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,span) UIWindow *window;
@property(nullable,nonatomic,readonly,span) 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
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