浅谈iOS11新特性：新增拖拽交互体验

- (void)viewDidLoad {
  [super viewDidLoad];
  [self.view addSubview:self.dragView];
}
//创建View
-(UIView *)dragView{
  if (!_dragView) {
    _dragView = [[UIView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
    _dragView.backgroundColor = [UIColor redColor];
    [_dragView addInteraction:self.dragInteraction];
  }
  return _dragView;
}
//创建拖拽行为对象
-(UIDragInteraction *)dragInteraction{
  if (!_dragInteraction) {
    _dragInteraction = [[UIDragInteraction alloc]initWithDelegate:self];
    //要设置可用 注意！！！
    [_dragInteraction setEnabled:YES];
  }
  return _dragInteraction;
}

//实现提供数据的代理方法
- (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForBeginningSession:(id<UIDragSession>)session{
  //数据提供者
  NSItemProvider * provider = [[NSItemProvider alloc]initWithObject:@"Hello World"];
  UIDragItem * item = [[UIDragItem alloc]initWithItemProvider:provider];
  return @[item];
}

//初始化方法
- (instancetype)initWithDelegate:(id<UIDragInteractionDelegate>)delegate;
//代理
@property (nonatomic, nullable, readonly, weak) id<UIDragInteractionDelegate> delegate;
//是否支持多种手势都接收响应
@property (nonatomic) BOOL allowsSimultaneousRecognitionDuringLift;
//设置是否有效
@property (nonatomic, getter=isEnabled) BOOL enabled;
//获取默认是否有效 不同的设备这个值将有所区别
@property (class, nonatomic, readonly, getter=isEnabledByDefault) BOOL enabledByDefault;

/*
这个方法是必须实现的用来返回拖拽源提供的数据
需要注意，这个函数需要返回一个数组，数组中可以有多个数据源
如果返回空数组，则拖拽行为不会开始
*/
- (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForBeginningSession:(id<UIDragSession>)session;
/*
这个方法用来自定义拖拽效果的预览视图 关于预览视图，后面会介绍
需要注意，系统默认会提供一个预览视图，不实现这个方法即是使用系统默认的
如果返回nil，则会去除预览动画
*/
- (nullable UITargetedDragPreview *)dragInteraction:(UIDragInteraction *)interaction previewForLiftingItem:(UIDragItem *)item session:(id<UIDragSession>)session;
/*
拖拽动画即将开始时会调用此函数
*/
- (void)dragInteraction:(UIDragInteraction *)interaction willAnimateLiftWithAnimator:(id<UIDragAnimating>)animator session:(id<UIDragSession>)session;
//拖拽行为会话即将开始时调用的方法
- (void)dragInteraction:(UIDragInteraction *)interaction sessionWillBegin:(id<UIDragSession>)session;
//这个方法设置数据的防止是否允许数据的 移动操作，需要注意，这个只有在app内有效，跨app的操作会总是复制数据
- (BOOL)dragInteraction:(UIDragInteraction *)interaction sessionAllowsMoveOperation:(id<UIDragSession>)session;
//设置是否允许跨应用程序进行拖拽 ipad
- (BOOL)dragInteraction:(UIDragInteraction *)interaction sessionIsRestrictedToDraggingApplication:(id<UIDragSession>)session;
//设置预览视图是否显示原始大小
- (BOOL)dragInteraction:(UIDragInteraction *)interaction prefersFullSizePreviewsForSession:(id<UIDragSession>)session;
/*
当拖拽源被移动时调用，可以用如下方法获取其坐标
NSLog(@"%f,%f",[session locationInView:self.view].x,[session locationInView:self.view].y);
*/
- (void)dragInteraction:(UIDragInteraction *)interaction sessionDidMove:(id<UIDragSession>)session;
//拖拽行为将要结束时调用
- (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session willEndWithOperation:(UIDropOperation)operation;
//拖拽行为已经结束时调用
- (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session didEndWithOperation:(UIDropOperation)operation;
//拖拽源进行了放置操作后调用
- (void)dragInteraction:(UIDragInteraction *)interaction sessionDidTransferItems:(id<UIDragSession>)session;
//设置拖拽动作取消的视图动画 返回nil则消除动画
-(nullable UITargetedDragPreview *)dragInteraction:(UIDragInteraction *)interaction previewForCancellingItem:(UIDragItem *)item withDefault:(UITargetedDragPreview *)defaultPreview;
//拖拽动作即将取消时调用的方法
- (void)dragInteraction:(UIDragInteraction *)interaction item:(UIDragItem *)item willAnimateCancelWithAnimator:(id<UIDragAnimating>)animator;
//设置是否允许向拖拽中的项目添加数据
/*
可以返回数据载体数组 当拖拽过程中 点击可拖拽的组件时会触发
*/
- (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForAddingToSession:(id<UIDragSession>)session withTouchAtPoint:(CGPoint)point;
//设置允许进行拖拽中追加数据的拖拽行为会话
- (nullable id<UIDragSession>)dragInteraction:(UIDragInteraction *)interaction sessionForAddingItems:(NSArray<id<UIDragSession>> *)sessions withTouchAtPoint:(CGPoint)point;
//将要向拖拽组件中追加数据时调用
- (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session willAddItems:(NSArray<UIDragItem *> *)items forInteraction:(UIDragInteraction *)addingInteraction;

