Java tutorial
/* * 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.core.client.Scheduler; import com.google.gwt.core.client.Scheduler.ScheduledCommand; import com.google.gwt.dom.client.Document; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.Style.Position; import com.google.gwt.dom.client.Style.Unit; import com.google.gwt.event.shared.HandlerRegistration; import com.google.gwt.user.client.Command; import com.google.gwt.user.client.Event; import com.google.gwt.user.client.Window; /** * A panel that adds user-positioned splitters between each of its child * widgets. * * <p> * This panel is used in the same way as {@link DockLayoutPanel}, except that * its children's sizes are always specified in {@link Unit#PX} units, and each * pair of child widgets has a splitter between them that the user can drag. * </p> * * <p> * This widget will <em>only</em> work in standards mode, which requires that * the HTML page in which it is run have an explicit <!DOCTYPE> * declaration. * </p> * * <h3>CSS Style Rules</h3> * <ul class='css'> * <li>.gwt-SplitLayoutPanel { the panel itself }</li> * <li>.gwt-SplitLayoutPanel .gwt-SplitLayoutPanel-HDragger { horizontal dragger * }</li> * <li>.gwt-SplitLayoutPanel .gwt-SplitLayoutPanel-VDragger { vertical dragger } * </li> * </ul> * * <p> * <h3>Example</h3> * {@example com.google.gwt.examples.SplitLayoutPanelExample} * </p> */ public class SplitLayoutPanel extends DockLayoutPanel { class HSplitter extends Splitter { public HSplitter(Widget target, boolean reverse) { super(target, reverse); getElement().getStyle().setPropertyPx("width", splitterSize); setStyleName("gwt-SplitLayoutPanel-HDragger"); } @Override protected int getAbsolutePosition() { return getAbsoluteLeft(); } @Override protected double getCenterSize() { return getCenterWidth(); } @Override protected int getEventPosition(Event event) { return event.getClientX(); } @Override protected int getTargetPosition() { return target.getAbsoluteLeft(); } @Override protected int getTargetSize() { return target.getOffsetWidth(); } } abstract class Splitter extends Widget { protected final Widget target; private int offset; private boolean mouseDown; private ScheduledCommand layoutCommand; private final boolean reverse; private int minSize; private double centerSize, syncedCenterSize; public Splitter(Widget target, boolean reverse) { this.target = target; this.reverse = reverse; setElement(Document.get().createDivElement()); sinkEvents(Event.ONMOUSEDOWN | Event.ONMOUSEUP | Event.ONMOUSEMOVE | Event.ONDBLCLICK); } @Override public void onBrowserEvent(Event event) { switch (event.getTypeInt()) { case Event.ONMOUSEDOWN: mouseDown = true; /* * Resize glassElem to take up the entire scrollable window area, * which is the greater of the scroll size and the client size. */ int width = Math.max(Window.getClientWidth(), Document.get().getScrollWidth()); int height = Math.max(Window.getClientHeight(), Document.get().getScrollHeight()); glassElem.getStyle().setHeight(height, Unit.PX); glassElem.getStyle().setWidth(width, Unit.PX); Document.get().getBody().appendChild(glassElem); offset = getEventPosition(event) - getAbsolutePosition(); Event.setCapture(getElement()); event.preventDefault(); fireEvent(new SplitterBeforeResizeEvent()); break; case Event.ONMOUSEUP: mouseDown = false; glassElem.removeFromParent(); Event.releaseCapture(getElement()); event.preventDefault(); fireEvent(new SplitterResizedEvent()); break; case Event.ONMOUSEMOVE: if (mouseDown) { int size; if (reverse) { size = getTargetPosition() + getTargetSize() - getEventPosition(event) - offset; } else { size = getEventPosition(event) - getTargetPosition() - offset; } setAssociatedWidgetSize(size); event.preventDefault(); } break; } } public void setMinSize(int minSize) { this.minSize = minSize; LayoutData layout = (LayoutData) target.getLayoutData(); // Try resetting the associated widget's size, which will enforce the new // minSize value. setAssociatedWidgetSize((int) layout.size); } protected abstract int getAbsolutePosition(); protected abstract double getCenterSize(); protected abstract int getEventPosition(Event event); protected abstract int getTargetPosition(); protected abstract int getTargetSize(); private double getMaxSize() { // To avoid seeing stale center size values due to deferred layout // updates, maintain our own copy up to date and resync when the // DockLayoutPanel value changes. double newCenterSize = getCenterSize(); if (syncedCenterSize != newCenterSize) { syncedCenterSize = newCenterSize; centerSize = newCenterSize; } return Math.max(((LayoutData) target.getLayoutData()).size + centerSize, 0); } private void setAssociatedWidgetSize(double size) { double maxSize = getMaxSize(); if (size > maxSize) { size = maxSize; } if (size < minSize) { size = minSize; } LayoutData layout = (LayoutData) target.getLayoutData(); if (size == layout.size) { return; } // Adjust our view until the deferred layout gets scheduled. centerSize += layout.size - size; layout.size = size; // Defer actually updating the layout, so that if we receive many // mouse events before layout/paint occurs, we'll only update once. if (layoutCommand == null) { layoutCommand = new Command() { public void