读 Beginning Android Games 2nd Edition (五) 创建对象池类

package com.badlogic.androidgames.framework;

import java.util.ArrayList;
import java.util.List;

public class Pool<T> {
	
    public interface PoolObjectFactory<T> {
        public T createObject();
    }

    private final List<T> freeObjects;
    private final PoolObjectFactory<T> factory;
    private final int maxSize;

    public Pool(PoolObjectFactory<T> factory, int maxSize) {
        this.factory = factory;
        this.maxSize = maxSize;
        this.freeObjects = new ArrayList<T>(maxSize);
    }

    public T newObject() {
        T object = null;

        if (freeObjects.isEmpty())
            object = factory.createObject();
        else
            object = freeObjects.remove(freeObjects.size() - 1);
        return object;
    }

    public void free(T object) {
        if (freeObjects.size() < maxSize)
            freeObjects.add(object);
    }
}

下面是使用方法

PoolObjectFactory <TouchEvent> factory = new PoolObjectFactory <TouchEvent> () {
    @Override
    public TouchEvent createObject() {
        return new TouchEvent();
    }
};
Pool <TouchEvent> touchEventPool = new Pool <TouchEvent> (factory, 50);
TouchEvent touchEvent = touchEventPool.newObject();
. . . do something here . . .
touchEventPool.free(touchEvent);

当我们想从对象池类中创建一个新的TouchEvent对象时,我们调用newObject(),起初,对象池是空的,因此我们可以使用factory创建一组对象.

当我们不再需要TouchEvent时,我们调用对象池类的free方法,将它重新插入对象池中.这样当下次我们需要再次使用到TouchEvent实例时,

我们调用对象池的newObject时,就可以得到与上次调用时相同的实例,这样就可以循环的使用对象从而避免垃圾回收的问题了.