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In every instance in all of my classes where I reference R.id.something, the R is in red and it says "cannot resolve symbol R". Also every time there is R.layout.something it is underlined in red and says "cannot resolve method setContentView(?)". The project always builds fine. It is annoying to see this all the time. I have read many other questions on here about something similar but most involved importing projects from Eclipse. I am using what I believe to be the most recent version of Android Studio and the project was created with Android Studio and worked without any "cannot resolve R" problems. I would like to know what causes this if anyone knows.
I had this this issue too. A simple 'gradlew clean' and 'gradlew build' did the trick.
Click on Build->Clean Project and that will perform a gradle clean
In the latest versions of Android Studio, at least for me, the following works:
"Tools" -> "Android" -> "Sync Project with Gradle Files"
In latest Android Studio 3.1.3 (July 2018), "Sync Project with Gradle Files" is available in main menu bar.
I was using gradle 3.3.0. It was the main culprit. Wasted 6.50 hours from my life. Gradle 3.2.1 removed the error.
classpath 'com.android.tools.build:gradle:3.2.1'
Problem resolved after changing the gradle version. Details history can be found here.
I have a similar problem and here is what I did:
Clean Project and Sync Project with Gradle ,
check buildTools version in my sdk
From build gradle (module ) change minSdkVersion from 8 to 9
defaultConfig {
applicationId "PackageName"
minSdkVersion 9
targetSdkVersion 22
versionCode 1
versionName "1.0"
}
But all this didn't help.
Finally I found the answer (this worked in my case)
Change from build.gradle(module:app)
android {
compileSdkVersion 21
buildToolsVersion '21.0.1'
......
....
}
Or
Select File | Project Structure change Build Tools Version to 21.1.1
Check your xml files.
Clean Project.
This is it.
For example I had an entry in my strings.xml:
<string name="A">Some text</string>
And in activity_main.xml I used this string entry
<TextView
android:id="#+id/textViewA"
android:text="#string/A"/>
While'd been working with project, I deleted that
<string name="A">Some text</string>
And consequently activity_main.xml became not valid. As the result: cannot resolve R.
So, check your *.xml files and clean project.
If you see this error after moving java files or directories to other locations, then you can guarantee that Android Studio has gotten confused. And guess what? undo-ing those actions doesn't fix the problem.
So you try a clean, but that doesn't work.
And restarting doesn't work either.
But try File -> Invalidate Caches / Restart... -> Invalidate and Restart
Android Studio maintains information about which files are dependent on which other files. And since moving files around is not implemented correctly, moving files causes errors. And that's not all: caches of these dependencies are used in an attempt to speed up the build.
This means you not only have to restart, but you need to invalidate those caches to restore (or more accurately, rebuild) sanity.
I think if you put your Activities files to another folder than the default one. You need to import the com.example.yourproject.R (this is your project R file NOT Android.R file) to ALL activities using R. For example, in MainActivity file insert this line:
import com.example.yourproject.R;
There seems to be many causes for this issue. Recently, I added an activity to test with called NewActivity. This created a file called res/menu/new.xml and gradle did not like that name because new is a reserved word.
gradlew clean
or
"Tools" -> "Android" -> "Sync Project with Gradle Files"
Those are definitely good things to try, but you may have some other issues you need to resolve before you run those commands.
You should do two things, first clean the project (in build menu) - it deletes the build directory which may be the culprit:
Next, Sync project with Gradle files (under file):
This is the placement for the items in Android Studio 3.6.1 on Windows 10.
If all else fails, Invalidate Caches and Restart (under file) usually does the trick. This closes down the whole program and takes the most amount of time, in my opinion.
To clarify, I am running this on windows 10, but it should work on MacOS and Linux as well.
R.java file contains the link between xml and java page. "R cannot be resolved" arise only if there is a problem with some of your resource files. So the best and effective way is delete the last done xml or drawable in res file. and then again start from there according to android coding norms. This is the only way. The effective and right way.
Also use Git for proper tracking of code. ..
Your code is just scrambled. The answer is fairly simple.
Just go to Build --> Clean Project.
That should do the trick.
Check also your version of Android Studio.
I'm currently using Android Studio 3.0.1.
Have you updated your SDK tools recently? Launch the android SDK manager and make sure you have the latest SDK tools, which is now separate from the platform tools. I had this same issue when I first updated my SDK manager, the SDK build tools package did not show up for install/update until I closed and reopened the SDK manager.
I had to import my R package in android studio. For ex: import com.example.<package name>.R
Just clean your project and Sync Project with Gradle File.
And the problem will be resolved.
