blocks|key|1361861|text|您不应该导入android.R。应该自动生成和识别。This+question包含了很多有用的提示，如果您在删除导入后引用R时出现了一些错误的话。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1361862|删除导入后的一些基本步骤(如果出现这些错误)：|1361863|清理你的建筑，然后重建|unordered-list-item|1361864|确保XML文件中没有错误或输入错误。|1361865|确保您的资源名由[a-z0-9.]组成。由于某些原因，不允许使用大写字母或符号。|1361866|执行分级同步(通过工具>+Android+>带有Gradle文件的同步项目)|1361867|1361868|1361869|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/885009/r-cannot-be-resolved-android-error?rq=1^0|6|9|1P|1|Q|D|0|0|0|0|0|8|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]]|E|$]]|$1|F|3|G|5|6|7|18|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@]|E|$]]|$1|K|3|L|5|J|7|1A|8|@]|D|@]|E|$]]|$1|M|3|N|5|J|7|1B|8|@$9|1C|A|1D|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|1E|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

You shouldn't be importing <code>android.R</code>. That should be automatically generated and recognized. <a href="https://stackoverflow.com/questions/885009/r-cannot-be-resolved-android-error?rq=1">This question</a> contains a lot of helpful tips if you get some error referring to <code>R</code> after removing the import.

Some basic steps after removing the import, if those errors appear:

<ul>
<li>Clean your build, then rebuild</li>
<li>Make sure there are no errors or typos in your XML files</li>
<li>Make sure your resource names consist of <code>[a-z0-9.]</code>. Capitals or symbols are not allowed for some reason.</li>
<li>Perform a Gradle sync (via Tools > Android > Sync Project with Gradle Files)</li>
</ul>

blocks|key|224561|text|如果您使用的是多种口味的？|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|224562|-make确保资源文件既没有声明/添加，也没有在主文件中声明/添加。
|blockquote|224563|224564|示例:包含符号变量的a_layout_file.xml文件|CODE|224565|src:|224566|风味1/res/布局/(无文件)|224567|flavor2/res/layout/a_layout_file.xml|224568|main/res/layout/a_layout_file.xml|224569|此设置将给出错误:无法找到符号变量，这是因为资源文件只能以或的两种风格出现在主文件中。|224570|entityMap^0|7|5|0|0|0|A|H|0|0|4|0|0|0|7|J|H|0|0|4|G|H|0|T|1|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$]]|$1|I|3|-4|5|6|7|12|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|13|8|@$9|14|A|15|B|L]]|D|@]|E|$]]|$1|M|3|N|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|19|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|L]]|D|@]|E|$]]|$1|S|3|T|5|6|7|1F|8|@$9|1G|A|1H|B|C]|$9|1I|A|1J|B|L]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1K|8|@$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]]|X|$]]

If you are using multiple flavors? 

<blockquote>
 -make sure the resource file is not declared/added both in only one of the flavors and in main.
</blockquote>

Example: <code>a_layout_file.xml</code> file containing the symbol variable(s)

src:

flavor1/res/layout/(no file)

flavor2/res/layout/<code>a_layout_file.xml</code>

main/res/layout/<code>a_layout_file.xml</code>

This setup will give the error: cannot find symbol variable, this is because the resource file can only be in both flavors or only in the main.

blocks|key|224611|text|如果在项目中使用String+build+config字段，则可能是这样：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|224612|buildConfigField+"String",+"source",+"play"|code-block|syntax|javascript|224613|如果您像上面那样声明您的字符串，它将导致错误发生。解决方法是将其更改为：|224614|buildConfigField+"String",+"source",+"\"play\""|224615|entityMap^0|8|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

If you are using a <code>String</code> build config field in your project, this might be the case:

<pre><code>buildConfigField "String", "source", "play"
</code></pre>

If you declare your String like above it will cause the error to happen. The fix is to change it to:

<pre><code>buildConfigField "String", "source", "\"play\""
</code></pre>

blocks|key|3982291|text|确保将MainActivity和.ScanActivity保存到AndroidManifest.xml文件中：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3982292|<activity+android:name=".MainActivity">
++++++++<intent-filter>
++++++++++++<action+android:name="android.intent.action.MAIN"+/>
++++++++++++<category+android:name="android.intent.category.LAUNCHER"+/>
++++++++</intent-filter>
++++</activity>
++++<activity+android:name=".ScanActivity">

++++</activity>|code-block|syntax|javascript|3982293|entityMap^0|3|C|G|D|W|J|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

