Related
I just downloaded and installed the new Android SDK. I wanted to create a simple application to test drive it.
The wizard created this code:
package eu.mauriziopz.gps;
import android.app.Activity;
import android.os.Bundle;
public class ggps extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
but Eclipse gives me the error
R cannot be resolved
on line
setContentView(R.layout.main);
Why?
PS: I do have an XML file named main.xml under res/layout/.
After tracking down this problem as well, I found this note in the Android documentation:
http://source.android.com/source/using-eclipse.html
*Note: Eclipse sometimes likes to add an "import android.R" statement at the
top of your files that use resources,
especially when you ask Eclipse to
sort or otherwise manage imports. This
will cause your make to break. Look
out for these erroneous import
statements and delete them.*
While going through the Android sample tutorials, I would often use the Ctrl + Shift + O command to "Organize Imports" and generate any missing import statements. Sometimes this would generate the incorrect import statement which would hide the R.java class that is automatically generated when you build.
Each time I had a problem with R not been generated, or even disappeared, this was due to some problem in the XML layout file that prevented the application from being built.
Whenever you get
R cannot be resolved
then check for the /res directory and there must be some file that have some error in it and that is preventing the application from being built. For example, it may be a layout file or it may be due to some missing resource is, but you already defined it in the XML file.
If you have any additional, even unused (!) or unreferenced (!) images in a folder like res/drawables-mdpi which do not comply to the file naming conventions (may contain only [a-z0-9_.]), the R.java class might not generate, causing the chain of events all the other posts referred to.
my project have include a r.java.at the beginning ,R.layout.main work good.But,after adding some code it doesn't work,and the error is R.layout.main can't resolved.what's the problem?
Look at your imports. Chances are that the line:
import android.R;
will be there. If that's the case, remove it, so that your project will resolve R not with the default Android Resources class, but with the one auto-generated from your /res/ folder.
And another thing which may cause this problem:
I installed the new ADT (v. 22). It stopped creating gen folder which includes R.java. The solution was to also install new Android SDK Build Tools from Android SDK Manager.
Solution found here
What Will said was right
R is an automatically generated class that holds the constants used to identify your >resources. If you don't have an R.java file (it would be gen/eu.mauriziopz.gps/R.java in >Eclipse with the 1.5 SDK) I would recommend closing and reopening your project or going to >Project > Build all (and selecting "Build Automatically" while there as recommended by >Josef). If that doesn't work than try making a new project, if the problem is recreated than >post here again and we'll go into more detail.
but I've found out that there was another problem that was causing the first one. The tools in the SDK directory didn't have the permissions to be executed, so it was like the didn't exist for Eclipse, thus it didn't build the R.java file.
So modifying the permission and selecting "Build Automatically" solved the problem.
R.java is a file that the Android Eclipse plugins creates while
building your application. R.java is created under the "gen"
directory. This file is generated from the information in the "res"
directory. If you run select "Project" -> "Clean..." on the Eclipse
menu, it will remove and then regenerate the R.java file.
The problem "R cannot be resolved" happens when you change your
package name in the AndroidManifest.xml file. It uses your Android
package name to create a subdirectory under the "gen" directory where
it stores the R.java file.
Eclipse may have problems executing clean, because it is confused about
where the R.java file is when you have changed the Android package
name. You can either rename the subdirectory under gen to match your
new package name, or you can change your package name back to the old
name. Do the clean and then change the package name to the new name
you want. This works best if you stop Eclipse from trying to build
while you are changing the package name. Under the "Project" menu
uncheck the option to "Build Automatically" and also when the
"Clean..." dialog asks if it should "Start a build immediately"
uncheck the box so it doesn't try to build while you are changing the
package name. After you have changed the name you can turn "Build
Automatically" back on again.
Note that if your AndroidManifest.xml file package name does not match
your Java package name, Eclipse will end up automatically adding an
"import <your Android package name>.R;" line in all your .java files
that have any references to R. If you change your AndroidManifest.xml
package name, sometimes Eclipse does not update all of these added
imports. If that happens, use the Eclipse refactoring (ALT +
Shift + R) to change the import statement in one of your Java files to
your new AndroidManifest.xml package name. It is best to do this
while you have disabled "Build Automatically".
