Java tutorial
/* * Copyright 2008-2013 Sergey Skladchikov * * 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 geogebra.web.gui.advanced.client.ui.widget; import geogebra.web.gui.advanced.client.datamodel.ListDataModel; import geogebra.web.gui.advanced.client.ui.AdvancedWidget; import geogebra.web.gui.advanced.client.ui.widget.combo.ComboBoxChangeEvent; import geogebra.web.gui.advanced.client.ui.widget.combo.DropDownPosition; import geogebra.web.gui.advanced.client.ui.widget.combo.ListItemFactory; import com.google.gwt.event.dom.client.ChangeEvent; import com.google.gwt.event.dom.client.ChangeHandler; import com.google.gwt.event.dom.client.ClickEvent; import com.google.gwt.event.dom.client.ClickHandler; import com.google.gwt.event.dom.client.FocusEvent; import com.google.gwt.event.dom.client.HasChangeHandlers; import com.google.gwt.event.dom.client.MouseOutEvent; import com.google.gwt.event.dom.client.MouseOutHandler; import com.google.gwt.event.dom.client.MouseOverEvent; import com.google.gwt.event.dom.client.MouseOverHandler; import com.google.gwt.event.dom.client.ScrollEvent; import com.google.gwt.event.dom.client.ScrollHandler; import com.google.gwt.event.logical.shared.ResizeEvent; import com.google.gwt.event.logical.shared.ResizeHandler; import com.google.gwt.event.shared.HandlerRegistration; import com.google.gwt.user.client.DOM; import com.google.gwt.user.client.Element; import com.google.gwt.user.client.Event; import com.google.gwt.user.client.Window; import com.google.gwt.user.client.ui.FlowPanel; import com.google.gwt.user.client.ui.FocusPanel; import com.google.gwt.user.client.ui.PopupPanel; import com.google.gwt.user.client.ui.ScrollPanel; import com.google.gwt.user.client.ui.Widget; /** * This widget displays a scrollable list of items.<p/> * Don't try to use it directly. It's just for the combo box widget. * * @author <a href="mailto:sskladchikov@gmail.com">Sergey Skladchikov</a> * @since 1.2.0 */ public class ListPopupPanel extends PopupPanel implements AdvancedWidget, HasChangeHandlers { /** a list of items */ private FlowPanel list; /** items scrolling widget */ private ScrollPanel scrollPanel; /** a flag meaning whether this widget is hidden */ private boolean hidden = true; /** a parent selection box */ private ComboBox comboBox; /** item click handler */ private ClickHandler itemClickHandler; /** mouse event handler */ private ListMouseHandler mouseEventsListener; /** list of displayed items scroll handler */ private ScrollHandler listScrollHandler; /** the row that is currently highlight in the list but my be not selected in the model */ private int highlightRow = -1; /** number of visible rows in the scrollable area of the popup list. Limited by 30% of screen height by default */ private int visibleRows = -1; /** the top item index to be displayed in the visible area of the list */ private int startItemIndex = 0; /** enables or disables lazy rendering of the items list */ private boolean lazyRenderingEnabled; /** registration of the {@link org.gwt.advanced.client.ui.widget.ListPopupPanel.ClickSpyHandler} */ private HandlerRegistration clickSpyRegistration; /** drop down list position */ private DropDownPosition dropDownPosition = DropDownPosition.AUTO; /** * Creates an instance of this class and sets the parent combo box value. * * @param selectionTextBox is a selection box value. */ protected ListPopupPanel(ComboBox selectionTextBox) { super(false, false); this.comboBox = selectionTextBox; setStyleName("advanced-ListPopupPanel"); setWidget(getScrollPanel()); getList().setStyleName("list"); Window.addResizeHandler(new ListWindowResizeHandler()); } /** * This method adds a handler that will be invoked on choice. * * @param handler is a handler to be added. */ @Override public HandlerRegistration addChangeHandler(ChangeHandler handler) { return addHandler(handler, ChangeEvent.getType()); } /** * Getter for property 'hidden'. * * @return Value for property 'hidden'. */ public boolean isHidden() { return hidden; } /** * Gets a currently highlight row.<p/> * Note that it may not be equal to the selected row index in the model. * * @return a row number that is currently highlight. */ public int getHighlightRow() { return highlightRow; } /** * This method gets an actual number of items displayed in the drop down. * * @return an item count. */ public int getItemCount() { return getList().getWidgetCount(); } /** * Gets an item by its index<p/> * If index < 0 or index >= {@link #getItemCount()} it throws an exception. * * @param index is an index of the item to get. * @return a found item. * @throws IndexOutOfBoundsException if index is invalid. */ public Widget getItem(int index) { return getList().getWidget(index); } /** * Gets an item index if it's displayed in the drop down list.