Question

我是iOS新手，我在项目中使用UIPanGestureRecognizer。我在拖动视图时需要获取当前触摸点和上一个触摸点。我很难得到这两点。

如果我使用touchesBegan方法而不是使用UIPanGestureRecognizer，我可以通过以下代码获得这两点：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    CGPoint touchPoint = [[touches anyObject] locationInView:self];
    CGPoint previous=[[touches anyObject]previousLocationInView:self];
}

我需要在UIPanGestureRecognizer事件触发方法中获得这两点。我怎样才能做到这一点？请指导我。

Answer 1

您可以使用：

CGPoint currentlocation = [recognizer locationInView:self.view];

通过设置当前位置（如果未找到）并每次添加当前位置来存储先前位置。

previousLocation = [recognizer locationInView:self.view];

Answer 2

当您将UIPanGestureRecognizer链接到IBAction时，将在每次更改时调用该操作。手势识别器还提供名为state的属性，该属性指示它是第一个UIGestureRecognizerStateBegan，最后一个UIGestureRecognizerStateEnded还是UIGestureRecognizerStateChanged之间的事件。

要解决您的问题，请尝试以下操作：

- (IBAction)panGestureMoveAround:(UIPanGestureRecognizer *)gesture {
    if ([gesture state] == UIGestureRecognizerStateBegan) {
        myVarToStoreTheBeganPosition = [gesture locationInView:self.view];
    } else if ([gesture state] == UIGestureRecognizerStateEnded) {
       CGPoint myNewPositionAtTheEnd = [gesture locationInView:self.view];
       // and now handle it ;)
    }
}

您还可以查看名为translationInView:的方法。

Answer 3

您应该按如下方式实例化您的平移手势识别器：

UIPanGestureRecognizer* panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];

然后你应该将panRecognizer添加到你的视图中：

[aView addGestureRecognizer:panRecognizer];

当用户与视图交互时，将调用- (void)handlePan:(UIPanGestureRecognizer *)recognizer方法。在handlePan：你可以得到这样的点：

CGPoint point = [recognizer locationInView:aView];

您还可以获取panRecognizer的状态：

if (recognizer.state == UIGestureRecognizerStateBegan) {
    //do something
} else if (recognizer.state == UIGestureRecognizerStateEnded) {
   //do something else
}

Answer 4

UITouch中有一个功能可以在视图中进行上一次触摸

（CGPoint）locationInView：（UIView *）view;
（CGPoint）previousLocationInView：（UIView *）view;

Answer 5

如果您不想存储任何东西，也可以这样做：

let location = panRecognizer.location(in: self)
let translation = panRecognizer.translation(in: self)
let previousLocation = CGPoint(x: location.x - translation.x, y: location.y - translation.y)

如何在UIPanGestureRecognizer方法中获取当前触摸点和上一个触摸点？

5 个答案: