javax.* cannot be imported in my Android app?

Question

I'm trying to import some javax.* classes in my android app, but I keep getting compiler errors inside Android Studio. I'm using Ubuntu Linux 13.04.

Here are my imports:

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
// Here are the imports I am having trouble with:
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.SourceDataLine;

And when I try to run the app or even compile the activity java file, I get these errors:

Gradle: error: package javax.sound.sampled does not exist
Gradle: error: package javax.sound.sampled does not exist
Gradle: error: package javax.sound.sampled does not exist

I just can't figure out this problem. Any help would be awesome!

Answer 1

Be aware that when you run an Android app: you don't run/compile it on a standard JVM/JDK, you don't even execute java bytecode. Google choose the java language (or at least a subset of it) as the language to do Android development, but it's only the language.

At the end the compiled java code is not java bytecode, but this is dalvik bytecode. (there is no .class files, but .dex files)

So, when doing Android development: you cannot use the full JavaSE API: you are limited to the API supported by the dalvik VM (available here).

(Note that when you browse this API beware of the version in the top right corner of the page : Added in API level X. It informs you about the Android-API version supporting that class or method)

Answer 2

Those classes are not included in the Android library. You have to use the Android specific sounds APIs. See: http://developer.android.com/reference/android/media/package-summary.html

Answer 3

I had the same problem. I've resolved it by downloading sources of OpenJDK (for example, from here: http://hg.openjdk.java.net/jdk7/jdk7/jdk/file/9b8c96f96a0f/src/share/classes/javax/sound ) and exporting the required package into *.jar file to include that file into android app. It worked just fine for me.

Answer 4

If you download OpenJDK from the Red Hat Developer Program (free membership), you can find the .java source files for the entire OpenJDK including javax.sound.sampled. I was able to debug my Android app using OpenJDK8.

Please note, not all OpenJDK8 features are available in Android yet so only include the classes you need. For more information, see https://developer.android.com/studio/write/java8-support.html

Answer 5

I have been working on a javax.sound problem in Android for two days. I took the easy way out because using javax.sound would mean creating a jar file of the libs I needed and if there was C code in JNI under them, I would have to port that to arm. Or I could take an arm Linux dist and bring what I needed for mp3 to wav conversion from there into the JNI. You can use regular jar files in Android. I use an off-the-shelf FTP library from a third party for FTP Juju. My mp3s were not very big. So I just converted them into wavs in res/raw. But the above solutions are available to you.