iOS 4 Gesture Recognizers 应用实战

http://www.techotopia.com/index.php/An_iPhone_iOS_4_Gesture_Recognition_Tutorial_%28Xcode_4%29

在上一章，我们已经概要介绍了iPhone手势识别技的概念，本章的目的是通过一个实例演示各种UIGestureRecognizer子类的用法。本章所创建的程序，将创建和设置各种不同的手势识别器，然后用标签把每个侦测到的手势的具体信息显示出来。

创建项目Creating the Gesture Recognition Project

打开Xcode，创建一个View-baseapplication项目，命名为recognizer。

为Label设置出口

在View对象中，仅有一个label组件，用于显示侦测到的用户手势类型。label上的文字在程序运行过程中会被代码所改变，因此我们需要为它连接到一个出口上。在xcode的项目导航面板中，选中recognizerViewController.h文件，将它修改为：

#import <UIKit/UIKit.h>

@interface recognizerViewController: UIViewController {

 UILabel *statusLabel; 

} 

@property (retain, nonatomic) IBOutlet UILabel *statusLabel; 

@end 

接着，编辑recognizerViewController.m。在@synthesize语句中增加相应出口并在合适的地方释放它。

#import "recognizerViewController.h" 

@implementation recognizerViewController 

@synthesize statusLabel;

 . . 

- (void)dealloc {

 [statusLabel release];

 [super dealloc]; 

}

 . . 

- (void)viewDidUnload {

 [super viewDidUnload];

 self.statusLabel = nil; 

}

 . . 

@end 

设计界面

选择recognizerViewController.xib，在IB面板中编辑它。Xcode在创建项目时为我们创建了一个UIView，我们需要在这个UIView中增加一个label。从ObjectLibrary (View-> Utilities -> Object Library) 中拖一个Label对象，然后修改label属性让文本居中对齐：

图片

Ctrl+左键（或者右键）从File’sOwner 拖一条线到Label对象，然后释放按键。在弹出的菜单中选择statusLabel出口。

设置GusetureRecognizers对象

我们需要在代码中使用gesturerecognizers来识别轻击、轻扫、旋转和捏合。由于这些recognizers需要连接到view对象，因此创建它们的理想地是recognizerViewController类的viewDidLoad方法：

- (void)viewDidLoad {

 UITapGestureRecognizer *doubleTap = 

[[UITapGestureRecognizer alloc]

 initWithTarget:self

 action:@selector(tapDetected:)];

 doubleTap.numberOfTapsRequired = 2;

 [self.view addGestureRecognizer:doubleTap];

 [doubleTap release];

 UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc]

 initWithTarget:self

 action:@selector(pinchDetected:)];

 [self.view addGestureRecognizer:pinchRecognizer];

 [pinchRecognizer release];

 UIRotationGestureRecognizer *rotationRecognizer = [[UIRotationGestureRecognizer alloc]

 initWithTarget:self

 action:@selector(rotationDetected:)];

 [self.view addGestureRecognizer:rotationRecognizer];

 [rotationRecognizer release];

 UISwipeGestureRecognizer *swipeRecognizer = [[UISwipeGestureRecognizer alloc]

 initWithTarget:self

 action:@selector(swipeDetected:)];

 swipeRecognizer.direction = UISwipeGestureRecognizerDirectionRight;

 [self.view addGestureRecognizer:swipeRecognizer];

 [swipeRecognizer release];

 UILongPressGestureRecognizer *longPressRecognizer = [[UILongPressGestureRecognizer alloc]

 initWithTarget:self

 action:@selector(longPressDetected:)];

 longPressRecognizer.minimumPressDuration = 3;

 longPressRecognizer.numberOfTouchesRequired = 1;

 [self.view addGestureRecognizer:longPressRecognizer];

 [longPressRecognizer release];

 [super viewDidLoad]; 

} 

添加处理方法

设置完gesturerecognizer之后，就应当编写处理方法，处理方法将在相应手势侦测到之后被recognizer所调用。这些方法也放在了recognizerViewController.m文件里，同时这些方法会根据相应手势的具体信息来刷新label上显示的文字。

-(IBAction)longPressDetected:(UIGestureRecognizer *)sender{

 statusLabel.text = @"Long Press"; 

}

- (IBAction)swipeDetected:(UIGestureRecognizer *)sender {

 statusLabel.text = @"Right Swipe"; 

}

- (IBAction)tapDetected:(UIGestureRecognizer *)sender {

 statusLabel.text = @"Double Tap"; 

}

- (IBAction)pinchDetected:(UIGestureRecognizer *)sender {

 CGFloat scale = [(UIPinchGestureRecognizer *)sender scale];

 CGFloat velocity = [(UIPinchGestureRecognizer *)sender velocity];

 NSString *resultString = [[NSString alloc] initWithFormat:

 @"Pinch - scale = %f, velocity = %f",

 scale, velocity];

 statusLabel.text = resultString;

 [resultString release]; 

}

- (IBAction)rotationDetected:(UIGestureRecognizer *)sender {

 CGFloat radians = [(UIRotationGestureRecognizer *)sender rotation];

 CGFloat velocity = [(UIRotationGestureRecognizer *)sender velocity];

 NSString *resultString = [[NSString alloc] initWithFormat:

 @"Rotation - Radians = %f, velocity = %f",

 radians, velocity];

 statusLabel.text = resultString;

 [resultString release]; 

} 

测试程序

最后，编译和运行程序。为了能够充分测试捏合和旋转手势，最好是在物理设备中运行程序（因为模拟器上无法模拟多点触摸）。连接已激活的调试设备（参考TestingiOS 4 Apps on the iPhone – Developer Certificates and Provisioning Profiles),然后点击Xcode的Run按钮。当程序运行后，进行手势动作并观察label中显示文本的变化。