你真的了解UIEvent、UITouch吗？

一：首先查看一下关于UIEvent的定义

//事件类型
typedef NS_ENUM(NSInteger, UIEventType) {
    UIEventTypeTouches,
    UIEventTypeMotion,
    UIEventTypeRemoteControl,
};

 // 触摸事件的类型
typedef NS_ENUM(NSInteger, UIEventSubtype) {

    UIEventSubtypeNone                              = ,
    //摇晃 
    UIEventSubtypeMotionShake                       = ,
   //播放
    UIEventSubtypeRemoteControlPlay                 = ,
   //暂停
    UIEventSubtypeRemoteControlPause                = ,
    //停止
    UIEventSubtypeRemoteControlStop                 = ,
    //播放和暂停切换 
    UIEventSubtypeRemoteControlTogglePlayPause      = ,
    //下一首
    UIEventSubtypeRemoteControlNextTrack            = ,
    //上一首
    UIEventSubtypeRemoteControlPreviousTrack        = ,
     //开始后退 
    UIEventSubtypeRemoteControlBeginSeekingBackward = ,
    //结束后退 
    UIEventSubtypeRemoteControlEndSeekingBackward   = ,
    //开始快进 
    UIEventSubtypeRemoteControlBeginSeekingForward  = ,
    //结束快进
    UIEventSubtypeRemoteControlEndSeekingForward    = ,
};

NS_CLASS_AVAILABLE_IOS(2_0) @interface UIEvent : NSObject
//事件类型
@property(nonatomic,readonly) UIEventType     type NS_AVAILABLE_IOS(3_0);
// 触摸事件的类型
@property(nonatomic,readonly) UIEventSubtype  subtype NS_AVAILABLE_IOS(3_0);

//事件的时间戳
@property(nonatomic,readonly) NSTimeInterval  timestamp;

//所有的触摸 
- (nullable NSSet <UITouch *> *)allTouches;
//获得UIWindow的触摸
- (nullable NSSet <UITouch *> *)touchesForWindow:(UIWindow *)window;
//获得UIView的触摸  
- (nullable NSSet <UITouch *> *)touchesForView:(UIView *)view;
//获得事件中特定手势的触摸
- (nullable NSSet <UITouch *> *)touchesForGestureRecognizer:(UIGestureRecognizer *)gesture NS_AVAILABLE_IOS(3_2);

//会将丢失的触摸放到一个新的 UIEvent 数组中，你可以用 coalescedTouchesForTouch(_:) 方法来访问
- (nullable NSArray <UITouch *> *)coalescedTouchesForTouch:(UITouch *)touch NS_AVAILABLE_IOS(9_0);
//辅助UITouch的触摸，预测发生了一系列主要的触摸事件。这些预测可能不完全匹配的触摸的真正的行为，因为它的移动，所以他们应该被解释为一个估计。
- (nullable NSArray <UITouch *> *)predictedTouchesForTouch:(UITouch *)touch NS_AVAILABLE_IOS(9_0);

@end

UIEvent是代表iOS系统中的一个事件,一个事件包含一个或多个的UITouch；UIEvent分为三类:UIEventTypeTouches触摸事件(通过触摸、手势进行触发,例如手指点击、缩放)、UIEventTypeMotion运动事件,通过加速器进行触发（例如手机晃动）、UIEventTypeRemoteControl远程控制事件通过其他远程设备触发（例如耳机控制按钮）；

知识点1：在iOS中并不是所有的类都能处理接收并事件，只有继承自UIResponder类的对象才能处理事件，（如我们常用的UIView、UIViewController、UIApplication都继承自UIResponder，它们都能接收并处理事件）。在UIResponder中定义了上面三类事件相关的处理方法：

触摸事件：

(void)touchesBegan:(NSSet )touches withEvent:(UIEvent )event;
一根或多根手指开始触摸屏幕时执行；

(void)touchesMoved:(NSSet )touches withEvent:(UIEvent )event;
一根或多根手指在屏幕上移动时执行，注意此方法在移动过程中会重复调用；

