在窗口North上布置三个按钮，并完成按钮点击事件，点击三个按钮时，分别输出填充颜色的三角形，矩形和椭圆。-The arrangement of the three buttons in the window on the North, and the Done button click event, the three buttons is clicked, the output filled with colored triangles, rectangles and ellipses.