UIKit框架（16）手勢(shì)識(shí)別器

• UIGestureRecognizer

利用手勢(shì)識(shí)別器，能夠輕松識(shí)別用戶在某個(gè)view上面做一些常見(jiàn)的手勢(shì)

UIGestureRecognizer是一個(gè)抽象類，定義了所有手勢(shì)的基本行為，使用它的子類才能處理具體的手勢(shì)

     UITapGestureRecognizer                敲擊

     UIPinchGestureRecognizer            捏合手勢(shì)

     UIPanGestureRecognizer               拖拽

     UISwipeGestureRecognizer           輕掃

     UIRotationGestureRecognizer       旋轉(zhuǎn)

     UILongPressGestureRecognizer    長(zhǎng)按

• 手勢(shì)識(shí)別器使用的一般步驟 （以敲擊手勢(shì)為例）

創(chuàng)建手勢(shì)識(shí)別器對(duì)象

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

設(shè)置手勢(shì)識(shí)別器對(duì)象的具體屬性 ：

//連續(xù)敲擊2次且兩根手指敲擊時(shí)響應(yīng)
tap.numberOfTapsRequired = 2;
tap.numberOfTouchesRequired = 2;

添加手勢(shì)識(shí)別器到view上 ：

[self.iconView addGestureRecognizer:tap];

監(jiān)聽(tīng)手勢(shì)的觸發(fā) ：

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

實(shí)現(xiàn)觸發(fā)的方法

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

• 手勢(shì)識(shí)別器的狀態(tài)

• 手勢(shì)識(shí)別器的代理

代理協(xié)議<UIGestureRecognizerDelegate>

//是否接受這個(gè)touch對(duì)象（默認(rèn)返回YES），這個(gè)代理方法在一個(gè)觸摸事件產(chǎn)生時(shí)先調(diào)用
- (BOOL) gestureRecognizer:(UIGestureRecognizer*) gestureRecognizer shouldReceiveTouch:(UITouch*) touch;
//確定兩個(gè)類似的手勢(shì)識(shí)別器是否同時(shí)處理
- (BOOL) gestureRecognizer:(UIGestureRecognizer*) gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer*) otherGestureRecognizer;

• 示例：UITabBarController的滑動(dòng)手勢(shì)控制

1）UITabBarController子類，保存所有子控制器的截圖

    添加UIImage對(duì)象數(shù)組

@property (nonatomic, strong) NSMutableArray<UIImage*> * picArray;

    數(shù)組初始化為空對(duì)象

NSMutableArray * arr1 = [NSMutableArray array];
for ( int i =0; i<self.viewControllers.count; i++) {
    [arr1 addObject:[NSNull null]];
}
self.picArray = [arr1 mutableCopy];

    重寫(xiě)selectedIndex的setter方法：切換子控制器前，截圖保存

- (void)setSelectedIndex:(NSUInteger)selectedIndex
{
    //截圖操作
    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();
    //截圖保存到截圖數(shù)組
    NSLog(@"selectedIndex=%ld", self.selectedIndex);
    self.picArray[self.selectedIndex] = p_w_picpath;

    [super setSelectedIndex:selectedIndex];
}

    提供方法，返回當(dāng)前子控制器的前后兩個(gè)子控制器的截圖

- (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類

    UITabBarController的所有子控制器的類型就是繼承自一個(gè)共用父類

    父類中添加滑動(dòng)手勢(shì)識(shí)別器

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

    父類中添加UIImageView屬性，用于存儲(chǔ)當(dāng)前頁(yè)面左右兩個(gè)截圖p_w_picpathView

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

    手勢(shì)識(shí)別器：手勢(shì)開(kāi)始時(shí)，當(dāng)前view左右放置截圖

UIImage * imgLeft = [((ViewController*)self.tabBarController) p_w_picpathForCurrentViewControllerLeft];
if ( imgLeft == nil ) {
    self.ivLeft = nil;
}
else {
    if ( [imgLeft isKindOfClass:[NSNull class]] ) {
        //一張白***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);
}

    手勢(shì)識(shí)別器：手勢(shì)滑動(dòng)式時(shí)，當(dāng)前view隨之滑動(dòng)

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

    手勢(shì)識(shí)別器，手勢(shì)結(jié)束時(shí)，根據(jù)位置確定是否切換子控制器

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;
    }
}];