I am now coding Android apps without using Android Studio, and when I compile, I encountered the errors:

./src/com/example/projectname/GamePanel.java:8: error: cannot find symbol import androidx.annotation.NonNull;

where the "^" points at the period before "NonNull", and

error: package androidx.appcompat.app does not exist

And my compile command is:

javac -d obj -sourcepath src -classpath ../android/platforms/android-32/android.jar ./src/com/example/projectname/*.java

The internet tells me that I should set android.useAndroidX to true, but I am not using Android Studio. Is there any way to let javac know that I am using AndroidX?

CodePudding user response：

OK, so the problem is that the NonNull annotation is not defined in that JAR file. (Or at least, not in the android.jar that I found ... on Github.)

I managed to find a JAR containing androidx.annotation.NonNull in the Maven Central Repository: https://mvnrepository.com/artifact/androidx.annotation/annotation/1.3.0

But I suspect that you are going to find more of these issues as your project gets more complicated.

Is there any way to let javac know that I am using AndroidX?

No there isn't. The javac compiler understands nothing about Android let alone AndroidX. It only knows about what you added to the compile-time classpath. So if you are going to persist with compiling using javac directly, you are going to have to figure out how to find the JARs that you need for yourself¹.

My recommendation would be:

• Just use Android Studio. It really isn't that slow ... when you take into account all of the features it provides to make coding, testing, debugging, etc.

• You can also use the Gradle build tool² independently of Android Studio. It has a plugin designed especially for building Android apps; see https://developer.android.com/studio/build

^{1 - And down the track you will need to manually update the JARs that you manually downloaded, etc.
2 - There are alternatives such as Maven, Ant and so on, but AFAIK Gradle has the best integration for Android.}

CodePudding user response：

Is there any way to let javac know that I am using AndroidX?

Yes, you can download the JAR files for the libraries you are using and add them to the classpath.

However, this leads down a path of suffering and sadness because you will have to download many different JAR files that are implement different parts the androidx package, depending on what features you need.

I strongly suggest you to use Android Studio. It is an incredible tool that makes Android development easier than it otherwise would be.

If your goal here is to compile your app from the command line, then you need to learn about gradle. This is a tool that will download the dependencies for you then run javac with the correct classpath set. Basically it automates all the steps you would need to take to do this manually.