(void)touchesEnded:(NSSet )touches withEvent:(UIEvent )event;
一根或多根手指触摸结束离开屏幕时执行；

(void)touchesCancelled:(NSSet )touches withEvent:(UIEvent )event;
触摸意外取消时执行（例如正在触摸时打入电话）；

运动事件：

(void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event NS_AVAILABLE_IOS(3_0);
运动开始时执行；

(void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event NS_AVAILABLE_IOS(3_0);
运动结束后执行；

(void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event NS_AVAILABLE_IOS(3_0);
运动被意外取消时执行；

远程控制事件：

(void)remoteControlReceivedWithEvent:(UIEvent *)event NS_AVAILABLE_IOS(4_0);
接收到远程控制消息时执行；

知识点2：iOS「摇一摇」功能的实现（运动事件的运用）

- (void)viewDidLoad {
[super viewDidLoad];
// 设置允许摇一摇功能
[UIApplication sharedApplication].applicationSupportsShakeToEdit = YES;
// 并让自己成为第一响应者
[self becomeFirstResponder];
return;
}

//摇一摇相关方法
- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event {
NSLog(@"开始摇动");
return;
}  

- (void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event {
NSLog(@"取消摇动");
return;
}  

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if (event.subtype == UIEventSubtypeMotionShake) { // 判断是否是摇动结束
    NSLog(@"摇动结束");
}
return;
}

另外:监听运动事件前提，监听对象必须成为第一响应者；在模拟器中运行时，可以通过「Hardware」-「Shake Gesture」来测试「摇一摇」功能

知识点3：一个摇动随机图片显示的实例（运动事件的运用）

KCImageView.m

#import "KCImageView.h"

#define kImageCount 3

@implementation KCImageView

- (instancetype)initWithFrame:(CGRect)frame {

self = [super initWithFrame:frame];

if (self) {

self.image = [self getImage];

}

return self;

}

#pragma mark 设置控件可以成为第一响应者

- (BOOL)canBecomeFirstResponder{

return YES;

}

#pragma mark 运动开始

- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event{

//这里只处理摇晃事件

if (motion == UIEventSubtypeMotionShake) {

self.image = [self getImage];

}

}

#pragma mark 运动结束

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event{

}

#pragma mark 随机取得图片

- (UIImage *)getImage{

int index = arc4random() % kImageCount;

NSString *imageName = [NSString stringWithFormat:@"avatar%i.png",index];

UIImage *image = [UIImage imageNamed:imageName];

return image;

}

@end

KCShakeViewController.m

#import "KCShakeViewController.h"

#import "KCImageView.h"

@interface KCShakeViewController (){

KCImageView *_imageView;

}

@end

@implementation KCShakeViewController

- (void)viewDidLoad {

[super viewDidLoad];

}

#pragma mark 视图显示时让控件变成第一响应者

- (void)viewDidAppear:(BOOL)animated{

_imageView = [[KCImageView alloc] initWithFrame:[UIScreen mainScreen].applicationFrame];

_imageView.userInteractionEnabled = true;

[self.view addSubview:_imageView];

[_imageView becomeFirstResponder];

}

#pragma mark 视图不显示时注销控件第一响应者的身份

- (void)viewDidDisappear:(BOOL)animated{

[_imageView resignFirstResponder];

}

@end

知识点4：远程控制事件的运用

iOS远程控制事件，是通过其他远程设备触发的（比如耳机控制按钮），iOS远程控制事件相关的只有-(void)remoteControlReceivedWithEvent:(UIEvent *)event；监听远程控制事件的前提：启动远程事件接收，调用[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];UI控件同样要求必须成为第一响应者【使用参考运动事件】，但如果是视图控制器或UIApplication，就没有要求成为第一响应者，应用程序必须是 当前音频额控制者，目前iOS7给我们的远程控制权限仅限于音频控制；

