CODEWITHSUNDEEP
android
olivarra1
olivarra1

Reputation: 3409

Canvas.drawPoint() not working if there's Canvas.rotate(90)?

So i'm making a custom View that displays some graphs (plots), and in some ocasions i want to rotate the canvas 90 degrees.
All i can guess is that there's a bug in my device (HTC Desire, with android 2.3), i haven't test it yet in another device.

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    canvas.save();
    canvas.rotate((float) 90.0);
    canvas.drawPoint(10, 10, pointPaint); /* Sorry about missing that these
            * coordinates will fall out after being rotated... it's just an
            * example. put 10, -10 and it should work, but it doesn't */
    canvas.restore();
}

This won't draw the point, but if we change that 90.0 for a 90.014 (i found that this was the minimum, 90.013 doesn't work either) then the point will show up.

So... is it something i'm doing wrong, or it's just Android's bug? I googled a lot, but couldn't find nothing....

-Victor -

edit: Additional info: Only points doesn't work. Rects, lines and circles work perfect.
edit: screenshot of my app, you can see how the red line has dots on the 90.014 degree version, and the 90.0 doesn't.: enter image description here

(As you can see, the 90.014 it looks like a little bit flipped (you can see how the Y axis is 'broken')

Upvotes: 2

Views: 1419

Answers (2)

devsnd
devsnd

Reputation: 7722

Setting the Paint of the dots to use a ROUND stroke cap resolves the problem, even though it doesn't yet explain the strange behavior you are experiencing. e.g.:

paint.setStrokeCap(Paint.Cap.ROUND)

Upvotes: 2

devsnd
devsnd

Reputation: 7722

The canvas rotates through its origin, so if you rotate your canvas by 90 degrees you are effectively rotating your view out of your screen. You should translate the canvas to the axis you want to rotate on first:

canvas.save();
canvas.translate(-axispointx,-axispointy);
canvas.rotate((float) 90.0);
canvas.translate(axispointx,axispointy);
canvas.drawPoint(10, 10, pointPaint);
canvas.restore();

Upvotes: 2

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