用于ArcShape的Android自定义动画

Question

首先让我解释一下我的目标.我试图Animation改变一个属性ArcShape.一个ArcShape's构造函数有两个领域:startAngle和sweepAngle.我想要制作动画sweepAngle,使其在屏幕上显示为一个不断缩小的圆圈.

您可以通过想象PacMan来拍摄这个动画.想象一下,他的嘴闭上了.这个动画将类似于他越来越多地打开他的上颌,直到没有更多的PacMan.

现在......我有一些实施这个问题.首先,一旦ArcShape创建了一个,就没有内置的方法来改变它sweepAngle.这让我想到了第一个问题:有没有办法覆盖ArcShape并实现某些setSweepAngle方法？或者我是否必须new ArcShape为每个sweepAngle我希望展示的内容创建一个？

现在转到第二个问题......假设我找到了第一个问题的解决方案,我怎么能创建它Animation呢？这是我现在所拥有的要点:

public class OpenPacman extends Animation {
  public OpenPacman(float startAngle, float sweepAngle) {
    mStartAngle = startAngle;
    mSweepAngle = sweepAngle;
  }

  @Override
  protected void applyTransformation(float interpolatedTime, Transformation t) {
    /* This represents the current sweepAngle */
    float currAngle = mStartAngle + ((mSweepAngle - mStartAngle) * interpolatedTime);

    //Now I need to update the ArcShape's sweepAngle to currAngle. But HOW?
  }
}

Answer 1

我找到了解决方案.我有一个扩展的类View我们称之为Pacman嵌套我Animation在这个Pacman类中的自定义.这让我可以访问member variables该Pacman课程.

public class Pacman extends View {
  float mSweepAngle;
  ...
  //include constructors
  //override onMeasure
  ...

  /* Here we override onDraw */
  @Override
  protected void onDraw(final Canvas canvas) {
    Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
    RectF oval = new RectF(canvas.getClipBounds());
    canvas.drawArc(oval, 0, mCurrAngle, true, p);
  }

  /* Here we define our nested custom animation */
  public class OpenPacman extends Animation {
    float mStartAngle;
    float mSweepAngle;

    public OpenPacman (int startAngle, int sweepAngle, long duration) {
      mStartAngle = startAngle;
      mSweepAngle = sweepAngle;
      setDuration(duration);
      setInterpolator(new LinearInterpolator());
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
      float currAngle = mStartAngle + ((mSweepAngle - mStartAngle) * interpolatedTime);
      Pacman.this.mCurrAngle = -currAngle; //negative for counterclockwise animation.
    }
  }
}

现在,当自定义动画更新容器类时mCurrAngle,onDraw会自动调用,从而绘制相应的ArcShape.