Android™ Application Development - Bahar Ali Khan

}
Chapter 11: Advanced Android Development
String displayString = String.valueOf(displayPos);
float stringSizeWidth = textPaint.measureText(displayString);
canvas.drawText(displayString,
(int)(center.x-stringSizeWidth/2),
(int)(ypos)+1,
textPaint);
12. Now draw a thicker line at the earth/sky interface. Change the stroke thickness of the
markerPaint object before drawing the line (then set it back to the previous value).
markerPaint.setStrokeWidth(2);
canvas.drawLine(center.x - radius / 2,
(float)justTiltY,
center.x + radius / 2,
(float)justTiltY,
markerPaint);
markerPaint.setStrokeWidth(1);
13. To make it easier to read the exact roll, you should draw an arrow and display a text string that
shows the exact value.
Create a new Path, and use the moveTo / lineTo methods to construct an open arrow that
points straight up. Draw the path and a text string that shows the current roll.
// Draw the arrow
Path rollArrow = new Path();
rollArrow.moveTo(center.x - 3, (int)innerBoundingBox.top + 14);
rollArrow.lineTo(center.x, (int)innerBoundingBox.top + 10);
rollArrow.moveTo(center.x + 3, innerBoundingBox.top + 14);
rollArrow.lineTo(center.x, innerBoundingBox.top + 10);
canvas.drawPath(rollArrow, markerPaint);
// Draw the string
String rollText = String.valueOf(rollDegree);
double rollTextWidth = textPaint.measureText(rollText);
canvas.drawText(rollText,
(float)(center.x - rollTextWidth / 2),
innerBoundingBox.top + textHeight + 2,
textPaint);
14. Spin the canvas back to upright so that you can draw the rest of the face markings.
canvas.restore();
15. Draw the roll dial markings by rotating the canvas 10 degrees at a time to draw either a mark or
a value. When you’ve completed the face, restore the canvas to its upright position.
canvas.save();
canvas.rotate(180, center.x, center.y);
for (int i = -180; i < 180; i += 10)
{
// Show a numeric value every 30 degrees
if (i % 30 == 0) {
String rollString = String.valueOf(i*-1);
float rollStringWidth = textPaint.measureText(rollString);
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