R is an automatically generated class that holds the constants used to identify your resources. If you don't have an R.java file (it would be gen/eu.mauriziopz.gps/R.java in Eclipse with the 1.5 SDK) I would recommend closing and reopening your project or going to Project > Build all (and selecting "Build Automatically" while there as recommended by Josef). If that doesn't work than try making a new project, if the problem is recreated than post here again and we'll go into more detail.
Close all files, clean project, restart Eclipse.
It is worth checking in AndroidManifest.xml. The attribute package has the correct value.
That is:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="your.correct.package.name"
...
After you change that, the R.java will be re-generated.
This error can also be caused by adding an activity to a namespace that is different to the root namespace for your package.
For example, if com.example.myapp is the root namespace for your package, you can then add an activity to the com.example.myapp.activities namespace.
This will produce the "R cannot be resolved" error.
To fix the import the R in the default namespace in your activity should be:
import com.example.myapp.R;
Along with the great suggestions in the previous answers, make sure your Android target is set:
Right-click on your project
Choose Properties
Choose Android in the left menu
Tick a box next to the appropriate Project Build Target.
Click Apply and OK
Edit: A year later I found another cause. I had a .jpg image in my drawable folder with the same name as a .png image. Referencing this image in my code must have confused the program and it gave the "R cannot be resolved" error.
Make sure you installed the Android build tool form sdk manager
project right click properties-> Java BuildPath select Library and add android-support.jar the follow these step.
Go to Project->Properties->Java Build Path than select Order and export tab. Set android-support .jar library checked and up it into top of the list. And clean and rebuild..It works for most of the cases
I just had this problem for the millionth time and realized what was causing it: I created an XML file with uppercase letters in the name. All your XML filenames in /res must match [a-z0-9\\._].
Simplest solution - Sometimes you just need to save the XML file you were working on to get the autogenerator to kick in.
Save the file (e.g. main.xml) then delete the R.java file and see if the regenerated R.java resolves the R resolve problem.
Check the XML file names. Be sure that they're all in lowercase.
Also make sure that any image resource names are also all in LOWER CASE. I had a capital letter in the name of my jpg file, and it caused the R unresolved error right across my project.
R is a generated class. If you are using the Android Development Tools (ADT) it is generated whenever the project is built. You may have 'Build Automatically' turned off.
This error cropped up on my x64 Linux Mint installation. It turned out that the result was a failure in the ADB binary, because the ia32-libs package was not installed. Simply running apt-get install ia32-libs and relaunching Eclipse fixed the error.
If your x64 distro does not have ia32-libs, you'll have to go Multiarch.
Check #4 and #5 on this post:
http://crunchbang.org/forums/viewtopic.php?pid=277883#p277883
Hope this helps someone.
You may need to update/install SDK tools. Relaunch Android SDK Manager again and install a new item: Android SDK Build-tools.one by one delete,fix which one work for you.
I had this problem as well. It turned out that I had inadvertently deleted the "app_name" string resource from the strings.xml file, which was causing a silent error. Once I added it back, the R class was generated successfully and everything was back up and running.
You may need to update SDK tools. Relaunch Android SDK Manager again and install a new item: Android SDK Build-tools.
Try to make your new XML layout file name lower case. For example, use my_file.xml instead of myFile.xml.
Yet another reason R.java might not get autogenerated is if you have directories like res/drawable-hdpi, res/drawable-mdpi, or res/drawable-ldpi.
1.6+ seems to be OK with these directories, but 1.5 doesn't want them. When I removed those directories, R.java started autogenerating for me again.
Often times this is because of the MinSDK version number you supplied when creating the project. Example:
If you want 2.1 to be the minimum, Android 2.1 is actually API Level 7.
You can see what I am talking about when you browse the SDK you downloaded and installed. Navigate to the place you installed the SDK to (C:\android-sdk-windows for example) and open the folder named "platforms". You will see something like "android-7" listed as a folder, and if you open that there is a source.properties file that, when opened with a text editor, will show you the corresponding platform version.
