IOS学习之 手势操作

参考文章 http://blog.jobbole.com/65846/

1. UIGestureRecognizer介绍
UIGestureRecognizer类是个抽象类，下面的子类是具体的手势，开发这可以直接使用这些手势识别。

UITapGestureRecognizer // 点击
UIPinchGestureRecognizer // 二指往內或往外拨动，平时经常用到的缩放
UIRotationGestureRecognizer // 旋转
UISwipeGestureRecognizer // 滑动，快速移动
UIPanGestureRecognizer // 拖移，慢速移动
UILongPressGestureRecognizer // 长按

2、使用手势的步骤
使用手势很简单，分为两步：
(1)创建手势实例。当创建手势时，指定一个回调方法，当手势开始，改变、或结束时，回调方法被调用。
(2)添加到需要识别的View中。每个手势只对应一个View，当屏幕触摸在View的边界内时，如果手势和预定的一样，那就会回调方法。
ps：一个手势只能对应一个View，但是一个View可以有多个手势。

3、Pan 拖动手势：

// 新建一个ImageView，然后添加手势
UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]];
snakeImageView.frame = CGRectMake(50, 50, 100, 160);
UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
initWithTarget:self
action:@selector(handlePan:)];
[snakeImageView addGestureRecognizer:panGestureRecognizer];
[self.view setBackgroundColor:[UIColor whiteColor]];
[self.view addSubview:snakeImageView];

// 回调方法：
- (void) handlePan:(UIPanGestureRecognizer*) recognizer  {
CGPoint translation = [recognizer translationInView:self.view];
recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
recognizer.view.center.y + translation.y);
[recognizer setTranslation:CGPointZero inView:self.view];
}

4、Pinch缩放手势

UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc]
initWithTarget:self
action:@selector(handlePinch:)];

- (void) handlePinch:(UIPinchGestureRecognizer*) recognizer  {
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1;
}

5、Rotation旋转手势

UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc]
initWithTarget:self
action:@selector(handleRotate:)];
[snakeImageView addGestureRecognizer:rotateRecognizer];

- (void) handleRotate:(UIRotationGestureRecognizer*) recognizer  {
recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
recognizer.rotation = 0;
}

6、添加第二个ImagView并添加手势
记住：一个手势只能添加到一个View，两个View当然要有两个手势的实例了

- (void)viewDidLoad  {
[super viewDidLoad];

UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]];
UIImageView *dragonImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"dragon.png"]];
snakeImageView.frame = CGRectMake(120, 120, 100, 160);
dragonImageView.frame = CGRectMake(50, 50, 100, 160);
[self.view addSubview:snakeImageView];
[self.view addSubview:dragonImageView];

for (UIView *view in self.view.subviews) {
UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
initWithTarget:self
action:@selector(handlePan:)];

UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc]
initWithTarget:self
action:@selector(handlePinch:)];

UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc]
initWithTarget:self
action:@selector(handleRotate:)];

[view addGestureRecognizer:panGestureRecognizer];
[view addGestureRecognizer:pinchGestureRecognizer];
[view addGestureRecognizer:rotateRecognizer];
[view setUserInteractionEnabled:YES];
}
[self.view setBackgroundColor:[UIColor whiteColor]];
}

7、拖动(pan手势)速度(以较快的速度拖放后view有滑行的效果)
如何实现呢？
1.监视手势是否结束
2.监视触摸的速度

- (void) handlePan:(UIPanGestureRecognizer*) recognizer  {
CGPoint translation = [recognizer translationInView:self.view];
recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
recognizer.view.center.y + translation.y);
[recognizer setTranslation:CGPointZero inView:self.view];

if (recognizer.state == UIGestureRecognizerStateEnded) {

CGPoint velocity = [recognizer velocityInView:self.view];
CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
CGFloat slideMult = magnitude / 200;
NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult);

float slideFactor = 0.1 * slideMult; // Increase for more of a slide
CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor),
recognizer.view.center.y + (velocity.y * slideFactor));
finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width);
finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height);

[UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
recognizer.view.center = finalPoint;
} completion:nil];
}

代码实现解析：
1.计算速度向量的长度（估计大部分都忘了）这些知识了。
2.如果速度向量小于200，那就会得到一个小于的小数，那么滑行会很短
3.基于速度和速度因素计算一个终点
4.确保终点不会跑出父View的边界
5.使用UIView动画使view滑动到终点
运行后，快速拖动图像view放开会看到view还会在原来的方向滑行一段路。

8、同时触发两个view的手势
手势之间是互斥的，如果你想同时触发蛇和龙的view，那么需要实现协议UIGestureRecognizerDelegate，
并在协议这个方法里返回YES。

