1、UIGestureRecognizer介绍
手势识别在iOS上非常重要，手势操作移动设备的重要特征，极大的增加了移动设备使用便捷性。
iOS系统在3.2以后，为方便开发这使用一些常用的手势，提供了UIGestureRecognizer类。手势识别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。
上面的手势对应的操作是：
Tap（点一下）
Pinch（二指往內或往外拨动，平时经常用到的缩放）
Rotation（旋转）
Swipe（滑动，快速移动）
Pan （拖移，慢速移动）
LongPress（长按）
UIGestureRecognizer的继承关系如下：
使用手势很简单，分为两步：
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。
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。
建议在真机上运行这些手势,模拟器操作不太方便，可能导致你认为手势失效。
[cpp]view plaincopy
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];
新建一个ImageView，然后添加手势
回调方法：
[cpp]view plaincopy
- (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];
}
[cpp]view plaincopy
UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc]
initWithTarget:self
action:@selector(handlePinch:)];[snakeImageView addGestureRecognizer:pinchGestureRecognizer];
[cpp]view plaincopy
- (void) handlePinch:(UIPinchGestureRecognizer*) recognizer
{
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1;
}
[cpp]view plaincopy
UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc]
initWithTarget:self
action:@selector(handleRotate:)];
[snakeImageView addGestureRecognizer:rotateRecognizer];
[cpp]view plaincopy
- (void) handleRotate:(UIRotationGestureRecognizer*) recognizer
{
recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
recognizer.rotation = 0;
}
添加了这几个手势后，运行看效果，程序中的imageView放了一个
/^\/^\
_|__| O|
\/ /~ \_/ \
\____|__________/ \
\_______ \
`\ \ \
| | \
/ / \
/ / \\
/ / \ \
/ / \ \
/ / _----_ \ \
/ / _-~ ~-_ | |
( ( _-~ _--_ ~-_ _/ |
\ ~-____-~ _-~ ~-_ ~-_-~ /
~-_ _-~ ~-_ _-~
~--______-~ ~-___-~
的图片，在模拟器上拖动是没问题的。缩放和旋转有点问题，估计是因为在模拟器上的模拟的两个接触点距离在imageView的边界外了，所以操作无效果。
建议在真机上运行这个手势。
在模拟器上缩放和选择的操作技巧：
可以把imageView的frame值设置大一点，按住alt键，按下触摸板(不按下不行)，这样就可以旋转和缩放了。
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
[cpp]view plaincopy
- (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]];
}
多添加了一条龙的view，两个view都能接收上面的三种手势。运行效果如下：
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？
监视手势是否结束
监视触摸的速度
[cpp]view plaincopy
- (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);
floatslideFactor = 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：
计算速度向量的长度（估计大部分都忘了）这些知识了。
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
基于速度和速度因素计算一个终点
确保终点不会跑出父View的边界
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。
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，
[cpp]view plaincopy
@interface ViewController : UIViewController
@end
并在协议这个方法里返回YES。
[cpp]view plaincopy
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
returnYES;
}
把self作为代理设置给手势：
[cpp]view plaincopy
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。
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。
[cpp]view plaincopy
- (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];
}
returnplayer;
}
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。
[cpp]view plaincopy
#import
#import
@interface ViewController : UIViewController
@property (strong) AVAudioPlayer * chompPlayer;
@property (strong) AVAudioPlayer * hehePlayer;
@end
[cpp]view plaincopy
- (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。
在viewDidLoad的循环里添加这段代码：
[cpp]view plaincopy
[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。
自定义手势继承：UIGestureRecognizer，实现下面的方法：
[cpp]view plaincopy
– touchesBegan:withEvent:
– touchesMoved:withEvent:
– touchesEnded:withEvent:
- touchesCancelled:withEvent:
新建一个类，继承UIGestureRecognizer，代码如下：
.h文件
[cpp]view plaincopy
#import
typedefenum{
DirectionUnknown = 0,
DirectionLeft,
DirectionRight
} Direction;
@interface HappyGestureRecognizer : UIGestureRecognizer
@property (assign)inttickleCount;
@property (assign) CGPoint curTickleStart;
@property (assign) Direction lastDirection;
@end
.m文件
[cpp]view plaincopy
#import "HappyGestureRecognizer.h"
#import
#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：
[cpp]view plaincopy
- (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。