<p/> * Otherwise returns <code>-1</code>. * * @param item an item that is required to return. * @return an item index value or <code>-1</code>. */ public int getItemIndex(Widget item) { return getList().getWidgetIndex(item); } /** * Sets the highlight row number. * * @param row is a row number to become highlight. */ protected void setHighlightRow(int row) { if (row < getList().getWidgetCount()) { Widget widget = null; if (this.highlightRow >= 0 && getList().getWidgetCount() > this.highlightRow) widget = getList().getWidget(this.highlightRow); if (widget != null) widget.removeStyleName("selected-row"); this.highlightRow = row; if (row >= 0) { widget = getList().getWidget(this.highlightRow); widget.addStyleName("selected-row"); } } } /** * Checks whether the specified item is visible in the scroll area.<p/> * The result is <code>true</code> if whole item is visible. * * @param index is an index of the item. * @return a result of check. */ public boolean isItemVisible(int index) { Widget item = getList().getWidget(index); int itemTop = item.getAbsoluteTop(); int top = getScrollPanel().getAbsoluteTop(); return itemTop >= top && itemTop + item.getOffsetHeight() <= top + getScrollPanel().getOffsetHeight(); } /** * Makes the item visible in the list according to the check done by the {@link #isItemVisible(int)} method. * * @param item is an item to check. */ public void ensureVisible(Widget item) { if (!isItemVisible(getList().getWidgetIndex(item))) { getScrollPanel().ensureVisible(item); } } /** {@inheritDoc} */ public void hide() { if (clickSpyRegistration != null) { clickSpyRegistration.removeHandler(); clickSpyRegistration = null; } super.hide(); setHidden(true); } /** {@inheritDoc} */ public void show() { clickSpyRegistration = Event.addNativePreviewHandler(new ClickSpyHandler()); setHidden(false); super.show(); adjustSize(); setHighlightRow(getComboBox().getModel().getSelectedIndex()); getComboBox().getDelegateHandler().onFocus(new FocusEvent() { }); } /** * Gets a number of visible rows.<p/> * Values <= 0 interpreted as undefined. * * @return a visible rows to be displayed without scrolling. */ public int getVisibleRows() { return visibleRows; } /** * Sets visible rows number.<p/> * You can pass a value <= 0. It will mean that this parameter in undefined. * * @param visibleRows is a number of rows to be displayed without scrolling. */ public void setVisibleRows(int visibleRows) { this.visibleRows = visibleRows; if (isShowing()) adjustSize(); } /** * Sets an item index that must be displayed on top.<p/> * If the item is outside the currently visible area the list will be scrolled down * to this item. * * @param index is an index of the element to display. */ public void setStartItemIndex(int index) { if (index < 0) index = 0; this.startItemIndex = index; if (isShowing()) adjustSize(); } public int getStartItemIndex() { return startItemIndex; } /** * Gets applied position of the drop down list. * * @return a drop down list position value. */ public DropDownPosition getDropDownPosition() { return dropDownPosition; } /** * Sets applied position of the drop down list.<p/> * Being set the drop down is immediately applied if the list is opened. * * @param dropDownPosition is a drop down list position value. */ public void setDropDownPosition(DropDownPosition dropDownPosition) { this.dropDownPosition = dropDownPosition; if (isShowing()) adjustSize(); } /** Adjusts drop down list sizes to make it take optimal area on the screen. */ protected void adjustSize() { ScrollPanel table = getScrollPanel(); int visibleRows = getVisibleRows(); int delta = getElement().getOffsetWidth() - getElement().getClientWidth(); getScrollPanel().setWidth((getComboBox().getOffsetWidth() - delta) + "px"); if (visibleRows <= 0) { table.setHeight(""); int spaceAbove = getComboBox().getAbsoluteTop(); int spaceUnder = Window.getClientHeight() - getComboBox().getAbsoluteTop() - getComboBox().getOffsetHeight(); DOM.setStyleAttribute(table.getElement(), "maxHeight", Math.min(Window.getClientHeight() * 0.3, Math.max(spaceAbove, spaceUnder)) + "px"); } else if (getComboBox().getModel().getCount() > visibleRows) { int index = getStartItemIndex(); int count = getItemCount(); if (index + visibleRows > count) { index = count - visibleRows + 1; if (index < 0) index = 0; } int listHeight = 0; int scrollPosition = 0; for (int i = 0; i < index + visibleRows && i < count; i++) { int height = getList().getWidget(i).getOffsetHeight(); if (i < index) scrollPosition += height; else listHeight += height; } table.setSize(table.getOffsetWidth() + "px", listHeight + "px"); table.setScrollPosition(scrollPosition); DOM.setStyleAttribute(table.getElement(), "maxHeight", ""); } else { table.setHeight(""); DOM.setStyleAttribute(table.getElement(), "maxHeight", ""); } resetPosition(); } /** Chooses and