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; import java.util.ArrayList; import java.util.Arrays; import java.util.HashSet; import com.google.gwt.animation.client.Animation; import com.google.gwt.core.client.Duration; import com.google.gwt.core.client.GWT; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.NativeEvent; import com.google.gwt.dom.client.Node; import com.google.gwt.dom.client.NodeList; import com.google.gwt.dom.client.Style; import com.google.gwt.dom.client.Touch; import com.google.gwt.event.dom.client.ScrollHandler; import com.google.gwt.event.dom.client.TouchStartEvent; import com.google.gwt.event.dom.client.TouchStartHandler; import com.google.gwt.event.shared.HandlerRegistration; 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.Widget; import com.vaadin.client.BrowserInfo; import com.vaadin.client.VConsole; /** * Provides one finger touch scrolling for elements with once scrollable * elements inside. One widget can have several of these scrollable elements. * Scrollable elements are provided in the constructor. Users must pass * touchStart events to this delegate, from there on the delegate takes over * with an event preview. Other touch events needs to be sunken though. * <p> * This is bit similar as Scroller class in GWT expenses example, but ideas * drawn from iscroll.js project: * <ul> * <li>uses GWT event mechanism. * <li>uses modern CSS trick during scrolling for smoother experience: * translate3d and transitions * </ul> * <p> * Scroll event should only happen when the "touch scrolling actually ends". * Later we might also tune this so that a scroll event happens if user stalls * her finger long enought. * * TODO static getter for active touch scroll delegate. Components might need to * prevent scrolling in some cases. Consider Table with drag and drop, or drag * and drop in scrollable area. Optimal implementation might be to start the * drag and drop only if user keeps finger down for a moment, otherwise do the * scroll. In this case, the draggable component would need to cancel scrolling * in a timer after touchstart event and take over from there. * * TODO support scrolling horizontally * * TODO cancel if user add second finger to the screen (user expects a gesture). * * TODO "scrollbars", see e.g. iscroll.js * * TODO write an email to sjobs t apple dot com and beg for this feature to be * built into webkit. Seriously, we should try to lobbying this to webkit folks. * This sure ain't our business to implement this with javascript. * * TODO collect all general touch related constant to better place. * * @author Matti Tahvonen, Vaadin Ltd */ public class TouchScrollDelegate implements NativePreviewHandler { private static final double FRICTION = 0.002; private static final double DECELERATION = 0.002; private static final int MAX_DURATION = 1500; private int origY; private HashSet<Element> scrollableElements; private Element scrolledElement; private int origScrollTop; private HandlerRegistration handlerRegistration; private double lastAnimatedTranslateY; private int lastClientY; private int deltaScrollPos; private boolean transitionOn = false; private int finalScrollTop; private ArrayList<Element> layers; private boolean moved; private ScrollHandler scrollHandler; private static TouchScrollDelegate activeScrollDelegate; private static final boolean androidWithBrokenScrollTop = BrowserInfo.get().isAndroidWithBrokenScrollTop(); /** * A helper class for making a widget scrollable. Uses native scrolling if * supported by the browser, otherwise registers a touch start handler * delegating to a TouchScrollDelegate instance. */ public static class TouchScrollHandler implements TouchStartHandler { private static final String SCROLLABLE_CLASSNAME = "v-scrollable"; private TouchScrollDelegate delegate; private final boolean requiresDelegate = BrowserInfo.get().requiresTouchScrollDelegate(); private Widget widget; /** * Constructs a scroll handler. You must call * {@link #init(Widget, Element...)} before using the scroll handler. */ public TouchScrollHandler() { } /** * Attaches the scroll handler to the widget. This method must be called * before calling any other methods in this class. * * @param widget * The widget that contains scrollable elements * @param scrollables * The elements of the widget that should be scrollable. * * @deprecated Use {@link GWT#create(Class)} and * {@link #init(Widget, Element...)