导航控件中央是一个圆，您可以单击它，以将光标放在屏幕上所需的位置。

In the center of the navigation control is a circle that you can click to place the cursor at the required position in the screen.

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添加代码以在图像的50x, 50y位置绘制一个蓝色圆。

Add the code to draw a blue circle on the image at position 50x, 50y.

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将这个代码添加在main . c文件中，这样更容易修改圆的位置。

Adding this in the main.c file will allow for easier changing of the location of the circle.

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