我只有一个“简单”同步锁定块：

private final Object screenLock = new Object();

public void Update(double deltaTime)
{
    synchronized (screenLock)
    {
        screenManager.Update(deltaTime);
    }
}

public void Draw()
{
    synchronized (screenLock)
    {
        screenManager.Draw();
    }
}

deltaTime不为null,screenManager不为null,所以我有点迷失.

我知道我不应该锁定这么高的级别,但是无论我把Block放在哪里,问题都会存在.我有两个线程运行更新和绘制与screenLock.

什么会导致锁上的NullPointerException？

跟踪：

java.lang.NullPointerException at
com.dnx.manavo.ScreenManager.Update(ScreenManager.java:107) at
com.dnx.manavo.ApplicationActivity.Update(ApplicationActivity.java:98)
at com.dnx.manavo.GameThread.run(GameThread.java:43)