com.badlogic.gdx.ai.btree.BehaviorTree.java Source code

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Here is the source code for com.badlogic.gdx.ai.btree.BehaviorTree.java

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/*******************************************************************************
 * Copyright 2014 See AUTHORS file.
 * 
 * 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.badlogic.gdx.ai.btree;

/** The behavior tree itself.
 * 
 * @param <E> type of the blackboard object that tasks use to read or modify game state
 * 
 * @author implicit-invocation
 * @author davebaol */
public class BehaviorTree<E> extends Task<E> {

    private Task<E> rootTask;

    /** Creates a {@code BehaviorTree} with no root task and no blackboard object. Both the root task and the blackboard object must
     * be set before running this behavior tree, see {@link #addChild(Task) addChild()} and {@link #setObject(Object) setObject()}
     * respectively. */
    public BehaviorTree() {
        this(null, null);
    }

    /** Creates a behavior tree with a root task and no blackboard object. Both the root task and the blackboard object must be set
     * before running this behavior tree, see {@link #addChild(Task) addChild()} and {@link #setObject(Object) setObject()}
     * respectively.
     * 
     * @param rootTask the root task of this tree. It can be {@code null}. */
    public BehaviorTree(Task<E> rootTask) {
        this(rootTask, null);
    }

    /** Creates a behavior tree with a root task and a blackboard object. Both the root task and the blackboard object must be set
     * before running this behavior tree, see {@link #addChild(Task) addChild()} and {@link #setObject(Object) setObject()}
     * respectively.
     * 
     * @param rootTask the root task of this tree. It can be {@code null}.
     * @param object the blackboard. It can be {@code null}. */
    public BehaviorTree(Task<E> rootTask, E object) {
        this.rootTask = rootTask;
        this.object = object;
    }

    /** Returns the blackboard object of this behavior tree. */
    public E getObject() {
        return object;
    }

    /** Sets the blackboard object of this behavior tree.
     * 
     * @param object the new blackboard */
    public void setObject(E object) {
        this.object = object;
    }

    /** This method will add a child to the list of this task's children
     * 
     * @param child the child task which will be added
     * @exception IllegalStateException if the root task is already set. */
    @Override
    public void addChild(Task<E> child) {
        if (this.rootTask != null)
            throw new IllegalStateException("A behavior tree cannot have more than one root task");
        this.rootTask = child;
    }

    @Override
    public int getChildCount() {
        return rootTask == null ? 0 : 1;
    }

    @Override
    public Task<E> getChild(int i) {
        if (i == 0 && rootTask != null)
            return rootTask;
        throw new IndexOutOfBoundsException("index can't be >= size: " + i + " >= " + getChildCount());
    }

    /** This method should be called when game entity needs to make decisions: call this in game loop or after a fixed time slice if
     * the game is realtime, or on entity's turn if the game is turn-based */
    public void step() {
        if (runningTask != null) {
            runningTask.run(object);
        } else {
            rootTask.setControl(this);
            rootTask.object = object;
            rootTask.start(object);
            rootTask.run(object);
        }
    }

    @Override
    public void run(E object) {
    }

    @Override
    protected Task<E> copyTo(Task<E> task) {
        BehaviorTree<E> tree = (BehaviorTree<E>) task;
        tree.rootTask = rootTask.cloneTask();

        return task;
    }

}