I recently had this issue and the clean/build etc. didn't resolve it. I guessed I had an issue somewhere but wasn't sure where to look to find it (was it in the manifest, resource xml files etc?).
When something is wrong, you can find out what it is by doing a code analysis run.
From the menu at the top choose:
Analyze -> Inspect code, scan the whole project using the 'Default' profile.
Your inspection results will contain an element called 'Android'. In here you will get a list of anything that is causing issues in your resources and manifest file. The errors will open up the generated xml files from your build which will show any errors in red.
My exact issue was caused because I was using flavour based manifest files and I copied some permissions inside the <application> tag in the flavour by accident.
UPDATE: I did have an issue after where Android Studio still showed the error after the fix, even though I could now build and run perfectly fine while the error was still there. (I am running a canary build so putting it down to that for now)
I have had this with
An uppercase letter in my drawable resources.
Import Android.R being added by Android Studio (or Eclipse)
Error in xml file
I faced this issue when I manually renamed the domain folder of my app. To fix this issue, I had to
Set the proper package folder structure of <manifest> in AndroidManifest.xml.
Set the new package location for android:name of <activity> in AndroidManifest.xml.
Clear cache by
File Menu -> Invalidate Caches / Restart ...
The issue will be gone, once the Android studio restarts and builds the fresh index.
I had the same issue:
Android Studio 3.2
The project compiles and runs fine, but I am getting "Cannot resolve symbol "R" on-screen warnings
Does not help:
Build->Clean Project
Build->Rebuild Project
File->Invalidate Caches/Restart
Helps:
either
in build.gradle
dependencies {
classpath 'com.android.tools.build:gradle:3.3.0'
...
}
replace with
dependencies {
classpath 'com.android.tools.build:gradle:3.2.1'
...
}
or
Update Android Studio to 3.3
This is a very old question, but it still happens a lot and there is no truly comprehensive answer here.
I have had this problem more times than I want to admit. It can be caused by a wide variety of issues that mostly all have to do with your project structure not matching what's expected. Here's a list of all the problems I've had:
Importing from Eclipse to Android Studio does not always work smoothly, especially with older versions of Android Studio. Make sure you're using the correct directory tree. It should look like this for a moderately mature app:
AppName/ // AppName is your app's name, obviously
.gradle/ // This is a compiler created directory. You should normally leave it alone
.idea/ // Ditto
build/ // This too
gradle/ // And this
app/
build/
libs/
src/
androidTest/ // Tests based on the Android instrumentation runner should go here
main/
java/
fully/ // Typically com
qualified/ // the domain name. Longer package
// names may have deeper folder trees
AppName/ // All your java files go here
res/
drawable-*/ // One of these for each resolution you support
layout/ // All of your general layouts
menu/ // All of your menu layouts
values/ // All of your resource xml files
xml/ // PreferenceScreen layouts go here
AndroidManifest.xml
debug/
test/ // Pure jUnit tests should go here
.gitignore
app.iml
build.gradle // This is the gradle file you should be making most changes to
proguard-rules.pro
.gitignore
build.gradle // This gradle file should mostly be left alone
gradle.properties
gradlew
local.properties
AppName.iml
settings.gradle
It may not look like this in your IDE. There is a drop-down above the file tree that displays your files in different ways, and it defaults on my system to one called Android that breaks your files out into their different types. It's easier to fix this kind of problem from the one called Project, and even easier directly from your OS's file system, because Android Studio collapses folders that only contain another folder onto a single line.
Especially if you ever change the name of your app, you need to make sure that the source tree main/java/com/domain/AppName is updated. Also make sure that the package tag in your AndroidManifest.xml is correct.
If there are errors in either your Gradle files or your AndroidManifest.xml, this will prevent Android Studio from properly building your resource files. Gradle files can be broken by upgrading Android Studio sometimes, especially from the pre-1.0 versions. Sometimes this is because it stops supporting older versions of the Gradle plugin, so you need to update your version numbers. It can sometimes be hard to find what the current versions are. As of today, 7/17/15, my apps are compiling fine with com.android.tools.build:gradle:1.2.3. This is in the dependencies block in the outermost gradle file,
If your AndroidManifest references a non-existent drawable or string resource or activity, it will break and cause this error. Sometimes if anything references a nonexistent drawable or string resource you will get this error.
If you have a file in your resources that is corrupted, or an invalid xml file, you will get this error.
In my experience, sometimes Android Studio just hiccups for no reason, and you need to restart it and/or your PC. I don't know why, but sometimes it works.
