TL;DR, if you get the error «package R does not exist», possible reasons are
- some error in the XML resource files
-> fix XML errors - the current package is different from the
Rpackage (seepackage
attribute in AndroidManifest.xml)
-> importRclass, e.g.import com.example.android.R;
-> or use the appropriate package in your source, e.g.package com.example.android;
-> or change the package attribute in AndroidManifest.xml to
<manifest xmlns:android="..." package="com.example.android" ...>, if that’s appropriate - the used
Rids are from the system resources
-> do not importandroid.R, but prefix the offending ids withandroid., e.g.android.R.layout.simple_list_item_2
You may importandroid.Rinstead of prefixing the ids of course, but then you cannot import the applicationRclass anymore and must prefix the application ids, e.g.com.example.android.R.id.main_menu.
The R class is generated automatically from the application’s
resources. It contains the ids for these resources and is contained
in the package named in the
<manifest>
tag in the corresponding AndroidManifest.xml file.
If there are no errors in the resource XML files, the R.java source
will be generated in a package subdirectory below gen/ and compiled.
There is another R class located in the android package. This android.R class contains some nested classes, which in turn contain ids and other values for system resources.
To use a class in Java, you must name the class with the whole
package, e.g.
java.util.List<Object> list = new java.util.ArrayList<Object>();
or import the class and then use it without package
import java.util.List;
import java.util.ArrayList;
List<Object> list = new ArrayList<Object>();
You can also use a class without naming the package, if both the
current class and the used class are in the same package, e.g.
package com.example.android;
public class A {
/* ... */
}
package com.example.android;
public class B {
public void useA() {
A a = new A();
}
}
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R.java plays a vital role in Android application advancement. It is utilized to distinguish all assets’ information; for example, ID, format, picture, drawable assets, and so forth. R.java is produced by the Android Studio. In any case, it is at some point mistaken for a designer to utilize it. This article will assist you in resolving these issues you may be experiencing in R.java.
Where Is R.java Saved?
R.java is commonly saved in a directory like:
Exampleappbuildgeneratedsourcerdebugcomdev2qaexampleimage.
You can also find it in an Android Studio project view list like below:
Why Can I Not Find the R Class In the Android Studio?
This is a common dilemma because you select the wrong subview in the project view. You can change the project view’s subview, which is demonstrated below:
Click View —> ToolWindows —> Project in the top menu bar.
In the above action, it will show the project view in the left panel. At the top left in the project view, there is a drop-down list where you can choose the project view’s subview.
Choose the project on the subview drop-down list, then you can see all the folders for the current project listed in the bottom panel. You can find the R class in the directory tree also. If you choose another subview, it will display different content of that subview.
What Data Is Saved In R.java?
Double click R.java file. It will display its content in the right panel. The source code includes a lot of int-type variables, and each int variable refers to one resource in the current Android application.
You will find that there are some inner public static final classes defined in R.java also. Each inner class represents one kind of resource, such as ID, layout, string, color, drawable, etc.
You do not need to care about those int variables and their values. Also, you do not need to edit them. If you change the value, you may encounter some strange errors when building the Android project.
How To Resolve the Package R Does Not Exist Error?
Sometimes, you may encounter strange errors about the R.class, like package R dost not exist or R cannot be resolved as a type. You can fix these errors by using the following steps:
Click Build —> Clean Project or Build —> Rebuild Project in the top menu bar of the Android Studio. This will let the Android Studio regenerate R.java again. It will clean the cache and include all newly added resources.
If the above method still does not take effect, you should check your AndroidManifest.xml file carefully. You need to make sure that the package value in the AndroidManifest.xml root XML element matches your activity package.
In the above picture, the manifest root XML element’s package value is com.dev2qa.example , and the launcher activity class is in the package com.dev2qa.example.image . So, if you change the package value, the error is resolved.
If the error still exists, you should check AndroidManifest.xml carefully to find the potential code that may generate the error. Or, you can restart the Android Studio or even your computer.
R (programming language)
Android Studio
Android (robot)
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The “package r does not exist” error message is a problem that shows up in Android Studio. Android Studio is a program for Android application advancement and development. It is associated with an important file used in building the application. Unfortunately, it is not as easy to solve as a code mistake.
The circumstances of this error.
