继承自UIViewController的自定义TabbarViewController，支持自定义tabbar高度，使用方法简单，在子类中实现指定方法，解决系统tabbar隐藏困难，可定制性差的问题。

兼容性：最低iOS目标：iOS 6

使用方法：使用CocoaPods安装

pod 'XHTabbarViewController', '~> 1.0.7’

代码调用：DemoTabbar : XHTabbar 重写XHTabbar -(void) createUI 方法

DemoTabbarViewController : XHTabbarViewController 重写XHTabbarViewController -(void) makeTabbar 方法

UINavigationController *nav1 = [[UINavigationController alloc] initWithRootViewController:[ViewController1 new]];
UINavigationController *nav2 = [[UINavigationController alloc] initWithRootViewController:[ViewController2 new]];
UINavigationController *nav3 = [[UINavigationController alloc] initWithRootViewController:[ViewController3 new]];
DemoTabbarViewController *tabVC = [[DemoTabbarViewController alloc] initWithViewController:@[nav1,nav2,nav3]];
self.window.rootViewController = tabVC;
[self.window makeKeyAndVisible];

显示/隐藏tabbar：XHTabbarViewController 的tabbar.hidden = NO; //或 YES

自定义tab切换动画：在DemoTabbarViewController中添加以下block

__weak XHTabbarViewController *weakSelf = self;
//自定义切换动画，发挥想象力吧
self.tAnimationBlcok = ^(UIViewController *fromVC,UIViewController *toVC)
{
    toVC.view.transform = CGAffineTransformMakeScale(0.1, 0.1);
    toVC.view.alpha = 0;
    [UIView animateWithDuration:0.35 animations:^{

        fromVC.view.transform = CGAffineTransformMakeScale(0.1, 0.1);
        toVC.view.transform = CGAffineTransformMakeScale(1, 1);
        fromVC.view.alpha = 0;
        toVC.view.alpha = 1;

    }completion:^(BOOL finished)
     {
         //动画完成，需要掉用此方法，完成后续
         [weakSelf tAnimationBlockCompliated:fromVC toController:toVC];
         fromVC.view.transform = CGAffineTransformMakeScale(1, 1);
     }];
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