When you create a project, and you must select a "Build Target" API, the last column in that list named "API Level" shows the number you are looking for when populating the MinSDK setting.
This is probably one of the most common mistakes that results in the R.java file not being created under Project > gen > packagename > R.java.
Remove main.out.xml. I'm new to this and don't yet know what this file is used for, but removing it cleared the problem.
Just go to Android Top menu list. click on Build Menu, in under Build click on Rebuild Project.
First check is there any error in any xml layout or not, if then resolve it first.
Otherwise remove junit dependency from project and rebuild the project.
In case anyone is interested (I might be saving your life here), I had the error, R.xml cannot be resolved, slightly different on a GLS project. Hmmmm. After looking in R.java, I found an auto-generated class, XML.java, (I think) was not there.
Solution? It needed a new folder in res: res\xml and a file called default_values.xml
in there. Then all was OK.
Just in case you have not got that file, it's:
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
xmlns:android="http://schemas.android.com/apk/res/android">
</PreferenceScreen>
So I have run into this problem multiple times when switching build targets. Usually doing a Project >> Clean worked for me. This last time, however, it did not. Finally I tried to open my default.properties file, located under the root project folder. I received an error message stating that it was out of sync with the file system. I actually deleted it and copied a coworkers version which allowed eclipse to rebuild my R file. I will paste what it looks like below. It is named 'default.properties'.
# This file is automatically generated by Android Tools.
# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
#
# This file must be checked in Version Control Systems.
#
# To customize properties used by the Ant build system use,
# "build.properties", and override values to adapt the script to your
# project structure.
# Indicates whether an apk should be generated for each density.
split.density=false
# Project target.
target=android-3
I had the examples of Android 8 and was trying to use Android 7 SDK. When I closed the project and reopened the application folder and chose to use Android 8 SDK, it was able to find the R file. Hope this helps.
I just downloaded and installed the new Android SDK. I wanted to create a simple application to test drive it.
The wizard created this code:
package eu.mauriziopz.gps;
import android.app.Activity;
import android.os.Bundle;
public class ggps extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
but Eclipse gives me the error
R cannot be resolved
on line
setContentView(R.layout.main);
Why?
PS: I do have an XML file named main.xml under res/layout/.
After tracking down this problem as well, I found this note in the Android documentation:
http://source.android.com/source/using-eclipse.html
*Note: Eclipse sometimes likes to add an "import android.R" statement at the
top of your files that use resources,
especially when you ask Eclipse to
sort or otherwise manage imports. This
will cause your make to break. Look
out for these erroneous import
statements and delete them.*
While going through the Android sample tutorials, I would often use the Ctrl + Shift + O command to "Organize Imports" and generate any missing import statements. Sometimes this would generate the incorrect import statement which would hide the R.java class that is automatically generated when you build.
Each time I had a problem with R not been generated, or even disappeared, this was due to some problem in the XML layout file that prevented the application from being built.
Whenever you get
R cannot be resolved
then check for the /res directory and there must be some file that have some error in it and that is preventing the application from being built. For example, it may be a layout file or it may be due to some missing resource is, but you already defined it in the XML file.
If you have any additional, even unused (!) or unreferenced (!) images in a folder like res/drawables-mdpi which do not comply to the file naming conventions (may contain only [a-z0-9_.]), the R.java class might not generate, causing the chain of events all the other posts referred to.
my project have include a r.java.at the beginning ,R.layout.main work good.But,after adding some code it doesn't work,and the error is R.layout.main can't resolved.what's the problem?
Look at your imports. Chances are that the line:
import android.R;
will be there. If that's the case, remove it, so that your project will resolve R not with the default Android Resources class, but with the one auto-generated from your /res/ folder.
And another thing which may cause this problem:
I installed the new ADT (v. 22). It stopped creating gen folder which includes R.java. The solution was to also install new Android SDK Build Tools from Android SDK Manager.
