Javascript Adobe Animate CC按钮在用于控制电影剪辑时无法正常工作

我使用4个关键帧来区分按钮的活动和非活动状态。当我从头到尾运行MovieClip，然后使用按钮返回到前面的步骤时，会发生错误

在开始帧上，只有“按钮播放”和“下一步”处于活动状态

var root = this;

root.stop();

root.btnPlay.on('click', function () {
    root.gotoAndStop('playing');
    root.mcAnimate.play();
});

root.btnNext.on('click', function () {
    root.gotoAndStop('middle');
    root.mcAnimate.gotoAndStop('First state');
});

var root = this;

root.stop();

root.btnPrev.on('click', function(){
    root.gotoAndStop('middle');
    root.mcAnimate.gotoAndStop('Third state');
});

root.btnReload.on('click', function(){
    root.gotoAndStop('start');
    root.mcAnimate.gotoAndStop('Intial state');
});

单击“播放”按钮后，转到播放帧，将“播放”更改为“暂停”，启用“重新加载”按钮

var root = this;

root.stop();

root.btnPause.on('click', function(){
    root.gotoAndStop('middle');
    root.mcAnimate.stop();
});

root.btnReload.on('click', function(){
    root.gotoAndStop('start');
    root.mcAnimate.gotoAndStop('Intial state');
});

结束帧，只有按钮Prev和Reload处于活动状态

var root = this;

root.stop();

root.btnPlay.on('click', function () {
    root.gotoAndStop('playing');
    root.mcAnimate.play();
});

root.btnNext.on('click', function () {
    root.gotoAndStop('middle');
    root.mcAnimate.gotoAndStop('First state');
});

var root = this;

root.stop();

root.btnPrev.on('click', function(){
    root.gotoAndStop('middle');
    root.mcAnimate.gotoAndStop('Third state');
});

root.btnReload.on('click', function(){
    root.gotoAndStop('start');
    root.mcAnimate.gotoAndStop('Intial state');
});

中间帧最硬，因为每个按钮都处于活动状态，下一步取决于MovieClip帧标签

var root = this;
var currentLabel = '';

root.stop();

root.btnPrev.on('click', function() {
     var destination = '';
     checkCurrentLabel();
     if (currentLabel == 'First state') {
          root.gotoAndStop('start');
          destination = 'Intial state';
     } else if (currentLabel == 'Second state') {
          destination = 'First state';
     } else if (currentLabel == 'Third state') {
          destination = 'Second state';
     } else if (currentLabel == 'End state') {
          destination = 'Third state';
     } else {
          return;
     }
     root.mcAnimate.gotoAndStop(destination);
     currentLabel = destination;
});

root.btnPlay.on('click', function(){
     root.gotoAndStop('playing');
     root.mcAnimate.play();
     currentLabel = '';
});

root.btnNext.on('click', function(event){
     var destination = '';
     checkCurrentLabel();
     if (currentLabel == 'Intial state') {
          destination = 'First state';
     } else if (currentLabel == 'First state') {
          destination = 'Second state';
     } else if (currentLabel == 'Second state') {
          destination = 'Third state';
     } else if (currentLabel == 'Third state') {
          root.gotoAndStop('end');
          destination = 'End state';
     } else return;
     root.mcAnimate.gotoAndStop(destination);
     currentLabel = destination;
});

root.btnReload.on('click', function(){
    root.gotoAndStop('start');
    root.mcAnimate.gotoAndStop('Intial state');
    currentLabel = '';
});

function checkCurrentLabel() {
     if (currentLabel == '') {
          currentLabel = root.mcAnimate.getCurrentLabel();
     }
}

在电影剪辑中，帧标签的命名如下： 初始状态-->第一状态-->第二状态-->第三状态-->结束状态

当我从头到尾播放电影时。成功了！ 但若我在那个之后按下“上一步”和“下一步”按钮，就会发生错误。请帮忙