execute() { layoutCommand = null; forceLayout(); } }; Scheduler.get().scheduleDeferred(layoutCommand); } } } class VSplitter extends Splitter { public VSplitter(Widget target, boolean reverse) { super(target, reverse); getElement().getStyle().setPropertyPx("height", splitterSize); setStyleName("gwt-SplitLayoutPanel-VDragger"); } @Override protected int getAbsolutePosition() { return getAbsoluteTop(); } @Override protected double getCenterSize() { return getCenterHeight(); } @Override protected int getEventPosition(Event event) { return event.getClientY(); } @Override protected int getTargetPosition() { return target.getAbsoluteTop(); } @Override protected int getTargetSize() { return target.getOffsetHeight(); } } private static final int DEFAULT_SPLITTER_SIZE = 8; /** * The element that masks the screen so we can catch mouse events over * iframes. */ private static Element glassElem = null; private final int splitterSize; /** * Construct a new {@link SplitLayoutPanel} with the default splitter size of * 8px. */ public SplitLayoutPanel() { this(DEFAULT_SPLITTER_SIZE); } /** * Construct a new {@link SplitLayoutPanel} with the specified splitter size * in pixels. * * @param splitterSize the size of the splitter in pixels */ public SplitLayoutPanel(int splitterSize) { super(Unit.PX); this.splitterSize = splitterSize; setStyleName("gwt-SplitLayoutPanel"); if (glassElem == null) { glassElem = Document.get().createDivElement(); glassElem.getStyle().setPosition(Position.ABSOLUTE); glassElem.getStyle().setTop(0, Unit.PX); glassElem.getStyle().setLeft(0, Unit.PX); glassElem.getStyle().setMargin(0, Unit.PX); glassElem.getStyle().setPadding(0, Unit.PX); glassElem.getStyle().setBorderWidth(0, Unit.PX); // We need to set the background color or mouse events will go right // through the glassElem. If the SplitPanel contains an iframe, the // iframe will capture the event and the slider will stop moving. glassElem.getStyle().setProperty("background", "white"); glassElem.getStyle().setOpacity(0.0); } } /** * Return the size of the splitter in pixels. * * @return the splitter size */ public int getSplitterSize() { return splitterSize; } @Override public void insert(Widget child, Direction direction, double size, Widget before) { super.insert(child, direction, size, before); if (direction != Direction.CENTER) { insertSplitter(child, before); } } @Override public boolean remove(Widget child) { assert !(child instanceof Splitter) : "Splitters may not be directly removed"; int idx = getWidgetIndex(child); if (super.remove(child)) { // Remove the associated splitter, if any. // Now that the widget is removed, idx is the index of the splitter. if (idx < getWidgetCount()) { // Call super.remove(), or we'll end up recursing. super.remove(getWidget(idx)); } return true; } return false; } /** * Sets the minimum allowable size for the given widget. * * <p> * Its associated splitter cannot be dragged to a position that would make it * smaller than this size. This method has no effect for the * {@link DockLayoutPanel.Direction#CENTER} widget. * </p> * * @param child the child whose minimum size will be set * @param minSize the minimum size for this widget */ public void setWidgetMinSize(Widget child, int minSize) { assertIsChild(child); Splitter splitter = getAssociatedSplitter(child); // The splitter is null for the center element. if (splitter != null) { splitter.setMinSize(minSize); } } private Splitter getAssociatedSplitter(Widget child) { // If a widget has a next sibling, it must be a splitter, because the only // widget that *isn't* followed by a splitter must be the CENTER, which has // no associated splitter. int idx = getWidgetIndex(child); if (idx > -1 && idx < getWidgetCount() - 1) { Widget splitter = getWidget(idx + 1); assert splitter instanceof Splitter : "Expected child widget to be splitter"; return (Splitter) splitter; } return null; } private void insertSplitter(Widget widget, Widget before) { assert getChildren().size() > 0 : "Can't add a splitter before any children"; LayoutData layout = (LayoutData) widget.getLayoutData(); Splitter splitter = null; switch (getResolvedDirection(layout.direction)) { case WEST: splitter = new HSplitter(widget, false); break; case EAST: splitter = new HSplitter(widget, true); break; case NORTH: splitter = new VSplitter(widget, false); break; case SOUTH: splitter = new VSplitter(widget, true); break; default: assert false : "Unexpected direction"; } splitter.addHandler(new SplitterBeforeResizeHandler() { public void onSplitterBeforeResize(SplitterBeforeResizeEvent event) { delegateEvent(SplitLayoutPanel.this, event); } }, SplitterBeforeResizeEvent.TYPE); splitter.addHandler(new SplitterResizedHandler() { public void onSplitterResized(SplitterResizedEvent event) { delegateEvent(SplitLayoutPanel.this, event); } }, SplitterResizedEvent.TYPE); super.insert(splitter, layout.direction, splitterSize, before); } public HandlerRegistration addSplitterBeforeResizeHandler(SplitterBeforeResizeHandler handler) { return addHandler(handler, SplitterBeforeResizeEvent.TYPE); } public HandlerRegistration addSplitterResizedHandler(SplitterResizedHandler handler) { return addHandler(handler, SplitterResizedEvent.TYPE); } }