Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.waveprotocol.wave.client.autohide; import com.google.gwt.dom.client.Element; import com.google.gwt.event.dom.client.KeyCodes; import com.google.gwt.event.logical.shared.ResizeEvent; import com.google.gwt.event.logical.shared.ResizeHandler; import com.google.gwt.event.logical.shared.ValueChangeEvent; import com.google.gwt.event.logical.shared.ValueChangeHandler; import com.google.gwt.event.shared.HandlerRegistration; import com.google.gwt.user.client.Event; import com.google.gwt.user.client.History; import com.google.gwt.user.client.Window; import com.google.gwt.user.client.Event.NativePreviewEvent; import com.google.gwt.user.client.Event.NativePreviewHandler; import org.waveprotocol.wave.client.common.util.SignalEvent; import org.waveprotocol.wave.client.common.util.SignalEventImpl; import org.waveprotocol.wave.client.common.util.SignalEvent.KeySignalType; import java.util.ArrayList; import java.util.List; /** * Detects auto-hide events by installing an event preview. * * This registrar handles multiple simultaneous AutoHiders by treating the ones * opened later as 'higher up' than the ones opened earlier, and so events that * cause auto-hides will be routed to the higher AutoHiders first. This * behaviour can be changed in the future by introducing a more sophisticated * structure to store the AutoHiders in and, for instance, having each AutoHider * declaring a parent AutoHider. * */ public class EventPreviewAutoHiderRegistrar implements AutoHiderRegistrar, NativePreviewHandler, ResizeHandler, ValueChangeHandler<String> { /** * List of AutoHiders that currently need to be considered when interpreting * incoming events. */ private final List<AutoHider> autoHiders = new ArrayList<AutoHider>(); /** * Used to deregister this object from the event preview when there are no * registered AutoHiders. */ private HandlerRegistration eventPreviewRegistration; private HandlerRegistration onResizeRegistration; private HandlerRegistration onHistoryRegistration; @Override public void registerAutoHider(final AutoHider autoHider) { autoHider.setRegistered(true); autoHiders.add(autoHider); if (eventPreviewRegistration == null) { eventPreviewRegistration = Event.addNativePreviewHandler(this); } if (onResizeRegistration == null) { onResizeRegistration = Window.addResizeHandler(this); } if (onHistoryRegistration == null) { onHistoryRegistration = History.addValueChangeHandler(this); } } @Override public void deregisterAutoHider(AutoHider autoHider) { autoHiders.remove(autoHider); autoHider.setRegistered(false); if (autoHiders.isEmpty()) { if (eventPreviewRegistration != null) { eventPreviewRegistration.removeHandler(); eventPreviewRegistration = null; } if (onResizeRegistration != null) { onResizeRegistration.removeHandler(); onResizeRegistration = null; } if (onHistoryRegistration != null) { onHistoryRegistration.removeHandler(); onHistoryRegistration = null; } } } @Override public void onPreviewNativeEvent(NativePreviewEvent previewEvent) { if (autoHiders.isEmpty()) { return; } // TODO(danilatos,user,user): Push signal down a layer - clean this up. Event event = Event.as(previewEvent.getNativeEvent()); int lowLevelType = event.getTypeInt(); // TODO(danilatos): Insert this logic deeply rather than // sprinkling it in event handlers. Also the return value // of onEventPreview is the reverse of signal handlers. SignalEvent signal = SignalEventImpl.create(event, false); if (signal == null) { return; } // Key events (excluding escape) and mousewheel events use hideTopmostAutoHiderForKeyEvent if (lowLevelType == Event.ONMOUSEWHEEL || signal.isKeyEvent()) { if (hideTopmostAutoHiderForKeyEvent(false)) { // TODO(user): We don't call previewEvent.cancel() here, since for the floating-buttons // menu we want, for example, space-bar to still shift focus to the next blip. // The to-do is to audit the previewEvent.cancel call below and see why it's there (and if // it's not needed, eliminate it). return; } } // Pressing escape at any time causes us to close and discard the event. if (signal.getKeySignalType() == KeySignalType.NOEFFECT && event.getKeyCode() == KeyCodes.KEY_ESCAPE) { if (hideTopmostAutoHiderForKeyEvent(true)) { previewEvent.cancel(); return; } } // Click events and mouse-wheel events that fall through use hideAllAfter. if (lowLevelType == Event.ONMOUSEDOWN || lowLevelType == Event.ONMOUSEWHEEL) { hideAllAfter(signal.getTarget()); } // Otherwise we don't do anything and the event continues as usual. } /** * Causes all AutoHiders after the one that contains the given element to hide. * * @param target An element. */ private void hideAllAfter(Element target) { List<AutoHider> toHide = new ArrayList<AutoHider>(); for (int i = autoHiders.size() - 1; i >= 0; i--) { AutoHider autoHider = autoHiders.get(i); if (autoHider.doesContain(target)) { break; } toHide.add(autoHider); } for (AutoHider autoHider : toHide) { autoHider.hide(); } } /** * Hides the topmost AutoHider that is supposed to hide on key events. */ private boolean hideTopmostAutoHiderForKeyEvent(boolean keyIsEscape) { for (int i = autoHiders.size() - 1; i >= 0; i--) { AutoHider autoHider = autoHiders.get(i); if (autoHider.shouldHideOnAnyKey() || (keyIsEscape && autoHider.shouldHideOnEscape())) { autoHider.hide(); return true; } } return false; } @Override public void onResize(ResizeEvent event) { List<AutoHider> toHide = new ArrayList<AutoHider>(); for (AutoHider autoHider : autoHiders) { if (autoHider.shouldHideOnWindowResize()) { toHide.add(autoHider); } } for (AutoHider autoHider : toHide) { autoHider.hide(); } } @Override public void onValueChange(ValueChangeEvent<String> event) { List<AutoHider> toHide = new ArrayList<AutoHider>(); for (AutoHider autoHider : autoHiders) { if (autoHider.shouldHideOnHistoryEvent()) { toHide.add(autoHider); } } for (AutoHider autoHider : toHide) { autoHider.hide(); } } }