1、介绍
用过网易新闻客户端的同学都会发现，网易新闻向左滑动时，左侧的导航栏会跟着拖动出来，新闻内容列表会拉到最右侧。像一个抽屉拉出来一样。很酷。除了网易新闻，现在好多应用都采用了这样的交互。
对手势识别不熟悉的请参考上篇： iOS手势识别的详细使用(拖动,缩放,旋转,点击,手势依赖,自定义手势)
这个交互效果主要用到两个手势，一个是pan拖拽，一个是tap点击。拖拽可以把抽屉拉出来，再推回去。点击可以把抽屉推回去。
效果如下：
那么这个效果如何实现呢？
2、实现思路和步骤
思路：从实现的效果分析出来，可以这样实现：
这个交互是由两个View组成，左侧导航的View在下面，显示内容列表的View在上面，内容列表的View覆盖住了导航View,拖动内容列表的View向右，这时候导航View就显示出来了。
实现步骤：
- 自定义一个View，它做为显示内容的View。给这个View添加两个手势，pan拖拽，tap点击。
- 当拖拽这个View时，让view.center向右移动，这样就能看到内容View向右移动了。
- 定义一个抽屉打开停止时的x值为：OPENCENTERX，这个是内容View最终停止的位置
- 当内容View越过中间靠右的一个x值时，view自动向右动画移动到右边位置停下。
- 当内容View在打开的状态下，点击内容View，利用UIView动画把内容View.center移动回到中间。
- 设置内容View的阴影效果
3、代码实现
新建CustomView继承UIView
- #import <UIKit/UIKit.h>
-
- @interface CustomView : UIView
- {
- CGPoint openPointCenter;
- CGPoint closePointCenter;
- }
- -(id)initWithView:(UIView*)contentview parentView:(UIView*) parentview;
-
- @property (nonatomic, strong) UIView *parentView;
- @property (nonatomic, strong) UIView *contenView;
- @end
两个手势在Custom里实现，并在初始化的时候传入内容View和父视图。
- #import "CustomView.h"
-
- #define OPENCENTERX 220.0
- #define DIVIDWIDTH 70.0 //OPENCENTERX 对应确认是否打开或关闭的分界线。
-
- @implementation CustomView
-
- - (id)initWithFrame:(CGRect)frame
- {
- self = [super initWithFrame:frame];
- if (self) {
-
- }
- return self;
- }
-
- - (id)initWithView:(UIView *)contentview parentView:(UIView *)parentview
- {
- self = [super initWithFrame:CGRectMake(0,0,contentview.frame.size.width, contentview.frame.size.height)];
-
- if (self) {
- self.contenView = contentview;
- self.parentView = parentview;
-
- [self addSubview:contentview];
- UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
- initWithTarget:self
- action:@selector(handlePan:)];
- [self addGestureRecognizer:panGestureRecognizer];
-
- UITapGestureRecognizer *tapGestureRecognizer = [[UITapGestureRecognizer alloc]
- initWithTarget:self
- action:@selector(handleTap:)];
-
- [self addGestureRecognizer:tapGestureRecognizer];
- openPointCenter = CGPointMake(self.parentView.center.x + OPENCENTERX,
- self.parentView.center.y);
-
- NSLog(@"openPointCenter x:%f, openPointCenter y:%f",
- openPointCenter.x,
- openPointCenter.y);
-
-
- }
-
-
-
- return self;
- }
-
- -(void) handlePan:(UIPanGestureRecognizer*) recognizer
- {
- CGPoint translation = [recognizer translationInView:self.parentView];
-
- float x = self.center.x + translation.x;
- NSLog(@"translation x:%f", translation.x);
-
- if (x < self.parentView.center.x) {
- x = self.parentView.center.x;
- }
- self.center = CGPointMake(x, openPointCenter.y);
-
- if(recognizer.state == UIGestureRecognizerStateEnded)
- {
- [UIView animateWithDuration:0.75
- delay:0.01
- options:UIViewAnimationCurveEaseInOut
- animations:^(void)
- {
- if (x > openPointCenter.x - DIVIDWIDTH) {
- self.center = openPointCenter;
- }else{
- self.center = CGPointMake(openPointCenter.x - OPENCENTERX,
- openPointCenter.y);
-
- }
-
- }completion:^(BOOL isFinish){
-
- }];
- }
-
- [recognizer setTranslation:CGPointZero inView:self.parentView];
- }
-
- -(void) handleTap:(UITapGestureRecognizer*) recognizer
- {
- [UIView animateWithDuration:0.75
- delay:0.01
- options:UIViewAnimationTransitionCurlUp animations:^(void){
- self.center = CGPointMake(openPointCenter.x - OPENCENTERX,
- openPointCenter.y);
- }completion:nil];
-
- }
- @end
4、viewController的调用
为了实现自定义视图的阴影，添加需要使用QuartzCore框架。在项目里添加QuartzCore框架后引入头文件。
- - (void)viewDidLoad
- {
- [super viewDidLoad];
-
- CGRect rect = CGRectMake(0, 0,
- self.view.frame.size.width,
- self.view.frame.size.height);
- NSLog(@"w:%f, h:%f", rect.size.width, rect.size.height);
- UIImageView *imageleft = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"left.png"]];
- imageleft.frame = rect;
- [self.view addSubview:imageleft];
-
- UIView *contentView = [[UIView alloc] initWithFrame:rect];
-
- UIImageView *imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"index.png"]];
- imageView.frame = rect;
- [contentView addSubview:imageView];
-
- CustomView *customView = [[CustomView alloc] initWithView:contentView
- parentView:self.view];
- [[customView layer] setShadowOffset:CGSizeMake(10, 10)];
- [[customView layer] setShadowRadius:20];
- [[customView layer] setShadowOpacity:1];
- [[customView layer] setShadowColor:[UIColor blackColor].CGColor];
-
- [self.view addSubview:customView];
-
- }
为了看起来好看，我弄了两张截图了，一个是内容视图，一个是左侧导航栏的视图，然后作为背景图放到上面的两个view的里。
所以不要点里面的内容，点不了滴，那是图片而已。这里只是演示抽屉的效果。
最后，网易新闻的这个交互能从右边拉出来的效果，原理差不多，可能需要多一个view。还有交互时左侧栏里还有由明变暗，忽大忽小的效果。这些以后有时间再实现。
