Nokia UI学习范例FishTank研究[2]

                long timeTaken = System.currentTimeMillis() - startTime;
                if (timeTaken < MILLIS_PER_TICK)
                {
                    synchronized (this)
                    {
                        wait(MILLIS_PER_TICK - timeTaken);
                    }
                } else
                {
                    currentThread.yield();
                }
            }
        } catch (InterruptedException e)
        {
        }
    }
由于在屏幕的下方有一部分是泥土，因此在这里调用了repaint(0,0,waterWidth,waterLength)。其实FishTankCanvas同时也是一个容器类，它是Fish和Weeds的容器。他去更新Fish和Weeds的状态然后调用各自的draw（）方法来重新绘制。下面我们看看FishTankCanvas是如何绘制的
    private synchronized void drawFishTank(Graphics g)
    {
        // Draw the water
        g.setColor(0, 255, 255);
        g.fillRect(0, 0, waterWidth, waterHeight);

        // Draw the sand
        g.setColor(255, 128, 64);
        g.fillRect(0, waterHeight, waterWidth, getHeight());

        // Draw the weeds and fishes
        for (int plane = 0; plane < NUM_PLANES; plane++)
        {
            if (plane == WEEDS_PLANE)
            {
                weeds.draw(g);
            }

            for (int i = 0; i < fishes.size(); i++)
            {
                Fish fish = (Fish) (fishes.elementAt(i));
                if (fish.getZ() == plane)
                {
                    fish.draw(g);
                }
            }
        }
    }

    接下来我们研究一下Fish和Weeds的代码，它们就是有很多图片构成的。实现的结果和MIDP2.0中的Sprite差不多。Fish和Weeds的图片都是有类型之分的，每个类型又有几个桢。这样才可以构造出不同的对象，并且相同的对象在不同的时刻也有不同的状态。
    private static final int TYPE_NUM = 3;

    private static final int FRAME_NUM = 2;

    private static final Image[][] fishImage;
Fish和Weeds都是采用了静态初始化块的方式来初始化相应的二维数组。例如
    static
    {
        fishImage = new Image[TYPE_NUM][FRAME_NUM];