Java tutorial
/* * Copyright 2000-2014 Vaadin Ltd. * * 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.vaadin.client.ui.dd; import com.google.gwt.core.client.GWT; import com.google.gwt.core.client.Scheduler; import com.google.gwt.core.client.Scheduler.RepeatingCommand; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.EventTarget; import com.google.gwt.dom.client.NativeEvent; import com.google.gwt.dom.client.Node; import com.google.gwt.dom.client.Style; 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.Event.NativePreviewEvent; import com.google.gwt.user.client.Event.NativePreviewHandler; import com.google.gwt.user.client.ui.RootPanel; import com.google.gwt.user.client.ui.Widget; import com.vaadin.client.ApplicationConnection; import com.vaadin.client.ComponentConnector; import com.vaadin.client.MouseEventDetailsBuilder; import com.vaadin.client.Profiler; import com.vaadin.client.UIDL; import com.vaadin.client.VConsole; import com.vaadin.client.ValueMap; import com.vaadin.client.WidgetUtil; import com.vaadin.client.ui.VOverlay; import com.vaadin.shared.ApplicationConstants; import com.vaadin.shared.MouseEventDetails; import com.vaadin.shared.ui.dd.DragEventType; /** * Helper class to manage the state of drag and drop event on Vaadin client * side. Can be used to implement most of the drag and drop operation * automatically via cross-browser event preview method or just as a helper when * implementing own low level drag and drop operation (like with HTML5 api). * <p> * Singleton. Only one drag and drop operation can be active anyways. Use * {@link #get()} to get instance. * * TODO cancel drag and drop if more than one touches !? */ public class VDragAndDropManager { public static final String ACTIVE_DRAG_SOURCE_STYLENAME = "v-active-drag-source"; /** * Implementation if this interface is provided as a parameter to * DDEventHandleStrategy methods. The mediator instance allows to manage * DnD. * * @since 7.4.4 */ public interface DDManagerMediator { /** * Returns DnD manager instance. */ VDragAndDropManager getManager(); /** * Returns current drag event. */ VDragEvent getDragEvent(); /** * Clean up server communication callback. */ void clearServerCallback(); } private final class DefaultDragAndDropEventHandler implements NativePreviewHandler { @Override public void onPreviewNativeEvent(NativePreviewEvent event) { if (getEventHandleStrategy().isDragInterrupted(event, managerMediator)) { // end drag if ESC is hit interruptDrag(); event.cancel(); event.getNativeEvent().preventDefault(); return; } int typeInt = event.getTypeInt(); if (typeInt == Event.ONKEYDOWN) { getEventHandleStrategy().handleKeyDownEvent(event, managerMediator); return; } NativeEvent nativeEvent = event.getNativeEvent(); currentDrag.setCurrentGwtEvent(nativeEvent); String display = getEventHandleStrategy().updateDragImage(event, managerMediator); Element targetElement = getEventHandleStrategy().getTargetElement(event, managerMediator); try { if (handleDragImage(targetElement, event)) { return; } } catch (RuntimeException e) { // ApplicationConnection.getConsole().log( // "ERROR during elementFromPoint hack."); throw e; } finally { getEventHandleStrategy().restoreDragImage(display, managerMediator, event); } getEventHandleStrategy().handleEvent(targetElement, event, managerMediator); } private boolean handleDragImage(Element target, NativePreviewEvent event) { if (!WidgetUtil.isTouchEvent(event.getNativeEvent()) && getDragElement() == null) { return false; } else if (target == null) { // ApplicationConnection.getConsole().log( // "Event on dragImage, ignored"); event.cancel(); event.getNativeEvent().stopPropagation(); return true; } else if (getEventHandleStrategy().handleDragImageEvent(target, event, managerMediator)) { return true; } else { // just update element over and let the actual // handling code do the thing // ApplicationConnection.getConsole().log( // "Target just modified on " // + event.getType()); currentDrag.setElementOver(target); return false; } } } /* * #13381, #14796. The drag only actually starts when the mouse move or * touch move event is more than 3 pixel away. */ public static final int MINIMUM_DISTANCE_TO_START_DRAG = 3; private static VDragAndDropManager instance; private HandlerRegistration handlerRegistration; private VDragEvent currentDrag; private DDManagerMediator managerMediator = new DDManagerMediator() { @Override public VDragAndDropManager getManager() { return VDragAndDropManager.this; } @Override public VDragEvent getDragEvent() { return currentDrag; } @Override public void clearServerCallback() { serverCallback = null; } }; private DDEventHandleStrategy eventHandleStrategy; /** * If dragging is currently on a drophandler, this field has reference to it */ private VDropHandler currentDropHandler; public VDropHandler getCurrentDropHandler() { return currentDropHandler; } /** * If drag and drop operation is not handled by {@link VDragAndDropManager}s * internal handler, this can be used to update current {@link VDropHandler} * . * * @param currentDropHandler */ public void setCurrentDropHandler(VDropHandler currentDropHandler) { this.currentDropHandler = currentDropHandler; } private VDragEventServerCallback serverCallback; private HandlerRegistration deferredStartRegistration; public static VDragAndDropManager get() { if (instance == null) { instance = GWT.create(VDragAndDropManager.class); } return instance; } /* Singleton */ protected VDragAndDropManager() { } private final NativePreviewHandler defaultDragAndDropEventHandler = new DefaultDragAndDropEventHandler(); /** * Flag to indicate if drag operation has really started or not. Null check * of currentDrag field is not enough as a lazy start may be pending. */ private boolean isStarted; /** * This method is used to start Vaadin client side drag and drop operation. * Operation may be started by virtually any Widget. * <p> * Cancels possible existing drag. TODO figure out if this is always a bug * if one is active. Maybe a good and cheap lifesaver thought. * <p> * If possible, method automatically detects current {@link VDropHandler} * and fires {@link VDropHandler#dragEnter(VDragEvent)} event on it. * <p> * May also be used to control the drag and drop operation. If this option * is used, {@link VDropHandler} is searched on mouse events and appropriate * methods on it called automatically. * * @param transferable * @param nativeEvent * @param handleDragEvents * if true, {@link VDragAndDropManager} handles the drag and drop * operation GWT event preview. * @return */ public VDragEvent startDrag(VTransferable transferable, final NativeEvent startEvent, final boolean handleDragEvents) { interruptDrag(); isStarted = false; currentDrag = new VDragEvent(transferable, startEvent); currentDrag.setCurrentGwtEvent(startEvent); final Command startDrag = new Command() { @Override public void execute() { isStarted = true; addActiveDragSourceStyleName(); VDropHandler dh = null; if (startEvent != null) { dh = findDragTarget(Element.as(currentDrag.getCurrentGwtEvent().getEventTarget())); } if (dh != null) { // drag has started on a DropHandler, kind of drag over // happens currentDropHandler = dh; dh.dragEnter(currentDrag); } if (handleDragEvents) { handlerRegistration = Event.addNativePreviewHandler(defaultDragAndDropEventHandler); if (dragElement != null && dragElement.getParentElement() == null) { attachDragElement(); } } // just capture something to prevent text selection in IE Event.setCapture(RootPanel.getBodyElement()); } private void addActiveDragSourceStyleName() { ComponentConnector dragSource = currentDrag.getTransferable().getDragSource(); dragSource.getWidget().addStyleName(ACTIVE_DRAG_SOURCE_STYLENAME); } }; final int eventType = Event.as(startEvent).getTypeInt(); if (handleDragEvents && (eventType == Event.ONMOUSEDOWN || eventType == Event.ONTOUCHSTART)) { // only really start drag event on mousemove deferredStartRegistration = Event.addNativePreviewHandler(new NativePreviewHandler() { private int startX = WidgetUtil.getTouchOrMouseClientX(currentDrag.getCurrentGwtEvent()); private int startY = WidgetUtil.getTouchOrMouseClientY(currentDrag.getCurrentGwtEvent()); @Override public void onPreviewNativeEvent(NativePreviewEvent event) { int typeInt = event.getTypeInt(); if (typeInt == -1 && event.getNativeEvent().getType().toLowerCase().contains("pointer")) { /* * Ignore PointerEvents since IE10 and IE11 send * also MouseEvents for backwards compatibility. */ return; } switch (typeInt) { case Event.ONMOUSEOVER: if (dragElement == null) { break; } EventTarget currentEventTarget = event.getNativeEvent().getCurrentEventTarget(); if (Node.is(currentEventTarget) && !dragElement.isOrHasChild(Node.as(currentEventTarget))) { // drag image appeared below, ignore break; } case Event.ONKEYDOWN: case Event.ONKEYPRESS: case Event.ONKEYUP: case Event.ONBLUR: case Event.ONFOCUS: // don't cancel possible drag start break; case Event.ONMOUSEOUT: if (dragElement == null) { break; } EventTarget relatedEventTarget = event.getNativeEvent().getRelatedEventTarget(); if (Node.is(relatedEventTarget) && !dragElement.isOrHasChild(Node.as(relatedEventTarget))) { // drag image appeared below, ignore break; } case Event.ONMOUSEMOVE: case Event.ONTOUCHMOVE: int currentX = WidgetUtil.getTouchOrMouseClientX(event.getNativeEvent()); int currentY = WidgetUtil.getTouchOrMouseClientY(event.getNativeEvent()); if (Math.abs(startX - currentX) > MINIMUM_DISTANCE_TO_START_DRAG || Math.abs(startY - currentY) > MINIMUM_DISTANCE_TO_START_DRAG) { ensureDeferredRegistrationCleanup(); currentDrag.setCurrentGwtEvent(event.getNativeEvent()); startDrag.execute(); } break; default: ensureDeferredRegistrationCleanup(); currentDrag = null; clearDragElement(); break; } } }); } else { startDrag.execute(); } return currentDrag; } protected void updateDragImagePosition(NativeEvent gwtEvent, Element dragImage) { if (gwtEvent != null && dragImage != null) { Style style = dragImage.getStyle(); int clientY = WidgetUtil.getTouchOrMouseClientY(gwtEvent); int clientX = WidgetUtil.getTouchOrMouseClientX(gwtEvent); style.setTop(clientY, Unit.PX); style.setLeft(clientX, Unit.PX); } } /** * First seeks the widget from this element, then iterates widgets until one * implement HasDropHandler. Returns DropHandler from that. * * @param element * @return */ protected VDropHandler findDragTarget(Element element) { try { Widget w = WidgetUtil.findWidget(element, null); if (w == null) { return null; } while (!(w instanceof VHasDropHandler) || !isDropEnabled((VHasDropHandler) w)) { w = w.getParent(); if (w == null) { break; } } if (w == null) { return null; } else { VDropHandler dh = ((VHasDropHandler) w).getDropHandler(); return dh; } } catch (Exception e) { // ApplicationConnection.getConsole().log( // "FIXME: Exception when detecting drop handler"); // e.printStackTrace(); return null; } } /** * Checks if the given {@link VHasDropHandler} really is able to accept * drops. */ private static boolean isDropEnabled(VHasDropHandler target) { VDropHandler dh = target.getDropHandler(); return dh != null && dh.getConnector().isEnabled(); } /** * Drag is ended (drop happened) on current drop handler. Calls drop method * on current drop handler and does appropriate cleanup. */ public void endDrag() { endDrag(true); } /** * The drag and drop operation is ended, but drop did not happen. If * operation is currently on a drop handler, its dragLeave method is called * and appropriate cleanup happens. */ public void interruptDrag() { endDrag(false); } private void endDrag(boolean doDrop) { ensureDeferredRegistrationCleanup(); ensureHandlerRegistrationCleanup(); boolean sendTransferableToServer = false; if (currentDropHandler != null) { if (doDrop) { // we have dropped on a drop target sendTransferableToServer = currentDropHandler.drop(currentDrag); if (sendTransferableToServer) { doRequest(DragEventType.DROP); /* * Clean active source class name deferred until response is * handled. E.g. hidden on start, removed in drophandler -> * would flicker in case removed eagerly. */ final ComponentConnector dragSource = currentDrag.getTransferable().getDragSource(); final ApplicationConnection client = currentDropHandler.getApplicationConnection(); Scheduler.get().scheduleFixedDelay(new RepeatingCommand() { @Override public boolean execute() { if (!client.getMessageSender().hasActiveRequest()) { removeActiveDragSourceStyleName(dragSource); return false; } return true; } }, 30); } } else { currentDropHandler.dragLeave(currentDrag); currentDrag.setCurrentGwtEvent(null); } currentDropHandler = null; serverCallback = null; visitId = 0; // reset to ignore ongoing server check } /* * Remove class name indicating drag source when server visit is done * iff server visit was not initiated. Otherwise it will be removed once * the server visit is done. */ if (!sendTransferableToServer && currentDrag != null) { removeActiveDragSourceStyleName(currentDrag.getTransferable().getDragSource()); } currentDrag = null; clearDragElement(); // release the capture (set to prevent text selection in IE) Event.releaseCapture(RootPanel.getBodyElement()); } private void ensureHandlerRegistrationCleanup() { if (handlerRegistration != null) { handlerRegistration.removeHandler(); handlerRegistration = null; } } private void ensureDeferredRegistrationCleanup() { if (deferredStartRegistration != null) { deferredStartRegistration.removeHandler(); deferredStartRegistration = null; } } private void removeActiveDragSourceStyleName(ComponentConnector dragSource) { dragSource.getWidget().removeStyleName(ACTIVE_DRAG_SOURCE_STYLENAME); } private void clearDragElement() { if (dragElement != null) { if (dragElement.getParentElement() != null) { dragElement.removeFromParent(); } dragElement = null; } } private int visitId = 0; private Element dragElement; /** * Visits server during drag and drop procedure. Transferable and event type * is given to server side counterpart of DropHandler. * * If another server visit is started before the current is received, the * current is just dropped. TODO consider if callback should have * interrupted() method for cleanup. * * @param acceptCallback */ public void visitServer(VDragEventServerCallback acceptCallback) { doRequest(DragEventType.ENTER); serverCallback = acceptCallback; } private void doRequest(DragEventType drop) { if (currentDropHandler == null) { return; } ComponentConnector paintable = currentDropHandler.getConnector(); ApplicationConnection client = currentDropHandler.getApplicationConnection(); /* * For drag events we are using special id that are routed to * "drag service" which then again finds the corresponding DropHandler * on server side. * * TODO add rest of the data in Transferable * * TODO implement partial updates to Transferable (currently the whole * Transferable is sent on each request) */ visitId++; client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "visitId", visitId, false); client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "eventId", currentDrag.getEventId(), false); client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "dhowner", paintable, false); VTransferable transferable = currentDrag.getTransferable(); client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "component", transferable.getDragSource(), false); client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "type", drop.ordinal(), false); if (currentDrag.getCurrentGwtEvent() != null) { try { MouseEventDetails mouseEventDetails = MouseEventDetailsBuilder .buildMouseEventDetails(currentDrag.getCurrentGwtEvent()); currentDrag.getDropDetails().put("mouseEvent", mouseEventDetails.serialize()); } catch (Exception e) { // NOP, (at least oophm on Safari) can't serialize html dd event // to mouseevent } } else { currentDrag.getDropDetails().put("mouseEvent", null); } client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "evt", currentDrag.getDropDetails(), false); client.updateVariable(ApplicationConstants.DRAG_AND_DROP_CONNECTOR_ID, "tra", transferable.getVariableMap(), true); } public void handleServerResponse(ValueMap valueMap) { if (serverCallback == null) { return; } Profiler.enter("VDragAndDropManager.handleServerResponse"); UIDL uidl = (UIDL) valueMap.cast(); int visitId = uidl.getIntAttribute("visitId"); if (this.visitId == visitId) { serverCallback.handleResponse(uidl.getBooleanAttribute("accepted"), uidl); serverCallback = null; } runDeferredCommands(); Profiler.leave("VDragAndDropManager.handleServerResponse"); } /** * Returns DnD strategy to handle native preview events used by the manager. * * Subclasses can override this method to return custom strategy or use GWT * deferred binding. * * @return internal DnD native preview event handler */ protected DDEventHandleStrategy getEventHandleStrategy() { if (eventHandleStrategy == null) { eventHandleStrategy = GWT.create(DDEventHandleStrategy.class); } return eventHandleStrategy; } private void runDeferredCommands() { if (deferredCommand != null) { Command command = deferredCommand; deferredCommand = null; command.execute(); if (!isBusy()) { runDeferredCommands(); } } } void setDragElement(Element node) { if (currentDrag != null) { if (dragElement != null && dragElement != node) { clearDragElement(); } else if (node == dragElement) { return; } dragElement = node; dragElement.addClassName("v-drag-element"); updateDragImagePosition(currentDrag.getCurrentGwtEvent(), dragElement); if (isStarted) { attachDragElement(); } } } Element getDragElement() { return dragElement; } private void attachDragElement() { if (dragElement != null && dragElement.getParentElement() == null) { ApplicationConnection connection = getCurrentDragApplicationConnection(); Element dragImageParent; if (connection == null) { VConsole.error( "Could not determine ApplicationConnection for current drag operation. The drag image will likely look broken"); dragImageParent = RootPanel.getBodyElement(); } else { dragImageParent = VOverlay.getOverlayContainer(connection); } dragImageParent.appendChild(dragElement); } } private Command deferredCommand; private boolean isBusy() { return serverCallback != null; } protected ApplicationConnection getCurrentDragApplicationConnection() { if (currentDrag == null) { return null; } final ComponentConnector dragSource = currentDrag.getTransferable().getDragSource(); if (dragSource == null) { return null; } return dragSource.getConnection(); } /** * Method to que tasks until all dd related server visits are done * * @param command */ private void defer(Command command) { deferredCommand = command; } /** * Method to execute commands when all existing dd related tasks are * completed (some may require server visit). * <p> * Using this method may be handy if criterion that uses lazy initialization * are used. Check * <p> * TODO Optimization: consider if we actually only need to keep the last * command in queue here. * * @param command */ public void executeWhenReady(Command command) { if (isBusy()) { defer(command); } else { command.execute(); } } }