blocks|key|4103498|text|这对我很有效。它的工作量取决于你的项目有多大。我启动了一个新项目，创建了所需的模块(XML、Kotlin、colors、strings等)，然后将代码从旧项目的模块复制到新项目的模块中。与重新创建UI相比，复制XML可以节省大量时间。总而言之，这需要一点时间，但我花了更多的时间来修复没有它的未解决的引用错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4103499|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

This worked for me. How much work it is depends on how big your project is. I started a new project, created the required modules (XML, Kotlin, colors, strings, etc.), then copied the code into the modules in the new project from the modules in the old project. Copying XML saves a lot of time compared to recreating the UI. All in all, it take a little while, but I have spent much more time tring to fix the unresolved reference error without it.

blocks|key|4103517|text|使用gradle命令。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4103518|在Android+Studio的右侧菜单上：|4103519|Gradle+->+:app+->+Tasks+->+build+->+clean。|offset|length|style|CODE|4103520|之后，Gradle+->+:app+->+Tasks+->+build+->+build|4103521|entityMap^0|0|0|0|15|0|3|15|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|P|8|@$F|Q|G|R|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|S|8|@$F|T|G|U|H|I]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|M|$]]

Use gradle commands. 
In Android Studio, on the right menu: 
<code>Gradle -&gt; :app -&gt; Tasks -&gt; build -&gt; clean</code>. 
After that, <code>Gradle -&gt; :app -&gt; Tasks -&gt; build -&gt; build</code>

blocks|key|4103629|text|我使用com.android.tools.build:gradle:3.3.0-alpha13，也遇到了同样的问题。更改到稳定版本3.2.1为我解决了这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4103630|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I used com.android.tools.build:gradle:3.3.0-alpha13 and had the same issue. Changing to stable Version 3.2.1 solved this problem for me.

blocks|key|4103719|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4103720|转到content_main.xml文件，在那里您需要更改|4103721|将代码行android:id="@%2Bid/??????">为您为文件指定的任何id。|offset|length|style|CODE|4103722|将问号??????替换为相关的文件id名称。(如果您不知道id，请转到底部的design选项卡并单击related+Asset。|4103723|在attributes下方的右侧，您可以找到您为其指定的ID。如果它是空的，你可以重新命名它，Android+Studio将编写代码。|4103724|然后重启Android+Studio。希望这能有所帮助。祝你编码愉快。|4103725|entityMap^0|0|0|4|P|0|3|6|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|T|8|@$F|U|G|V|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|W|8|@$F|X|G|Y|H|I]]|9|@]|A|$]]|$1|L|3|M|5|6|7|Z|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|10|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|Q|$]]

TRY THIS

Go to the content_main.xml file and there you need to change the

<code>android:id="@+id/??????"&gt;</code> line of code to whatever id you have given to your file.

Replace question mark <code>??????</code> with the related file id name.(IF you dont know the id go to the design tab on the bottom and click on the related Asset.

On the right side below attributes, you can find the ID you have given to it.
If it is blank you can freshly name it and Android Studio will write the code.

Then restart Android Studio. Hope this will help. Happy coding.

blocks|key|4104646|text|我相信我找到了真正的答案(尽管是偶然的)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4104647|同样，由于OP使我的KT文件无法定位R，以及碰巧在java中的其他类。我注意到的是文件名有一个大小写的区别。一旦我更正了import语句以匹配包的大小写(也就是文件夹)，错误就解决了。|4104648|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I believe that I came across the real answer (though by accident).

