iOS中的触摸事件

@interface ViewController ()
@property (nonatomic, weak) UIView *redView;
@end
 
- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 1. 实例化红色的视图
    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(110, 100, 100, 100)];
    view.backgroundColor = [UIColor redColor];
    
    [self.view addSubview:view];
    
    self.redView = view;
}

#pragma mark - 移动
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSLog(@"touchesMoved");
    
    // 1. 获取到集合中的触摸对象
    UITouch *touch = [touches anyObject];
    // 2. 获取手指所在的位置
    CGPoint location = [touch locationInView:self.view];
    
    // 根据运行发现，手指第一次移动时，红色视图会出现跳跃的情况，会影响用户的使用
    // 1) 取出前一次的手指位置
    CGPoint preLocation = [touch previousLocationInView:self.view];
    
    // 2) 计算两次手指之间的距离差值
    CGPoint offset = CGPointMake(location.x - preLocation.x, location.y - preLocation.y);
    // 3) 修正红色视图的中心点
    CGPoint center = CGPointMake(_redView.center.x + offset.x, _redView.center.y + offset.y);
    
    // 3. 设置红色视图的位置
    self.redView.center = center;
}

@interface MultiTouchViewController ()
@property (nonatomic, strong) NSArray *images;
@end
 
- (void)viewDidLoad
{
    [super viewDidLoad];

    // 初始化图像
    _images = @[[UIImage imageNamed:@"spark_blue"],
                [UIImage imageNamed:@"spark_red"]];
    
    // 让视图支持多选，如果不设置多点选项，默认只支持单点
    [self.view setMultipleTouchEnabled:YES];
}
#pragma mark - 触摸事件
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSInteger i = 0;
    
    for (UITouch *touch in touches) {
        // 2. 取出手指触摸位置
        CGPoint location = [touch locationInView:self.view];
        
        // 3. 在相应位置绘制图像
        UIImageView *imageView = [[UIImageView alloc] initWithImage:_images[i]];
        imageView.center = location;
        
        // 4. 添加到视图
        [self.view addSubview:imageView];
       
        // 5. 添加动画，让图像的透明度降低，然后消失
        [UIView animateWithDuration:1.0f animations:^{
            imageView.alpha = 0.5f;
        } completion:^(BOOL finished) {
            // 将图像视图从视图中删除
            [imageView removeFromSuperview];
        }];
        
        i++;
    }
}

 1 - (BOOL)canBecomeFirstResponder
 2 {
 3     return YES;
 4 }
 5 
 6 - (void)viewDidAppear:(BOOL)animated
 7 {
 8     [self becomeFirstResponder];
 9 }
10 
11 - (void)viewDidDisappear:(BOOL)animated
12 {
13     [self resignFirstResponder];
14 }
15 
16 #pragma mark 摇晃开始事件
17 - (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event
18 {
19     if (motion == UIEventSubtypeMotionShake) {
20         NSLog(@"摇晃了");
21     }
22 }