• UIGestureRecognizer

利用手势识别器，能够轻松识别用户在某个view上面做一些常见的手势

UIGestureRecognizer是一个抽象类，定义了所有手势的基本行为，使用它的子类才能处理具体的手势

     UITapGestureRecognizer                敲击

     UIPinchGestureRecognizer            捏合手势

     UIPanGestureRecognizer               拖拽

     UISwipeGestureRecognizer           轻扫

     UIRotationGestureRecognizer       旋转

     UILongPressGestureRecognizer    长按

• 手势识别器使用的一般步骤 （以敲击手势为例）

创建手势识别器对象

UITapGestureRecognizer * tap = [[UITapGestureRecognizer alloc] init];

     

设置手势识别器对象的具体属性 ：

//连续敲击2次且两根手指敲击时响应tap.numberOfTapsRequired = 2;tap.numberOfTouchesRequired = 2;

添加手势识别器到view上 ：

[self.iconView addGestureRecognizer:tap];

监听手势的触发 ：

[tap addTarger:self action:@selector(tapIconView:)];

实现触发的方法

- (void) tapIconView:(UITapGestureRecognizer*) tapGR{    NSLog(@"tap响应");}

     

• 手势识别器的状态

    

• 手势识别器的代理

代理协议<UIGestureRecognizerDelegate>

//是否接受这个touch对象（默认返回YES），这个代理方法在一个触摸事件产生时先调用- (BOOL) gestureRecognizer:(UIGestureRecognizer*) gestureRecognizer shouldReceiveTouch:(UITouch*) touch;//确定两个类似的手势识别器是否同时处理- (BOOL) gestureRecognizer:(UIGestureRecognizer*) gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer*) otherGestureRecognizer;

• 示例：UITabBarController的滑动手势控制

1）UITabBarController子类，保存所有子控制器的截图

    添加UIImage对象数组

@property (nonatomic, strong) NSMutableArray
     
       * picArray;
     

    数组初始化为空对象

NSMutableArray * arr1 = [NSMutableArray array];for ( int i =0; i

    重写selectedIndex的setter方法：切换子控制器前，截图保存

- (void)setSelectedIndex:(NSUInteger)selectedIndex{    //截图操作    float width = [UIScreen mainScreen].bounds.size.width;    float height = [UIScreen mainScreen].bounds.size.height;    UIGraphicsBeginImageContext(CGSizeMake(width, height));    CGContextRef context = UIGraphicsGetCurrentContext();    [[UIApplication sharedApplication].keyWindow.layer renderInContext:context];    UIImage *p_w_picpath = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    //截图保存到截图数组    NSLog(@"selectedIndex=%ld", self.selectedIndex);    self.picArray[self.selectedIndex] = p_w_picpath;    [super setSelectedIndex:selectedIndex];}

    提供方法，返回当前子控制器的前后两个子控制器的截图

- (UIImage *) p_w_picpathForCurrentViewControllerLeft{    if ( self.selectedIndex == 0 ) {        return nil;    }    return self.picArray[self.selectedIndex-1];}- (UIImage *) p_w_picpathForCurrentViewControllerRight{    if ( self.selectedIndex == self.viewControllers.count - 1 ) {        return nil;    }    return self.picArray[self.selectedIndex+1];}

2）添加子控制器的共用父类

    UITabBarController的所有子控制器的类型就是继承自一个共用父类

    父类中添加滑动手势识别器

UIPanGestureRecognizer * gr1 = [[UIPanGestureRecognizer alloc] init];[gr1 addTarget:self action:@selector(panGR:)];[self.view addGestureRecognizer:gr1];

    父类中添加UIImageView属性，用于存储当前页面左右两个截图p_w_picpathView

@property (nonatomic, weak) UIImageView * ivLeft;@property (nonatomic, weak) UIImageView * ivRight;

    手势识别器：手势开始时，当前view左右放置截图

UIImage * imgLeft = [((ViewController*)self.tabBarController) p_w_picpathForCurrentViewControllerLeft];if ( imgLeft == nil ) {    self.ivLeft = nil;}else {    if ( [imgLeft isKindOfClass:[NSNull class]] ) {        //一张白***片        imgLeft = [UIImage p_w_picpathNamed:@"white_bg"];    }    UIImageView * ivLeft = [[UIImageView alloc] initWithImage:imgLeft];    self.ivLeft = ivLeft;    [self.view addSubview:ivLeft];    self.ivLeft.frame = CGRectMake(-self.view.frame.size.width, 0, self.view.frame.size.width, self.view.frame.size.height);}UIImage * imgRight = [((ViewController*)self.tabBarController) p_w_picpathForCurrentViewControllerRight];if ( imgRight == nil ) {    self.ivRight = nil;}else {    if ( [imgRight isKindOfClass:[NSNull class]] ) {        imgRight = [UIImage p_w_picpathNamed:@"white_bg"];    }    UIImageView * ivRight= [[UIImageView alloc] initWithImage:imgRight];    self.ivRight = ivRight;    [self.view addSubview:self.ivRight];    self.ivRight.frame = CGRectMake(self.view.frame.size.width, 0, self.view.frame.size.width, self.view.frame.size.height);}

    手势识别器：手势滑动式时，当前view随之滑动

if ( p.x > 0 && self.ivLeft == nil ) {    return ;}if ( p.x < 0 && self.ivRight == nil ) {    return ;}self.view.transform = CGAffineTransformMakeTranslation(p.x, 0);

    手势识别器，手势结束时，根据位置确定是否切换子控制器

if ( self.view.transform.tx > self.view.frame.size.width/2 && self.ivLeft != nil ) {    self.view.transform = CGAffineTransformIdentity;    self.tabBarController.selectedIndex--;    if ( self.ivLeft != nil ) {        [self.ivLeft removeFromSuperview];        self.ivLeft = nil;    }    if ( self.ivRight != nil ) {        [self.ivRight removeFromSuperview];        self.ivRight = nil;    }    return ;}if ( self.view.transform.tx < -self.view.frame.size.width/2 && self.ivRight != nil ) {    self.view.transform = CGAffineTransformIdentity;    self.tabBarController.selectedIndex++;    if ( self.ivLeft != nil ) {        [self.ivLeft removeFromSuperview];        self.ivLeft = nil;    }    if ( self.ivRight != nil ) {        [self.ivRight removeFromSuperview];        self.ivRight = nil;    }    return ;}[UIView animateWithDuration:0.5 animations:^{    self.view.transform = CGAffineTransformIdentity;} completion:^(BOOL finished) {    if ( self.ivLeft != nil ) {        [self.ivLeft removeFromSuperview];        self.ivLeft = nil;    }    if ( self.ivRight != nil ) {        [self.ivRight removeFromSuperview];        self.ivRight = nil;    }}];