I also, as the OP had my KT file fail to location R. as well as other classes that happen to be in java. What I noticed was that there was a case difference I the filenames. Once I corrected the import statements to match the case of the package (aka, folder) the errors resolved.

blocks|key|4104689|text|我在R引用上也遇到了同样的问题。终于，Android+Studio3.3发布了，使用'com.android.tools.build:gradle:3.3.0'解决了这个问题！|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4104690|entityMap^0|16|12|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

I had the same problem with R reference too.
Finally Android Studio 3.3 has been released and using <code>'com.android.tools.build:gradle:3.3.0'</code> the problem has been fixed!

blocks|key|4104723|text|我也有同样的问题，我尽量不要从gradle版本3.3降级到gradle版本3.2.1。相反，我将Android+Studio更新到了3.3版本，这为我带来了好处;-)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4104724|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I had the same problem, and I tried not to downgrade from gradle version 3.3 to gradle version 3.2.1. Instead I updated Android Studio to version 3.3, which made the trick for me ;-)

blocks|key|4104738|text|我更新了Android+Studio到3.3.1版本，并解决了这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4104739|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I update Android Studio to version 3.3.1 and solved this problem.

blocks|key|4104780|text|这就是解决方案，File->Project+Structure->Project，从下拉列表中选择Android+Gradle+Plugin+Version+as+3.2.1。然后单击apply。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4104781|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Here is the solution,
File->Project Structure->Project, select Android Gradle Plugin Version as 3.2.1 from the drop-down. then click apply.

blocks|key|4103989|text|如果您在Kotlin中遇到此问题，因为您无法通过If引用xml布局的元素。(例如R.id.adView)，然后尝试从kotlin文件中删除行import+android.R。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4103990|entityMap^0|14|B|1Y|G|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

If your are experiencing this issue in Kotlin because you cannot reference the elements of the xml layout by ids. (e.g. <code>R.id.adView</code>) then try removing the line <code>import android.R</code> from your kotlin file.

blocks|key|4104915|text|对我来说，这是因为我创建了一个新的包，而R在我从上面的包中导入之前是不可用的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4104916|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

For me it was because I had created a new package and R wasn't available until I imported it from the package above

blocks|key|4104940|text|我使用了错误的导入语句import+android.R而不是import+my.project.package.R。修复它解决了问题|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4104941|entityMap^0|B|G|U|R|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

I had wrong import statement <code>import android.R</code> instead of <code>import my.project.package.R</code>. Fixing it solved the problem

blocks|key|4104967|text|由于这个导入，我遇到了一个问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4104968|import+android.os.Build.VERSION_CODES.*|code-block|syntax|javascript|4104969|在最新版本中，它包含R|4104970|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I had an issue because of this import:
<pre><code>import android.os.Build.VERSION_CODES.*
</code></pre>
In the latest version it contains R

blocks|key|4104228|text|我在使用auto-manifest插件时也遇到了同样的问题。添加AndroidManifest.xml显式地解决了我的问题。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4104229|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/GradleUp/auto-manifest^0|W|J|4|D|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

I had same problem while using <a href="https://github.com/GradleUp/auto-manifest" rel="nofollow noreferrer">auto-manifest</a> plugin. Adding <code>AndroidManifest.xml</code> explicitly solved the problem to me.

I am new to kotlin, i have converted some code from java but it seems like there's something wrong, The R in findViewById(R.id.my_id) is highlighted in red and it shows this message : "Unresolved reference: R".. I've been looking for a solution but i seem not to figure it out, So what should i do?
Here's a screenshot :

<a href="https://i.stack.imgur.com/n4TCM.png" rel="noreferrer"><img src="https://i.stack.imgur.com/n4TCM.png" alt="enter image description here"></a>

Android Studio 3.1.3 - Unresolved reference: R - Kotlin

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我刚接触kotlin，我已经从java转换了一些代码，但似乎有问题，findViewById(R.id.my_id)中的R以红色突出显示，并显示此消息："Unresolved :R“。我一直在寻找一个解决方案，但我似乎没有弄清楚，所以我该怎么办？这是一个截图：​​

问Android Studio 3.1.3 -未解析的参考:R- Kotlin
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问Android Studio 3.1.3 -未解析的参考:R- KotlinEN