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
return YES;
}

把self作为代理设置给手势：

panGestureRecognizer.delegate = self;
pinchGestureRecognizer.delegate = self;
rotateRecognizer.delegate = self;

这样可以同时拖动或旋转缩放两个view了。

9、tap点击手势

这里为了方便看到tap的效果，当点击一下屏幕时，播放一个声音。
为了播放声音，我们加入AVFoundation.framework这个框架。

- (AVAudioPlayer *)loadWav:(NSString *)filename {
NSURL * url = [[NSBundle mainBundle] URLForResource:filename withExtension:@"wav"];
NSError * error;
AVAudioPlayer * player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
if (!player) {
NSLog(@"Error loading %@: %@", url, error.localizedDescription);
} else {
[player prepareToPlay];
}
return player;
}

我会在最后例子代码给出完整代码，添加手势的步骤和前面一样的。

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
@interface ViewController : UIViewController<UIGestureRecognizerDelegate>
@property (strong) AVAudioPlayer * chompPlayer;
@property (strong) AVAudioPlayer * hehePlayer;
@end

- (void)handleTap:(UITapGestureRecognizer *)recognizer {
[self.chompPlayer play];
}

运行，点一下某个图，就会播放一个咬东西的声音。
不过这个点击播放声音有点缺陷，就是在慢慢拖动的时候也会播放。这使得两个手势重合了。怎么解决呢？使用手势的：requireGestureRecognizerToFail方法。

10、手势的依赖性
在viewDidLoad的循环里添加这段代码：

[tapRecognizer requireGestureRecognizerToFail:panGestureRecognizer];

意思就是，当如果pan手势失败，就是没发生拖动，才会出发tap手势。这样如果你有轻微的拖动，那就是pan手势发生了。tap的声音就不会发出来了。

11、自定义手势
自定义手势继承：UIGestureRecognizer，实现下面的方法：

– touchesBegan:withEvent:
– touchesMoved:withEvent:
– touchesEnded:withEvent:
- touchesCancelled:withEvent:

新建一个类，继承UIGestureRecognizer，代码如下：
.h文件

#import <UIKit/UIKit.h>
typedef enum {
DirectionUnknown = 0,
DirectionLeft,
DirectionRight
} Direction;

@interface HappyGestureRecognizer : UIGestureRecognizer
@property (assign) int tickleCount;
@property (assign) CGPoint curTickleStart;
@property (assign) Direction lastDirection;

@end

.m文件

#import "HappyGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>
#define REQUIRED_TICKLES        2
#define MOVE_AMT_PER_TICKLE     25

@implementation HappyGestureRecognizer

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch * touch = [touches anyObject];
self.curTickleStart = [touch locationInView:self.view];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
// Make sure we've moved a minimum amount since curTickleStart
UITouch * touch = [touches anyObject];
CGPoint ticklePoint = [touch locationInView:self.view];
CGFloat moveAmt = ticklePoint.x - self.curTickleStart.x;
Direction curDirection;
if (moveAmt < 0) {
curDirection = DirectionLeft;
} else {
curDirection = DirectionRight;
}
if (ABS(moveAmt) < MOVE_AMT_PER_TICKLE) return;

// 确认方向改变了
if (self.lastDirection == DirectionUnknown ||
(self.lastDirection == DirectionLeft && curDirection == DirectionRight) ||
(self.lastDirection == DirectionRight && curDirection == DirectionLeft)) {

// 挠痒次数
self.tickleCount++;
self.curTickleStart = ticklePoint;
self.lastDirection = curDirection;

// 一旦挠痒次数超过指定数，设置手势为结束状态
// 这样回调函数会被调用。
if (self.state == UIGestureRecognizerStatePossible && self.tickleCount > REQUIRED_TICKLES) {
[self setState:UIGestureRecognizerStateEnded];
}
}

}

- (void)reset {
self.tickleCount = 0;
self.curTickleStart = CGPointZero;
self.lastDirection = DirectionUnknown;
if (self.state == UIGestureRecognizerStatePossible) {
[self setState:UIGestureRecognizerStateFailed];
}
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[self reset];
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[self reset];
}

@end

调用自定义手势和上面一样，回到这样写：

- (void)handleHappy:(HappyGestureRecognizer *)recognizer{
[self.hehePlayer play];
}

手势成功后播放呵呵笑的声音。
在真机上运行，按住某个view，快速左右拖动，就会发出笑的声音了。
代码解析：
先获取起始坐标：curTickleStart
通过和ticklePoint的x值对比，得出当前的放下是向左还是向右。再算出移动的x的值是否比MOVE_AMT_PER_TICKLE距离大，如果太则返回。
再判断是否有三次是不同方向的动作，如果是则手势结束，回调。