扩展QNX TileList组件以创建液体布局

Posted 2021-02-25

public class LiquidTileList extends TileList {
	/**
	 * if true, when changing the size of the tiles
	 * scrolls the list so the first tile from the previous
	 * state is still visible
	 */
	public var keepVisibleItem:Boolean;
 
	public function LiquidTileList() {
		super();
		setSkin(PictureCellRenderer);
	}
	/**
	 * Overriding the draw method to inject 
	 * our method of calculating the number of
	 * tiles that fit the screen
	 * This method is called every time the width/height
	 * is changed
	 */
	override protected function draw():void {
		var i:int;
		if (keepVisibleItem && firstVisibleItem)
			i = firstVisibleItem.index;
		scrollIndexVisible(0, 0);
		calculateColumns();
		super.draw();
		if (keepVisibleItem && i)
			scrollIndexVisible(i, 0);
	}
	/**
	 * Calculates the number of tiles that fit
	 * the width
	 */
        private function calculateColumns():void {
		var columnNumber:int = Math.floor( (width - (cellPadding * columnCount -1) )
                                                      / columnWidth);
		if (columnNumber != columnCount)
			columnCount = columnNumber;
	}
}