背景

Application.LoadLevelAsync函数来异步加载游戏场景，通过查询AsyncOperation.progress的值来得到场景加载的进度。

遇到问题

LoadGame函数开始加载游戏场景，使用异步加载的方式加载场景1(Loading场景为0，主场景为1)，通过Unity提供的Coroutine机制，我们可以方便的在每一帧结束后调用SetLoadingPercentage函数来更新界面中显示的进度条的数值。 

<code class="csharp" style="word-wrap: break-word;"><span class="k" style="word-wrap: break-word;">public</span> <span class="k" style="word-wrap: break-word;">void</span> <span class="nf" style="word-wrap: break-word;">LoadGame</span><span class="p" style="word-wrap: break-word;">()</span> <span class="p" style="word-wrap: break-word;">{</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">StartCoroutine</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">StartLoading_1</span><span class="p" style="word-wrap: break-word;">(</span><span class="m" style="word-wrap: break-word;">1</span><span class="p" style="word-wrap: break-word;">));</span>
<span class="p" style="word-wrap: break-word;">}</span>

<span class="k" style="word-wrap: break-word;">private</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">IEnumerator</span> <span class="nf" style="word-wrap: break-word;">StartLoading_1</span><span class="p" style="word-wrap: break-word;">(</span><span class="kt" style="word-wrap: break-word;">int</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">scene</span><span class="p" style="word-wrap: break-word;">)</span> <span class="p" style="word-wrap: break-word;">{</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">AsyncOperation</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">Application</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">LoadLevelAsync</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">scene</span><span class="p" style="word-wrap: break-word;">);</span>
    <span class="k" style="word-wrap: break-word;">while</span><span class="p" style="word-wrap: break-word;">(!</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">isDone</span><span class="p" style="word-wrap: break-word;">)</span> <span class="p" style="word-wrap: break-word;">{</span>            
        <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">SetLoadingPercentage</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">progress</span> <span class="p" style="word-wrap: break-word;">*</span> <span class="m" style="word-wrap: break-word;">100</span><span class="p" style="word-wrap: break-word;">);</span>
        <span class="k" style="word-wrap: break-word;">yield</span> <span class="k" style="word-wrap: break-word;">return</span> <span class="k" style="word-wrap: break-word;">new</span> <span class="nf" style="word-wrap: break-word;">WaitForEndOfFrame</span><span class="p" style="word-wrap: break-word;">();</span>
    <span class="p" style="word-wrap: break-word;">}</span>        
<span class="p" style="word-wrap: break-word;">}</span>
</code>


最后进度条的效果显示如下:


Application.LoadLevelAsync并不是真正的后台加载，它在每一帧加载一些游戏资源，并给出一个progress值，所以在加载的时候还是会造成游戏卡顿，AsyncOperation.progress的值也不够精确。当主场景加载完毕后Unity就自动切换场景，所以上述代码中的while循环体内的代码是不会被调用的，导致进度条不会显示100%。

修补——100%完成

AsyncOperation.progress的值乘上2，这样当加载到50%的时候界面上就显示100%了。缺点是当界面上显示100%的时候，用户还要等待一段时间才会进入游戏。其实Unity提供了手动切换场景的方法，把AsyncOperation.allowSceneActivation设为false就可以禁止Unity加载完毕后自动切换场景，修改后的StartLoading_2代码如下: 

<code class="csharp" style="word-wrap: break-word;"><span class="c1" style="word-wrap: break-word;">// this function is not work</span>
<span class="k" style="word-wrap: break-word;">private</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">IEnumerator</span> <span class="nf" style="word-wrap: break-word;">StartLoading_2</span><span class="p" style="word-wrap: break-word;">(int scene)</span> <span class="p" style="word-wrap: break-word;">{</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">AsyncOperation</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">Application</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">LoadLevelAsync</span><span class="p" style="word-wrap: break-word;">(scene</span><span class="p" style="word-wrap: break-word;">);</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">allowSceneActivation</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="k" style="word-wrap: break-word;">false</span><span class="p" style="word-wrap: break-word;">;</span>
    <span class="k" style="word-wrap: break-word;">while</span><span class="p" style="word-wrap: break-word;">(!</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">isDone</span><span class="p" style="word-wrap: break-word;">)</span> <span class="p" style="word-wrap: break-word;">{</span>
        <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">SetLoadingPercentage</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">progress</span> <span class="p" style="word-wrap: break-word;">*</span> <span class="m" style="word-wrap: break-word;">100</span><span class="p" style="word-wrap: break-word;">);</span>
        <span class="k" style="word-wrap: break-word;">yield</span> <span class="k" style="word-wrap: break-word;">return</span> <span class="k" style="word-wrap: break-word;">new</span> <span class="nf" style="word-wrap: break-word;">WaitForEndOfFrame</span><span class="p" style="word-wrap: break-word;">();</span>
    <span class="p" style="word-wrap: break-word;">}</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">allowSceneActivation</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="k" style="word-wrap: break-word;">true</span><span class="p" style="word-wrap: break-word;">;</span>   
<span class="p" style="word-wrap: break-word;">}</span>
</code>


