我发现这发生在我与一个破碎的布局和一切爆炸。放松，这就像你第一次学习编程时犯的错误一样，你忘记了一个分号，它就会产生100个错误。许多人惊慌失措，按下所有的按钮，使事情变得更糟。

解决方案

Make sure that anything the R. links to is not broken. Fix all errors in your XML files. If anything in the ADKs are broken, R will not regenerate. If you somehow hit something and created import android.R in your activity, remove it. Run Project -> Clean. This will delete and regenerate R and BuildConfig. Make sure Project -> Build Automatically is ticked. If not, build it manually via Menu -> Project -> Build Project . Wait a few seconds for the errors to disappear. If it doesn't work, delete everything inside the /gen/ folder If it still doesn't work, try right-clicking your project -> Android Tools -> Fix Project Properties. Check your *.properties files (in the root folder of your app folder) and make sure that the links in there are not broken. Right-click your project > properties > Android. Look at the Project Build Target and Library sections on the right side of the page. Your Build Target should match the target in your AndroidManifest.xml. So if it's set to target 17 in AndroidManifest, make sure that the Target Name is Android 4.2. If your Library has an X under the reference, remove and re-add the library until there's a green tick. This might happen if you've moved a few files and folders around.

如果R不能再生怎么办

这通常发生在XML文件损坏时。

Check errors inside your XML files, mainly within the /res/ folder Common places are /layout/ and /values/, especially if you've changed one of them recently Check AndroidManifest.xml. I find that often I change a string and forget to change the string name from AndroidManifest.xml. Check that Android SDK Build-tools is installed. Window -> Android SDK Manager -> Tools -> Android SDK Build-tools Make sure when you update the Android SDK Tools, you also update the Android SDK Platform-tools and Android ADK Build-tools. Build fails silently if they don't match. If you can't find the issue, right click /gen/ -> Restore from local history... -> tick R.java -> click Restore. Even if it doesn't solve the problem, it will clear out the extra errors to make the problem easier to find.

在main.xml中使用硬编码文本作为按钮文本属性时，没有出现任何错误，只有三个警告。 就像这样:

<Button
    android:id="@+id/scan"
    .....
    android:text="Scan" />

在将文本属性更改为android:text="@string/scan_device"后，立即生成了R.java。

因此，只要某个XML文件中出现任何错误/警告，它就会在我的机器/Eclipse上发生。

不过IntelliJ IDEA在警告方面没有这个问题。

如果你使用Lint错误检查器，它将识别虚假的“R”导入。 一旦XML系统抓住了错误的一端，一切都完了!!

通过更改文件项目来解决问题。属性:我添加了一个android-17目标。

对于这个问题，显然没有一个最终答案，但这里有另一个我还没有看到的答案:

我曾经让R.java在(尝试)团队同步后消失，并且在项目中存在冲突解决文件(即thing .xml.mine,thing .xml)。r35,等等)。删除它们/解决冲突再生R。

清理项目，关闭Eclipse，重新打开并启动我的项目，最终使我的R.java重新出现…希望能有所帮助