Solution found here
What Will said was right
R is an automatically generated class that holds the constants used to identify your >resources. If you don't have an R.java file (it would be gen/eu.mauriziopz.gps/R.java in >Eclipse with the 1.5 SDK) I would recommend closing and reopening your project or going to >Project > Build all (and selecting "Build Automatically" while there as recommended by >Josef). If that doesn't work than try making a new project, if the problem is recreated than >post here again and we'll go into more detail.
but I've found out that there was another problem that was causing the first one. The tools in the SDK directory didn't have the permissions to be executed, so it was like the didn't exist for Eclipse, thus it didn't build the R.java file.
So modifying the permission and selecting "Build Automatically" solved the problem.
R.java is a file that the Android Eclipse plugins creates while
building your application. R.java is created under the "gen"
directory. This file is generated from the information in the "res"
directory. If you run select "Project" -> "Clean..." on the Eclipse
menu, it will remove and then regenerate the R.java file.
The problem "R cannot be resolved" happens when you change your
package name in the AndroidManifest.xml file. It uses your Android
package name to create a subdirectory under the "gen" directory where
it stores the R.java file.
Eclipse may have problems executing clean, because it is confused about
where the R.java file is when you have changed the Android package
name. You can either rename the subdirectory under gen to match your
new package name, or you can change your package name back to the old
name. Do the clean and then change the package name to the new name
you want. This works best if you stop Eclipse from trying to build
while you are changing the package name. Under the "Project" menu
uncheck the option to "Build Automatically" and also when the
"Clean..." dialog asks if it should "Start a build immediately"
uncheck the box so it doesn't try to build while you are changing the
package name. After you have changed the name you can turn "Build
Automatically" back on again.
Note that if your AndroidManifest.xml file package name does not match
your Java package name, Eclipse will end up automatically adding an
"import <your Android package name>.R;" line in all your .java files
that have any references to R. If you change your AndroidManifest.xml
package name, sometimes Eclipse does not update all of these added
imports. If that happens, use the Eclipse refactoring (ALT +
Shift + R) to change the import statement in one of your Java files to
your new AndroidManifest.xml package name. It is best to do this
while you have disabled "Build Automatically".
R is an automatically generated class that holds the constants used to identify your resources. If you don't have an R.java file (it would be gen/eu.mauriziopz.gps/R.java in Eclipse with the 1.5 SDK) I would recommend closing and reopening your project or going to Project > Build all (and selecting "Build Automatically" while there as recommended by Josef). If that doesn't work than try making a new project, if the problem is recreated than post here again and we'll go into more detail.
Close all files, clean project, restart Eclipse.
It is worth checking in AndroidManifest.xml. The attribute package has the correct value.
That is:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="your.correct.package.name"
...
After you change that, the R.java will be re-generated.
This error can also be caused by adding an activity to a namespace that is different to the root namespace for your package.
For example, if com.example.myapp is the root namespace for your package, you can then add an activity to the com.example.myapp.activities namespace.
This will produce the "R cannot be resolved" error.
To fix the import the R in the default namespace in your activity should be:
import com.example.myapp.R;
Along with the great suggestions in the previous answers, make sure your Android target is set:
Right-click on your project
Choose Properties
Choose Android in the left menu
Tick a box next to the appropriate Project Build Target.
Click Apply and OK
Edit: A year later I found another cause. I had a .jpg image in my drawable folder with the same name as a .png image. Referencing this image in my code must have confused the program and it gave the "R cannot be resolved" error.
Make sure you installed the Android build tool form sdk manager
project right click properties-> Java BuildPath select Library and add android-support.jar the follow these step.
Go to Project->Properties->Java Build Path than select Order and export tab. Set android-support .jar library checked and up it into top of the list. And clean and rebuild..It works for most of the cases
I just had this problem for the millionth time and realized what was causing it: I created an XML file with uppercase letters in the name. All your XML filenames in /res must match [a-z0-9\\._].
Simplest solution - Sometimes you just need to save the XML file you were working on to get the autogenerator to kick in.
