仿QQ左侧滑动菜单的实现

冲动

最近接手的一个老项目有个侧滑菜单的需求，这个老项目的侧滑菜单用了网络上的一个第三方库，但是这个库竟然没有处理好导航条的显示，以至于项目中很多需要导航条展示信息的视图都通过添加subView的方式模仿了导航条。这简直是暴殄天物啊，放着真正的导航栏那强大的作用不用，浪费了多少时间和精力啊，都是青春啊，开发的前路上早已挖了无数的坑等着身心疲惫的我们往里跳啊。对此深恶痛绝的我，早就下了不杀此贼誓不罢休的决心。好吧，最近看三国看的有点多了。

暗渡陈仓

实在忍不了，换了小图了

哎，炫酷没法比啊。

iOS5之后每个UIViewController都可以轻松当一个容器了，可以同时管理许多其他的UIViewController了。

addChildViewController:
willMoveToParentViewController: 
didMoveToParentViewController:

现在的话我有两个子视图控制器了，把他们的view分别放在了我自定义的menuViewContainer和contentViewContainer这两个View里。OK，基础已打好。
理所应当，我在contentViewCcontainer上添加一个滑动手势，滑动时移动视图的位置就行了。那怎么确定手指在滑动时相应的视图应该滑动到哪呢？滑动到哪里结束呢？怎么确定同时改缩放到什么程度呢？
这些问题我本来想一一说讲一遍，发现自己太啰嗦，又不知道该怎么讲，所以还是直接上代码吧。
- (void)panGestureRecognizer:(UIScreenEdgePanGestureRecognizer *)recognizer{

    CGPoint point = [recognizer translationInView:self.view];

    if(recognizer.state == UIGestureRecognizerStateBegan) {
       [self updateContentViewShadow];
    }else if(recognizer.state == UIGestureRecognizerStateChanged){

       CGFloat menuVisibleWidth = self.view.bounds.size.width-self.realContentViewVisibleWidth;
       CGFloat delta = self.menuHidden ? point.x/menuVisibleWidth : (menuVisibleWidth+point.x)/menuVisibleWidth;
       CGFloat scale = 1-(1-MinScaleContentView)*delta;
       CGFloat menuScale = MinScaleMenuView + (1-MinScaleMenuView)*delta;

       if(self.menuHidden){
          //以内容视图最小缩放为界限
          if(scale < MinScaleContentView){//A
            self.contentViewContainer.transform = CGAffineTransformMakeTranslation(menuVisibleWidth, 0);
            self.contentViewContainer.transform = CGAffineTransformScale(self.contentViewContainer.transform,MinScaleContentView,MinScaleContentView);
            self.contentViewScale = MinScaleContentView;
            self.menuViewContainer.transform = CGAffineTransformMakeScale(1, 1);
            self.menuViewContainer.transform = CGAffineTransformTranslate(self.menuViewContainer.transform, 0, 0);
           }else{//大于最小界限又分大于等于1和小于1两种情况
             if(scale < 1){//B
                self.contentViewContainer.transform = CGAffineTransformMakeTranslation(point.x, 0);
                self.contentViewContainer.transform = CGAffineTransformScale(self.contentViewContainer.transform,scale, scale);
                self.contentViewScale = scale;
                self.menuViewContainer.transform = CGAffineTransformMakeScale(menuScale, menuScale);
                self.menuViewContainer.transform = CGAffineTransformTranslate(self.menuViewContainer.transform, -MoveDistanceMenuView *(1-delta), 0);
             }else{//C
                self.contentViewContainer.transform = CGAffineTransformMakeTranslation(0, 0);
                self.contentViewContainer.transform = CGAffineTransformScale(self.contentViewContainer.transform,1, 1);
                self.contentViewScale = 1;
                self.menuViewContainer.transform = CGAffineTransformMakeScale(MinScaleMenuView, MinScaleMenuView);
                self.menuViewContainer.transform = CGAffineTransformTranslate(self.menuViewContainer.transform, -MoveDistanceMenuView, 0);
            }
        }          
    }else{         
        if(scale > 1){//D
            self.contentViewContainer.transform = CGAffineTransformMakeTranslation(0, 0);
            self.contentViewContainer.transform = CGAffineTransformScale(self.contentViewContainer.transform,1,1);
            self.contentViewScale = 1;
            self.menuViewContainer.transform = CGAffineTransformMakeScale(MinScaleMenuView, MinScaleMenuView);
            self.menuViewContainer.transform = CGAffineTransformTranslate(self.menuViewContainer.transform, -MoveDistanceMenuView, 0);
        }else{
            if(scale>MinScaleContentView){//E
                self.contentViewContainer.transform = CGAffineTransformMakeTranslation(point.x+menuVisibleWidth, 0);
                self.contentViewContainer.transform = CGAffineTransformScale(self.contentViewContainer.transform,scale, scale);
                self.contentViewScale = scale;
                self.menuViewContainer.transform = CGAffineTransformMakeScale(menuScale, menuScale);
                self.menuViewContainer.transform = CGAffineTransformTranslate(self.menuViewContainer.transform, -MoveDistanceMenuView * (1-delta), 0);
            }else{//F
                self.contentViewContainer.transform =CGAffineTransformMakeTranslation(self.view.bounds.size.width-self.realContentViewVisibleWidth, 0);
                self.contentViewContainer.transform = CGAffineTransformScale(self.contentViewContainer.transform,MinScaleContentView, MinScaleContentView);
                self.contentViewScale = MinScaleContentView;
                self.menuViewContainer.transform = CGAffineTransformMakeScale(1, 1);
                self.menuViewContainer.transform = CGAffineTransformTranslate(self.menuViewContainer.transform, 0, 0);
            }
        }
    }        
  }else if(recognizer.state == UIGestureRecognizerStateEnded){
    [self showMenu:(self.contentViewContainer.frame.origin.x > self.view.bounds.size.width/2)];
  }
}

这样的结尾是不是太不负责任了？？？
好吧，我提醒大家，整段代码的精华全在delta的计算，视图滑动后的最终状态是由menuVisibleWidth和MinSacleContentView来决定。根据当前手势滑动的距离占menuVisibleWidth的百分比来计算滑动动作完成度，然后根据这个值来移动和缩放相应的视图。