iOS开发之触摸事件以及手势

iOS中的事件分为三类：触摸事件、加速计事件、远程控制事件。只有继承了UIResponder的对象才能接收并处理事件，称之为“响应者对象”。UIApplication、UIViewController、UIView都继承自UIResponder。UIResponder内部提供的方法来处理事件：

触摸事件：touchesBegan、touchesMoved、touchesEnded、touchesCancelled

加速计事件：motionBegan、motionEnded、motionCancelled

远程控制事件：remoteControlReceivedWithEvent

UIVeiw的触摸事件处理过程：

/**
 * 当手指开始触摸view时调用
 *
 * @param touches <#touches description#>
 * @param event  <#event description#>
 */
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

  NSLog(@"%s",__func__);
}

/**
 * 当手指在view上移动时调用
 *
 * @param touches <#touches description#>
 * @param event  <#event description#>
 */
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
  NSLog(@"%s",__func__);
}

/**
 * 当手指离开view时调用
 *
 * @param touches <#touches description#>
 * @param event  <#event description#>
 */
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

  NSLog(@"%s",__func__);
}

/**
 * 当触摸事件被系统事件打断时调用
 *
 * @param touches <#touches description#>
 * @param event  <#event description#>
 */
- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

  NSLog(@"%s",__func__);
}

一次触摸动作必然会调用touchesBeagn、touchesMoved和touchesEnded这三个方法。

说到这几个触摸方法，首先要知道UITouch这个对象。当一根手指触摸屏幕时就会产生一个与之关联的UITouch对象，一根手指对应一个UITouch对象。这个对象里面保存着这次触摸的信息，比如触摸的位置，时间，阶段等，当手指移动时，系统会更新同一个UITouch对象。使其能一直保存该手指所在的触摸位置信息。当手指离开屏幕时，系统会销毁对应的UITouch对象。

@interface UITouch : NSObject

@property(nonatomic,readonly) NSTimeInterval   timestamp;
@property(nonatomic,readonly) UITouchPhase    phase;
@property(nonatomic,readonly) NSUInteger     tapCount;  // touch down within a certain point within a certain amount of time

// majorRadius and majorRadiusTolerance are in points
// The majorRadius will be accurate +/- the majorRadiusTolerance
@property(nonatomic,readonly) CGFloat majorRadius NS_AVAILABLE_IOS(8_0);
@property(nonatomic,readonly) CGFloat majorRadiusTolerance NS_AVAILABLE_IOS(8_0);

@property(nullable,nonatomic,readonly,strong) UIWindow            *window;
@property(nullable,nonatomic,readonly,strong) UIView             *view;
@property(nullable,nonatomic,readonly,copy)  NSArray <UIGestureRecognizer *> *gestureRecognizers NS_AVAILABLE_IOS(3_2);

//获取当前位置
- (CGPoint)locationInView:(nullable UIView *)view;
//获取上一个触摸点的位置
- (CGPoint)previousLocationInView:(nullable UIView *)view;

// Force of the touch, where 1.0 represents the force of an average touch
@property(nonatomic,readonly) CGFloat force NS_AVAILABLE_IOS(9_0);
// Maximum possible force with this input mechanism
@property(nonatomic,readonly) CGFloat maximumPossibleForce NS_AVAILABLE_IOS(9_0);

@end

eg:让一个view随着手指的移动而移动

/**
 * 当手指在view上移动时调用
 *
 * @param touches <#touches description#>
 * @param event  <#event description#>
 */
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
  NSLog(@"%s",__func__);

  //获取UITouch对象
  UITouch *touch = [touches anyObject];

  //获取当前点的位置
  CGPoint curP = [touch locationInView:self];

  //获取上一个点的位置
  CGPoint preP = [touch previousLocationInView:self];

  //计算x的偏移量
  CGFloat offsetX = curP.x - preP.x;

  //计算y的偏移量
  CGFloat offsetY = curP.y = preP.y;

  //修改view的位置
  self.transform = CGAffineTransformTranslate(self.transform, offsetX, offsetY);
}

就是根据UITouch对象中保存的位置信息来实现的。

事件的产生和传递：

当触摸事件产生后，系统会将该事件添加到一个由UIApplication管理的事件队列中去。UIApplication会从队列中取出最前面的事件，发送给应用程序的主窗口的处理。主窗口会在视图层次结构中，找一个最合适的视图并调用touches方法来处理触摸事件。触摸事件的传递是从父控件传递到子控件。如果父控件不能接收到触摸事件，那么子控件就不可能 接收到触摸事件。

如何找到最合适的控件来处理事件？首先判断自己是否能接收触摸事件？触摸点是否在自己身上？从后往前遍历子控件，重复之前的两个步骤，如果没有符合条件的子控件，那么就自己最合适处理。

控件用hitTest:withEvent:方法来寻找最合适的view，用pointInside这个方法判断这个点在不在方法调用者即控件身上。

hitTest方法的底层实现：

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {

  //判断当前控件是否能接收触摸事件
  if (self.userInteractionEnabled == NO || self.hidden == YES || self.alpha <= 0.01) {
    return nil;
  }

  //判断触摸点是否在当前控件上
  if ([self pointInside:point withEvent:event] == NO) {
    return nil;
  }

  //从后往前遍历自己的子控件
  NSInteger count = self.subviews.count;
  for (NSInteger i = count - 1; i >= 0; i--) {
    UIView *childView = self.subviews[i];

    //把当前控件上的坐标系转换成子控件上的坐标系
    CGPoint childPoint = [self convertPoint:point toView:childView];

