Moving a ball with help of accelerometer in android?

I guess your problem is that you assume that the sensor origin (x=0,y=0) is the screen center. The sensor origin is the top left corner of the screen (X pointing left and Y pointing down), so comparing a & be to canvas.getWidth() & canvas.getHeight() is not correct since you already added centerX & centerY . Also, negating sensorX will cause the condition a > canvas.getWidth() to never occur since X is never negative.

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