Save the file (e.g. main.xml) then delete the R.java file and see if the regenerated R.java resolves the R resolve problem.
Check the XML file names. Be sure that they're all in lowercase.
Also make sure that any image resource names are also all in LOWER CASE. I had a capital letter in the name of my jpg file, and it caused the R unresolved error right across my project.
R is a generated class. If you are using the Android Development Tools (ADT) it is generated whenever the project is built. You may have 'Build Automatically' turned off.
This error cropped up on my x64 Linux Mint installation. It turned out that the result was a failure in the ADB binary, because the ia32-libs package was not installed. Simply running apt-get install ia32-libs and relaunching Eclipse fixed the error.
If your x64 distro does not have ia32-libs, you'll have to go Multiarch.
Check #4 and #5 on this post:
http://crunchbang.org/forums/viewtopic.php?pid=277883#p277883
Hope this helps someone.
You may need to update/install SDK tools. Relaunch Android SDK Manager again and install a new item: Android SDK Build-tools.one by one delete,fix which one work for you.
I had this problem as well. It turned out that I had inadvertently deleted the "app_name" string resource from the strings.xml file, which was causing a silent error. Once I added it back, the R class was generated successfully and everything was back up and running.
You may need to update SDK tools. Relaunch Android SDK Manager again and install a new item: Android SDK Build-tools.
Try to make your new XML layout file name lower case. For example, use my_file.xml instead of myFile.xml.
Yet another reason R.java might not get autogenerated is if you have directories like res/drawable-hdpi, res/drawable-mdpi, or res/drawable-ldpi.
1.6+ seems to be OK with these directories, but 1.5 doesn't want them. When I removed those directories, R.java started autogenerating for me again.
Often times this is because of the MinSDK version number you supplied when creating the project. Example:
If you want 2.1 to be the minimum, Android 2.1 is actually API Level 7.
You can see what I am talking about when you browse the SDK you downloaded and installed. Navigate to the place you installed the SDK to (C:\android-sdk-windows for example) and open the folder named "platforms". You will see something like "android-7" listed as a folder, and if you open that there is a source.properties file that, when opened with a text editor, will show you the corresponding platform version.
When you create a project, and you must select a "Build Target" API, the last column in that list named "API Level" shows the number you are looking for when populating the MinSDK setting.
This is probably one of the most common mistakes that results in the R.java file not being created under Project > gen > packagename > R.java.
Remove main.out.xml. I'm new to this and don't yet know what this file is used for, but removing it cleared the problem.
Just go to Android Top menu list. click on Build Menu, in under Build click on Rebuild Project.
First check is there any error in any xml layout or not, if then resolve it first.
Otherwise remove junit dependency from project and rebuild the project.
In case anyone is interested (I might be saving your life here), I had the error, R.xml cannot be resolved, slightly different on a GLS project. Hmmmm. After looking in R.java, I found an auto-generated class, XML.java, (I think) was not there.
Solution? It needed a new folder in res: res\xml and a file called default_values.xml
in there. Then all was OK.
Just in case you have not got that file, it's:
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
xmlns:android="http://schemas.android.com/apk/res/android">
</PreferenceScreen>
So I have run into this problem multiple times when switching build targets. Usually doing a Project >> Clean worked for me. This last time, however, it did not. Finally I tried to open my default.properties file, located under the root project folder. I received an error message stating that it was out of sync with the file system. I actually deleted it and copied a coworkers version which allowed eclipse to rebuild my R file. I will paste what it looks like below. It is named 'default.properties'.
# This file is automatically generated by Android Tools.
# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
#
# This file must be checked in Version Control Systems.
#
# To customize properties used by the Ant build system use,
# "build.properties", and override values to adapt the script to your
# project structure.
# Indicates whether an apk should be generated for each density.
split.density=false
# Project target.
target=android-3
I had the examples of Android 8 and was trying to use Android 7 SDK. When I closed the project and reopened the application folder and chose to use Android 8 SDK, it was able to find the R file. Hope this helps.