    //递归调用hitTest方法寻找最合适的view
    UIView *fitView = [childView hitTest:childPoint withEvent:event];

    if (fitView) {
      return fitView;
    }
  }

  //循环结束，没有比自己更合适的view，返回自己
  return self;

}

然而使用touches方法监听触摸事件是有缺点的，比如要自定义view，所以iOS3.2之后苹果推出了手势识别功能UIGestureRecognizer。UIGestureRecognizer是一个抽象类，它的子类才能处理具体的某个手势。

具体有以下几种手势：

//点按手势
//  UITapGestureRecognizer *tap = [UITapGestureRecognizer alloc]initWithTarget:<#(nullable id)#> action:<#(nullable SEL)#>

  //长按手势 默认是触发两次
//  UILongPressGestureRecognizer *longP = [UILongPressGestureRecognizer alloc]initWithTarget:<#(nullable id)#> action:<#(nullable SEL)#>

  //轻扫手势 默认方向是往右
//  UISwipeGestureRecognizer *swipe = [UISwipeGestureRecognizer alloc]initWithTarget:<#(nullable id)#> action:<#(nullable SEL)#>

  //旋转手势
//  UIRotationGestureRecognizer *rotation = [UIRotationGestureRecognizer alloc]initWithTarget:<#(nullable id)#> action:<#(nullable SEL)#>

  //捏合手势
//  UIPinchGestureRecognizer *pinch = [UIPinchGestureRecognizer alloc]initWithTarget:<#(nullable id)#> action:<#(nullable SEL)#>

  //拖拽手势
//  UIPanGestureRecognizer *pan = [UIPanGestureRecognizer alloc]initWithTarget:<#(nullable id)#> action:<#(nullable SEL)#>

实际运用：

@interface ViewController ()<UIGestureRecognizerDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

@implementation ViewController

- (void)viewDidLoad {
  [super viewDidLoad];

  [self setUpPinch];

  [self setUpRotation];

  [self setUpPan];

}
#pragma mark - 手势代理方法
// 是否允许开始触发手势
//- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
//{
//  return NO;
//}

// 是否允许同时支持多个手势，默认是不支持多个手势
// 返回yes表示支持多个手势
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
  return YES;
}

// 是否允许接收手指的触摸点
//- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch{
//  // 获取当前的触摸点
//  CGPoint curP = [touch locationInView:self.imageView];
//
//  if (curP.x < self.imageView.bounds.size.width * 0.5) {
//    return NO;
//  }else{
//    return YES;
//  }
//}

#pragma mark - 点按手势

- (void)setUpTap
{
  // 创建点按手势
  UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)];

  tap.delegate = self;

  [_imageView addGestureRecognizer:tap];
}

- (void)tap:(UITapGestureRecognizer *)tap
{
  NSLog(@"%s",__func__);
}

#pragma mark - 长按手势
// 默认会触发两次
- (void)setUpLongPress
{
  UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];

  [self.imageView addGestureRecognizer:longPress];
}

- (void)longPress:(UILongPressGestureRecognizer *)longPress
{

  if (longPress.state == UIGestureRecognizerStateBegan) {

    NSLog(@"%s",__func__);
  }
}

#pragma mark - 轻扫
- (void)setUpSwipe
{
  // 默认轻扫的方向是往右
  UISwipeGestureRecognizer *swipe = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe)];

  swipe.direction = UISwipeGestureRecognizerDirectionUp;

  [self.imageView addGestureRecognizer:swipe];

  // 如果以后想要一个控件支持多个方向的轻扫，必须创建多个轻扫手势，一个轻扫手势只支持一个方向
  // 默认轻扫的方向是往右
  UISwipeGestureRecognizer *swipeDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipe)];

  swipeDown.direction = UISwipeGestureRecognizerDirectionDown;

  [self.imageView addGestureRecognizer:swipeDown];

}

- (void)swipe
{
  NSLog(@"%s",__func__);
}

#pragma mark - 旋转手势
- (void)setUpRotation
{
  UIRotationGestureRecognizer *rotation = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotation:)];
  rotation.delegate = self;
  [self.imageView addGestureRecognizer:rotation];
}

// 默认传递的旋转的角度都是相对于最开始的位置
- (void)rotation:(UIRotationGestureRecognizer *)rotation
{

  self.imageView.transform = CGAffineTransformRotate(self.imageView.transform, rotation.rotation);

  // 复位
  rotation.rotation = 0;

  // 获取手势旋转的角度
  NSLog(@"%f",rotation.rotation);
}

#pragma mark - 捏合
- (void)setUpPinch
{
  UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinch:)];
  pinch.delegate = self;
  [self.imageView addGestureRecognizer:pinch];
}

- (void)pinch:(UIPinchGestureRecognizer *)pinch
{
  self.imageView.transform = CGAffineTransformScale(self.imageView.transform, pinch.scale, pinch.scale);

  // 复位

  pinch.scale = 1;
}

#pragma mark - 拖拽
- (void)setUpPan
{
  UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];

  [self.imageView addGestureRecognizer:pan];
}

- (void)pan:(UIPanGestureRecognizer *)pan
{
  // 获取手势的触摸点
  // CGPoint curP = [pan locationInView:self.imageView];

  // 移动视图
  // 获取手势的移动，也是相对于最开始的位置
  CGPoint transP = [pan translationInView:self.imageView];

  self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, transP.x, transP.y);

  // 复位
  [pan setTranslation:CGPointZero inView:self.imageView];

 // NSLog(@"%@",NSStringFromCGPoint(curP));
}

@end

以上就是iOS触摸事件以及手势的相关内容介绍，希望对大家学习iOS程序设计有所帮助。