} instead of this * constructor to enable overriding. */ @Deprecated public TouchScrollHandler(Widget widget, Element... scrollables) { this(); init(widget, scrollables); } /** * Attaches the scroll handler to the widget. This method must be called * once before calling any other method in this class. * * @param widget * The widget that contains scrollable elements * @param scrollables * The elements of the widget that should be scrollable. */ public void init(Widget widget, Element... scrollables) { this.widget = widget; if (requiresDelegate()) { delegate = new TouchScrollDelegate(); widget.addDomHandler(this, TouchStartEvent.getType()); } else { delegate = null; } setElements(scrollables); } @Override public void onTouchStart(TouchStartEvent event) { assert delegate != null; delegate.onTouchStart(event); } public void debug(Element e) { VConsole.log("Classes: " + e.getClassName() + " overflow: " + e.getStyle().getProperty("overflow") + " w-o-s: " + e.getStyle().getProperty("WebkitOverflowScrolling")); } /** * Registers the given element as scrollable. */ public void addElement(Element scrollable) { scrollable.addClassName(SCROLLABLE_CLASSNAME); if (requiresDelegate()) { delegate.scrollableElements.add(scrollable); } } /** * Unregisters the given element as scrollable. Should be called when a * previously-registered element is removed from the DOM to prevent * memory leaks. */ public void removeElement(Element scrollable) { scrollable.removeClassName(SCROLLABLE_CLASSNAME); if (requiresDelegate()) { delegate.scrollableElements.remove(scrollable); } } /** * Registers the given elements as scrollable, removing previously * registered scrollables from this handler. * * @param scrollables * The elements that should be scrollable */ public void setElements(Element... scrollables) { if (requiresDelegate()) { for (Element e : delegate.scrollableElements) { e.removeClassName(SCROLLABLE_CLASSNAME); } delegate.scrollableElements.clear(); } for (Element e : scrollables) { addElement(e); } } /** * Checks if a delegate for scrolling is required or if the native * scrolling of the device should be used. By default, relies on * {@link BrowserInfo#requiresTouchScrollDelegate()}, override to change * the behavior. * * @return true if a Javascript delegate should be used for scrolling, * false to use the native scrolling of the device */ protected boolean requiresDelegate() { return requiresDelegate; } /** * @return The widget this {@link TouchScrollHandler} is connected to. */ protected Widget getWidget() { return widget; } } /** * Makes the given elements scrollable, either natively or by using a * TouchScrollDelegate, depending on platform capabilities. * * @param widget * The widget that contains scrollable elements * @param scrollables * The elements inside the widget that should be scrollable * @return A scroll handler for the given widget. */ public static TouchScrollHandler enableTouchScrolling(Widget widget, Element... scrollables) { TouchScrollHandler handler = GWT.create(TouchScrollHandler.class); handler.init(widget, scrollables); return handler; } public TouchScrollDelegate(Element... elements) { setElements(elements); } public void setScrollHandler(ScrollHandler scrollHandler) { this.scrollHandler = scrollHandler; } public static TouchScrollDelegate getActiveScrollDelegate() { return activeScrollDelegate; } /** * Has user moved the touch. * * @return */ public boolean isMoved() { return moved; } /** * Forces the scroll delegate to cancels scrolling process. Can be called by * users if they e.g. decide to handle touch event by themselves after all * (e.g. a pause after touch start before moving touch -> interpreted as * long touch/click or drag start). */ public void stopScrolling() { handlerRegistration.removeHandler(); handlerRegistration = null; if (moved) { moveTransformationToScrolloffset(); } else { activeScrollDelegate = null; } } public void onTouchStart(TouchStartEvent event) { if (activeScrollDelegate == null && event.getTouches().length() == 1) { NativeEvent nativeEvent = event.getNativeEvent(); doTouchStart(nativeEvent); } else { /* * Touch scroll is currenly on (possibly bouncing). Ignore. */ } } private void doTouchStart(NativeEvent nativeEvent) { if (transitionOn) { momentum.cancel(); } Touch touch = nativeEvent.getTouches().get(0); if (detectScrolledElement(touch)) { VConsole.log("TouchDelegate takes over"); nativeEvent.stopPropagation(); handlerRegistration = Event.addNativePreviewHandler(this); activeScrollDelegate = this; origY = touch.getClientY(); yPositions[0] = origY; eventTimeStamps[0] = getTimeStamp(); nextEvent = 1; origScrollTop = getScrollTop(); VConsole.log("ST" + origScrollTop); moved = false; // event.preventDefault(); // event.stopPropagation(); } } private int getScrollTop() { if (androidWithBrokenScrollTop) { if (scrolledElement.getPropertyJSO("_vScrollTop") != null) { return scrolledElement.getPropertyInt("_vScrollTop"); } return 0; } return scrolledElement.getScrollTop(); } private void onTransitionEnd() { if (finalScrollTop < 