iOS

Question

当用户在视图上移动手指时，我需要获取每个触摸点。

这就是我在 CustomView.m

中获得积分的方式

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];

    UITouch *touch = [[touches allObjects] objectAtIndex:0];

    CGPoint touchLocation = [touch locationInView:self];

    NSLog(@"touch location is %f", touchLocation.x);
}

然后我查看日志，输出是：

2016-05-23 19:49:45.116 AutoLayoutTest[32321:3809723] touch location is 6.000000
2016-05-23 19:49:45.134 AutoLayoutTest[32321:3809723] touch location is 10.500000
2016-05-23 19:49:45.151 AutoLayoutTest[32321:3809723] touch location is 17.500000
2016-05-23 19:49:45.169 AutoLayoutTest[32321:3809723] touch location is 29.000000
2016-05-23 19:49:45.185 AutoLayoutTest[32321:3809723] touch location is 41.500000
2016-05-23 19:49:45.202 AutoLayoutTest[32321:3809723] touch location is 52.000000
2016-05-23 19:49:45.220 AutoLayoutTest[32321:3809723] touch location is 62.500000
2016-05-23 19:49:45.237 AutoLayoutTest[32321:3809723] touch location is 68.500000
2016-05-23 19:49:45.254 AutoLayoutTest[32321:3809723] touch location is 77.000000
2016-05-23 19:49:45.272 AutoLayoutTest[32321:3809723] touch location is 84.500000
2016-05-23 19:49:45.288 AutoLayoutTest[32321:3809723] touch location is 90.000000
2016-05-23 19:49:45.305 AutoLayoutTest[32321:3809723] touch location is 96.000000
2016-05-23 19:49:45.322 AutoLayoutTest[32321:3809723] touch location is 100.500000
2016-05-23 19:49:45.339 AutoLayoutTest[32321:3809723] touch location is 105.500000
2016-05-23 19:49:45.357 AutoLayoutTest[32321:3809723] touch location is 109.500000
2016-05-23 19:49:45.374 AutoLayoutTest[32321:3809723] touch location is 116.000000
2016-05-23 19:49:45.391 AutoLayoutTest[32321:3809723] touch location is 121.000000
2016-05-23 19:49:45.409 AutoLayoutTest[32321:3809723] touch location is 127.000000
2016-05-23 19:49:45.426 AutoLayoutTest[32321:3809723] touch location is 132.500000
2016-05-23 19:49:45.443 AutoLayoutTest[32321:3809723] touch location is 138.500000
2016-05-23 19:49:45.460 AutoLayoutTest[32321:3809723] touch location is 145.000000
2016-05-23 19:49:45.478 AutoLayoutTest[32321:3809723] touch location is 151.000000
2016-05-23 19:49:45.495 AutoLayoutTest[32321:3809723] touch location is 156.000000
2016-05-23 19:49:45.512 AutoLayoutTest[32321:3809723] touch location is 161.500000
2016-05-23 19:49:45.529 AutoLayoutTest[32321:3809723] touch location is 166.500000
2016-05-23 19:49:45.546 AutoLayoutTest[32321:3809723] touch location is 173.000000
2016-05-23 19:49:45.563 AutoLayoutTest[32321:3809723] touch location is 178.500000
2016-05-23 19:49:45.580 AutoLayoutTest[32321:3809723] touch location is 183.500000
2016-05-23 19:49:45.597 AutoLayoutTest[32321:3809723] touch location is 189.000000
2016-05-23 19:49:45.614 AutoLayoutTest[32321:3809723] touch location is 194.000000
2016-05-23 19:49:45.632 AutoLayoutTest[32321:3809723] touch location is 199.500000
2016-05-23 19:49:45.649 AutoLayoutTest[32321:3809723] touch location is 204.000000
2016-05-23 19:49:45.666 AutoLayoutTest[32321:3809723] touch location is 209.500000
2016-05-23 19:49:45.683 AutoLayoutTest[32321:3809723] touch location is 214.500000
2016-05-23 19:49:45.700 AutoLayoutTest[32321:3809723] touch location is 220.000000
2016-05-23 19:49:45.717 AutoLayoutTest[32321:3809723] touch location is 224.000000
2016-05-23 19:49:45.735 AutoLayoutTest[32321:3809723] touch location is 229.000000
2016-05-23 19:49:45.752 AutoLayoutTest[32321:3809723] touch location is 233.500000
2016-05-23 19:49:45.769 AutoLayoutTest[32321:3809723] touch location is 237.500000
2016-05-23 19:49:45.786 AutoLayoutTest[32321:3809723] touch location is 240.500000
2016-05-23 19:49:45.803 AutoLayoutTest[32321:3809723] touch location is 244.000000
2016-05-23 19:49:45.821 AutoLayoutTest[32321:3809723] touch location is 247.000000
2016-05-23 19:49:45.838 AutoLayoutTest[32321:3809723] touch location is 249.000000
2016-05-23 19:49:45.855 AutoLayoutTest[32321:3809723] touch location is 251.000000
2016-05-23 19:49:45.872 AutoLayoutTest[32321:3809723] touch location is 252.000000
2016-05-23 19:49:45.889 AutoLayoutTest[32321:3809723] touch location is 254.000000
2016-05-23 19:49:45.907 AutoLayoutTest[32321:3809723] touch location is 255.000000
2016-05-23 19:49:45.925 AutoLayoutTest[32321:3809723] touch location is 256.000000
2016-05-23 19:49:45.955 AutoLayoutTest[32321:3809723] touch location is 256.500000
2016-05-23 19:49:46.056 AutoLayoutTest[32321:3809723] touch location is 257.500000
2016-05-23 19:49:46.073 AutoLayoutTest[32321:3809723] touch location is 258.500000
2016-05-23 19:49:46.090 AutoLayoutTest[32321:3809723] touch location is 260.500000
2016-05-23 19:49:46.108 AutoLayoutTest[32321:3809723] touch location is 261.500000
2016-05-23 19:49:46.125 AutoLayoutTest[32321:3809723] touch location is 262.500000
2016-05-23 19:49:46.142 AutoLayoutTest[32321:3809723] touch location is 263.500000
2016-05-23 19:49:46.159 AutoLayoutTest[32321:3809723] touch location is 264.500000
2016-05-23 19:49:46.191 AutoLayoutTest[32321:3809723] touch location is 265.000000
2016-05-23 19:49:46.268 AutoLayoutTest[32321:3809723] touch location is 265.500000
2016-05-23 19:49:46.293 AutoLayoutTest[32321:3809723] touch location is 266.500000
2016-05-23 19:49:46.317 AutoLayoutTest[32321:3809723] touch location is 267.000000
2016-05-23 19:49:46.334 AutoLayoutTest[32321:3809723] touch location is 268.000000
2016-05-23 19:49:46.355 AutoLayoutTest[32321:3809723] touch location is 269.000000
2016-05-23 19:49:46.387 AutoLayoutTest[32321:3809723] touch location is 269.500000
2016-05-23 19:49:46.412 AutoLayoutTest[32321:3809723] touch location is 270.000000
2016-05-23 19:49:46.443 AutoLayoutTest[32321:3809723] touch location is 271.000000
2016-05-23 19:49:46.488 AutoLayoutTest[32321:3809723] touch location is 272.000000
2016-05-23 19:49:46.544 AutoLayoutTest[32321:3809723] touch location is 272.500000
2016-05-23 19:49:46.598 AutoLayoutTest[32321:3809723] touch location is 273.500000
2016-05-23 19:49:46.624 AutoLayoutTest[32321:3809723] touch location is 274.000000

