FlingAnimationUtils.java 文件源码

private AnimatorProperties getDismissingProperties(float currValue, float endValue,
        float velocity, float maxDistance) {
    float maxLengthSeconds = (float) (mMaxLengthSeconds
            * Math.pow(Math.abs(endValue - currValue) / maxDistance, 0.5f));
    float diff = Math.abs(endValue - currValue);
    float velAbs = Math.abs(velocity);
    float y2 = calculateLinearOutFasterInY2(velAbs);

    float startGradient = y2 / LINEAR_OUT_FASTER_IN_X2;
    Interpolator mLinearOutFasterIn = new PathInterpolator(0, 0, LINEAR_OUT_FASTER_IN_X2, y2);
    float durationSeconds = startGradient * diff / velAbs;
    if (durationSeconds <= maxLengthSeconds) {
        mAnimatorProperties.interpolator = mLinearOutFasterIn;
    } else if (velAbs >= mMinVelocityPxPerSecond) {

        // Cross fade between linear-out-faster-in and linear interpolator with current
        // velocity.
        durationSeconds = maxLengthSeconds;
        VelocityInterpolator velocityInterpolator
                = new VelocityInterpolator(durationSeconds, velAbs, diff);
        InterpolatorInterpolator superInterpolator = new InterpolatorInterpolator(
                velocityInterpolator, mLinearOutFasterIn, Interpolators.LINEAR_OUT_SLOW_IN);
        mAnimatorProperties.interpolator = superInterpolator;
    } else {

        // Just use a normal interpolator which doesn't take the velocity into account.
        durationSeconds = maxLengthSeconds;
        mAnimatorProperties.interpolator = Interpolators.FAST_OUT_LINEAR_IN;
    }
    mAnimatorProperties.duration = (long) (durationSeconds * 1000);
    return mAnimatorProperties;
}