0) { animateToScrollPosition(0, finalScrollTop); finalScrollTop = 0; } else if (finalScrollTop > getMaxFinalY()) { animateToScrollPosition(getMaxFinalY(), finalScrollTop); finalScrollTop = getMaxFinalY(); } else { moveTransformationToScrolloffset(); } } private void animateToScrollPosition(int to, int from) { int dist = Math.abs(to - from); int time = getAnimationTimeForDistance(dist); if (time <= 0) { time = 1; // get animation and transition end event } VConsole.log("Animate " + time + " " + from + " " + to); int translateTo = -to + origScrollTop; int fromY = -from + origScrollTop; if (androidWithBrokenScrollTop) { fromY -= origScrollTop; translateTo -= origScrollTop; } translateTo(time, fromY, translateTo); } private int getAnimationTimeForDistance(int dist) { return 350; // 350ms seems to work quite fine for all distances // if (dist < 0) { // dist = -dist; // } // return MAX_DURATION * dist / (scrolledElement.getClientHeight() * 3); } /** * Called at the end of scrolling. Moves possible translate values to * scrolltop, causing onscroll event. */ private void moveTransformationToScrolloffset() { if (androidWithBrokenScrollTop) { scrolledElement.setPropertyInt("_vScrollTop", finalScrollTop); if (scrollHandler != null) { scrollHandler.onScroll(null); } } else { for (Element el : layers) { Style style = el.getStyle(); style.setProperty("webkitTransform", "translate3d(0,0,0)"); } scrolledElement.setScrollTop(finalScrollTop); } activeScrollDelegate = null; handlerRegistration.removeHandler(); handlerRegistration = null; } /** * Detects if a touch happens on a predefined element and the element has * something to scroll. * * @param touch * @return */ private boolean detectScrolledElement(Touch touch) { Element target = touch.getTarget().cast(); for (Element el : scrollableElements) { if (el.isOrHasChild(target) && el.getScrollHeight() > el.getClientHeight()) { scrolledElement = el; layers = getElements(scrolledElement); return true; } } return false; } public static ArrayList<Element> getElements(Element scrolledElement2) { NodeList<Node> childNodes = scrolledElement2.getChildNodes(); ArrayList<Element> l = new ArrayList<Element>(); for (int i = 0; i < childNodes.getLength(); i++) { Node item = childNodes.getItem(i); if (item.getNodeType() == Node.ELEMENT_NODE) { l.add((Element) item); } } return l; } private void onTouchMove(NativeEvent event) { if (!moved) { double l = (getTimeStamp() - eventTimeStamps[0]); VConsole.log(l + " ms from start to move"); } boolean handleMove = readPositionAndSpeed(event); if (handleMove) { int deltaScrollTop = origY - lastClientY; int finalPos = origScrollTop + deltaScrollTop; if (finalPos > getMaxFinalY()) { // spring effect at the end int overscroll = (deltaScrollTop + origScrollTop) - getMaxFinalY(); overscroll = overscroll / 2; if (overscroll > getMaxOverScroll()) { overscroll = getMaxOverScroll(); } deltaScrollTop = getMaxFinalY() + overscroll - origScrollTop; } else if (finalPos < 0) { // spring effect at the beginning int overscroll = finalPos / 2; if (-overscroll > getMaxOverScroll()) { overscroll = -getMaxOverScroll(); } deltaScrollTop = overscroll - origScrollTop; } quickSetScrollPosition(0, deltaScrollTop); moved = true; event.preventDefault(); event.stopPropagation(); } } private void quickSetScrollPosition(int deltaX, int deltaY) { deltaScrollPos = deltaY; if (androidWithBrokenScrollTop) { deltaY += origScrollTop; translateTo(-deltaY); } else { translateTo(-deltaScrollPos); } } private static final int EVENTS_FOR_SPEED_CALC = 3; public static final int SIGNIFICANT_MOVE_THRESHOLD = 3; private int[] yPositions = new int[EVENTS_FOR_SPEED_CALC]; private double[] eventTimeStamps = new double[EVENTS_FOR_SPEED_CALC]; private int nextEvent = 0; private Animation momentum; /** * * @param event * @return */ private boolean readPositionAndSpeed(NativeEvent event) { Touch touch = event.getChangedTouches().get(0); lastClientY = touch.getClientY(); int eventIndx = nextEvent++; eventIndx = eventIndx % EVENTS_FOR_SPEED_CALC; eventTimeStamps[eventIndx] = getTimeStamp(); yPositions[eventIndx] = lastClientY; return isMovedSignificantly(); } private boolean isMovedSignificantly() { return moved ? moved : Math.abs(origY - lastClientY) >= SIGNIFICANT_MOVE_THRESHOLD; } private void onTouchEnd(NativeEvent event) { if (!moved) { activeScrollDelegate = null; handlerRegistration.removeHandler(); handlerRegistration = null; return; } int currentY = origScrollTop + deltaScrollPos; int maxFinalY = getMaxFinalY(); int pixelsToMove; int finalY; int duration = -1; if (currentY > maxFinalY) { // we are over the max final pos, animate to end pixelsToMove = maxFinalY - currentY; finalY = maxFinalY; } else if (currentY < 0) { // we are below the max