UI 触摸与手势

触摸（UITouch）

• UITouch方法

// 触摸开始
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;

// 触摸移动
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;

// 触摸结束
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;

// 触摸取消
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;

• 场景举例
  有时需要用户触摸某个视图移动，并且视图会跟着触摸手势轨迹的移动的时候，我们可通过触摸移动方法touchesMoved实现。

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(@"%@", NSStringFromSelector(_cmd)); UITouch *touch = [touches anyObject]; if (touch.view == _showView) {
// 前一个点
CGPoint previousLocation = [touch previousLocationInView:_showView]; // 当前点
CGPoint currentLocation = [touch locationInView:_showView]; // 偏移
CGPoint offset = CGPointMake(currentLocation.x - previousLocation.x,currentLocation.y - previousLocation.y); // 改变视图位置
_showView.center = CGPointMake(_showView.center.x + offset.x,_showView.center.y + offset.y); }
}

手势（UIGestureRecognizer）

简介

• Cocoa Touch中为我们提供了便利的手势处理类：UIGestureRecognizer

• 由UIGestureRecognizer衍生的常用子类有：
  点击手势：UITapGestureRecognizer
  缩放手势：UIPinchGestureRecognizer
  旋转手势：UIRotationGestureRecognizer
  滑动手势：UISwipeGestureRecognizer
  拖动手势：UIPanGestureRecognizer
  长按手势：UILongPressGestureRecognizer

• 初始化手势

- (id)initWithTarget:(id)target action:(SEL)action;

• 添加或移除指定视图上的手势

// 添加手势 
- (void)addGestureRecognizer:(UIGestureRecognizer*)gestureRecognizer;

// 移除手势
- (void)removeGestureRecognizer:(UIGestureRecognizer*)gestureRecognizer;

• 当同一视图上存在多个手势时，会出现冲突，可以使用一个方法来避免多手势带来的冲突

- (void)requireGestureRecognizerToFail:(UIGestureRecognizer *)otherGestureRecognizer;

代码示例

#import "UIGestureRecognizerViewController.h" 

#define vc_title @"Gesture" 

@interface UIGestureRecognizerViewController ()

@property (nonatomic, strong)UILabel *stateLabel; 
@property (nonatomic, strong)UIView *gestureView; 
/**
*  初始化用户界面
*/ - (void)initializeUserInterface; /**
*  初始化手势
*/ - (void)initializeGestureRecognizer; 
@end 

@implementation UIGestureRecognizerViewController 

- (void)viewDidLoad {
[super viewDidLoad];
[self initializeUserInterface];
[self initializeGestureRecognizer];
}

- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated]; // autolayout自动布局 [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[_stateLabel]-0-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_stateLabel)]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[_stateLabel(==30)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_stateLabel)]];
} 

#pragma mark - init 

- (void)initializeUserInterface
{ 
self.view.backgroundColor = [UIColor whiteColor]; 
self.title = vc_title;

[self.view addSubview:self.stateLabel];
[self.view addSubview:self.gestureView];
}

- (void)initializeGestureRecognizer
{
// 1、点击手势识别器
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(respondsToGestureRecognizer:)];
// 设置点击次数
tapGesture.numberOfTapsRequired = 1;
// 设置手指数量
tapGesture.numberOfTouchesRequired = 1;
// 添加手势
[_gestureView addGestureRecognizer:tapGesture];

// 2、长按手势识别器
UILongPressGestureRecognizer *longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(respondsToGestureRecognizer:)];
[_gestureView addGestureRecognizer:longPressGesture];

// 3、滑动手势识别器
UISwipeGestureRecognizer *swipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(respondsToGestureRecognizer:)];
// 设置滑动方向:right、left、up、down
swipeGesture.direction = UISwipeGestureRecognizerDirectionRight;
[_gestureView addGestureRecognizer:swipeGesture];

// 4、拖拽手势识别器
UIPanGestureRecognizer *panPress = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(respondsToGestureRecognizer:)];
[_gestureView addGestureRecognizer:panPress];

// 5、捏合手势识别器
UIPinchGestureRecognizer * pinchPress = [[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(respondsToGestureRecognizer:)];
[_gestureView addGestureRecognizer:pinchPress];

// 6、旋转手势识别器
UIRotationGestureRecognizer * rotationPress = [[UIRotationGestureRecognizer alloc]initWithTarget:self action:@selector(respondsToGestureRecognizer:)];
[_gestureView addGestureRecognizer:rotationPress];
// 手势识别器冲突
[swipeGesture requireGestureRecognizerToFail:panPress];
// 如果冲突，执行后面的
}

#pragma mark - responds event 

- (void)respondsToGestureRecognizer:(UIGestureRecognizer *)gesture
{
// 点击手势识别器
if ([gesture isKindOfClass:[UITapGestureRecognizer class]]) {
UITapGestureRecognizer *tap = (UITapGestureRecognizer *)gesture;
// state 属性：获取用户手势状态
if (tap.state == UIGestureRecognizerStateBegan) {
[_stateLabel setText:@"用户开始点击"];
} else if (tap.state == UIGestureRecognizerStateEnded) {
[_stateLabel setText:@"用户点击结束"];
}
}
// 长按手势识别器
else if ([gesture isKindOfClass:[UILongPressGestureRecognizer class]]) {
UILongPressGestureRecognizer *longPress = (UILongPressGestureRecognizer *)gesture;
if (longPress.state == UIGestureRecognizerStateBegan) {
[_stateLabel setText:@"长按手势开始"];
} else if (longPress.state == UIGestureRecognizerStateEnded) {
[_stateLabel setText:@"长按手势结束"];
}
}
// 滑动手势识别器
else if ([gesture isKindOfClass:[UISwipeGestureRecognizer class]]) {

UISwipeGestureRecognizer *swipePress = (UISwipeGestureRecognizer *)gesture;
if (swipePress.state == UIGestureRecognizerStateBegan) {
[_stateLabel setText:@"滑动手势开始"];

} else if(swipePress.state == UIGestureRecognizerStateChanged) {
[_stateLabel setText:@"滑动手势滑动中"];
}else if (swipePress.state == UIGestureRecognizerStateEnded) {
[_stateLabel setText:@"滑动手势结束"];
}

}
// 拖拽手势识别器
else if ([gesture isKindOfClass:[UIPanGestureRecognizer class]]) {
UIPanGestureRecognizer *pan = (UIPanGestureRecognizer *)gesture;
// 声明一个静态的变量记录拖拽视图前时的中心点
static CGPoint firstCenter;
if (pan.state == UIGestureRecognizerStateBegan) {
// 给firstCenter赋值
firstCenter = self.view.center;
[_stateLabel setText:@"拖拽手势开始"];
} else if (pan.state == UIGestureRecognizerStateChanged) {
// 获取手势在某一个视图上的移动了多少
CGPoint translation = [pan translationInView:self.view];
_gestureView.center = CGPointMake(firstCenter.x + translation.x, firstCenter.y + translation.y);
[_stateLabel setText:@"拖拽手势拖动中"];
} else if (pan.state == UIGestureRecognizerStateEnded) {
// 更新静态变量firstCenter的值，供下次识别这个手势时使用
firstCenter = _gestureView.center;
[_stateLabel setText:@"拖拽手势结束"];
}
}
// 捏合手势识别器
else if ([gesture isKindOfClass:[UIPinchGestureRecognizer class]]) {
UIPinchGestureRecognizer * pinch = (UIPinchGestureRecognizer *)gesture;
static CGFloat lastScale;
if (pinch.state == UIGestureRecognizerStateBegan) {
lastScale = pinch.scale;
[_stateLabel setText:@" 捏合手势开始"];
} else if (pinch.state == UIGestureRecognizerStateChanged) {

CGFloat changeScale = (pinch.scale - lastScale)/2 + 1;

if (_gestureView.bounds.size.width < 100) {
// 当视图<100,就不能再缩小
return;

} else {
_gestureView.transform = CGAffineTransformScale(_gestureView.transform, changeScale, changeScale);
lastScale = pinch.scale;

}
} else if (pinch.state == UIGestureRecognizerStateEnded){
lastScale = 1;
[_stateLabel setText:@" 捏合手势结束"];
}
}
// 旋转手势识别器
else if ([gesture isKindOfClass:[UIRotationGestureRecognizer class]]) {

UIRotationGestureRecognizer * rotation = (UIRotationGestureRecognizer *)gesture;
static CGFloat lastRotate;
if (rotation.state == UIGestureRecognizerStateBegan) {
lastRotate = rotation.rotation;
[_stateLabel setText:@"旋转手势开始"];
} else if (rotation.state == UIGestureRecognizerStateChanged) {
CGFloat changeRotate = rotation.rotation - lastRotate;
_gestureView.transform = CGAffineTransformRotate(_gestureView.transform, changeRotate);
lastRotate = rotation.rotation;
} else if (rotation.state) {
lastRotate = 0;
}
}
}

#pragma mark - getter

- (UILabel *)stateLabel {
if (!_stateLabel) {
_stateLabel = [[UILabel alloc] init];
_stateLabel.translatesAutoresizingMaskIntoConstraints = NO;
_stateLabel.textAlignment = NSTextAlignmentCenter;
_stateLabel.font = [UIFont systemFontOfSize:25];
}
return _stateLabel;
}

- (UIView *)gestureView {
if (!_gestureView) {
_gestureView = [[UIView alloc] init];
_gestureView.bounds = CGRectMake(0, 0, 200, 200);
_gestureView.center = self.view.center;
_gestureView.backgroundColor = [UIColor redColor];
// 开启用户交互
_gestureView.userInteractionEnabled = YES;
}
return _gestureView;
}

@end