滚动时自动显示与隐藏导航条定制

//
//  AMScrollingNavbarViewController.h
//  AMScrollingNavbar
//
//  Created by Andrea on 08/11/13.
//  Copyright (c) 2013 Andrea Mazzini. All rights reserved.
//

#import <UIKit/UIKit.h>

/*!
 * @name   HYBScrollRenderController
 * @brief  在滚动视图向上滚动时，慢慢隐藏导航条或者向下滚动时，慢慢显示导航条，支持6.0以上版本系统。
 *         在任何需要使用此功能的控制器类中，只要直接继承于此HYBScrollRenderController类，并在
 *         创建滚动视图的时候，调用-followScrollView:方法来设置即可。
 * @note   如果此类需要继承更多的特性，可直接修改继承的父类为自定义的控制器类。也可以把此类作为所有
 *         类的基础父类，在继承此类的基础上，扩展所有基础属性。如HYBSuperBaseController : HYBScrollRenderController
 * @author huangyibiao
 */
@interface HYBScrollRenderController : UIViewController

/*!
 * @brief 允许滚动的视图，支付UIScrollView、UITableView、UIWebView
 * @param scrollableView 可滚动的视图
 */
- (void)followScrollView:(UIView *)scrollableView;

@end

//
//  AMScrollingNavbarViewController.m
//  AMScrollingNavbar
//
//  Created by Andrea on 08/11/13.
//  Copyright (c) 2013 Andrea Mazzini. All rights reserved.
//

#import "HYBScrollRenderController.h"

@interface HYBScrollRenderController () <UIGestureRecognizerDelegate>

@property (nonatomic, weak)	  UIView                 *scrollableView;
@property (assign, nonatomic) float                  lastContentOffset;
@property (strong, nonatomic) UIPanGestureRecognizer *panGesture;
@property (strong, nonatomic) UIView                 *overlay;
@property (assign, nonatomic) BOOL                   isCollapsed;
@property (assign, nonatomic) BOOL                   isExpanded;

@end

@implementation HYBScrollRenderController

- (void)followScrollView:(UIView *)scrollableView {
	self.scrollableView = scrollableView;
	
	self.panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
	[self.panGesture setMaximumNumberOfTouches:1];
	
	[self.panGesture setDelegate:self];
	[self.scrollableView addGestureRecognizer:self.panGesture];

	/* The navbar fadeout is achieved using an overlay view with the same barTintColor.
	 this might be improved by adjusting the alpha component of every navbar child */
	CGRect frame = self.navigationController.navigationBar.frame;
	frame.origin = CGPointZero;
	self.overlay = [[UIView alloc] initWithFrame:frame];
	if ([self isIOS7]) {
        if (self.navigationController.navigationBar.barTintColor) {
            [self.overlay setBackgroundColor:self.navigationController.navigationBar.barTintColor];
        }
    }
	
	[self.overlay setUserInteractionEnabled:NO];
	[self.navigationController.navigationBar addSubview:self.overlay];
	[self.overlay setAlpha:0];
    return;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
	return YES;
}

- (void)handlePan:(UIPanGestureRecognizer*)gesture {
	CGPoint translation = [gesture translationInView:[self.scrollableView superview]];
	
	float delta = self.lastContentOffset - translation.y;
	self.lastContentOffset = translation.y;
	CGRect frame;
	
	if (delta > 0) {
		if (self.isCollapsed) {
			return;
		}
		
		frame = self.navigationController.navigationBar.frame;
		if (frame.origin.y - delta < -24) {
			delta = frame.origin.y + 24;
		}
		
		frame.origin.y = MAX(-24, frame.origin.y - delta);
		self.navigationController.navigationBar.frame = frame;
		if (frame.origin.y == -24) {
			self.isCollapsed = YES;
			self.isExpanded = NO;
		}
		
		[self updateSizingWithDelta:delta];
		
		// Keeps the view's scroll position steady until the navbar is gone
		if ([self.scrollableView isKindOfClass:[UIScrollView class]]) {
            UIScrollView *scrollView = (UIScrollView *)self.scrollableView;
			[scrollView setContentOffset:CGPointMake(scrollView.contentOffset.x,
                                                     scrollView.contentOffset.y - delta)];
		}
	}
	
	if (delta < 0) {
		if (self.isExpanded) {
			return;
		}
		
		frame = self.navigationController.navigationBar.frame;
		if (frame.origin.y - delta > 20) {
			delta = frame.origin.y - 20;
		}
		frame.origin.y = MIN(20, frame.origin.y - delta);
		self.navigationController.navigationBar.frame = frame;
		if (frame.origin.y == 20) {
			self.isExpanded = YES;
			self.isCollapsed = NO;
		}
		
		[self updateSizingWithDelta:delta];
	}
	
	if ([gesture state] == UIGestureRecognizerStateEnded) {
		self.lastContentOffset = 0;
		[self checkForPartialScroll];
	}
    return;
}

- (void)checkForPartialScroll {
	CGFloat pos = self.navigationController.navigationBar.frame.origin.y;
	
	// Get back down
	if (pos >= -2) {
		[UIView animateWithDuration:0.2 animations:^{
			CGRect frame;
			frame = self.navigationController.navigationBar.frame;
			CGFloat delta = frame.origin.y - 20;
			frame.origin.y = MIN(20, frame.origin.y - delta);
			self.navigationController.navigationBar.frame = frame;
			
			self.isExpanded = YES;
			self.isCollapsed = NO;
			[self updateSizingWithDelta:delta];
		}];
	} else {
		// And back up
		[UIView animateWithDuration:0.2 animations:^{
			CGRect frame;
			frame = self.navigationController.navigationBar.frame;
			CGFloat delta = frame.origin.y + 24;
			frame.origin.y = MAX(-24, frame.origin.y - delta);
			self.navigationController.navigationBar.frame = frame;
			
			self.isExpanded = NO;
			self.isCollapsed = YES;
			[self updateSizingWithDelta:delta];
		}];
	}
    return;
}

- (void)updateSizingWithDelta:(CGFloat)delta {
	CGRect frame = self.navigationController.navigationBar.frame;
	
	float alpha = (frame.origin.y + 24) / frame.size.height;
	[self.overlay setAlpha:1 - alpha];
	self.navigationController.navigationBar.tintColor = [self.navigationController.navigationBar.tintColor
                                                         colorWithAlphaComponent:alpha];
	
	frame = self.scrollableView.superview.frame;
    
	frame.origin.y = self.navigationController.navigationBar.frame.origin.y;
    frame.origin.y += self.navigationController.navigationBar.frame.size.height;
    
    // 判断是否是ios7及其以上版本
    if (![self isIOS7]) {
        frame.origin.y =  self.navigationController.navigationBar.frame.origin.y - 20;
    }
	frame.size.height = frame.size.height + delta;
	self.scrollableView.superview.frame = frame;
	
	// Changing the layer's frame avoids UIWebView's glitchiness
	frame = self.scrollableView.layer.frame;
	frame.size.height += delta;
	self.scrollableView.layer.frame = frame;
    return;
}

- (BOOL)isIOS7 {
    return ([UIDevice currentDevice].systemVersion.integerValue >= 7) ? YES : NO;
}

@end