This sample is to display the horizontal line in the background of the chart. 
GridLine
direction: horizontal - horizontal line, vertical - vertical line, both - horizontal line + vertical line
horizontalChangeCount: Filling color by using horizontalFill and horizontalAlternateFill alternately 
by the number of times set as the value of the horizontalChangeCount property.
horizontalStroke: The color of the line between horizontalFill and horizontalAlternateFill.
horizontalFill: The initial fill color.
horizontalAlternateFill: The alternate fill color.

ā—¸Layout
<backgroundElements>
	<GridLines direction="horizontal" horizontalChangeCount="1">
		<horizontalStroke>
			<Stroke color="0xFF9966" alpha="0.5" weight="1"/>
			color:sets color, alpha: sets transparency, weight: sets thickness
		</horizontalStroke>
		<horizontalFill>
			<SolidColor color="0xFFCC99" alpha="0.5"/>
			color:sets color, alpha: sets transparency
		</horizontalFill>
		<horizontalAlternateFill>
			<SolidColor color="0xFFFFCC" alpha="0.5"/>
			color:sets color, alpha: sets transparency
		</horizontalAlternateFill>
	</GridLines>
</backgroundElements>