If you have two xml resources with the same name, in directories that do not override each other, you can have this problem. For instance, you can have the same name in drawable-mhdpi and drawable-xhdpi because they override each other depending on the target device, but if you have the same name in layout and in menu, it will cause a problem. Rename or delete one of the files.
If only some resources are having this problem, those resources are most likely in the wrong directory.
In one case I had to completely reinstall Android Studio. I don't know what was wrong, but it worked.
In one case I moved my entire project to a different directory and re-imported it as a new project. I don't know what was wrong, but it worked.
Xml files with reserved words for names can cause this problem. Rename or delete them.
There are a few ways your Gradle file can end up referencing a version of the build-tools that you do not have installed. Correct this by changing Gradle or downloading the appropriate build-tools.
Finally, after you've fixed whatever is wrong, you need to clean your Gradle project. You do this by going to the Build menu at the top and selecting Clean Project.
Just go to Android Top menu list. click on Build Menu, in under Build click on Rebuild Project.
I have a special case for this problem.
In my project, every thing goes well, it can compile and build successfully, but in my Android Studio IDE(and I also tried Intelligent IDEA, they are in the same situation) the R.java file can not be resolved well and always be drop in red line.
Just like this:
This almost made me crazy, I can't bear the read color when I am programing.
At last I found this tricky problem is cause by my R.java's file size.
My project is very a huge one, it supports many multi-languages and multi screen sizes. There are so many resources that my R.java's file size is about 2.5M.
The max size of a file in Android Studio is 2.5M in default settings, so files bigger than this limit can't not be resolved well. And you can change the default settings in "AndroidStudio-root/bin/idea.properties".
change this line:
idea.max.intellisense.filesize=2500
to :
idea.max.intellisense.filesize=5000
Then restart Android studio, the red color dismissed, I can program happily again.
Build > Clean Project
This worked for me. Had the same problem a few times, and this seems to set it right. Unless you have changed something or called a variable R. This issue usually happens out of nowhere, when it happens to me, so I imagine its just Android studios freaking out. haha
Have a good one, and good luck with your projects.
Do: Build > Clean Project
IMPORTANT: Make sure you don't have any Errors after Clean Project in Message Pane (Alt+0). If you find any red circles with exclamation mark, than you must remove those errors in your code.
Mostly these errors are related to #string/ or #array/. Clean Project again and done!
I had the same problem and most times it is resolved by
Sync project with gradle files
Doing Build -> Clean Project
Doing File -> Invalidate Caches
But this time the error persisted even after doing all these things and at last i found the culprit.
The problem was in an xml file, where i have given ordinary string value for an android:id instead of an id resource type.
MISTAKE
android:id="username"
CORRECTION
android:id="#id/username"
Messing up things related to resources in xml files is a major
reason for this error.Beware of the fact that it may not be shown as an error in the xml layout file.
NOTE
In most cases the compiler shows you the source of error in the Message.
Try to check it first before attempting other solutions
I had the same problem, and it happens when I create a new project.
What I do is:
check for SDK updates
then android studio updates,
then reopen the project
open the andoridmanifest.xml
erase a space between a "_>" in the android:label and save.
That works for me.
I had a hard time fixing this myself.
Make sure you have no errors in your layout.xml files.
Go to Build > Clean project
It worked for me, hope it works for you too.
`I had same problem and it solved by :
1) Sync Project with gradle files
2) Build -> Clean Project
3) Build -> Rebuild Project
4) File -> Invalidate caches
//imp step
5) Check your xml files properly.`
This notation seems to work fine.
android:id="#+id/viewID"
Android Studio's design panel doesn't seem to work well.
Same problem. Started when I added a few images in my drawable folder and tried to access them. Also the images added were having the extension with capital letters. That seems to have crashed the build, since even if I renamed them, the message was the same and R was inaccessible. What I did is, in the .iml file I looked for the excludeFolder and removed them (like bellow):
<excludeFolder url="file://$MODULE_DIR$/build/apk" />
<excludeFolder url="file://$MODULE_DIR$/build/assets" />
<excludeFolder url="file://$MODULE_DIR$/build/bundles" />
<excludeFolder url="file://$MODULE_DIR$/build/classes" />
<excludeFolder url="file://$MODULE_DIR$/build/dependency-cache" />
<excludeFolder url="file://$MODULE_DIR$/build/incremental" />
<excludeFolder url="file://$MODULE_DIR$/build/libs" />
<excludeFolder url="file://$MODULE_DIR$/build/manifests" />
<excludeFolder url="file://$MODULE_DIR$/build/res" />
<excludeFolder url="file://$MODULE_DIR$/build/symbols" />
<excludeFolder url="file://$MODULE_DIR$/build/tmp" />
After that I rebuilt the project and R magically re-appeared.
