Unity通过Animator获取动画clip时长

///获取动画状态机animator的动画clip的播放持续时长
public static float GetClipLength(Animator animator, string clipName) 
{
    if(null== animator || 
     string.IsNullOrEmpty(clip) || 
     null == animator.runtimeAnimatorController)
        return 0;
    // 获取所有的clips	
    var clips = animator.runtimeAnimatorController.animationClips;
    if( null == clips || clips.Length <= 0) return 0;
    AnimationClip  clip ;
    for (int i = 0, len = clips.Length; i < len ; ++i) 
    {
        clip = ac.animationClips[i];
        if(null != clip && clip.name == clipName)
            return clip.Length;
    }
    return 0f;
}