final pos, animate to beginning pixelsToMove = -currentY; finalY = 0; } else { double pixelsPerMs = calculateSpeed(); // we are currently within scrollable area, calculate pixels that // we'll move due to momentum VConsole.log("pxPerMs" + pixelsPerMs); pixelsToMove = (int) (0.5 * pixelsPerMs * pixelsPerMs / FRICTION); if (pixelsPerMs < 0) { pixelsToMove = -pixelsToMove; } // VConsole.log("pixels to move" + pixelsToMove); finalY = currentY + pixelsToMove; if (finalY > maxFinalY + getMaxOverScroll()) { // VConsole.log("To max overscroll"); finalY = getMaxFinalY() + getMaxOverScroll(); int fixedPixelsToMove = finalY - currentY; pixelsToMove = fixedPixelsToMove; } else if (finalY < 0 - getMaxOverScroll()) { // VConsole.log("to min overscroll"); finalY = -getMaxOverScroll(); int fixedPixelsToMove = finalY - currentY; pixelsToMove = fixedPixelsToMove; } else { duration = (int) (Math.abs(pixelsPerMs / DECELERATION)); } } if (duration == -1) { // did not keep in side borders or was outside borders, calculate // a good enough duration based on pixelsToBeMoved. duration = getAnimationTimeForDistance(pixelsToMove); } if (duration > MAX_DURATION) { VConsole.log("Max animation time. " + duration); duration = MAX_DURATION; } finalScrollTop = finalY; if (Math.abs(pixelsToMove) < 3 || duration < 20) { VConsole.log("Small 'momentum' " + pixelsToMove + " | " + duration + " Skipping animation,"); moveTransformationToScrolloffset(); return; } int translateTo = -finalY + origScrollTop; int fromY = -currentY + origScrollTop; if (androidWithBrokenScrollTop) { fromY -= origScrollTop; translateTo -= origScrollTop; } translateTo(duration, fromY, translateTo); } private double calculateSpeed() { if (nextEvent < EVENTS_FOR_SPEED_CALC) { VConsole.log("Not enough data for speed calculation"); // not enough data for decent speed calculation, no momentum :-( return 0; } int idx = nextEvent % EVENTS_FOR_SPEED_CALC; final int firstPos = yPositions[idx]; final double firstTs = eventTimeStamps[idx]; idx += EVENTS_FOR_SPEED_CALC; idx--; idx = idx % EVENTS_FOR_SPEED_CALC; final int lastPos = yPositions[idx]; final double lastTs = eventTimeStamps[idx]; // speed as in change of scrolltop == -speedOfTouchPos return (firstPos - lastPos) / (lastTs - firstTs); } /** * Note positive scrolltop moves layer up, positive translate moves layer * down. */ private void translateTo(double translateY) { for (Element el : layers) { Style style = el.getStyle(); style.setProperty("webkitTransform", "translate3d(0px," + translateY + "px,0px)"); } } /** * Note positive scrolltop moves layer up, positive translate moves layer * down. * * @param duration */ private void translateTo(int duration, final int fromY, final int finalY) { if (duration > 0) { transitionOn = true; momentum = new Animation() { @Override protected void onUpdate(double progress) { lastAnimatedTranslateY = (fromY + (finalY - fromY) * progress); translateTo(lastAnimatedTranslateY); } @Override protected double interpolate(double progress) { return 1 + Math.pow(progress - 1, 3); } @Override protected void onComplete() { super.onComplete(); transitionOn = false; onTransitionEnd(); } @Override protected void onCancel() { int delta = (int) (finalY - lastAnimatedTranslateY); finalScrollTop -= delta; moveTransformationToScrolloffset(); transitionOn = false; } }; momentum.run(duration); } } private int getMaxOverScroll() { return androidWithBrokenScrollTop ? 0 : scrolledElement.getClientHeight() / 3; } private int getMaxFinalY() { return scrolledElement.getScrollHeight() - scrolledElement.getClientHeight(); } @Override public void onPreviewNativeEvent(NativePreviewEvent event) { int typeInt = event.getTypeInt(); if (transitionOn) { /* * TODO allow starting new events. See issue in onTouchStart */ event.cancel(); if (typeInt == Event.ONTOUCHSTART) { doTouchStart(event.getNativeEvent()); } return; } switch (typeInt) { case Event.ONTOUCHMOVE: if (!event.isCanceled()) { onTouchMove(event.getNativeEvent()); if (moved) { event.cancel(); } } break; case Event.ONTOUCHEND: case Event.ONTOUCHCANCEL: if (!event.isCanceled()) { if (moved) { event.cancel(); } onTouchEnd(event.getNativeEvent()); } break; case Event.ONMOUSEMOVE: if (moved) { // no debug message, mobile safari generates these for some // compatibility purposes. event.cancel(); } break; default: VConsole.log("Non touch event:" + event.getNativeEvent().getType()); event.cancel(); break; } } public void setElements(Element[] elements) { scrollableElements = new HashSet<Element>(Arrays.asList(elements)); } /** * long calcucation are not very efficient in GWT, so this helper method * returns timestamp in double. * * @return */ public static double getTimeStamp() { return Duration.currentTimeMillis(); } }