There are many causes for this error.
Sometimes it occurs for replacing an image file keeping same name.
Suppose you deleted an item from your layout .xml say a <Button/> but it is still declared in any Activity or Fragment .java.
Many more.
Best way to track the error is Rebuild it rather clean or sync doing some intentional error.
If it doesn't solve your problem then there must have to be some flaw or runtime error or error occurred due to improper use of resources in may be both java or xml file in your code or design which is forcing gradle to stop because (R)esource file can't index your resources properly and you have to admit that.
If your project ran before you made the changes then comment out the changes you have made and try to rebuild the project.
It will surely work since there will be no changes.
To track down the exact error, check the changes by breaking the changes into smaller module.
For example - If you are making a list visible with a button click and inserting list values in the adapter, first check if you are able to make it visible or not then check for adapter errors.
Using "Import Project" in Android Studio for an Eclipse project used to change the project structure and generate Gradle files, but right now (I'm using AS 0.5.3) it's only generating IDEA files (.iml, .idea) but not Gradle and it's not touching the file structure either.
How do you import an Eclipse project into Android Studio now?
Update: Trying to export gradle files in Eclipse won't export them for the app, it doesn't show up as a module in Android Studio either.
In newer versions of Android Studio, the best way to bring in an Eclipse/ADT (Android Development Tool) project is to import it directly into Android Studio; we used to recommend you export it from Eclipse to Gradle first, but we haven't been updating ADT often enough to keep pace with Android Studio.
In any event, if you choose "Import Project" from the File menu or from the Welcome screen when you launch Android Studio, it should take you through a specialized wizard that will prompt you that it intends to copy the files into a new directory structure instead of importing them in-place, and it will offer to fix up some common things like converting dependencies into Maven-style includes and such.
It doesn't seem like you're getting this specialized flow. I think it may not be recognizing your imported project as an ADT project, and it's defaulting to the old built-into-IntelliJ behavior which doesn't know about Gradle. To get the specialized import working, the following must be true:
The root directory of the project you import must have an AndroidManifest.xml file.
Either:
The root directory must contain the .project and .classpath files from Eclipse
or
The root directory must contain res and src directories.
If your project is complex, perhaps you're not pointing it as the root directory it wants to see for the import to succeed.
Export from Eclipse
Update your Eclipse ADT Plugin to 22.0 or higher, then go to File | Export
Go to Android now then click on Generate Gradle build files, then it would generate gradle file for you.
Select your project you want to export
Click on finish now
Import into Android Studio
In Android Studio, close any projects currently open. You should see the Welcome to Android Studio window.
Click Import Project.
Locate the project you exported from Eclipse, expand it, select it and click OK.
Try these steps:
1- click on Import project (Eclipse, ADT, ...)
2- Choose main directory of your Eclipse project
3- Keep the defaults. The first two options is for changing jar files into remote libraries (dependencies). It mean while building Android studio try to find library in local system or remote repositories. The last option is for showing only one folder as app after importing.
4- Then, you will see the summary of changes
5- Then, if you see Gradle project sync failed, you should go to project view (top left corner). Then, you should go to your project-> app and open build.gradle.
6- Then, you should change your compilesdkVersion and targetsdkVersion to your current version that you see in buildToolsVersion (mine is 23). For example, in my project I should change 17 to 23 in two places
7- If you see an error in your dependencies, you should change the version of it. For example, in my project I need to check which version of android support library I am using. So, I open the SDK manager and go to bottom to see the version. Then, I should replace my Android studio version with my current version and click try again from top right corner
I hope it helps.
Its Got simpler with Android Studio
All you need is to first choose
import project(eclipse.....)
then choose your folder eclipse based project.like this one below
3.based on the type of project and library you used like (ActionBarSherlock) you may prompted special import wizard so go ahead and click next then finish.
in this case it was simple one
4.And you are done.
but sometimes the debug or Run options do not work and a error msg shows like
"this project structure is not gradle based or migrate it to gradle"
something
to solve this
close the opened eclipse project and reopen same project through the same process as we did before with import project (eclipse adt,gradle,etc)) this time android studio gonna add all necessary gradle files and green debug option will work too.
i have did this somehow accidentally but it worked, i just hope it works for you too.
Android Studio has been improved since this question was posted, and the latest versions of Android Studio (as of this writing, we are at 2.1.1) have fairly good Eclipse importing capabilities, so importing Eclipse projects directly into Android Studio is now the best approach for migrating projects from Eclipse into Android Studio.