sets a mostly appropriate position of the drop down list */ protected void resetPosition() { if (getDropDownPosition() == DropDownPosition.ABOVE || getDropDownPosition() == DropDownPosition.AUTO && Window.getClientHeight() - getComboBox().getAbsoluteTop() - getComboBox().getOffsetHeight() < getComboBox().getAbsoluteTop()) { setPopupPosition(getComboBox().getAbsoluteLeft(), getComboBox().getAbsoluteTop() - getOffsetHeight()); } else if (getDropDownPosition() == DropDownPosition.UNDER || getDropDownPosition() == DropDownPosition.AUTO) { setPopupPosition(getComboBox().getAbsoluteLeft(), getComboBox().getAbsoluteTop() + getComboBox().getOffsetHeight()); } } /** * {@inheritDoc} * * @deprecated you don't have to invoke this method to display the widget any more */ public void display() { } /** * Checks whether the lazy rendering option is enabled. * * @return a result of check. */ protected boolean isLazyRenderingEnabled() { return lazyRenderingEnabled; } /** * Enables or disables lazy rendering option.<p/> * If this option is enabled the list displays only several items on lazily reders other ones on scroll down.<p/> * By default lazy rendering is disabled. Switch it on for really large (over 500 items) lists only. * * @param lazyRenderingEnabled is an option value. */ protected void setLazyRenderingEnabled(boolean lazyRenderingEnabled) { this.lazyRenderingEnabled = lazyRenderingEnabled; } /** This method prepares the list of items for displaying. */ protected void prepareList() { FlowPanel panel = getList(); if (!isLazyRenderingEnabled() || getComboBox().getModel().getCount() != getItemCount()) panel.clear(); fillList(); int selected = getComboBox().getModel().getSelectedIndex(); selectRow(selected); if (selected >= 0 && selected < getItemCount()) ensureVisible(getItem(selected)); } /** * Fills the list of items starting from the current position and ending with rendering limits<p/> * See {2link #isRenderingLimitReached()} for additional details since it's used in the body of this method. */ protected void fillList() { FlowPanel panel = getList(); ListDataModel model = getComboBox().getModel(); ListItemFactory itemFactory = getComboBox().getListItemFactory(); int count = getItemCount(); int previouslyLoadedRows = count; while (!isRenderingLimitReached(previouslyLoadedRows)) panel.add(adoptItemWidget(itemFactory.createWidget(model.get(count++)))); } /** * This method checks whether the limit of displayed items reached.<p/> * It takes into account different aspects including setting of the widget, geometrical size of the * drop down list and selected value that must be displayed.<p/> * This method optimally chooses a number of items to display. * * @param previouslyRenderedRows is a number of rows previously loaded in the list * (items count before filling the list). * @return a result of check. */ protected boolean isRenderingLimitReached(int previouslyRenderedRows) { ListDataModel model = getComboBox().getModel(); int previousHeight = 0; if (previouslyRenderedRows > 0) { Widget last = getItem(previouslyRenderedRows - 1); Widget first = getItem(0); previousHeight = last.getOffsetHeight() + last.getAbsoluteTop() - first.getAbsoluteTop(); } return model.getCount() <= 0 // no data // OR a selected value has already been displayed || getItemCount() > getComboBox().getSelectedIndex() // AND one of the following conditions is true: && (getItemCount() >= model.getCount() //no items any more // OR no limit but there are too many items || isLazyRenderingEnabled() && getVisibleRows() <= 0 && getList().getOffsetHeight() - previousHeight >= Window.getClientHeight() * 0.6 // OR visible rows number is limited and there was a new page rendered excepting the first page // since two pages may be displayed if the list is rendered first time || isLazyRenderingEnabled() && getVisibleRows() > 0 && getItemCount() - previouslyRenderedRows > 0 && (getItemCount() - previouslyRenderedRows) % getVisibleRows() == 0 && (getItemCount() - previouslyRenderedRows) / getVisibleRows() != 1); } /** * This method higlights a selected row. * * @param newRow a row for selection. */ protected void selectRow(int newRow) { ListDataModel model = getComboBox().getModel(); model.setSelectedIndex(newRow); } /** * This method wraps the specified widget into the focus panel and adds necessary listeners. * * @param widget is an item widget to be wraped. * @return a focus panel adopted for displaying. */ protected FocusPanel adoptItemWidget(Widget widget) { FocusPanel panel = new FocusPanel(widget); panel.addClickHandler(getItemClickHandler()); panel.addMouseOverHandler(getMouseEventsHandler()); panel.addMouseOutHandler(getMouseEventsHandler()); panel.setStyleName("item"); DOM.removeElementAttribute(panel.getElement(), "tabindex"); return panel; } /** * Setter for property 