bob wrote:
> So, I'm trying to learn how to make an android [sic] compass.
>
> Naturally, I used a site called google and typed the following in:
>
> "making an android compass"
>
> I found myself at this URL:
>
>
> http://android-er.blogspot.com/2010/08/simple-compass-sensormanager-and.html
>
> After looking thru it, I'm thinking it's incorrect.
>
>
You are mistaken.
> There is this suspiciously simple method:
>
>
What does "suspiciously simple" even mean?
Why should simplicity engender suspicion?
It's obviously a cover method for one that is less "suspicious".
> public void onSensorChanged(SensorEvent event) {
> // TODO Auto-generated method stub
> myCompassView.updateDirection((float)event.values[0]);
> }
>
>
> Basically, it seems like they are using the x component of the force
> vector as if it were an angle. Can someone else look at this and let me
> know what you think?
>
>
I think, no, wait, I am certain because I read the code to which you linked
that it uses the x component
to calculate the angle.
It's trigonometry. I know, it must seem like magic.
>From the site to which you linked:
canvas.drawLine(cxCompass, cyCompass,
(float)(cxCompass + radiusCompass * Math.sin((double)(-direction) *
3.14/180)),
(float)(cyCompass - radiusCompass * Math.cos((double)(-direction) *
3.14/180)),
paint);
I think I might've used
http://developer.android.com/reference/java/lang/Math.html#PI
and predefined
private static final double CONVERT = Math.PI / 180.0;
but that's neither here nor there.
--
Lew
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