I will describe how to do this below, including a few of the pitfalls that one might encounter. I will deal in particular with importing an Eclipse workspace that contains multiple apps sharing one or more project libraries (the approaches posted thus far seem limited to importing just one Eclipse app project and its project libraries). While I don't deal with every possible issue, I do go into a lot of detail regarding some of them, which I hope will be helpful to those going through this process for the first time themselves.
I recently imported the projects from an Eclipse workspace. This workspace included four library projects that were shared between up to nine projects each.
Some background:
An Eclipse workspace contains multiple projects, which may be library projects or apps.
An Android Studio project is analogous to an Eclipse workspace, in that it can contain both library projects and apps. However, a library project or an app is represented by a "module" in Android Studio, whereas it is represented by a "project" in Eclipse.
So, to summarize: Eclipse workspaces will end up as Android Studio projects, and Eclipse projects inside a workspace will end up as Android Studio modules inside a project.
You should start the import process by creating an Android Studio project (File / New / New Project). You might give this project the same (or similar) name as you gave your Eclipse workspace. This project will eventually hold all of your modules, one each for each Eclipse project (including project libraries) that you will import.
The import process does not change your original Eclipse files, so long as you place the imported files in a different folder hierarchy, so you should choose a folder for this project that is not in your original Eclipse hierarchy. For example, if your Eclipse projects are all in a folder called Android, you might create a sibling folder called AStudio.
Your Android Studio project can then be created as a sub-folder of this new folder. The New Project wizard will prompt you to enter this top-level project folder, into which it will create your project.
Android Studio's new project wizard will then ask you to configure a single module at the time you create the project. This can be a little confusing at first, because they never actually tell you that you are creating a module, but you are; you are creating a project with a single module in it. Apparently, every project is required to have at least one module, so, since you are relying on Eclipse to provide your modules, your initial module will be a placeholder to vacuously satisfy that formal requirement.
Thus, you probably will want to create an initial module for your project that does as little as possible. Therefore, select Phone and Tablet as the type of your module, accept the default minimum SDK (API level 8), and select Add No Activity for your module.
Next, select one of the Eclipse app projects in your workspace that requires the largest number of libraries as your first project to import. The advantage of doing this is that when you import that project, all the library projects that it uses (directly, or indirectly, if some of your library projects themselves require other library projects) will get imported along with it as part of the importing process.
Each of these imported projects will get its own module within your Android Studio project. All of these modules will be siblings of one another (both in your project hierarchy, and in the folder hierarchy where their files are placed), just as if you had imported the modules separately. However, the dependencies between the modules will be created for you (in your app's build.gradle files) as part of the importing process.
Note that after you finish importing, testing and debugging this "most dependent" Eclipse project and its supporting library projects, you will go on to import a second Eclipse app project (if you have a second one in your workspace) and its library project modules (with those imported earlier getting found by the import wizard as existing modules and re-used for this new module, rather than being duplicated).
So, you should never have to import even a single library project from Eclipse directly; they will all be brought in indirectly, based on their dependencies upon app projects that you import. This is assuming that all of your library projects in the workspace are created to serve the needs of one or more app projects in that same workspace.
To perform the import of this first app project, back in Android Studio, while you are in the project that you just created, select File / New / New Module. You might think that you should be using File / New / Import Module, but no, you should not, because if you do that, Android Studio will create a new project to hold your imported module, and it will import your module to that project. You actually could create your first module that way, but then the second through Nth modules would still require that you use this other method (for importing a module into an existing project), and so I think that just starting with an "empty" project (or rather, one with its own vacuous, do-nothing placeholder module), and then importing each of your Eclipse projects as a new module into that project (i.e., the approach we are taking here), may be less confusing.
So, you are going to take your practically-empty new project, and perform a File / New / New Module in it. The wizard that this invokes will give you a choice of what kind of module you want to create. You must select "Import Eclipse ADT Project." That is what accesses the wizard that knows how to convert an Eclipse project into an Android Studio module (along with the library modules on which it depends) within your current Android Studio project.
When prompted for a source folder, you should enter the folder for your Eclipse project (this is the folder that contains that project's AndroidManifest.xml file).
The import wizard will then display the module name that it intends to create (similar to your original Eclipse project's name, but with a lower-case first letter because that is a convention that distinguishes module names from project names (which start with an upper-case letter). It usually works pretty well to accept this default.