AsyncOperation.allowSceneActivation设为false，当加载完成后再设为true。代码看上去没有错，但是执行的结果是进度条最后会一直停留在90%上，场景不会切换。通过打印log发现AsyncOperation.isDone一直为false，AsyncOperation.progress的值增加到0.9后就保持不变了，也就是说场景永远不会被加载完毕。

allowSceneActivation设置为false后，Unity就只会加载场景到90%，剩下的10%要等到allowSceneActivation设置为true后才加载，这不得不说是一个坑。所以代码改为如下。当AsyncOperation.progress到达0.9后，就直接把进度条的数值更新为100%，然后设置AsyncOperation.allowSceneActivation为ture，让Unity继续加载未完成的场景。 

<code class="csharp" style="word-wrap: break-word;"><span class="k" style="word-wrap: break-word;">private</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">IEnumerator</span> <span class="nf" style="word-wrap: break-word;">StartLoading_3</span><span class="p" style="word-wrap: break-word;">(int scene)</span> <span class="p" style="word-wrap: break-word;">{</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">AsyncOperation</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">Application</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">LoadLevelAsync</span><span class="p" style="word-wrap: break-word;">(scene</span><span class="p" style="word-wrap: break-word;">);</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">allowSceneActivation</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="k" style="word-wrap: break-word;">false</span><span class="p" style="word-wrap: break-word;">;</span>
    <span class="k" style="word-wrap: break-word;">while</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">progress</span> <span class="p" style="word-wrap: break-word;"><</span> <span class="m" style="word-wrap: break-word;">0.9f</span><span class="p" style="word-wrap: break-word;">)</span> <span class="p" style="word-wrap: break-word;">{</span>
        <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">SetLoadingPercentage</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">progress</span> <span class="p" style="word-wrap: break-word;">*</span> <span class="m" style="word-wrap: break-word;">100</span><span class="p" style="word-wrap: break-word;">);</span>
        <span class="k" style="word-wrap: break-word;">yield</span> <span class="k" style="word-wrap: break-word;">return</span> <span class="k" style="word-wrap: break-word;">new</span> <span class="nf" style="word-wrap: break-word;">WaitForEndOfFrame</span><span class="p" style="word-wrap: break-word;">();</span>
    <span class="p" style="word-wrap: break-word;">}</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">SetLoadingPercentage</span><span class="p" style="word-wrap: break-word;">(</span><span class="m" style="word-wrap: break-word;">100</span><span class="p" style="word-wrap: break-word;">);</span>
    <span class="k" style="word-wrap: break-word;">yield</span> <span class="k" style="word-wrap: break-word;">return</span> <span class="k" style="word-wrap: break-word;">new</span> <span class="nf" style="word-wrap: break-word;">WaitForEndOfFrame</span><span class="p" style="word-wrap: break-word;">();</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">allowSceneActivation</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="k" style="word-wrap: break-word;">true</span><span class="p" style="word-wrap: break-word;">;</span>   
<span class="p" style="word-wrap: break-word;">}</span>
</code>


最后的效果如下：


打磨——增加动画

AsyncOperation.progress的值后，不立即更新进度条的数值，而是每一帧在原有的数值上加1，这样就会产生数字不停滚动的动画效果了，迅雷中显示下载进度就用了这个方法。 

