iOS:如何获得长按手势的持续时间？

Question

我正在开发一种游戏,通过长按对象本身来设置游戏对象的属性.属性的值由长按手势的持续时间确定.我正在使用UILongPressGestureRecognizer来实现这个目的,所以它是这样的:

[gameObjectView addGestureRecognizer:[[UILongPressGestureRecognizer alloc] 
                                       initWithTarget:self action:@selector(handle:)]];

然后是处理函数

- (void)handle:(UILongPressGestureRecognizer)gesture {
  if (gesture.state == UIGestureRecognizerStateEnded) {
    // Get the duration of the gesture and calculate the value for the attribute
  }
}

在这种情况下,如何获得长按手势的持续时间？

Answer 1

我很确定这个手势不会存储这些信息供您访问.您只能在其上设置名为minimumPressDuration的属性,该属性是识别手势之前的时间量.

使用ios 5(未经测试)的解决方法:

创建一个名为timer的NSTimer属性: @property (nonatomic, strong) NSTimer *timer;

一个柜台: @property (nonatomic, strong) int counter;

然后 @synthesize

- (void)incrementCounter {
    self.counter++;
}

- (void)handle:(UILongPressGestureRecognizer)gesture {
    if (gesture.state == UIGestureRecognizerStateBegan) {
         self.counter = 0;
         self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(incrementCounter) userInfo:nil repeats:yes];
    }
    if (gesture.state == UIGestureRecognizerStateEnded) {
        [self.timer invalidate];
    }
}

因此,当手势开始时,启动定时器,该定时器每秒触发增量方法,直到手势结束.在这种情况下,您需要将其设置minimumPressDuration为0,否则手势将不会立即开始.然后用计数器做你想做的事!

Answer 2

不需要计时器.你可以用这种方式实现它:

- (void)handleRecognizer:(UILongPressGestureRecognizer *)gesture
{
    static NSTimeInterval pressStartTime = 0.0; //This an be moved out and be kept as a property

    switch ([gesture state])
    {
        case UIGestureRecognizerStateBegan:
            //Keeping start time...
            pressStartTime = [NSDate timeIntervalSinceReferenceDate];
            break; /* edit*/
        case UIGestureRecognizerStateEnded:
        {
            //Calculating duration
            NSTimeInterval duration = [NSDate timeIntervalSinceReferenceDate] - pressStartTime;
            //Note that NSTimeInterval is a double value...
            NSLog(@"Duration : %f",duration);
            break;
        }
        default:
            break;
    }
}

另外不要忘记设置手势识别的minimumPressDuration,以0在创建它,如果你想获得长按真正的持续时间:
myLongPressGestureRecognizer.minimumPressDuration = 0

Answer 3

到目前为止,面向对象的Cocoa Touch中最干净,最简单的解决方案似乎是UILongPressGesture的子类.这是一个用Swift编写的例子.

    class MyLongPressGesture : UILongPressGestureRecognizer {
        var startTime : NSDate?
    }

    func installGestureHandler() {
            let longPress = MyLongPressGesture(target: self, action: "longPress:")
            button.addGestureRecognizer(longPress)
    }

    @IBAction func longPress(gesture: MyLongPressGesture) {
            if gesture.state == .Began {
                    gesture.startTime = NSDate()
            }
            else if gesture.state == .Ended {
                    let duration = NSDate().timeIntervalSinceDate(gesture.startTime!)
                    println("duration was \(duration) seconds")
            }
    }

如果要包括第一次点击的时间,可以在计算持续时间时将其包括在内,方法是添加回手势.minimumPressDuration.鉴于在被触发的手势和被调用的.Start处理程序之间可能存在少量(微小的)时间,缺点是它可能不是微秒精确的.但对于绝大多数应用而言并不重要.