'hidden'. * * @param hidden Value to set for property 'hidden'. */ protected void setHidden(boolean hidden) { this.hidden = hidden; } /** * Getter for property 'comboBox'. * * @return Value for property 'comboBox'. */ protected ComboBox getComboBox() { return comboBox; } /** * Getter for property 'list'. * * @return Value for property 'list'. */ protected FlowPanel getList() { if (list == null) list = new FlowPanel(); return list; } /** * Getter for property 'scrollPanel'. * * @return Value for property 'scrollPanel'. */ public ScrollPanel getScrollPanel() { if (scrollPanel == null) { scrollPanel = new ScrollPanel(); scrollPanel.setAlwaysShowScrollBars(false); scrollPanel.setWidget(getList()); DOM.setStyleAttribute(scrollPanel.getElement(), "overflowX", "hidden"); scrollPanel.addScrollHandler(getListScrollHandler()); } return scrollPanel; } /** * Getter for property 'itemClickHandler'. * * @return Value for property 'itemClickHandler'. */ protected ClickHandler getItemClickHandler() { if (itemClickHandler == null) itemClickHandler = new ItemClickHandler(); return itemClickHandler; } /** * Getter for property 'mouseEventsListener'. * * @return Value for property 'mouseEventsListener'. */ protected ListMouseHandler getMouseEventsHandler() { if (mouseEventsListener == null) mouseEventsListener = new ListMouseHandler(); return mouseEventsListener; } /** * Getter for property 'listScrollHandler'. * * @return Value for property 'listScrollHandler'. */ public ScrollHandler getListScrollHandler() { if (listScrollHandler == null) { listScrollHandler = new ListScrollHandler(); } return listScrollHandler; } /** This is a click handler required to dispatch click events. */ protected class ItemClickHandler implements ClickHandler { /** {@inheritDoc} */ @Override public void onClick(ClickEvent event) { int row = getList().getWidgetIndex((Widget) event.getSource()); selectRow(row); ChangeEvent changeEvent = new ComboBoxChangeEvent(row, ComboBoxChangeEvent.ChangeEventInputDevice.MOUSE); fireEvent(changeEvent); } } /** This listener is required to handle mouse moving events over the list. */ protected class ListMouseHandler implements MouseOverHandler, MouseOutHandler { /** {@inheritDoc} */ @Override public void onMouseOut(MouseOutEvent event) { if (getComboBox().isKeyPressed()) return; ((Widget) event.getSource()).removeStyleName("selected-row"); } /** {@inheritDoc} */ @Override public void onMouseOver(MouseOverEvent event) { if (getComboBox().isKeyPressed()) return; int index = getComboBox().getModel().getSelectedIndex(); if (index >= 0) getList().getWidget(index).removeStyleName("selected-row"); Widget sender = (Widget) event.getSource(); sender.addStyleName("selected-row"); setHighlightRow(getList().getWidgetIndex(sender)); } } /** * This scroll handler is invoked on any scrolling event caotured by the items list.<p/> * It check whether the scrolling position value is equal to the last item position and tries to * render the next page of data. */ protected class ListScrollHandler implements ScrollHandler { /** the list has been scrolled programatically */ private boolean autoScrollingEnabled; /** see class docs */ @Override public void onScroll(ScrollEvent event) { if (isLazyRenderingEnabled() && !autoScrollingEnabled && getList().getOffsetHeight() - getScrollPanel().getScrollPosition() <= getScrollPanel().getOffsetHeight()) { int firstItemOnNextPage = getItemCount() - 1; fillList(); //next page of data if (firstItemOnNextPage >= 0 && firstItemOnNextPage < getItemCount()) { autoScrollingEnabled = true; ensureVisible(getItem(firstItemOnNextPage)); } } else autoScrollingEnabled = false; } } /** * This handler is invoked on window resize and changes opened list popup panel position * according to new coordinates of the {@link ComboBox}. */ protected class ListWindowResizeHandler implements ResizeHandler { /** See class docs */ @Override public void onResize(ResizeEvent resizeEvent) { if (!isShowing()) { return; } int delta = getElement().getOffsetWidth() - getElement().getClientWidth(); getScrollPanel().setWidth((getComboBox().getOffsetWidth() - delta) + "px"); adjustSize(); } } /** * This handler spies for click events if the list is opened and hides it if there is any element clicked excepting * the combo box elements and list elements. */ protected class ClickSpyHandler implements Event.NativePreviewHandler { /** See class docs */ @Override public void onPreviewNativeEvent(Event.NativePreviewEvent nativePreviewEvent) { if (nativePreviewEvent.getTypeInt() != Event.ONCLICK) { return; } Element source = (Element) Element.as(nativePreviewEvent.getNativeEvent().getEventTarget()); if (!DOM.isOrHasChild(getElement(), source) && !DOM.isOrHasChild(getComboBox().getElement(), source)) { hide(); getComboBox().getChoiceButton().setDown(false); } } } }