@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// The view displays 90 degrees across its width so that one 90 degree
// head rotation is equal to one full view cycle.
float pixelsPerDegree = getWidth() / 90.0f;
float degreesPerTick = 360.0f / mDirections.length;
float centerX = getWidth() / 2.0f;
float centerY = getHeight() / 2.0f;
canvas.save();
canvas.translate(-mHeading * pixelsPerDegree + centerX, centerY);
mPaint.setColor(Color.WHITE);
// We draw two extra ticks/labels on each side of the view so that the
// full range is visible even when the heading is approximately 0.
for (int i = -2; i <= mDirections.length + 2; i++) {
if (MathUtils.mod(i, 2) == 0) {
// Draw a text label for the even indices.
String direction = mDirections[MathUtils.mod(i, mDirections.length)];
mPaint.getTextBounds(direction, 0, direction.length(), mTextBounds);
canvas.drawText(
direction,
i * degreesPerTick * pixelsPerDegree - mTextBounds.width() / 2,
mTextBounds.height() / 2,
mPaint);
} else {
// Draw a tick mark for the odd indices.
canvas.drawLine(
i * degreesPerTick * pixelsPerDegree,
-TICK_HEIGHT / 2,
i * degreesPerTick * pixelsPerDegree,
TICK_HEIGHT / 2,
mTickPaint);
}
}
canvas.restore();
mPaint.setColor(NEEDLE_COLOR);
drawNeedle(canvas, false);
drawNeedle(canvas, true);
}
/**
* Converts the specified heading angle into an index between 0-15 that can be used to retrieve
* the direction name for that heading (known as "boxing the compass", down to the half-wind
* level).
*
* @param heading the heading angle
* @return the index of the direction name for the angle
*/
public static int getHalfWindIndex(float heading) {
float partitionSize = 360.0f / NUMBER_OF_HALF_WINDS;
float displacedHeading = MathUtils.mod(heading + partitionSize / 2, 360.0f);
return (int) (displacedHeading / partitionSize);
}
/**
* Sets the current heading in degrees and redraws the compass. If the angle is not between 0 and
* 360, it is shifted to be in that range.
*
* @param degrees the current heading.
*/
public void setHeading(float degrees) {
mHeading = MathUtils.mod(degrees, 360.0f);
invalidate();
}