After renaming my project package name (with Refactor), I got this error:
Error:(7, 44) error: cannot find symbol class R
All of my R usages are invalid. I tried to fix it manually but it doesn't work for me. Invalidate chases/Restart doesn't help me, either.
Try the following :
Try deleting your R.java file , android studio will regenerate it.
Clean Project
Rebuild Project
And check:
Check the AndroidManifest.xml, there's a package attribute on the top-level element
(Well it depends on how you renamed your package name)
Just do the following:
Ensure that the package name at the header of the AndroidManifest file has been renamed to your new package name. This worked for me.
Try to change application Id in build.gradle.
Or remove any imports of com.***.R in your activity and let android studio to automatically import for you.
Seems like, you changed the application package name but didn't change the import statements. So look for import statement of class R. It must be like
import <package_name>.R;
If it's not a problem with import statements then look whether the R.java file has generated or not. It generally doesn't get generated if there is a problem with the application layout(xml) files. The R class file is generated only when all your xml layout files are correct.
Clean the project and check.
3 packages you may see as marked, When you edit the package name make sure you change all 3 of them else you may face R error which will prompt you to press alt+enter to name it as ur old package name
When all these answers do not work:
In Android Studio : Menu File -> Invalidate Caches and restart Android Studio
Check your AndroidManifest.xml ( com.package1.package2 )
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.package1.package2">
90% of symbol R errors because of that line.
When you refactor your old package, mostly cases this package didn't change
In my case, this error showed because I changed the package name without ticking the boxes (Search in comments and strings and Search for text occurrences)
The solution for me:
Rename package again and make sure you tick the two boxes as in the photo, then Do Refactor
if you rename your android manifest package you have to rename the "packages com.newname" sentence at the beginning of your class.
You have to first close android studio. Then
Delete "build" folder
open the commandline and type gradlew clean
Then type gradlew assembledebug
If the build succeeds, feel free to go back to android studio
At first the MainActivity.java didn't have an error.
I have configed id for button, text fields. And they are added in com.mikeyaworski.basiccalculations
but i don't know what I have done that the project has two R.java in gen package.
one is in package android.support.v7.appcompat.
other is in com.mikeyaworski.basiccalculations (my config is here).
MainActivity.java has an error because cannot find R.layout.activity_main (because this variable is in com.mikeyaworski.basiccalculations package but i think the project use R.java from package android.support.v7.appcompat)
what should I do for this problem?
Try to clean built your project and check proper R file(i.e com.mikeyaworski.basiccalculations.R) is imported, done the trick for me.Hope solve your issue :)
Read this Managing Projects - Library Projects:
I'm getting the dreaded package R does not exist, it's killing me.
The code is fine I have apps in the market running the code.
Now it's effecting simple webview applications. o.0
R.string.app_name is error'd my main.xml and string.xml is fine. I'm sooo confused.
I re opened an older version to "borrow" some code and it was flooded with R. errors. I did a clean and nothing changed except for import R.android being added at the top.
I even loaded into Netbeans and I get the same thing. Clean is not working. Can I write the R.java file myself?
What is this R thing? isn't R. supposed to correspond to R.java
For anyone who ran into this,
I refactored by renaming the namespace folders. I just forgot to also edit AndroidManifest and that's why I got this error.
Make sure you check this as well.
Just to make this simple:
import your.app.package.R;
Of course, replacing your.app.package with your app package.
In all the classes which use R resource references, remove any other import with .R, i.e. import android.R;
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 R package (see package
attribute in AndroidManifest.xml)
-> import R class, 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 R ids are from the system resources
-> do not import android.R, but prefix the offending ids with android., e.g. android.R.layout.simple_list_item_2
You may import android.R instead of prefixing the ids of course, but then you cannot import the application R class 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();
}
}
Never, ever try to write the R class yourself!
Have you imported the right R class in your files?
Doing
import android.R;
instead of
import com.example.R;
seems to be the problem for a lot of people. After cleaning and building, my classes sometimes import the wrong one.
if you are developing in android studio and refactored the package name then you should change the package name in android manifest and app gradle file.
applicationId "change here your package name"
and in manifest file
package="change here your package name"
R.java is an autogenerated file, it usually does not get compiled if you have errors in xml file.
