iOS开发Drag and Drop简介

1、Drag and Drop简介

　　Drag and Drop是iOS11的新特性，可以将文本、图片进行拖拽到不同app中，实现数据的传递。只不过只能在iPad上使用，iPhone上只能app内部拖拽！

2、简单使用

　　相关代码：

#import "ViewController.h"
#define CScreenWidth        [[UIScreen mainScreen] bounds].size.width
#define CScreenHeight       [[UIScreen mainScreen] bounds].size.height
#define ScreenHeight        self.view.frame.size.height
#define ScreenWidth         self.view.frame.size.width

@interface ViewController ()<UIDragInteractionDelegate,UIDropInteractionDelegate>

@property (nonatomic, strong)UIImageView *img;
@property (nonatomic, strong)UIImageView *img2;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.img =[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"pic4"]];
    self.img.frame = CGRectMake(, , CScreenWidth-, );
    self.img.userInteractionEnabled = YES;
    [self.view addSubview:self.img];
    //Drag发送数据，Drop接收数据
    UIDragInteraction *dragInter = [[UIDragInteraction alloc] initWithDelegate:self];
    dragInter.enabled = YES;
    [self.img addInteraction:dragInter];
    [self.view addInteraction:[[UIDropInteraction alloc] initWithDelegate:self]];

    self.img2 =[[UIImageView alloc] init];
    self.img2.frame = CGRectMake(, CScreenHeight-, CScreenWidth-, );
    self.img2.userInteractionEnabled = YES;
    [self.view addSubview:self.img2];

}
#pragma mark -UIDragInteractionDelegate
//提供数据源  开始拖拽
- (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForBeginningSession:(id<UIDragSession>)session{
    NSLog(@"11111----");
    self.img2.image = nil;
    NSItemProvider *item = [[NSItemProvider alloc] initWithObject:self.img.image];
    UIDragItem *dragItem = [[UIDragItem alloc] initWithItemProvider:item];
    dragItem.localObject = self.img.image;
    return @[dragItem];
}
//提供preview相关信息
- (nullable UITargetedDragPreview *)dragInteraction:(UIDragInteraction *)interaction previewForLiftingItem:(UIDragItem *)item session:(id<UIDragSession>)session{
    NSLog(@"22222----");
    UIDragPreviewParameters *parameters = [[UIDragPreviewParameters alloc] init];
    //设置蒙版mask
    parameters.visiblePath = [UIBezierPath bezierPathWithRoundedRect:self.img.bounds cornerRadius:];
    //设置在哪个父视图和哪个位置展示
    UIDragPreviewTarget *target = [[UIDragPreviewTarget alloc] initWithContainer:self.img.superview center:self.img.center];
    UITargetedDragPreview *dragePreview = [[UITargetedDragPreview alloc] initWithView:interaction.view parameters:parameters target:target];
    return dragePreview;
}
//drag进行时
- (void)dragInteraction:(UIDragInteraction *)interaction willAnimateLiftWithAnimator:(id<UIDragAnimating>)animator session:(id<UIDragSession>)session{
    NSLog(@"33333----");
    [animator addCompletion:^(UIViewAnimatingPosition finalPosition) {
        if (finalPosition == UIViewAnimatingPositionEnd) {
            self.img.alpha = 0.5;
        }
    }];
}
//drag将要结束时调用
- (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session willEndWithOperation:(UIDropOperation)operation{
    NSLog(@"44444----");
    [UIView animateWithDuration:0.5 animations:^{
        self.img.alpha = ;
    }];
}
//drag动画将要取消时
- (void)dragInteraction:(UIDragInteraction *)interaction item:(UIDragItem *)item willAnimateCancelWithAnimator:(id<UIDragAnimating>)animator{
    NSLog(@"55555----");
    [animator addAnimations:^{
        self.img.alpha = .;
    }];
}
//drag已经结束时调用
- (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session didEndWithOperation:(UIDropOperation)operation{
    NSLog(@"66666----");
    [UIView animateWithDuration:0.5 animations:^{
        self.img.alpha = ;
    }];
}

