插值器 Interpolator

• 内容
  接口 TimeInterpolator
  一些常见插值器
  自定义插值器

• 接口 TimeInterpolator
  表示输入和输出的关系

/**
 * A time interpolator defines the rate of change of an animation. This allows animations
 * to have non-linear motion, such as acceleration and deceleration.
 */
public interface TimeInterpolator {

    /**
     * Maps a value representing the elapsed fraction of an animation to a value that represents
     * the interpolated fraction. This interpolated value is then multiplied by the change in
     * value of an animation to derive the animated value at the current elapsed animation time.
     *
     * @param input A value between 0 and 1.0 indicating our current point
     *        in the animation where 0 represents the start and 1.0 represents
     *        the end
     * @return The interpolation value. This value can be more than 1.0 for
     *         interpolators which overshoot their targets, or less than 0 for
     *         interpolators that undershoot their targets.
     */
    float getInterpolation(float input);
}

• 常见插值器
  线性插值器 output = input

/**
 * An interpolator where the rate of change is constant
 */
@HasNativeInterpolator
public class LinearInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {

    public LinearInterpolator() {
    }

    public LinearInterpolator(Context context, AttributeSet attrs) {
    }

    public float getInterpolation(float input) {
        return input;
    }

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createLinearInterpolator();
    }
}

其他的可以看下源码解释，都是数学公式

• 自定义插值器
  重写 getInterpolation

• 用途
  Scroller 使用