Make sure you have <code>MainActivity</code> and <code>.ScanActivity</code> into your <code>AndroidManifest.xml</code> file:

<pre><code>&lt;activity android:name=".MainActivity"&gt;
 &lt;intent-filter&gt;
 &lt;action android:name="android.intent.action.MAIN" /&gt;
 &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
 &lt;/intent-filter&gt;
 &lt;/activity&gt;
 &lt;activity android:name=".ScanActivity"&gt;

 &lt;/activity&gt;
</code></pre>

blocks|key|1362005|text|确保您的变量在引用它的方法的作用域中。例如，我在类中的方法中本地定义了一个文本视图，并在另一个方法中引用它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1362006|我将文本视图定义移到了类定义下面的方法之外，以便其他方法可以访问定义，从而解决了问题。|1362007|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|$]]

Make sure your variables are in scope for the method that is referencing it. For example I had defined a textview locally in a method in the class and was referencing it in another method. 

I moved the textview definition outside the method right below the class definition so the other method could access the definition, which resolved the problem.

blocks|key|3982323|text|确保导入的R不是来自另一个模块。我把一个类从一个模块移到了主项目，而R是模块中的一个。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3982324|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|$]]

make sure that the imported R is not from another module. I had moved a class from a module to the main project, and the R was the one from the module.

blocks|key|3982399|text|@TouchBoarder上面的回答的另一种选择是，您也可能有两个具有相同名称的布局文件，但用于不同的api版本。您应该删除旧的my_file.xml文件|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3982400|my_file.xml
my_file.xml(v21)|code-block|syntax|javascript|3982401|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Another alternative to @TouchBoarder's answer above is that you may also have two layout files with the same name but for different api versions. You should delete the older my_file.xml file

<pre><code>my_file.xml
my_file.xml(v21)
</code></pre>

blocks|key|224689|text|在android中打开项目，单击“文件”并单击“无效缓存/重新启动”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|224690|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|$]]

Open project in android studio
click file
and click Invalidate Caches/Restart

blocks|key|224722|text|确保您在XML布局文件中引用的控件确实存在，即使它没有被使用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|224723|当我“移除未使用的资源”重新出厂时，我就有了这个。|224724|例如，如果布局中没有progressBar，则会得到此错误。|224725|rootView+=+inflater.inflate(R.layout.fragment_stats,+container,+false);

mProgressBar+=+rootView.findViewById(R.id.progressBar);|code-block|syntax|javascript|224726|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|P|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Make sure that the control you are referring to in the XML layout file really exists, even if it's not being used.
I had this after when I did &quot;removed unused resources&quot; refactory.
For example, you will get this error if there is no progressBar in the layout.
<pre><code>rootView = inflater.inflate(R.layout.fragment_stats, container, false);

mProgressBar = rootView.findViewById(R.id.progressBar);
</code></pre>

blocks|key|3982437|text|请检查您意外地将XML文件添加到布局文件夹中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3982438|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|$]]

Please check you accidentally added the XML file into the layout folder.

blocks|key|1362141|text|请确保您的包名在顶部正确，错误的包名可能会导致此问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1362142|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|$]]

Make Sure your package name correct at top, wrong package name may cause this issue.

I was working on my app and everything was normal until I tried to display image in java.

I ran the app once and it ran normally, the picture was displayed.
After that it asked me to import some libraries and I imported them. After that I got errors for my activities.

Errors like:

<pre><code>Gradle: error: cannot find symbol variable activity_main
Gradle: error: cannot find symbol variable button1
Gradle: error: cannot find symbol variable button2
Gradle: error: cannot find symbol variable textView
Gradle: error: cannot find symbol variable secondActivity
</code></pre>

In MainActivity I have imported these libraries: 

<pre><code>import android.R;
import android.content.Intent;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.Button;
</code></pre>

and in secondActivity these:

<pre><code>import android.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
</code></pre>

Does anyone know how to fix this?

EDIT: I deleted <code>import android.R;</code> and now it works normally.

Android Studio: Gradle: error: cannot find symbol variable

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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我正在开发我的应用程序，一切都很正常，直到我尝试用java显示图像。我运行了一次应用程序，它正常运行，图片显示。之后，它要求我导入一些库，然后我就导入了它们。在那之后，我的活动出了差错。错误，如：Gradle: error: cannot find symbol variable activity_mainGradle...

问Android : Gradle: error:无法找到符号变量
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问Android : Gradle: error:无法找到符号变量EN