Below the module name is a section titled "Additional required modules." This will list every library required by the module you are importing (or by any of its libraries, etc.). Since this is the first module you are importing, none of these will already be in your project, so each of them will have its Import box checked by default. You should leave these checked because you need these modules. (Note that when you import later Eclipse app projects, if a library that they need has already been imported, those libraries will still appear here, but there will be a note that "Project already contains module with this name," and the Import box will be un-checked by default. In that case, you should leave the box unchecked, so that the importer will hook up your newly-imported module(s) to the libraries that have already been imported. It may be that accepting the default names that Android Studio creates for your modules will be important for allowing the IDE to find and re-use these library modules.
Next, the importer will offer to replace any jars and library sources with Gradle dependencies, and to create camelCase module names for any dependent modules, checking all those options by default. You should generally leave these options checked and continue. Read the warning, though, about possible problems. Remember that you can always delete an imported module or modules (via the Project Structure dialog) and start the import process over again.
The next display that I got (YMMV) claims that the Android Support Repository is not installed in my SDK installation. It provides a button to open the Android SDK Manager for purposes of installing it. However, that button did not work for me. I manually opened the SDK manager as a separate app, and found that the Android Support Repository was already installed. There was an update, however. I installed that, and tapped the Refresh button in the import dialog, but that did nothing. So, I proceeded, and the perceived lack of this Repository did not seem to hurt the importing process (although I did get messages regarding it being missing from time to time later on, while working with the imported code, which I was able to appease by clicking a supplied link that corrected the problem - at least temporarily). Eventually this problem went away when I installed an update to the repository, so you may not experience it at all.
At this point, you will click Finish, and after a bit it should create your modules and build them. If all goes well, you should get a BUILD SUCCESSFUL message in your Gradle Console.
One quirk is that if the build fails, you may not see your imported modules in the Project hierarchy. It seems that you need to get to the first valid build before the new modules will appear there (my experience, anyway). You may still be able to see the new modules in the File / Project Structure dialog (e.g., if you want to delete them and start your import over).
Remember that since you are not changing your original Eclipse projects, you can always delete the modules that you have just imported (if importing goes badly), and start all over again. You can even make changes to the Eclipse side after deleting your Android Studio modules, if that will make importing go better the second time (so long as you preserve your fallback ability to build your existing source under Eclipse). As you'll see when we discuss version control below, it may be necessary for you to retain your ability to build under Eclipse, because the project structure is changed under Android Studio, so if you need to go back to a commit that precedes your move to Android Studio (e.g., to make a bug fix), you will want to have the ability to build that earlier commit in Eclipse.
To delete a module, you must select File / Project Structure, then select the module from the left side of the dialog, and then hit the delete key. For some reason, I was not able to delete a module directly in the Project hierarchy; it had to be done using this Project Structure dialog.
The import wizard generates an import-summary.txt file containing a detailed list of any issues it may have encountered, along with actions taken to resolve them. You should read it carefully, as it may provide clues as to what is happening if you have trouble building or running the imported code. It will also help you to find things that the importer moves around to accommodate the different structure of Android Studio projects.
If all does not go well, then have at look at these possible problems that you may encounter, along with solutions for those problems:
Generally speaking, there are two main kinds of problems that I encountered:
Proguard problems
Manifest problems
When Proguard is messed up, the (obfuscated) names of methods in your libraries may not match the names being used to invoke them from your app, and you will get compiler errors like "error: cannot find symbol class ..."
In Eclipse, Proguard stuff is pretty much ignored for library projects, with the Proguard stuff for any app project that you are building determining the obfuscation, etc. for not just itself, but for processing all of the libraries on which it depends. And that is generally what you want.
In Android Studio, however, you need to make some changes to attain this same effect. Basically, in the build.gradle files for each of your library project modules, you will want something like this:
buildTypes {
release {
minifyEnabled false
consumerProguardFiles 'proguard.cfg'
}
}
Where proguard.cfg is your library module's own proguard configuration file.
The term "consumer" in "consumerProguardFiles" apparently refers to the app module that is using this library module. So the proguard commands from that app are used in preference to those of the library module itself, and apparently this results in obfuscations that are coordinated and compatible, so that all calls from the app module to its library modules are made with matching symbols.
These "consumerProguardFiles" entries are not created automatically during the import process (at least that was my own experience) so you will want to make sure to edit that into your library modules' build.gradle files if they are not created for you during importing.
If you wanted to distribute your library projects separately, with obfuscation, then you would need an individual proguard file for them; I have not done this myself, and so that is beyond the scope of this answer.
In the app module, you will want something like this:
buildTypes {
release {
minifyEnabled true
proguardFiles 'proguard.cfg'
}
}
(BTW, as of this writing, while my apps are running just fine, I have not yet directly confirmed that things are actually getting obfuscated using this approach, so do check this yourself - e.g., by using a decompiler like apktool. I will be checking this later on, and will edit this answer when I get that info).
