Android Studio 表示“无法解析符号”，但项目已编译

我在 AndroidStudio 中导入 twitter4j，在 build.gradle 中使用以下代码:

dependencies {
compile 'com.android.support:support-v4:18.0.+'
compile files('libs/twitter4j-core-3.0.4.jar')
}

这个项目编译得很好，我可以毫无问题地创建 twitter 对象。然而，在 Android 工作室中，任何引用该库的内容都会显示为“无法解析符号”并显示为红色。我需要做什么才能让 Android Studio 识别这个库？

我已经尝试重建项目，./gradlew 干净，并关闭和重新开放我的项目。

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最佳答案

No idea if this will work or not but my only thought so far: right click the jar file in file tree within AS and select "Add as library..."

EDIT: You can do "File" -> "Invalidate Caches...", and select "Invalidate and Restart" option to fix this.

EDIT 2: This fix should work for all similar incidents and is not a twitter4j specific resolution.

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This problem happened for me when my Glass project was not using the SDK installed in Android Studio's default location. I was using another location I had previously from ADT, since I was trying to avoid re-downloading everything. Once I pointed the project back to the SDK location in Android Studio's install location the problem went away.

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Try changing the order of dependencies in File > Project Structure > (select your project) > Dependencies.

Invalidate Caches didn't work for me, but moving my build from the bottom of the list to the top did.

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This is what worked for me.

In the Project panel, right click on the project name, and select Open Module Settings from the popup menu.

then change the Compile SDK Version to the minimum version available (the minimum sdk version you set in the project). wait for android studio to load everything.

It will give you some errors, ignore those.

Now go to your java file and android studio will suggest you import

import android.support.v4.app.FragmentActivity;

Import it, then go back to Open Module Settings and change the compile sdk version back to what it was before.

Wait for things to load and voila.

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In my case, I had created a new file using the GUI and defined an interface within the file. I kept getting this symbol error because the file was not a "java" file. It had no extension on it at all.

After modifying the file extension to ".java", the system correctly finds the symbols.

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I had the very same problem recently with Android Studio 1.3. The only working solution was to remove the .gradle and .idea folders and re-import the project into Android Studio.

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I had this problem for a couple of days now and finally figured it out! All other solutions didn't work for me btw.

Solution: I had special characters in my project path!

Just make sure to have none of those and you should be fine or at least one of the other solutions should work for you.

Hope this helps someone!

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When i lived to this problem(red color codes but they work correctly) in my project;

As first, i made it that (File -> Indicate Cashes) --> (Invalidate and Restart).

As last, i resync my build.gradle file in my app. After problem was resolved.

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For those, who tried the accepted answer and have no success,

I tried also the accepted answer and did not work for me. After that, I updated my project with the repository and synchronized the project and the could not resolve warnings are gone.

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For mine was caused by the imported library project, type something in build.gradle and delete it again and press sync now, the error gone.

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You need to restart Android Studio.

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In my case the jar file did not have a META-INF/MANIFEST.MF file. After adding one, it worked!

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For my case working with AndroidStudio 2.2.3 the solution was to change the gradle wrapper/distribution to use local one in the Gradle Settings (despite of being "recommended"). enter image description here

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Invalidate Caches didn't work for me (this time). For me it was enough changing the gradle and syncing again. Or https://stackoverflow.com/a/29565362/2000162

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This worked for me-- (File -> Indicate Cashes) --> (Invalidate and Restart).

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I tried Invalidate cache/restart or clean Project -> rebuild project. These didn't work for me.

The final solution was open Project window on the left side of IDE, under Project mode, delete .gradle and .idea folder, THEN you can invalidate caches and restart. This fixed it.

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Invalidate Caches / Restart didn't work for me this time.

Found a solution like this:

  1. Remove the compile *** or implementation *** line in build.gradle.

  2. Clean and rebuild. Errors should be raised here.

  3. Add the line in step 1 back to build.gradle.

  4. Clean and rebuild.

Weird...

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If nothing else helped, you could do as Android Studio suddenly cannot resolve symbols recommends:

  • Exit Android Studio
  • Back up your project
  • Delete all the .iml files and the .idea folder
  • Relaunch Android Studio and reimport your project
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I also had this issue with my Android app depending on some of my own Android libraries (using Android Studio 3.0 and 3.1.1).

Whenever I updated a lib and go back to the app, triggering a Gradle Sync, Android Studio was not able to detect the code changes I made to the lib. Compilation worked fine, but Android Studio showed red error lines on some code using the lib.

After investigating, I found that it's because gradle keeps pointing to an old compiled version of my libs. If you go to yourProject/.idea/libraries/ you'll see a list of xml files that contains the link to the compiled version of your libs. These files starts with Gradle__artifacts_*.xml (where * is the name of your libs).

So in order for Android Studio to take the latest version of your libs, you need to delete these Gradle__artifacts_*.xml files, and Android Studio will regenerate them, pointing to the latest compiled version of your libs.

If you don't want to do that manually every time you click on "Gradle sync" (who would want to do that...), you can add this small gradle task in the build.gradle file of your app.

task deleteArtifacts {
doFirst {
File librariesFolderPath = file(getProjectDir().absolutePath + "/../.idea/libraries/")
File[] files = librariesFolderPath.listFiles({ File file -> file.name.startsWith("Gradle__artifacts_") } as FileFilter)


for (int i = 0; i < files.length; i++) {
files[i].delete()
}
}
}

And in order for your app to always execute this task before doing a gradle sync, you just need to go to the Gradle window, then find the "deleteArtifacts" task under yourApp/Tasks/other/, right click on it and select "Execute Before Sync" (see below).

Gradle window to configure task execution

Now, every time you do a Gradle sync, Android Studio will be forced to use the latest version of your libs.

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Change compile to implementation in the build.gradle.

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Changing the language injection settings worked for me.

Place the cursor on any of the red underlined code and Alt + Enter

enter image description here

Now select Language Injection Settings and a window will open as shown below.

enter image description here

Uncheck the selected option and click Ok

enter image description here

Hope this helps somebody.

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It happened to me when I removed the whole files in .gradle/caches, then studio downloaded the dependences. The dependences not showed in the External Libraries but I can build App successfully. rebuild clean Invalidate and Restart have no effect. I solved the problem by the steps:

  • Close Android Studio completely
  • Remove .idea package in your project
  • Restart Android Studio
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I have tried this but nothing worked for me:

  • Invalidate Caches / Restart
  • Changing the order of dependencies
  • Sync project with Gradle Files
  • Clean -> Rebuild Project

In my case, just do:

  • Delete all files in .idea/libraries folder
  • Rebuild Project
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For me I updated gradle-wrapper.properties into 4.4 

distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip
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I found easiest way

Identify the library which is causing syntax error in Studio.

For Example if AppCompatActivity is showing error then you will perform below operation on AppCompat Dependency.

  • Remove dependency which is showing syntax error & Sync.
  • Add again & Sync.

That's It, error gone!

Before

Before

After

After

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None of the answers above works for me.

After a lots of attempts, I upgraded com.android.tools.build:gradle in Project/build.gradle from 2.3.0 to 3.0.1, and it works.

I guess the version of the com.android.tools.build:gradle should be match to the version of AndroidStudio, and my AS version is 3.2.1

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Closing all files and closing Android Studio works for me.


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