一个关于音乐远程控制实例：

#import "ViewController.h"

@interface ViewController (){

UIButton *_playButton;

BOOL _isPlaying;

}

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

[self initLayout];

}

- (BOOL)canBecomeFirstResponder{

return NO;

}

- (void)viewDidAppear:(BOOL)animated{

[super viewDidAppear:animated];

NSURL *url = [NSURL URLWithString:@"http://stream.jewishmusicstream.com:8000"];

_player = [[AVPlayer alloc] initWithURL:url];

}

#pragma mark 远程控制事件

- (void)remoteControlReceivedWithEvent:(UIEvent *)event{

if(event.type == UIEventTypeRemoteControl){

switch (event.subtype) {

case UIEventSubtypeRemoteControlPlay:

[_player play];

_isPlaying = true;

break;

case UIEventSubtypeRemoteControlTogglePlayPause:

[self btnClick:_playButton];

break;

case UIEventSubtypeRemoteControlNextTrack:

NSLog(@"Next...");

break;

case UIEventSubtypeRemoteControlPreviousTrack:

NSLog(@"Previous...");

break;

case UIEventSubtypeRemoteControlBeginSeekingForward:

NSLog(@"Begin seek forward...");

break;

case UIEventSubtypeRemoteControlEndSeekingForward:

NSLog(@"End seek forward...");

break;

case UIEventSubtypeRemoteControlBeginSeekingBackward:

NSLog(@"Begin seek backward...");

break;

case UIEventSubtypeRemoteControlEndSeekingBackward:

NSLog(@"End seek backward...");

break;

default:

break;

}

[self changeUIState];

}

}

#pragma mark 界面布局

- (void)initLayout{

//专辑封面

UIImage *image = [UIImage imageNamed:@"wxl.jpg"];

CGRect *frame = [UIScreen mainScreen].applicationFrame;

UIImageView *imageView = [[UIImageView alloc] initWithFrame:frame];

imageView.image = image;

imageView.contentMode = UIViewContentModeScaleAspectFill;

[self.view addSubview:imageView];

//播放控制面板

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(, , , )];

view.backgroundColor = [UIColor lightGrayColor];

view.alpha = 0.9;

[self.view addSubview:view];

//添加播放按钮

_playButton = [UIButton buttonWithType:UIButtonTypeCustom];

_playButton.bounds = CGRectMake(, , , );

CGFloat playBtnX = view.frame.size.width/;

CGFloat playBtnY = view.frame.size.height/;

_playButton.center = CGPointMake(playBtnX, playBtnY);

[self changeUIState];

[_playButton addTarget:self

action:@selector(btnClick:)

forControlEvents:UIControlEventTouchUpInside];

[view addSubview:_playButton];

}

#pragma mark 界面状态

- (void)changeUIState{

if(_isPlaying){

UIImage *pauseImage = [UIImage imageNamed:@"playing_btn_pause_n.png"];

UIImage *pauseImageH = [UIImage imageNamed:@"playing_btn_pause_h.png"];

[_playButton setImage:pauseImage forState:UIControlStateNormal];

[_playButton setImage:pauseImageH forState:UIControlStateHighlighted];

}else{

UIImage *playImage = [UIImage imageNamed:@"playing_btn_play_n.png"];

UIImage *playImageH = [UIImage imageNamed:@"playing_btn_play_h.png"];

[_playButton setImage:playImage forState:UIControlStateNormal];

[_playButton setImage:playImageH forState:UIControlStateHighlighted];

}

}

- (void)btnClick:(UIButton *)btn{

if (_isPlaying) {

[_player pause];

}else{

[_player play];

}

_isPlaying =! _isPlaying;

[self changeUIState];

