在UIPanGestureRecognizer中使用velocityInView [英] Making use of velocityInView with UIPanGestureRecognizer

问题描述

我有一个自定义滑块类型的对象，我希望它更有用。目前我使用 UIPanGestureRecognizer 和 translationInView 来使其工作。它运作得很好，但我想在那里使用某种速度让它感觉更有用。我已经尝试过一些东西，但是无法弄清楚如何正确实现速度 changedLevel 等式。

I have a custom slider-type object, that I wish to make more usable. Currently I use UIPanGestureRecognizer and translationInView to make it work. It works pretty well but I'd like some sort of velocity in there to make it feel a bit more useful. I've tried a few things but cant quite figure out how to properly implement velocity changedLevel equation.

- (void)panDetected:(UIPanGestureRecognizer *)gesture {

    CGPoint swipeLocation = [gesture locationInView:self.tableView];
    NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:swipeLocation];
    LevelCounterTableCell *swipedCell = (LevelCounterTableCell *)[self.tableView cellForRowAtIndexPath:indexPath];

    if([gesture state] == UIGestureRecognizerStateBegan) {
        NSString *originalLevelString = swipedCell.levelNumber.text;
        originalLevel = [originalLevelString intValue]; // int originalLevel
    }

    if ([gesture state] == UIGestureRecognizerStateChanged) {

        CGFloat xTranslation = [gesture translationInView:[[gesture view] superview]].x;
        CGFloat xVelocity = [gesture velocityInView: [[gesture view] superview]].x;

        // Pan threshold is currently set to 8.0. 
        // 8.0 is a decent level for slow panning
        // for fast panning 2.0 is more reasonable
        changedLevel = ceilf((xTranslation / panThreshold) + originalLevel); // int changedLevel

        // Raw velocity seems to go from around 3 (slow)
        // to over 200 (fast)
        NSLog(@"raw velocity = %f", xVelocity);

        if (changedLevel >= 15 && changedLevel <= 100) {
            swipedCell.levelNumber.text = [NSString stringWithFormat:@"%i", changedLevel];
            swipedCell.meter.frame = [self updateMeter: changedLevel];

        }
    }

    if ([gesture state] == UIGestureRecognizerStateEnded || [gesture state] == UIGestureRecognizerStateCancelled) {
        if (changedLevel >= 15 && changedLevel <= 100) {
            //... Save the values...            
        }

    }
}

任何帮助将不胜感激。谢谢。

Any help would be greatly appreciated. Thank you.

推荐答案

根据我的经验， velocityInView：在用户抬起手指并且识别器完成之前，平移手势识别器并不重要。此时，您可以使用力度来计算移动视图的动画持续时间。

In my experience, the velocityInView: of a pan gesture recognizer isn't important until the user lifts their finger(s) and the recognizer finishes. At that point, you can use the velocity to calculate an animation duration to move your views.

只需坚持 translationInView：直到州为 UIGestureRecognizerStateEnded 然后使用 velocityInView：为屏幕上的任何视图更改设置动画。

Just stick with translationInView: until the state is UIGestureRecognizerStateEnded and then use velocityInView: to animate any onscreen view changes.

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