在iPhone SDK上实现动画的最佳方式？

Question

我知道如何通过移动/调整UIView来实现基本动画.但是,以下两个动画似乎有点复杂.

1)想象一下汽车游戏,当你按下踏板按钮时,速度表会旋转.如何将条形"填满"圆形的动画？

2)第二个动画更容易描述.如何在数字向下滑动的情况下增加数字动画,新数字从顶部出现,类似于老虎机.

Answer 1

对于你的第一个问题,我认为CGAffineTransform将是你要走的路.使用这个,我认为这样的东西可以工作:

// BarView is a derived class from UIView that knows how to draw a "bar"
BarView view[NumBars];
for(int i = 0; i < NumBars; i++)
{
  // First place the view at the center of the instrument
  [view[i] setCenter:CGPointMake(InstrumentX, InstrumentY)];

  // Now translate the view InstrumentWidth units on the positive X-Axis
  CGAffineTransform translate = CGAffineTransformMakeTranslation(InstrumentWidth, 0);

  // Rotate the view about the origin by an angle related to which "bar" this is
  CGAffineTransform rotate = CGAffineTransformMakeRotation(i*AngleBetweenBars);

  // create a transform matrix from the translation and rotation matrices and apply it to the view
  [view[i] setTransform:CGAffineTransformConcat(translate, rotate)];   
}