Even when you do add the ball to the panel, the ball has no size, so there is nothing to paint.
球还没有加入任何小组。即使你把球板，球没有大小，因此无油漆。
Your code is attempting to paint the ball at a location within the ball panel.
你的代码是要把球在球板的位置。
Your code is attempting to paint the ball at a location within the ball panel.
你的代码是要把球在球板的位置。
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