UIKit中包含了UIGestureRecognizer類，用於檢測發生在設備中的手勢。UIGestureRecognizer是一個抽象類，定義了所有手勢的基本行爲，它有下面一些子類用於處理具體的手勢：
1、拍擊UITapGestureRecognizer (任意次數的拍擊)
2、向裏或向外捏UIPinchGestureRecognizer (用於縮放)
3、搖動或者拖拽UIPanGestureRecognizer
4、擦碰UISwipeGestureRecognizer (以任意方向)
5、旋轉UIRotationGestureRecognizer (手指朝相反方向移動)
6、長按UILongPressGestureRecognizer
對於不同類型的手勢識別器，具有不同的配置屬性。比如UITapGestureRecognizer，可以配置拍擊次數。界面接收到手勢之後，可以發送一個消息，用於處理響應手勢動作後的任務。當然，不同的手勢識別器，發送的消息方法也會有所不同。下面列舉幾個具體示例代碼：
一個手指，拍擊兩次手勢
// 創建一個手勢識別器
UITapGestureRecognizer *oneFingerTwoTaps =
[[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(oneFingerTwoTaps)] autorelease];
// Set required taps and number of touches
[oneFingerTwoTaps setNumberOfTapsRequired:2];
[oneFingerTwoTaps setNumberOfTouchesRequired:1];
// Add the gesture to the view
[[self view] addGestureRecognizer:oneFingerTwoTaps];
消息方法oneFingerTwoTaps
- (void)oneFingerTwoTaps
{
NSLog(@”Action: One finger, two taps”);
}
兩個手指，拍擊兩次手勢
UITapGestureRecognizer *twoFingersTwoTaps =
[[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingersTwoTaps)] autorelease];
[twoFingersTwoTaps setNumberOfTapsRequired:2];
[twoFingersTwoTaps setNumberOfTouchesRequired:2];
[[self view] addGestureRecognizer:twoFingersTwoTaps];
消息方法twoFingersTwoTaps
- (void)twoFingersTwoTaps {
NSLog(@”Action: Two fingers, two taps”);
}
一個手指向上、向下擦碰手勢
// 向上擦碰
UISwipeGestureRecognizer *oneFingerSwipeUp =
[[[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(oneFingerSwipeUp:)] autorelease];
[oneFingerSwipeUp setDirection:UISwipeGestureRecognizerDirectionUp];
[[self view] addGestureRecognizer:oneFingerSwipeUp];
- (void)oneFingerSwipeUp:(UISwipeGestureRecognizer *)recognizer
{
CGPoint point = [recognizer locationInView:[self view]];
NSLog(@”Swipe up – start location: %f,%f”, point.x, point.y);
}
// 向下擦碰
UISwipeGestureRecognizer *oneFingerSwipeDown =
[[[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(oneFingerSwipeDown:)] autorelease];
[oneFingerSwipeDown setDirection:UISwipeGestureRecognizerDirectionDown];
[[self view] addGestureRecognizer:oneFingerSwipeDown];
- (void)oneFingerSwipeDown:(UISwipeGestureRecognizer *)recognizer
{
CGPoint point = [recognizer locationInView:[self view]];
NSLog(@”Swipe down – start location: %f,%f”, point.x, point.y);
}
旋轉手勢
UIRotationGestureRecognizer *twoFingersRotate =
[[[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingersRotate:)] autorelease];
[[self view] addGestureRecognizer:twoFingersRotate];
- (void)twoFingersRotate:(UIRotationGestureRecognizer *)recognizer
{
// Convert the radian value to show the degree of rotation
NSLog(@”Rotation in degrees since last change: %f”, [recognizer rotation] * (180 / M_PI));
}
向裏或向外捏的手勢
UIPinchGestureRecognizer *twoFingerPinch =
[[[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingerPinch:)] autorelease];
[[self view] addGestureRecognizer:twoFingerPinch];
- (void)twoFingerPinch:(UIPinchGestureRecognizer *)recognizer
{
NSLog(@”Pinch scale: %f”, recognizer.scale);
}