//添加视图
- (void)viewDidLoad {
  [super viewDidLoad];
  //有关拖拽源的代码 前面已经列举过 这里不再重复
  [self.view addSubview:self.dragView];
  [self.view addSubview:self.dropLabel];
}

-(UILabel *)dropLabel{
  if (!_dropLabel) {
    _dropLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, 300, 300, 30)];
    _dropLabel.backgroundColor = [UIColor greenColor];
    _dropLabel.userInteractionEnabled = YES;
    [_dropLabel addInteraction:self.dropInteraction];
  }
  return _dropLabel;
}
//放置目的地行为对象
-(UIDropInteraction*)dropInteraction{
  if (!_dropInteraction) {
    _dropInteraction = [[UIDropInteraction alloc]initWithDelegate:self];
  }
  return _dropInteraction;
}

//这个方法返回是否响应此放置目的地的放置请求
-(BOOL)dropInteraction:(UIDropInteraction *)interaction canHandleSession:(id<UIDropSession>)session{
  return YES;
}
//设置以何种方式响应拖放会话行为
-(UIDropProposal *)dropInteraction:(UIDropInteraction *)interaction sessionDidUpdate:(id<UIDropSession>)session{
  return [[UIDropProposal alloc]initWithDropOperation:UIDropOperationCopy];
}
//已经应用拖放行为后执行的操作
-(void)dropInteraction:(UIDropInteraction *)interaction performDrop:(id<UIDropSession>)session{ 
  [session loadObjectsOfClass:[NSString class] completion:^(NSArray<__kindof id<NSItemProviderReading>> * _Nonnull objects) {
    self.dropLabel.text = objects.firstObject;
  }];
}

//初始化方法
- (instancetype)initWithDelegate:(id<UIDropInteractionDelegate>)delegate;
//代理对象
@property (nonatomic, nullable, readonly, weak) id<UIDropInteractionDelegate> delegate;
//是否允许多个交互行为
@property (nonatomic, assign) BOOL allowsSimultaneousDropSessions;

//放置行为即将响应时触发的方法 返回值确定是否响应此次行为
- (BOOL)dropInteraction:(UIDropInteraction *)interaction canHandleSession:(id<UIDropSession>)session;
//当上面的协议方法返回YES时会接着调用这个函数
- (void)dropInteraction:(UIDropInteraction *)interaction sessionDidEnter:(id<UIDropSession>)session;
//将要处理数据时回调的方法
/*
当数据源数据添加时，这个方法也会被重新调用 
这个函数需要返回一个处理行为方式UIDropProposal对象，这个我们后面再说
*/
- (UIDropProposal *)dropInteraction:(UIDropInteraction *)interaction sessionDidUpdate:(id<UIDropSession>)session;
//放置行为相应结束的时候会调用此方法
- (void)dropInteraction:(UIDropInteraction *)interaction sessionDidExit:(id<UIDropSession>)session;
//这个方法当用户进行放置时会调用，可以从session中获取被传递的数据
- (void)dropInteraction:(UIDropInteraction *)interaction performDrop:(id<UIDropSession>)session;
//放置动画完成后会调用这个方法
- (void)dropInteraction:(UIDropInteraction *)interaction concludeDrop:(id<UIDropSession>)session;
//整个拖放行为结束后会调用
- (void)dropInteraction:(UIDropInteraction *)interaction sessionDidEnd:(id<UIDropSession>)session;
//下面这些方法用来自定义放置动画
//设置放置预览动画
- (nullable UITargetedDragPreview *)dropInteraction:(UIDropInteraction *)interaction previewForDroppingItem:(UIDragItem *)item withDefault:(UITargetedDragPreview *)defaultPreview;
//这个函数每当有一个拖拽数据项放入时都会调用一次 可以进行动画
- (void)dropInteraction:(UIDropInteraction *)interaction item:(UIDragItem *)item willAnimateDropWithAnimator:(id<UIDragAnimating>)animator;