#pragma mark --UIDropInteractionDelegate
//是否可以接收来自Drag数据
- (BOOL)dropInteraction:(UIDropInteraction *)interaction canHandleSession:(id<UIDropSession>)session{
    if(session.localDragSession == nil){//说明数据来自外界
    }
    return [session canLoadObjectsOfClass:[UIImage class]];
}

//第二次判断是否可以接收 无法接收用UIDropOperationCancel
- (UIDropProposal *)dropInteraction:(UIDropInteraction *)interaction sessionDidUpdate:(id<UIDropSession>)session{
    UIDropOperation opera = session.localDragSession? UIDropOperationCopy:UIDropOperationCancel;
    return [[UIDropProposal alloc] initWithDropOperation:opera];
}

//取出来自drag的数据
- (void)dropInteraction:(UIDropInteraction *)interaction performDrop:(id<UIDropSession>)session{
    if (session.localDragSession) {
      NSProgress *pregesss  = [session loadObjectsOfClass:[UIImage class]
                                               completion:^(NSArray<__kindof id<NSItemProviderReading>> * _Nonnull objects) {
                                                   // 回调的代码块默认就在主线程
                                                   for (id objc in objects) {
                                                       UIImage *image = (UIImage *)objc;
                                                       if (image) {
                                                           self.img2.image = image;
                                                       }
                                                   }
                                               }];
    }
}

@end

DragAndDrop.m文件

3、有关方法简介

　　UIDragInteraction和Delegate方法：

@protocol UIDragInteractionDelegate, UIDragSession;
@class UIDragItem, UITargetedDragPreview;
API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @protocol UIDragAnimating <NSObject>
- (void)addAnimations:(void (^)(void))animations;
- (void)addCompletion:(void (^)(UIViewAnimatingPosition finalPosition))completion;
@end

UIKIT_EXTERN API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @interface UIDragInteraction : NSObject <UIInteraction>
- (instancetype)initWithDelegate:(id<UIDragInteractionDelegate>)delegate NS_DESIGNATED_INITIALIZER;
- (instancetype)init NS_UNAVAILABLE;
+ (instancetype)new NS_UNAVAILABLE;
@property (nonatomic, nullable, readonly, weak) id<UIDragInteractionDelegate> delegate;
@property (nonatomic) BOOL allowsSimultaneousRecognitionDuringLift;
@property (nonatomic, getter=isEnabled) BOOL enabled;
@property (class, nonatomic, readonly, getter=isEnabledByDefault) BOOL enabledByDefault;
@end

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @protocol UIDragInteractionDelegate <NSObject>
@required
//提供数据源  长按UI开始拖拽
- (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForBeginningSession:(id<UIDragSession>)session;
@optional
//提供UITargetedDragPreview的相关信息  长按UI是有个lift（UI举起效果，系统自动生成）
//返回nil 没有效果；   不实现该方法 interaction.view自动生成UITargetedDragPreview
- (nullable UITargetedDragPreview *)dragInteraction:(UIDragInteraction *)interaction previewForLiftingItem:(UIDragItem *)item session:(id<UIDragSession>)session;
//drag发生时调用
- (void)dragInteraction:(UIDragInteraction *)interaction willAnimateLiftWithAnimator:(id<UIDragAnimating>)animator session:(id<UIDragSession>)session;
//将要开始drag
- (void)dragInteraction:(UIDragInteraction *)interaction sessionWillBegin:(id<UIDragSession>)session;
//是否允许数据移动 app内移动有效，跨app总是复制数据
- (BOOL)dragInteraction:(UIDragInteraction *)interaction sessionAllowsMoveOperation:(id<UIDragSession>)session;
//是否允许跨应用程序进行drag 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;
//已经结束移动
- (void)dragInteraction:(UIDragInteraction *)interaction sessionDidMove:(id<UIDragSession>)session;
//drag将要结束时调用
- (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session willEndWithOperation:(UIDropOperation)operation;
//drag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;
//设置是否允许向拖拽中的项目添加数据 返回数据载体数组 drag时点击拖拽的组件调用
- (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;
//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;
//drag动画将要取消时调用
- (void)dragInteraction:(UIDragInteraction *)interaction item:(UIDragItem *)item willAnimateCancelWithAnimator:(id<UIDragAnimating>)animator;

