iOS 4 Gesture Recognizers 應用實戰

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

在上一章，我們已經概要介紹了iPhone手勢識別技的概念，本章的目的是通過一個執行個體示範各種UIGestureRecognizer子類的用法。本章所建立的程式，將建立和設定各種不同的手勢辨識器，然後用標籤把每個偵測到的手勢的具體資訊顯示出來。

 

建立項目Creating the Gesture Recognition Project

 

開啟Xcode，建立一個View-baseapplication項目，命名為recognizer。

 

為Label設定出口

 

在View對象中，僅有一個label組件，用於顯示偵測到的使用者手勢類型。label上的文字在程式運行過程中會被代碼所改變，因此我們需要為它串連到一個出口上。在xcode的項目導航面板中，選中recognizerViewController.h檔案，將它修改為：

#import <UIKit/UIKit.h>

@interface recognizerViewController : UIViewController {

     UILabel *statusLabel; 

} 

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

@end 

接著，編輯recognizerViewController.m。在@synthesize語句中增加相應出口並在合適的地方釋放它。

#import "recognizerViewController.h"  

@implementation recognizerViewController 

@synthesize statusLabel;

 . . 

- (void)dealloc {

     [statusLabel release];

     [super dealloc]; 

}

 . . 

- (void)viewDidUnload {

     [super viewDidUnload];

     self.statusLabel = nil; 

}

 . . 

@end 

 設計介面

 

選擇recognizerViewController.xib，在IB面板中編輯它。Xcode在建立項目時為我們建立了一個UIView，我們需要在這個UIView中增加一個label。從ObjectLibrary (View-> Utilities -> Object Library) 中拖一個Label對象，然後修改label屬性讓文本置中對齊：

圖片

Ctrl+左鍵（或者右鍵）從File’sOwner 拖一條線到Label對象，然後釋放按鍵。在彈出的菜單中選擇statusLabel出口。

 

設定GusetureRecognizers對象

 

我們需要在代碼中使用gesturerecognizers來識別輕擊、輕掃、旋轉和捏合。由於這些recognizers需要串連到view對象，因此建立它們的理想地是recognizerViewController類的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]; 

}  

添加處理方法

 

設定完gesturerecognizer之後，就應當編寫處理方法，處理方法將在相應手勢偵測到之後被recognizer所調用。這些方法也放在了recognizerViewController.m檔案裡，同時這些方法會根據相應手勢的具體資訊來重新整理label上顯示的文字。

-(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]; 

} 

測試程式

 

最後，編譯和運行程式。為了能夠充分測試捏合和旋轉手勢，最好是在物理裝置中運行程式（因為模擬器上無法類比多點觸摸）。串連已啟用的調試裝置（參考TestingiOS 4 Apps on the iPhone – Developer Certificates and Provisioning Profiles), 然後點擊Xcode的Run按鈕。當程式運行後，進行手勢動作並觀察label中顯示文本的變化。