The second kind of problem is due to the fact that Eclipse pretty much ignores the manifest files for library projects when compiling an app project that uses those library projects, while in Android Studio, there is an interleaving of the two that apparently does not consistently prioritize the app's manifest over those of its libraries.
I encountered this because I had a library manifest that listed (just for documentation purposes) an abstract Activity class as the main activity. There was a class derived from this abstract class in my app that was declared in the manifest of each app that used the library.
In Eclipse, this never caused any problems, because the library manifests were ignored. But in Android Studio, I ended up with that abstract class as my activity class for the app, which caused a run-time error when the code made an attempt to instantiate that abstract class.
You have two choices in this case:
Use tools syntax to override specific library manifest stuff in your app manifest - for example:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.goalstate.WordGames.FullBoard.trialsuite"
xmlns:tools="http://schemas.android.com/tools"
.
.
<application
tools:replace="android:name"
or,
Strip out practically everything from your library modules' manifests, and rely upon the app module's manifest to provide every value. Note that you do need to have a manifest for each library module, but not much more is required than the header and a bare manifest element with just a package attribute in it.
I tried both and ended up with approach 2., above, as the simpler method. However, if you wanted to distribute your library modules separately, you would need to create a more meaningful manifest file that reflects each library module's own individual requirements.
There is probably a more "correct" way to do this which puts requirements (e.g., permissions) for each library in the library manifest itself, and allows the automatic interleaving process to combine these with those declared for the app. However, given that Eclipse ignores the manifests for libraries, it seems safer at least initially to rely entirely on the app manifests and just strip the library manifests down to the bare bones.
Be aware that some of the project properties, and also the manifest attributes, from your Eclipse project will have been used to construct portions of your build.gradle files. Specifically, your compileSdkVersion in build.gradle is set to the project build version from the Eclipse project properties, applicationId is the package name from your app's manifest, and minSdkVersion and targetSdkVersion are also copied from the app's manifest file. The dependencies section of build.gradle comes from the library project dependencies in your project's properties.
Note that this may make some of your AndroidManifest.xml values redundant and quite possibly residual (i.e., unused). This could create confusion. My understanding is that the build.gradle values are the ones that actually have an effect, and that the manifest values like targetSdkVersion are not used any more for purposes of building. However, they may still be used by app stores such as Google Play; I don't know for certain one way or the other, so at this point I am just maintaining them in tandem.
Besides the above two kinds of issue, there are more routine things like importing a project that has a project build level of 22 when you have only installed SDK level 23 in Android Studio. In that situation, it is probably better to edit your app module's build.gradle file to move compileSdkVersion from 22 (the imported value) to 23, than it would be to install the SDK for level 22, but either approach should work.
Throughout this entire process, when something does not build properly and you make a change to try to address it, you might want to try Build / Rebuild Project and/or Tools / Android / Sync Project with Gradle Files, and/or File / Invalidate Caches/Restart, to make sure that your changes have been fully incorporated. I don't know exactly when these are truly necessary, because I don't know how much is done incrementally when you haven't yet had a successful build, but I performed them all fairly regularly as a kind of superstitious ritual, and I'm fairly certain that it helped. For example, when I got a Resources$NotFound runtime error that appeared to be from an inability to find the launch icon resource, I tried all three, and the problem was fixed.
When you have performed the above for your first Eclipse project and have attained a successful build, then with luck, you can select your app module from the dropdown at the top of the Android Studio display to the left of the play button, then click the play button itself, then select a device or Android Virtual Device, and the app should be loaded for running.
Likewise, you should be able to create a signed copy of your app using the Build / Generate Signed APK feature. Note that some import-related errors may appear when running your signed copy that do not appear when using the play button, so you need to confirm that both are working before deciding that your import is complete.
Following this, you will probably want to turn on version control. I am using git myself, but there are a number of other options available.
Version control is mostly beyond the scope of this answer, but there are a few things that are affected by the importing process. First, in Eclipse you might have your various projects in various folders stuck all over the place, but when you import into Android Studio, all modules will be created as direct child folders of your main project folder. So if you had a separate git folder for each project in Eclipse, or for related groups of projects organized under a parent folder for each group (as I did), that is not going to translate very well to Android Studio.
My knowledge of this is limited as I have not worked with version control yet in Android Studio, so maybe there is a way around this, but it appears that all version control in Android Studio is unified at the project level, and so all of your modules will be under a single git archive.
This means that you may need to abandon your old git archive and start fresh with a new archive for your imported source code. And that means that you will want to keep your old git archive around, so that it can be used with Eclipse to perform any needed bug fixes, etc., at least for a while. And you also will want it to preserve a history of your project.
