UIButtonやUITableViewなどのイベントではなく、画面のタッチイベントについて。

UIResponderクラスで管理している。

#import 
#import 
#import 

UIKIT_EXTERN_CLASS @interface UIResponder : NSObject {
  @private
}

- (UIResponder*)nextResponder;

- (BOOL)canBecomeFirstResponder;    // default is NO
- (BOOL)becomeFirstResponder;

- (BOOL)canResignFirstResponder;    // default is YES
- (BOOL)resignFirstResponder;

- (BOOL)isFirstResponder;

// Generally, all responders which do custom touch handling should override all four of these methods.
// Your responder will receive either touchesEnded:withEvent: or touchesCancelled:withEvent: for each
// touch it is handling (those touches it received in touchesBegan:withEvent:).
// *** You must handle cancelled touches to ensure correct behavior in your application.  Failure to
// do so is very likely to lead to incorrect behavior or crashes.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;

- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);

- (void)remoteControlReceivedWithEvent:(UIEvent *)event __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0);

- (BOOL)canPerformAction:(SEL)action withSender:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
@property(nonatomic,readonly) NSUndoManager *undoManager __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);

@end

@interface NSObject(UIResponderStandardEditActions)   // these methods are not implemented in NSObject

- (void)cut:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)copy:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)paste:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)select:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)selectAll:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_0);
- (void)delete:(id)sender __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_2);

@end

@interface UIResponder (UIResponderInputViewAdditions)

// Called and presented when object becomes first responder.  Goes up the responder chain.
@property (readonly, retain) UIView *inputView __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_2);            
@property (readonly, retain) UIView *inputAccessoryView __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_2); 

// If called while object is first responder, reloads inputView and inputAccessoryView.  Otherwise ignored.
- (void)reloadInputViews __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_2);

@end

この中で頻度が高そうなメソッドは、

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;

かと。 これで、お絵描きソフトとかで描画したり。

ダブルタッチの判定

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    if ([touch tapCount] == 2) {
        NSLog(@"double touch");
    }
}

ただし、画面の上に他のUIViewが追加されていると当然ながらイベントは発生しません。