//初始化方法
/*
typedef NS_ENUM(NSUInteger, UIDropOperation) {
  //取消这次行为
  UIDropOperationCancel  = 0,
  //拒绝行为
  UIDropOperationForbidden = 1,
  //接收拷贝数据
  UIDropOperationCopy   = 2,
  //接收移动数据
  UIDropOperationMove   = 3,
}
*/
- (instancetype)initWithDropOperation:(UIDropOperation)operation;
//处理方式
@property (nonatomic, readonly) UIDropOperation operation;
//精准定位
@property (nonatomic, getter=isPrecise) BOOL precise;
//设置是否展示完整的预览尺寸
@property (nonatomic) BOOL prefersFullSizePreview;

//初始化方法
- (instancetype)initWithItemProvider:(NSItemProvider *)itemProvider;
//数据提供者实例
@property (nonatomic, readonly) __kindof NSItemProvider *itemProvider;
//用来传递一些额外的关联信息
@property (nonatomic, strong, nullable) id localObject;
//用来自定义每个item添加时的预览动画
@property (nonatomic, copy, nullable) UIDragPreview * _Nullable (^previewProvider)(void);

//继承于UIDragDropSession(提供基础数据), NSProgressReporting(提供数据读取进度)
@protocol UIDropSession <UIDragDropSession, NSProgressReporting>
//原始的dragSesstion会话 如果是跨应用的 则为nil
@property (nonatomic, readonly, nullable) id<UIDragSession> localDragSession;
//设置进度风格
/*
typedef NS_ENUM(NSUInteger, UIDropSessionProgressIndicatorStyle) {
  UIDropSessionProgressIndicatorStyleNone,    // 无
  UIDropSessionProgressIndicatorStyleDefault,  // 默认的
} API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos);
*/
@property (nonatomic) UIDropSessionProgressIndicatorStyle progressIndicatorStyle;
//进行数据的加载
- (NSProgress *)loadObjectsOfClass:(Class<NSItemProviderReading>)aClass completion:(void(^)(NSArray<__kindof id<NSItemProviderReading>> *objects))completion;
@end

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @protocol UIDragSession <UIDragDropSession>
//设置要传递的额外信息 只有在同个APP内可见
@property (nonatomic, strong, nullable) id localContext;
@end

//传递的数据数组
@property (nonatomic, readonly) NSArray<UIDragItem *> *items;
//当前操作行为的坐标
- (CGPoint)locationInView:(UIView *)view;
//此次行为是否允许移动操作
@property (nonatomic, readonly) BOOL allowsMoveOperation;
//是否支持应用程序层面的拖拽
@property (nonatomic, readonly, getter=isRestrictedToDraggingApplication) BOOL restrictedToDraggingApplication;
//验证传递的数据是否支持某个数据类型协议
- (BOOL)hasItemsConformingToTypeIdentifiers:(NSArray<NSString *> *)typeIdentifiers;
//验证传递的数据是否可以加载某个类
- (BOOL)canLoadObjectsOfClass:(Class<NSItemProviderReading>)aClass;