No You cannot write your own R.java file, it has to be generated by the resource compiler.
Check for errors in all your xml files.
I suppose it used to work but now it doesn't..
This can happen if you change PACKAGE name inside your MANIFEST file
<manifest
package="com.example.android...."
If you want to change package name
Change the package name manually in the manifest file.
Click on your R.java class and the press F6. It will allow you to move the class to other package, and all references to that class will be updated.
The R class is Java code auto-generated from your XML files (UI layout, internationalization strings, etc.) If the code used to be working before (as it seems it is), you need to tell your IDE to regenerate these files somehow:
in IntelliJ, select Tools > Android > Generate sources for <project>
(If you know the way in another IDE, feel free to edit this answer!)
I just ran into this error while using Bazel to build an Android app:
error: package R does not exist
+ mContext.getString(R.string.common_string),
^
Target //libraries/common:common_paidRelease failed to build
Use --verbose_failures to see the command lines of failed build steps.
Ensure that your android_library/android_binary is using an AndroidManifest.xml with the correct package= attribute, and if you're using the custom_package attribute on android_library or android_binary, ensure that it is spelled out correctly.
This might happen when using R in sub packages
Example:
com.example; // -app package and main Resources mapped to app package
com.example.order; // -sub package
in the sub package if you need to access a resource like,
R.Layout.orderLayout - Here R will not be available.
To solve this you would import the R from main package. ie.
For files in the com.example.order folder/package you would import
package com.example.order
import com.example.R;
Delete import android.R; from all the files.. once clean the the project and build the project.... It will generate
Sample: My package is com.example.mypc.f01, to fix error you add line below to Activity:
import com.example.mypc.f01.R;
Below are some technics which you can use to remove this error:-
Clean your project, Buidl->clean Project
Rebuild project, Build -> Rebuild Project
Open manifest and check is there any resource missing
Check-in layout to particular id if missing add it
If the above steps did not work then restart android studio with invalidating the cache
This is how i solved it
After several failed attempts of Build -> Clean Project followed by Build -> Rebuild Project
Step 0 : Made sure Package name is correct in AndroidManifest.xml
in my case it was
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myproject">
Step 1
Place the cursor before myproject and press Shift + F6 -> Rename Package -> Give your new package name and under Scope select All Places -> Refactor
Step 2 : Turn Off Auto Import
For Windows its File -> Settings -> Editor -> General -> Auto Import
Under Java
uncheck Add unambiguous imports on the fly
uncheck Optimize imports on the fly
Apply and save
Step 3: Clean and Rebuild
Build -> Clean Project followed by Build -> Rebuild Project
Now when you get the error during Build. Open the File that says R.java is missing or Cannot Find "R" class
Step 4:
Open the file and Go to its imports section in the code and add manually import com.example.myproject.R;
Repeat the same for all the files mentioned in the Build Section that has this error
Clean and Rebuild and you are good to go !
In my case I realized that I was creating multiple packages in the project. Within the Android Manifest I found that the provider name was incorrectly holding the value of MyContentProvider instead of .provider.MyContentProvider. My main package (with the UI) was co.companyname.database.provider instead of co.companyname.database.
Then on the import statements for the affected class I simply right-clicked and asked Android Studio (0.8.6) to optimize my import statements. I also noted that if you search for .R in the AS search bar at the top right corner of the IDE you can find an auto generated R.java file that is part of your package. At this point you don't have to change anything. Studio should fix up the project after you correct the Android Manifest file and rebuild.
One other item is that in one class I was doing making use of the toString().length() to evaluate a string but swapped those out for TextUtils.IsEmpty (stringVal); Can't think of anything else that I did to resolve the issue.
Hope this helps someone.
NB - All of this is with AS 0.8.6
P.S.
R.java is auto-generated so read the header:
/* AUTO-GENERATED FILE. DO NOT MODIFY.
*
* This class was automatically generated by the
* aapt tool from the resource data it found. It
* should not be modified by hand.
