UIViewでスワイプを検出する方法

スワイプ（ページをめくるような動作）を検出するコードです。あまりサンプルがなかったので、iPhoneデベロッパーズクックブックを参考に。速度も検出できるので、動作によって遅くor速くアニメーションを実行するなどの制御ができます。

MyView.h

#import <UIKit/UIKit.h>
@interface MyView : UIView {
  NSDate *startTime;
}
@property (nonatomic, retain) NSDate *startTime;
@end

MyView.m

#import "MyView.h"

#define HORIZ_SWIPE_MIN 12
#define VERT_SWIPE_MAX 8
#define SWIPE_NON 0
#define SWIPE_LEFT 1
#define SWIPE_RIGHT 2

@implementation MyView
@synthesize startTime;

CGPoint startPt;
int swipe_direction;

// タッチ開始
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
  startPt = [[touches anyObject] locationInView:self];	
  startTime = [[NSDate date] retain];	
  swipe_direction = SWIPE_NON;
}

// 移動
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
  CGPoint curPt = [[touches anyObject] locationInView:self];	
  // 水平のスワイプを検出
  if(fabsf(startPt.x - curPt.x) >= HORIZ_SWIPE_MIN && fabsf(startPt.y - curPt.y) <= VERT_SWIPE_MAX){
    if(startPt.x < curPt.x){
      swipe_direction = SWIPE_LEFT;
    }else{
      swipe_direction = SWIPE_RIGHT;
    }
  }
}

// タッチ終了
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
  CGPoint curPt = [[touches anyObject] locationInView:self];	
  if(swipe_direction != SWIPE_NON){
    // スワイプの速度を検出
    NSTimeInterval dt = -[startTime timeIntervalSinceNow];
    int dx = fabsf(startPt.x - curPt.x);
    double speed = dx / dt;		
    NSLog([NSString stringWithFormat:@"dir:%i, dx:%i, dt:%f, speed:%f", swipe_direction, dx, dt, speed]);	
  }
}

- (void)dealloc {
  [startTime release];
  [super dealloc];
}
@end

実行結果はこんな感じ。

2009-03-05 23:49:38.269 swipe[2143:20b] dir:2, dx:90, dt:0.135690, speed:663.276569
2009-03-05 23:49:40.197 swipe[2143:20b] dir:2, dx:68, dt:1.569752, speed:43.318944
2009-03-05 23:49:42.022 swipe[2143:20b] dir:1, dx:94, dt:1.280833, speed:73.389741
2009-03-05 23:49:42.574 swipe[2143:20b] dir:2, dx:27, dt:0.079615, speed:339.132086
2009-03-05 23:49:44.839 swipe[2143:20b] dir:2, dx:39, dt:0.087758, speed:444.403905
2009-03-05 23:49:45.479 swipe[2143:20b] dir:1, dx:134, dt:0.062301, speed:2150.848988