position); animate(0); } /** * Shows or hides the given widget and its layer. This method explicitly * calls {@link UIObject#setVisible(boolean)} on the child widget and ensures * that its associated layer is shown/hidden. * * @param child * @param visible */ public void setWidgetVisible(Widget child, boolean visible) { assertIsChild(child); getLayer(child).setVisible(visible); child.setVisible(visible); animate(0); } @Override protected void onAttach() { super.onAttach(); layout.onAttach(); } @Override protected void onDetach() { super.onDetach(); layout.onDetach(); } /** * Gets the {@link Layout} instance associated with this widget. This is made * package-protected for use by {@link RootLayoutPanel}. * * @return this widget's layout instance */ Layout getLayout() { return layout; } private void assertIsChild(Widget widget) { assert (widget == null) || (widget.getParent() == this) : "The specified widget is not a child of this panel"; } private Layout.Layer getLayer(Widget child) { assert child.getParent() == this : "The requested widget is not a child of this panel"; return (Layout.Layer) child.getLayoutData(); } }




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