<code class="csharp" style="word-wrap: break-word;"><span class="k" style="word-wrap: break-word;">private</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">IEnumerator</span> <span class="nf" style="word-wrap: break-word;">StartLoading_4</span><span class="p" style="word-wrap: break-word;">(int scene)</span> <span class="p" style="word-wrap: break-word;">{</span>
    <span class="kt" style="word-wrap: break-word;">int</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="m" style="word-wrap: break-word;">0</span><span class="p" style="word-wrap: break-word;">;</span>
    <span class="kt" style="word-wrap: break-word;">int</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">toProgress</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="m" style="word-wrap: break-word;">0</span><span class="p" style="word-wrap: break-word;">;</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">AsyncOperation</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">Application</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">LoadLevelAsync</span><span class="p" style="word-wrap: break-word;">(scene</span><span class="p" style="word-wrap: break-word;">);</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">allowSceneActivation</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="k" style="word-wrap: break-word;">false</span><span class="p" style="word-wrap: break-word;">;</span>
    <span class="k" style="word-wrap: break-word;">while</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">progress</span> <span class="p" style="word-wrap: break-word;"><</span> <span class="m" style="word-wrap: break-word;">0.9f</span><span class="p" style="word-wrap: break-word;">)</span> <span class="p" style="word-wrap: break-word;">{</span>
        <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">toProgress</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="p" style="word-wrap: break-word;">(</span><span class="kt" style="word-wrap: break-word;">int</span><span class="p" style="word-wrap: break-word;">)</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">progress</span> <span class="p" style="word-wrap: break-word;">*</span> <span class="m" style="word-wrap: break-word;">100</span><span class="p" style="word-wrap: break-word;">;</span>
        <span class="k" style="word-wrap: break-word;">while</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span> <span class="p" style="word-wrap: break-word;"><</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">toProgress</span><span class="p" style="word-wrap: break-word;">)</span> <span class="p" style="word-wrap: break-word;">{</span>
            <span class="p" style="word-wrap: break-word;">++</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span><span class="p" style="word-wrap: break-word;">;</span>
            <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">SetLoadingPercentage</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span><span class="p" style="word-wrap: break-word;">);</span>
            <span class="k" style="word-wrap: break-word;">yield</span> <span class="k" style="word-wrap: break-word;">return</span> <span class="k" style="word-wrap: break-word;">new</span> <span class="nf" style="word-wrap: break-word;">WaitForEndOfFrame</span><span class="p" style="word-wrap: break-word;">();</span>
        <span class="p" style="word-wrap: break-word;">}</span>
    <span class="p" style="word-wrap: break-word;">}</span>

    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">toProgress</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="m" style="word-wrap: break-word;">100</span><span class="p" style="word-wrap: break-word;">;</span>
    <span class="k" style="word-wrap: break-word;">while</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span> <span class="p" style="word-wrap: break-word;"><</span> <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">toProgress</span><span class="p" style="word-wrap: break-word;">){</span>
        <span class="p" style="word-wrap: break-word;">++</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span><span class="p" style="word-wrap: break-word;">;</span>
        <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">SetLoadingPercentage</span><span class="p" style="word-wrap: break-word;">(</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">displayProgress</span><span class="p" style="word-wrap: break-word;">);</span>
        <span class="k" style="word-wrap: break-word;">yield</span> <span class="k" style="word-wrap: break-word;">return</span> <span class="k" style="word-wrap: break-word;">new</span> <span class="nf" style="word-wrap: break-word;">WaitForEndOfFrame</span><span class="p" style="word-wrap: break-word;">();</span>
    <span class="p" style="word-wrap: break-word;">}</span>
    <span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">op</span><span class="p" style="word-wrap: break-word;">.</span><span class="n" style="word-wrap: break-word; padding-top: 15px; border: none; background-image: none !important; background-color: transparent !important; background-position: initial initial !important; background-repeat: initial initial !important;">allowSceneActivation</span> <span class="p" style="word-wrap: break-word;">=</span> <span class="k" style="word-wrap: break-word;">true</span><span class="p" style="word-wrap: break-word;">;</span>
<span class="p" style="word-wrap: break-word;">}</span>
</code>


displayProgress用来记录要显示在进度条上的数值，最后进度条的动画如下：

对比第一种的进度条


总结

如果在加载游戏主场景之前还需要解析数据表格，生成对象池，进行网络连接等操作，那么可以给这些操作赋予一个权值，利用这些权值就可以计算加载的进度了。如果你的场景加载速度非常快，那么可以使用一个假的进度条，让玩家看上几秒钟的loading动画，然后再加载场景。总之进度条虽然小，但要做好也是不容易的。