If you are fortunate enough to have had all of your projects organized under a single Eclipse workspace, and if you were using a single git archive for those projects, then it is possible that you might just copy your old git archive from in and under your Eclipse workspace folder to in and under your Android Studio project folder. Then, you could edit any still-relevant .gitignore items from you Eclipse project into the auto-generated .gitignore file for your Android Studio project, and let git figure out what has been changed during the importing process (and some things will have been moved around - for example, the manifest file is no longer at the top level of your module). Others have reported that git is pretty good at figuring out what has changed; I have not tried this myself.
But even if you did this, going back to a commit that precedes your move from Eclipse to Android Studio would be going back to a set of files that would only make sense from inside Eclipse. So it sounds, well, "difficult" to work with. Especially since Eclipse will still be pointing to its original set of project folders.
I personally had multiple git archives for my various sets of related projects, and so I decided to just make a clean break and start git over again in Android Studio. If you had to do this, it could affect your planning, because you would want to be at a very stable point in your code development before making the move in that case, since you will lose some accessibility to that older code within your version control system (e.g., ability to merge with post-import code) once you have made the move to Android Studio.
The part of this answer that pertains to git is partly speculative, since I have not actually worked with version control yet on my imported project files, but I wanted to include it to give some idea of the challenges, and I plan to update my answer after I have worked more with version control inside Android Studio.
According to http://tools.android.com/tech-docs/new-build-system/migrating-from-eclipse-projects,
You have a couple of choices
- simply importing
- pre-exporting first from Eclipse.
Pre-exporting from eclipse may be the better choice if your project contains a lot of relationships that are Eclipse-specific. A.S. cannot 'translate' everything Eclipse can produce. If you want to continue using Eclipse as well as A.S. on this project code, this is the better choice. If you choose this method, please read the above link, there are some important pre-requisites.
Simply importing into AS will let AS 'translate' and rearrange the project, and is the recommended method, especially if you have no intention of returning to Eclipse. In this case, you let the A.S. wizard do everything and you dont need to manually generate gradle files.
In addition to the answer by Scott Barta above, you may still have import problems if there are references to Eclipse workspace library files, with e.g.
/workspace/android-support-v7-appcompat
being a common one.
In this case the import will halt until you provide a reference (and if you've cloned from a git repo, it probably won't be there) and even pointing to your own install (e.g. something like /android-sdk-macosx/extras/android/m2repository/com/android/support/appcompat-v7) won't be recognised and will halt the import, leaving you in no-man's land.
To get around this, look for refs in the project.properties or .classpath files that came in from the Eclipse project and remove/comment them out, e.g.
<classpathentry combineaccessrules="false" kind="src" path="/android-support-v7-appcompat"/>
That will get you past the import stage and you can then add these refs in your build.gradle (Module:app) as indicated in the Android tutorial, like below:
dependencies {
compile 'com.android.support:appcompat-v7:22.2.0'
}
Here is a simpler way to migrate:
Start off with a sample Android Studio project.
Open android studio and create a new project (or) just download a ‘sample’ studio project here: https://github.com/AppLozic/eclipse-to-android-studio-migration.
Now, open the downloaded project in Android Studio by following the below instructions.
Import eclipse project modules into Android Studio.
Select File -> New -> Import Module
Image title
Next, select the path of the eclipse project and import the modules. In case, if you see the message “Failed to sync Gradle project,” then click on “Install Build Tools and sync project…”
Now, remove the sample project modules by following the below simple steps:
Open settings.gradle and remove “include ‘:app’”
Right click on “app” module and “Delete” it.
Now, what we have is the Eclipse project open in Android studio with the Gradle build.
Here are few other links which might help you:
http://developer.android.com/sdk/installing/migrate.html
Source: http://www.applozic.com/blog/migrating-project-from-eclipse-to-studio/
Simple steps:
1.Go to Android Studio.
2.Close all open projects if any.
3.There will be an option which says import non Android Studio Projects(Eclipse ect).
4.Click on it and choose ur project
Thats't it enjoy!!!
Stop installing android studio 3.0.1 and go back 2.3.3 ( Stable version) . Check for the stable version and you can find them a lot
All you have to do uninstall and go back to the other version. Yes it asks to create gradle file seperately which is completely new to me!
Failure is the stepping stone for success..
The best way to bring in an Eclipse/ADT project is to import it directly into Android Studio. At first GO to Eclipse project & delete the project.properties file.
After that, open the Android studio Tool & import Eclipse project(Eclipse ADT, Gradle etc).