}

@end

二：首先查看一下关于UITouch的定义

//触摸事件在屏幕上有一个周期
typedef NS_ENUM(NSInteger, UITouchPhase) {
    UITouchPhaseBegan,           //开始触摸
    UITouchPhaseMoved,           //移动
    UITouchPhaseStationary,      //停留
    UITouchPhaseEnded,            //触摸结束
    UITouchPhaseCancelled,       //触摸中断
};

//检测是否支持3DTouch
typedef NS_ENUM(NSInteger, UIForceTouchCapability) {
    UIForceTouchCapabilityUnknown = ,  //3D Touch检测失败
    UIForceTouchCapabilityUnavailable = ,  //3D Touch不可用
    UIForceTouchCapabilityAvailable =   //3D Touch可用
};

NS_CLASS_AVAILABLE_IOS(2_0) @interface UITouch : NSObject

//触摸产生或变化的时间戳 只读
@property(nonatomic,readonly) NSTimeInterval      timestamp;
//触摸周期内的各个状态
@property(nonatomic,readonly) UITouchPhase        phase;
//短时间内点击的次数 只读
@property(nonatomic,readonly) NSUInteger          tapCount;   

//获取手指与屏幕的接触半径 IOS8以后可用 只读
@property(nonatomic,readonly) CGFloat majorRadius NS_AVAILABLE_IOS(8_0);
//获取手指与屏幕的接触半径的误差 IOS8以后可用 只读
@property(nonatomic,readonly) CGFloat majorRadiusTolerance NS_AVAILABLE_IOS(8_0);

//触摸时所在的窗口 只读
@property(nullable,nonatomic,readonly,strong) UIWindow                        *window;
//触摸时所在视图
@property(nullable,nonatomic,readonly,strong) UIView                          *view;
//获取触摸手势
@property(nullable,nonatomic,readonly,copy)   NSArray <UIGestureRecognizer *> *gestureRecognizers NS_AVAILABLE_IOS(3_2);

//取得在指定视图的位置
// 返回值表示触摸在view上的位置
// 这里返回的位置是针对view的坐标系的（以view的左上角为原点(0,0)）
// 调用时传入的view参数为nil的话，返回的是触摸点在UIWindow的位置
- (CGPoint)locationInView:(nullable UIView *)view;
//该方法记录了前一个触摸点的位置
- (CGPoint)previousLocationInView:(nullable UIView *)view;

//获取触摸压力值，一般的压力感应值为1.0 IOS9 只读
@property(nonatomic,readonly) CGFloat force NS_AVAILABLE_IOS(9_0);

//获取最大触摸压力值
@property(nonatomic,readonly) CGFloat maximumPossibleForce NS_AVAILABLE_IOS(9_0);

@end

知识点1：触摸时，图片移动（实例）

- (void)viewDidLoad
{
    UIImageView *image = [[UIImageView alloc] initWithFrame:CGRectMake(20.0, 50.0, 45.0, 45.0)];
    image.image = [UIImage imageNamed:@"baby.png"];
    image.tag = ;
    [self.view addSubview:image];  

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}  

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    UIImageView *view1 = (UIImageView*)[self.view  viewWithTag:];
    CGPoint point = [touch  locationInView:self.view];
    CGRect  frame = view1.frame;
    frame.origin = point;
    view1.frame = frame;
}

知识点2：创建可以拖动的视图

CGPoint originalLocation;
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    originalLocation = [touch locationInView:self.view];
}  

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    CGPoint currentLocation = [touch locationInView:self.view];
    CGRect frame = self.view.frame;
    frame.origin.x += currentLocation.x-originalLocation.x;
    frame.origin.y += currentLocation.y-originalLocation.y;
    self.view.frame = frame;
} 

这里先在touchesBegan中通过[touch locationInView:self.view]获取手指触摸在当前视图上的位置，用CGPoint变量记录，然后在手指移动事件touchesMoved方法中获取触摸对象当前位置，并通过于与原始位置的差值计算出移动偏移量，再设置当前视图的位置。