//创建一个预览对象 
/*
view：要创建的预览视图 需要注意，这个视图必须在window上
param：配置参数
target：容器视图，用来展示预览，一般设置为view的父视图
*/
- (instancetype)initWithView:(UIView *)view parameters:(UIDragPreviewParameters *)parameters target:(UIDragPreviewTarget *)target;
//同上
-(instancetype)initWithView:(UIView *)view parameters:(UIDragPreviewParameters *)parameters;
//同上
- (instancetype)initWithView:(UIView *)view;
//动画承载者
@property (nonatomic, readonly) UIDragPreviewTarget* target;
//动画视图
@property (nonatomic, readonly) UIView *view;
//配置参数
@property (nonatomic, readonly, copy) UIDragPreviewParameters *parameters;
//尺寸
@property (nonatomic, readonly) CGSize size;
//返回新的对象
- (UITargetedDragPreview *)retargetedPreviewWithTarget:(UIDragPreviewTarget *)newTarget;

/*
初始化方法
container：必须是在window上的view
center：动画起点与终点
transform:进行变换
*/
- (instancetype)initWithContainer:(UIView *)container center:(CGPoint)center transform:(CGAffineTransform)transform;
//同上
- (instancetype)initWithContainer:(UIView *)container center:(CGPoint)center;
//对应属性
@property (nonatomic, readonly) UIView *container;
@property (nonatomic, readonly) CGPoint center;
@property (nonatomic, readonly) CGAffineTransform transform;

//构造方法并设置路径矩形
- (instancetype)initWithTextLineRects:(NSArray<NSValue /* CGRect */ *> *)textLineRects;
//显示的路径
@property (nonatomic, copy, nullable) UIBezierPath *visiblePath;
//背景色
@property (nonatomic, copy, null_resettable) UIColor *backgroundColor;

#import <Foundation/Foundation.h>
//遵守协议
@interface Person : NSObject<NSItemProviderWriting,NSItemProviderReading>
//自定义内容
@property(nonatomic,strong)NSString * name;
@property(nonatomic,assign)NSUInteger age;
@end

//.m文件
@implementation Person
//数据归档
- (nullable NSProgress *)loadDataWithTypeIdentifier:(NSString *)typeIdentifier
          forItemProviderCompletionHandler:(void (^)(NSData * _Nullable data, NSError * _Nullable error))completionHandler{
  NSProgress * pro = [NSProgress new];
  NSData * data = [NSKeyedArchiver archivedDataWithRootObject:self];
  completionHandler(data,nil);
  return pro;
}

+(NSItemProviderRepresentationVisibility)itemProviderVisibilityForRepresentationWithTypeIdentifier:(NSString *)typeIdentifier{
  return NSItemProviderRepresentationVisibilityAll;
}

- (NSItemProviderRepresentationVisibility)itemProviderVisibilityForRepresentationWithTypeIdentifier:(NSString *)typeIdentifier{
  return NSItemProviderRepresentationVisibilityAll;
}
//提供一个标识符
+(NSArray<NSString *> *)writableTypeIdentifiersForItemProvider{
  return @[@"object"];
}
-(NSArray<NSString *> *)writableTypeIdentifiersForItemProvider{
  return @[@"object"];
}

- (instancetype)initWithCoder:(NSCoder *)coder
{
  self = [super init];
  if (self) {
    self.name = [coder decodeObjectForKey:@"name"];
    self.age = [coder decodeIntegerForKey:@"age"];
  }
  return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder{
  [aCoder encodeObject:self.name forKey:@"name"];
  [aCoder encodeInteger:self.age forKey:@"age"];
}
//这两个是读协议
+(NSArray<NSString *> *)readableTypeIdentifiersForItemProvider{
  return @[@"object"];
}
//解归档返回
+ (nullable instancetype)objectWithItemProviderData:(NSData *)data
                   typeIdentifier:(NSString *)typeIdentifier
                       error:(NSError **)outError{
  Person * p = [NSKeyedUnarchiver unarchiveObjectWithData:data];
  return p;
}
@end

-(void)dropInteraction:(UIDropInteraction *)interaction performDrop:(id<UIDropSession>)session{
  NSLog(@"%@",session.items.lastObject.localObject);
  [session loadObjectsOfClass:[Person class] completion:^(NSArray<__kindof id<NSItemProviderReading>> * _Nonnull objects) {
    self.dropLabel.text = ((Person*)objects.firstObject).name;
  }];
}