UIPanGestureRecognizer使用小結

UIPanGestureRecognizer是UIGestureRecognizer類的一個擴充類，其擴充類有UITapGestureRecognizer，UIPinchGestureRecognizer，UIRotationGestureRecognizer，UISwipeGestureRecognizer，UIPanGestureRecognizer，UILongPressGestureRecognizer。 藉助這些類，可以實現UIView對象的一些操作如物件放大顯示縮小，移動，旋轉，滑動，輕擊等。再也不用去重寫UIView的touchBegin等方法來實現這些功能。 知識點：UIGestureRecognizer是一個定義基本手勢的抽象類別，具體什麼手勢，在以下子類中包含：    1、拍擊UITapGestureRecognizer (任意次數的拍擊)      2、向裡或向外捏UIPinchGestureRecognizer (用於縮放)      3、搖動或者拖拽UIPanGestureRecognizer (拖動)     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 (長按) 這些操作的目的都是用來修改UIView對象的frame,center,bounds屬性，還有一個Transform屬性。 我寫了一個例子，在UIView和UITableView上分別添加UIPanGestureRecognizer，實現兩個對象在手指按住對象於螢幕中拖動的效果。 聲明一個UIPanGestureRecognizer對象，添加到UIView對象上去。UIView類有這樣的方法用來動態添加和刪除UIPanGestureRecognizer對象。 UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];[testPanView addGestureRecognizer:panRecognizer]; UIView管理手勢辨識器的方法有：– addGestureRecognizer:– removeGestureRecognizer:  gestureRecognizers  property– gestureRecognizerShouldBegin:  我在viewDidAppear:方法中，動態添加視圖和手勢辨識器。然後，實現辨識器需要操作的兩個方法，用來行動裝置檢視對象。在這兩個方法中最終的方法是這個 CGPoint translatedPoint = [recognizer translationInView:self.view]; 每一次拖動操作狀態，都會擷取到translatedPoint，從開始到結束。它是一個絕對值，可以看著在”self.view“對應的座標體系中，拖動的視圖對象center的移動開始和結束的點差。最簡單的處理過程是這樣：    CGPoint translatedPoint = [recognizer translationInView:self.view];    CGFloat x = recognizer.view.center.x + translatedPoint.x;    CGFloat y = recognizer.view.center.y + translatedPoint.y;    recognizer.view.center = CGPointMake(x, y);    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view]; 首先擷取到移動點的值，然後算一下視圖的center值，相加一下，就得到在self.view座標體系中，視圖該移動到那個center上，一次結束就清零一次。因為拖動操作持續進行，所以，這個過程會持續執行。 稍微複雜點的處理過程，會捕獲到拖動開始，移動，結束等幾個狀態下的translatedPoint的值。然後做一下邏輯處理，如視圖不能溢出self.view的座標系中，如在結束時會根據方向自動滑動到某個位置。可以在handlePan2：方法中找到這些邏輯的實現代碼。     - (void)viewDidAppear:(BOOL)animated{    NSLog(@" viewDidAppear is at %@.", [NSDate date]);     UIImage *image = [UIImage imageNamed:@"5.jpg"];     testPanView = [[UIView alloc] initWithFrame:CGRectMake(18, 11, 100, 100)];     UIImageView *imageview = [[UIImageView alloc] initWithFrame:[testPanView frame]];    [imageview setImage:image];    [testPanView addSubview:imageview];     UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];    [panRecognizer setMinimumNumberOfTouches:1];    [panRecognizer setMaximumNumberOfTouches:1];    [panRecognizer setDelegate:self];    [testPanView addGestureRecognizer:panRecognizer];     [self.view addSubview:testPanView];     testPanTableView = [[UITableView alloc] initWithFrame:CGRectMake(118, 121, 100, 100) style:UITableViewStylePlain];     UIPanGestureRecognizer *panRecognizer2 = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan2:)];    [panRecognizer2 setMinimumNumberOfTouches:1];    [panRecognizer2 setMaximumNumberOfTouches:1];    [panRecognizer2 setDelegate:self];    [testPanTableView addGestureRecognizer:panRecognizer2];     [self.view addSubview:testPanTableView];} - (void)handlePan:(UIPanGestureRecognizer *)recognizer{    CGPoint translatedPoint = [recognizer translationInView:self.view];    NSLog(@"gesture translatedPoint  is %@", NSStringFromCGPoint(translatedPoint));    CGFloat x = recognizer.view.center.x + translatedPoint.x;    CGFloat y = recognizer.view.center.y + translatedPoint.y;     recognizer.view.center = CGPointMake(x, y);     NSLog(@"pan gesture testPanView moving  is %@,%@", NSStringFromCGPoint(recognizer.view.center), NSStringFromCGRect(recognizer.view.frame));     [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];}   - (void)handlePan2:(UIPanGestureRecognizer *)recognizer{    // NSLog(@"gesture translatedPoint  xxoo xxoo");    CGPoint translatedPoint = [recognizer translationInView:self.view];     if ([(UIPanGestureRecognizer *)recognizer state] == UIGestureRecognizerStateBegan) {        firstX = recognizer.view.center.x;        firstY = recognizer.view.center.y;        NSLog(@"self.view bounds is %@", NSStringFromCGRect(self.view.bounds));        NSLog(@"pan gesture testPanView begin  is %@,%@", NSStringFromCGPoint([recognizer view].center), NSStringFromCGRect([recognizer view].frame));    }     if ([(UIPanGestureRecognizer *)recognizer state] == UIGestureRecognizerStateChanged) {        CGFloat x = firstX + translatedPoint.x;        CGFloat y = firstX + translatedPoint.y;         if (x < recognizer.view.width / 2.0) {            x = recognizer.view.width / 2.0;        } else if (x + recognizer.view.width / 2.0 > self.view.width) {            x = self.view.width - recognizer.view.width / 2.0;        }         if (y < recognizer.view.height / 2.0) {            y = recognizer.view.height / 2.0;        } else if (y + recognizer.view.height / 2.0 > self.view.height) {            y = self.view.height - recognizer.view.height / 2.0;        }         NSLog(@"gesture translatedPoint moving  is %@", NSStringFromCGPoint(translatedPoint));         recognizer.view.center = CGPointMake(x, y);    }     if (([(UIPanGestureRecognizer *)recognizer state] == UIGestureRecognizerStateEnded) || ([(UIPanGestureRecognizer *)recognizer state] == UIGestureRecognizerStateCancelled)) {        CGFloat x = recognizer.view.center.x;        CGFloat y = recognizer.view.center.y;         if (x > firstX) {            x = self.view.width - recognizer.view.width / 2.0;        } else {            x = recognizer.view.width / 2.0;        }         if (y > firstY) {            y = self.view.height - recognizer.view.height / 2.0;        } else {            y = recognizer.view.height / 2.0;        }         CGFloat velocityX = (0.2 *[recognizer velocityInView:self.view].x);         [UIView beginAnimations:nil context:NULL];         [UIView setAnimationDuration:ABS(velocityX * 0.00002 + 0.2)];         [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];         recognizer.view.center = CGPointMake(x, y);         [UIView commitAnimations];         NSLog(@"gesture translatedPoint  end is %@", NSStringFromCGPoint(translatedPoint));         NSLog(@"pan gesture testPanView end  is %@,%@", NSStringFromCGPoint([recognizer view].center), NSStringFromCGRect([recognizer view].frame));    }}