如何检测同时手势的结束？ (iOS)

Question

在我的应用中，我同时使用 UIPinchGestureRecognizer、UIRotationGestureRecognizer 和 UIPanGestureRecognizer 来缩放、旋转和移动图像。

方法 gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: 总是返回 YES 并且图像处理效果很好，但是......如何检测所有同时手势的结束，以便我可以重置图像？

Answer 1

一个简单的解决方案怎么样，比如计算当前正在处理的手势，并在所有手势结束时采取行动？

.h 文件：

int handledGesturesCount;

.m 文件：

- (id)init {
    (...)
    handledGesturesCount = 0;
}

// gesture handlers - the code for -pinch: repeats for -pan: and -rotate:
- (void)pinch:(UIPinchGestureRecognizer *)recognizer {
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        handledGesturesCount += 1;
    } else if (recognizer.state == UIGestureRecognizerStateEnded ||
               recognizer.state == UIGestureRecognizerStateCancelled ||
               recognizer.state == UIGestureRecognizerStateFailed)
    {
        handledGesturesCount -= 1;
        if (handledGesturesCount == 0) {
            [self resetImage];
        }
    }
}

- (void)pan:(UIPanGestureRecognizer *)recognizer {
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        handledGesturesCount += 1;
    } else if (recognizer.state == UIGestureRecognizerStateEnded ||
               recognizer.state == UIGestureRecognizerStateCancelled ||
               recognizer.state == UIGestureRecognizerStateFailed)
    {
        handledGesturesCount -= 1;
        if (handledGesturesCount == 0) {
            [self resetImage];
        }
    }
}

- (void)rotate:(UIRotationGestureRecognizer *)recognizer {
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        handledGesturesCount += 1;
    } else if (recognizer.state == UIGestureRecognizerStateEnded ||
               recognizer.state == UIGestureRecognizerStateCancelled ||
               recognizer.state == UIGestureRecognizerStateFailed)
    {
        handledGesturesCount -= 1;
        if (handledGesturesCount == 0) {
            [self resetImage];
        }
    }
}