请注意：印刷值仅为 X 轴上的值。因为我只关心x轴的变化。

问题是为什么有些点没有检测到？我期望当用户在视图上拖动手指时，捕获的点应该是 6、7、8、9、10、11 而不是 6、10、17、29、41 ...

我非常确定，当我通过在视图上拖动手指进行测试时，我是以正常速度进行的，而不是滑动。所以我觉得抓点不应该是这样的

我还尝试从平移手势识别器中获取点数。结果大同小异

我做错了吗？或者有更好的方法吗？

Answer 1

关于精度。您无法执行任何操作，因为用户移动手指的速度太快，无法将每个像素作为值。

Answer 2

iPad 屏幕以 60 Hz 的频率扫描。您得到的触摸点坐标是在手指位置进行扫描时手指所在的位置。扫描本身是由数字化仪网格每条线持续 400 微秒的电脉冲完成的。

随着更新的 iPads，这个频率被提高到 120 Hz（iPad Air 2 和 2 mini），iPad Pro 系列甚至以 240 Hz 扫描。您可以使用 coalesced touches functionality 获得这些中间点。这是在 objC 中的实现方式：

- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    for (UITouch *touch in touches) {
        for (UITouch* coalescedTouch in [event coalescedTouchesForTouch:touch]) {
            CGPoint newPoint = [coalescedTouch locationInView:self];
        }
    }
}

如果手指移动的足够快，即使那样你的坐标也会有间隙。进行插值以获取手指位于中间位置的时间 - 屏幕不会为您提供更高的精度。

iOS - 如何正确获取触点？

iOS - How To Get Touch Points Correctly?

uitouch

cgpoint