This message tends to occur when compiling an application and the package r file cannot be found in the proper directory. Because it may not be a command line or source code problem it cannot be fixed by simply correcting a coding mistake. Unfortunately, this message can be triggered by a problem in any number of files that can prevent the r class package file from being created. This makes finding and correcting the error more difficult than simply tracking down some poorly written code in your new project data. Unfortunately, this means that the solution is usually more complicated in correcting decoding mistake.
What is causing this error?
The main cause of this message is that the software cannot find the package r.java. This manifest file contains critical class definitions for compiling your application. It is automatically generated by the software based on information contained in an XML file. This means that any errors that occur in AndroidManifest.xml or any other of these XML resource java files will stop the generation of the r.java layout file. If this happens r.java will not be in the folder your project looks for it in to import the needed default r packages. Put simply if r.java is not in the right working directory the program will return the message that the required package r does not exist in the project root directory.
Since this error is not a problem with the code you will not be correcting it at the command line. Since your problem is not with multiple packages one step is to actually check your app or project root directory for r.java. If you cannot find it then it was simply not created due to an error in some other java files.
The most common solution is to clean your Android project and then rebuild it. To do this find “build” on the menu in Android Studio and find the third item down. Selecting this option will clean up your new project or app. Next, go back to “build” on the menu in Android Studio and find the fourth item down. Selecting this option rebuilds your Android project. In most cases, this should fix the problem.
If you have enough experience you may want to look through Android Manifest.xml file for any problems. For example, the package value and launcher activity class attached package should match. So correcting this mismatch should correct it.
If all else fails try restarting Android Studio or if needed your computer. These actions have also been known to fix this problem.
The “package r does not exist” message is something you do not want to get when working with Android Studio. However, it does have simple solutions for you to try that should fix it. As with most problems in programming, this message is a nuisance but not an insurmountable one.
R Error: package r does not exist
R.java is very important in android application development. It is used to identify all resource data such as id, layout, image, drawable resource, etc. R.java is generated by android studio automatically. But it is sometimes confused for developers to use it. This article will help you to resolve these problems about R.java you may encounter.
1. Where R.java Is Saved At?
- R.java is commonly saved at directory like
Exampleappbuildgeneratedsourcerdebugcomdev2qaexampleimage. - You can also find it in the android studio left side Project view list like Example/app/build/generated/source/r/debug/com.dev2qa.example.image/R.class.
2. Why Can Not Find R Class In Android Studio?
- This is because you select the wrong subview in the android studio Project view. You can change the project view’s subview as following.
- Click the ” View —> Tool Windows —> Project ” menu item in the top menu bar.
- The above action will show the Project view in the android studio left panel. At the left top in the project view, there is a drop-down list where you can choose the project view’s subview.
- Choose Project in subview drop-down list, then you can see all the folders under the current project will be listed at below panel. You can find the R class in the directory tree also. If you choose other subviews, it will display different content of that subview.
3. What Data Is Saved In R.java?
- Double click the R.java file, it will display its content in the right panel. The source code includes a lot of int-type variables, each int variable refers to one resource in the current android application.
- You can find there are some inner public static final classes defined in R.java also, each inner class represents one kind of resource such as id, layout, string, color, drawable, etc.
- You do not need to care about those int variables and their values. And do not edit them also. If you change the value, you may encounter some strange error when building the android project.
4. How To Resolve Package R Dose Not Exist Error?
- Sometimes you may encounter strange errors about R.class. Such as package R dost not exist, R can not be resolved as a type. You can fix these errors follow the below steps.
- Click ” Build —> Clean Project ” or ” Build —> Rebuild Project ” in the top menu bar in android studio. This will let android studio regenerate R.java again. It will clean the cache and include all newly added resources.
- If the above method still does not take effect, you should check your AndroidManifest.xml file carefully. You need to make sure that the package value in the AndroidManifest.xml root XML element matches your activity package.
- In my example, the manifest root XML element’s package value is com.dev2qa.example and the launcher activity class is in package com.dev2qa.example.image. So after changing the package value, the error is resolved.
- If the error still exists, you should check AndroidManifest.xml carefully to find the potential code that may generate the error. Or you may need to restart android studio or even your computer to fix it 🙂
When I was compiling one of our previously written android application, I got following error,
error: package R does not existThis is because, in our app’s MainActivity we were using a code as below,
btn = (Button) findViewById(R.id.btn);Solution :
The right solution to this error is to import the Resources’s class i.e. R as,
import your_package_name.R;For example, our application’s package name is “com.demoapp.clickbutton” so we have to import R class as,
import com.demoapp.clickbutton.R;