Android系统事件的recycle原理 博客分类： Android Android

        //变量
	private MotionEvent mNext; //指向回收栈的下一个对象
	private boolean mRecycled; //标志是否是被回收掉的对象
	//静态变量
	static private final int MAX_RECYCLED = 10;//最大可回收的数目
	static private Object gRecyclerLock = new Object();//锁定整个类用的
	static private int gRecyclerUsed = 0;//回收栈中回收的对象数目
	static private MotionEvent gRecyclerTop = null;//回收栈的栈顶对象

static private MotionEvent obtain() {
        synchronized (gRecyclerLock) { //锁住整个类
            if (gRecyclerTop == null) {//栈顶不存在，就new一个新的
                return new MotionEvent();
            }
            MotionEvent ev = gRecyclerTop;//栈顶存在，就用一个引用ev指向它
            gRecyclerTop = ev.mNext;//然后把栈顶的下一个对象提到栈顶
            gRecyclerUsed--;//回收栈中的对象数目减少一个
            ev.mRecycledLocation = null;//是一个异常，作用未知
            ev.mRecycled = false;//当前对象标志为未回收状态
            return ev;
        }
    }

public void recycle() {
        // 确保recycle方法只调用一次
        if (TRACK_RECYCLED_LOCATION) {
            if (mRecycledLocation != null) {
                throw new RuntimeException(toString() + " recycled twice!", mRecycledLocation);
            }
            mRecycledLocation = new RuntimeException("Last recycled here");
        } else if (mRecycled) {
            throw new RuntimeException(toString() + " recycled twice!");
        }

        synchronized (gRecyclerLock) {//锁住类
            if (gRecyclerUsed < MAX_RECYCLED) { //如果回收栈中的对象还没达到最大值
                gRecyclerUsed++;	//回收栈中元素数目增加1
                mNumHistory = 0;	
	//这两句是把当前对象的next指向以前的栈顶，然后把当前对象放到栈顶
                mNext = gRecyclerTop;	
                gRecyclerTop = this;
            }
        }
    }