绘制分形图: 摇摆分形树，3. 在摇摆分形树的基础上加上对鼠标事件的处理, 用户按下左键, 动画开始, 再次按下左键, 动画暂停 -Draw fractal images: swing fractal tree, plus handling mouse events. Swing fractal tree based on the user presses the left button, the animation starts, press the left button again