设置cell背景色和选中色

 // 设置cell的背景色
 UIView *bg = [[[UIView alloc] init] autorelease];
 bg.backgroundColor = [UIColor colorWithRed:0.95 green:0.95 blue:0.95 alpha:];
 cell.backgroundView = bg;

 // 设置cell选中的背景
 UIView *selectdBg = [[[UIView alloc] init] autorelease];
 selectdBg.backgroundColor = [UIColor colorWithRed:0.85 green:0.85 blue:0.85 alpha:];
 cell.selectedBackgroundView = selectdBg;