　　UIDropInteraction和Delegate方法：

@protocol UIDragAnimating, UIDropInteractionDelegate, UIDropSession;
@class UIDragItem, UITargetedDragPreview;

UIKIT_EXTERN API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @interface UIDropInteraction : NSObject <UIInteraction>

- (instancetype)initWithDelegate:(id<UIDropInteractionDelegate>)delegate NS_DESIGNATED_INITIALIZER;
- (instancetype)init NS_UNAVAILABLE;
+ (instancetype)new NS_UNAVAILABLE;

@property (nonatomic, nullable, readonly, weak) id<UIDropInteractionDelegate> delegate;
@property (nonatomic, assign) BOOL allowsSimultaneousDropSessions;
@end
typedef NS_ENUM(NSUInteger, UIDropOperation) {
    UIDropOperationCancel   = ,
    UIDropOperationForbidden = ,
    UIDropOperationCopy      = ,
    UIDropOperationMove      = ,
} API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos);

UIKIT_EXTERN API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @interface UIDropProposal : NSObject <NSCopying>
- (instancetype)initWithDropOperation:(UIDropOperation)operation NS_DESIGNATED_INITIALIZER;
- (instancetype)init NS_UNAVAILABLE;
+ (instancetype)new NS_UNAVAILABLE;
@property (nonatomic, readonly) UIDropOperation operation;
@property (nonatomic, getter=isPrecise) BOOL precise;
@property (nonatomic) BOOL prefersFullSizePreview;
@end

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @protocol UIDropInteractionDelegate <NSObject>

@optional
//是否可以处理来自Drag的数据
- (BOOL)dropInteraction:(UIDropInteraction *)interaction canHandleSession:(id<UIDropSession>)session;
//Drag的UI元素进入Drop的区域
- (void)dropInteraction:(UIDropInteraction *)interaction sessionDidEnter:(id<UIDropSession>)session;
//第二次判断是否可以接收 无法接收用UIDropOperationCancel
- (UIDropProposal *)dropInteraction:(UIDropInteraction *)interaction sessionDidUpdate:(id<UIDropSession>)session;
//Drag的UI元素离开Drop的区域
- (void)dropInteraction:(UIDropInteraction *)interaction sessionDidExit:(id<UIDropSession>)session;
//取出来自drag的数据

NSLog(@"%f,%f",[session locationInView:self.view].x,[session locationInView:self.view].y)

- (void)dropInteraction:(UIDropInteraction *)interaction performDrop:(id<UIDropSession>)session;
//drop结束
- (void)dropInteraction:(UIDropInteraction *)interaction concludeDrop:(id<UIDropSession>)session;
//整个Drag和Drop结束
- (void)dropInteraction:(UIDropInteraction *)interaction sessionDidEnd:(id<UIDropSession>)session;
//手指松开，控制Drag Preview 如何自然的过渡到Drop之后的Preview
- (nullable UITargetedDragPreview *)dropInteraction:(UIDropInteraction *)interaction previewForDroppingItem:(UIDragItem *)item withDefault:(UITargetedDragPreview *)defaultPreview;
//手指松开Drop时，控制Drop区域的其他UI元素如何展示动画
- (void)dropInteraction:(UIDropInteraction *)interaction item:(UIDragItem *)item willAnimateDropWithAnimator:(id<UIDragAnimating>)animator;
@end