*/
When I experienced this, I created a new project, and copied the files from my old project to my new one.
Start a new project
Add the old files into the new project (copy and right click on Layout, drawables,com.packagename,...) to paste my old projects files
However, I still had the same problem: R does not exist. Then I realised that I had copied and pasted Manifest from my notepad into Android Studio manifests and I hadn't changed the package name in the manifest file.
Therefore, once I changed the package name in the manifest to the new project name, the new project I'd created worked fine.
Below are worked for me.
In AndroidManifest.xml file, check whether the package name is correctly typed.
import com.example.appName.R; (import package _name.R;)
If the first step is not worked try the second one.
After upgrading to AGP 7.2:
For the poor fellas that have upgraded to AGP 7.2 (stable version!!):
the AGP Upgrade Assistant will remove the package name from the Manifest
It is no longer needed, as it'll be just on the gradle file
But SafeArgs dependency still doesn't get that correctly though.. (link)
Hopefully you'll waste fewer hours that I did.. :)
What files are you importing into the files getting the R error?
My understanding of the R file are that they are automatically generated reference lists to all attributes within the Android app. Therefore, you can't change it yourself.
Are you using Eclipse to build this project?
Were the older projects getting these errors made before updating Eclipse?
What are the references that are getting errors?
Check to make sure that you've not imported another R file from other copied code in another app.
I run into this problem every time I switch computers and try to import old projects from files transferred via a USB.
My workaround is to just create a new project and copy (drag) the files into the IDE (currently using Netbeans) and rebuild. This is an annoyance and a bit of a hacky solution, but it fixes the problem.
If this happens to you, worst case is you might have to backup your files, delete the project, and just drag the files in there and recompile. Hopefully it won't come to that but that would be your nuclear option.
You may try
Android Studio top menu > File > Invalidate caches / restart...
Click on invalidate cache / restart button to restart your project
Resolve R.xxxx.xxx again if some of the fragment class R class didn't resolve properly
then rebuild your project
Hope it helps
Just got rid of the error in my project. I had imported a sample project, I had changed the package folders but I had not updated the package in one of the java files.
Most likely cause of this error 'package R does not exist' is that the package name in Java or manifest file is incorrect. Make sure it is correct and in sync and then do a clean build.
This error is 100% due to error in xml file. You can check that particular error in Logcat->error. and then solve that. If the xml error is solved the application would run. It's mostly arises when you copy a code from other source .In my case there was a error in Button in a xml file. I haven't typed Button correctly .If you solve that error your and your application would run smoothly. If yet it shows this error than don' worry and move forward.
finally found the solution.
Go to File>Invalidate Caches
Now "Check" Clear file system cache and
Local History & Clear VCS Log caches and index
Now Click on "INVALIDATE AND RESTART"
If you encounter this error in Android Studio:
Check the Gradle module file(s) -> defaultConfig -> applicationId setting.
Check the AndroidManifest.xml -> manifest package tag.
Check the package declarations in all src java files.
Sync, Clean then Rebuild with Gradle.
NEVER build your own R file. R is auto-generated from your source java files and build settings.
I had: "error: package R does not exist" and assumed javac
didn't have access to R.java.
So I appended %PROJ_LOC%\gen to sourcepath, and it worked!
SOURCEPATH=%PROJ_LOC%\src;%PROJ_LOC%\gen
I'm not using Android Studio or Ant (or XML).
If this error appeared after resolving merge conflicts, simple Build -> Clean project could help.
Sometimes, it gets solved when you just re-import the project into Android Studio.
Wrong path: Project "cashes" the pointers to the images and if you have made name changes to the path for example Refactored package or folders. Then just simply write the R letter again and the editor suggests the right path and it will work. In this case your filenames are right and the content that is referred in the R. pointer is present but the path is wrong, thus clean and build won't work.
Another case of R. breakage is Annotations Processing.
Some processing could refer to classes located in certain folders or folder levels. If you move required classes to other location, you can get R. as an unknown class.
Unfortunately the error-pointer to this problem is not evident in Android Studio.