Java tutorial
package com.badlogic.gdx.scenes.scene2d.utils; import com.badlogic.gdx.scenes.scene2d.Actor; import com.badlogic.gdx.scenes.scene2d.utils.ChangeListener.ChangeEvent; import com.badlogic.gdx.utils.Array; import com.badlogic.gdx.utils.OrderedSet; import com.badlogic.gdx.utils.Pools; import java.util.Iterator; /** Manages selected objects. Optionally fires a {@link ChangeEvent} on an actor. Selection changes can be vetoed via * {@link ChangeEvent#cancel()}. * @author Nathan Sweet */ public class Selection<T> implements Disableable, Iterable<T> { private Actor actor; final OrderedSet<T> selected = new OrderedSet(); private final OrderedSet<T> old = new OrderedSet(); boolean isDisabled; private boolean toggle; boolean multiple; boolean required; private boolean programmaticChangeEvents = true; T lastSelected; /** @param actor An actor to fire {@link ChangeEvent} on when the selection changes, or null. */ public void setActor(Actor actor) { this.actor = actor; } /** Selects or deselects the specified item based on how the selection is configured, whether ctrl is currently pressed, etc. * This is typically invoked by user interaction. */ public void choose(T item) { if (item == null) throw new IllegalArgumentException("item cannot be null."); if (isDisabled) return; snapshot(); try { if ((toggle || (!required && selected.size == 1) || UIUtils.ctrl()) && selected.contains(item)) { if (required && selected.size == 1) return; selected.remove(item); lastSelected = null; } else { boolean modified = false; if (!multiple || (!toggle && !UIUtils.ctrl())) { if (selected.size == 1 && selected.contains(item)) return; modified = selected.size > 0; selected.clear(); } if (!selected.add(item) && !modified) return; lastSelected = item; } if (fireChangeEvent()) revert(); } finally { cleanup(); } } public boolean hasItems() { return selected.size > 0; } public boolean isEmpty() { return selected.size == 0; } public int size() { return selected.size; } public OrderedSet<T> items() { return selected; } /** Returns the first selected item, or null. */ public T first() { return selected.size == 0 ? null : selected.first(); } void snapshot() { old.clear(); old.addAll(selected); } void revert() { selected.clear(); selected.addAll(old); } void cleanup() { old.clear(32); } /** Sets the selection to only the specified item. */ public void set(T item) { if (item == null) throw new IllegalArgumentException("item cannot be null."); if (selected.size == 1 && selected.first() == item) return; snapshot(); selected.clear(); selected.add(item); if (programmaticChangeEvents && fireChangeEvent()) revert(); else lastSelected = item; cleanup(); } public void setAll(Array<T> items) { boolean added = false; snapshot(); selected.clear(); for (int i = 0, n = items.size; i < n; i++) { T item = items.get(i); if (item == null) throw new IllegalArgumentException("item cannot be null."); if (selected.add(item)) added = true; } if (added && programmaticChangeEvents && fireChangeEvent()) revert(); else lastSelected = items.peek(); cleanup(); } /** Adds the item to the selection. */ public void add(T item) { if (item == null) throw new IllegalArgumentException("item cannot be null."); if (!selected.add(item)) return; if (programmaticChangeEvents && fireChangeEvent()) selected.remove(item); else lastSelected = item; } public void addAll(Array<T> items) { boolean added = false; snapshot(); for (int i = 0, n = items.size; i < n; i++) { T item = items.get(i); if (item == null) throw new IllegalArgumentException("item cannot be null."); if (selected.add(item)) added = true; } if (added && programmaticChangeEvents && fireChangeEvent()) revert(); else lastSelected = items.peek(); cleanup(); } public void remove(T item) { if (item == null) throw new IllegalArgumentException("item cannot be null."); if (!selected.remove(item)) return; if (programmaticChangeEvents && fireChangeEvent()) selected.add(item); else lastSelected = null; } public void removeAll(Array<T> items) { boolean removed = false; snapshot(); for (int i = 0, n = items.size; i < n; i++) { T item = items.get(i); if (item == null) throw new IllegalArgumentException("item cannot be null."); if (selected.remove(item)) removed = true; } if (removed && programmaticChangeEvents && fireChangeEvent()) revert(); else lastSelected = null; cleanup(); } public void clear() { if (selected.size == 0) return; snapshot(); selected.clear(); if (programmaticChangeEvents && fireChangeEvent()) revert(); else lastSelected = null; cleanup(); } /** Fires a change event on the selection's actor, if any. Called internally when the selection changes, depending on * {@link #setProgrammaticChangeEvents(boolean)}. * @return true if the change should be undone. */ public boolean fireChangeEvent() { if (actor == null) return false; ChangeEvent changeEvent = Pools.obtain(ChangeEvent.class); try { return actor.fire(changeEvent); } finally { Pools.free(changeEvent); } } public boolean contains(T item) { if (item == null) return false; return selected.contains(item); } /** Makes a best effort to return the last item selected, else returns an arbitrary item or null if the selection is empty. */ public T getLastSelected() { return lastSelected != null ? lastSelected : selected.first(); } public Iterator<T> iterator() { return selected.iterator(); } public Array<T> toArray() { return selected.iterator().toArray(); } public Array<T> toArray(Array<T> array) { return selected.iterator().toArray(array); } /** If true, prevents {@link #choose(Object)} from changing the selection. Default is false. */ public void setDisabled(boolean isDisabled) { this.isDisabled = isDisabled; } public boolean isDisabled() { return isDisabled; } public boolean getToggle() { return toggle; } /** If true, prevents {@link #choose(Object)} from clearing the selection. Default is false. */ public void setToggle(boolean toggle) { this.toggle = toggle; } public boolean getMultiple() { return multiple; } /** If true, allows {@link #choose(Object)} to select multiple items. Default is false. */ public void setMultiple(boolean multiple) { this.multiple = multiple; } public boolean getRequired() { return required; } /** If true, prevents {@link #choose(Object)} from selecting none. Default is false. */ public void setRequired(boolean required) { this.required = required; } /** If false, only {@link #choose(Object)} will fire a change event. Default is true. */ public void setProgrammaticChangeEvents(boolean programmaticChangeEvents) { this.programmaticChangeEvents = programmaticChangeEvents; } public String toString() { return selected.toString(); } }