如何通过手指触摸自动围绕中心点旋转图像

问题描述

在iPhone上，如何使用手指触摸实现围绕中心点旋转图像?

On iPhone, how to implement rotating image around the center point using finger touch ?

就像滚轮一样，如果你把手指放在iPhone屏幕上，然后突然移动，然后图像像滚轮一样围绕中心点旋转，过了一会儿，它变得越来越慢，最后停止了.

Just like wheel, if you put finger on the iPhone screen , then move suddenly, then the image becoming rotating around center point just like the wheel, after a while, it becomes more and more slow , finally stop.

谁能帮忙给出一些代码(Object-C)或一些建议?

Who can help to give some pieces of codes (Object-C) or some suggest ?

推荐答案

我昨天正在使用旋转瓶子"应用程序.在窗口上，我有一个带有瓶子的 ImageView，它可以响应触摸并旋转用户滑动手指的方式.在触摸事件(TouchesBegan、Touchesoved、TouchesEnd)期间，我很难让我的 ImageView 旋转.我在 TouchesMoved 中使用了这段代码来找出女巫旋转图像的角度.

I was working with a "spin the bottle"-app yesterday. On the window I have a ImageView with an bottle that's suppose to response to touches and rotate the way the user swipes his finger. I struggled to get my ImageView to rotate during the touch-events (TouchesBegan, Touchesoved, TouchesEnd). I used this code in TouchesMoved to find out the angle in witch to rotate the image.

public override void TouchesMoved (NSSet touches, UIEvent evt)
{    
  PointF pt = (touches.AnyObject as UITouch).LocationInView(this);

  float x = pt.X  - this.Center.X;
  float y = pt.Y  - this.Center.Y;
  double ang =  Math.Atan2(x,y);

  // yada yada, rotate image using this.Transform
}

这很重要！当 ImageView 旋转时，即使是 x &y 坐标会发生变化. 所以一直触摸同一个区域会给我在 pt 点和 prePt 点中的不同值.经过一番思考、谷歌搜索和阅读，我想出了一个简单的解决方案.ImageView 的SuperView"属性.

THIS IS IMPORTANT! When the ImageView rotates, even the x & y-coordinates changes. So touching the same area all the time would give me different values in the pt and prePt-points. After some thinking, googeling and reading I came up with an simple solution to the problem. The "SuperView"-property of the ImageView.

PointF pt = (touches.AnyObject as UITouch).LocationInView(this.SuperView);

有了这个小改动让它变得容易多了，不，我可以使用 UITouch-metohs LocationInView 和 PreviousLocationInView 并获得正确的 x &y 坐标.她是我代码的一部分.

Having that small change in place made it alot easier, no i can use the UITouch-metohs LocationInView and PreviousLocationInView and get the right x & y coordinates. Her is parts of my code.

float deltaAngle;

public override void TouchesMoved (NSSet touches, UIEvent evt)
{
    PointF pt = (touches.AnyObject as UITouch).LocationInView(this.Superview);

    float x = pt.X  - this.Center.X;
    float y = pt.Y  - this.Center.Y;
    float ang =  float.Parse(Math.Atan2(dx,dy).ToString());


    //do the rotation
     if (deltaAngle == 0.0) {
       deltaAngle = ang;
     }
else
    {
      float angleDif = deltaAngle - ang;
      this.Transform = CGAffineTransform.MakeRotation(angleDif);
    }   
}

希望这可以帮助某人花费数小时来弄清楚如何旋转瓶子！:)

Hope that helped someone from spending hours on how to figure out how to freaking rotate a bottle! :)

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