Find all classes in a package in Android

Question

How can i find all classes inside a package on Android? I use PathClassLoader, but it always returns an empty enumeration?

Additional info

Tried the suggested Reflections approach. Couple of important points about reflections library. The library available through maven central is not compatible with Android and gives dex errors. I had to include source and compile dom4j, java-assist.

The problem with reflections, and my original solution is that PathClassLoader in android returns an empty enumeration for package.

The issue with approach is that getResource in Android is always returning empty enumeration.

final String resourceName = aClass.getName().replace(".", "/") + ".class";

for (ClassLoader classLoader : loaders) {
      try {
            final URL url = classLoader.getResource(resourceName);
            if (url != null) {
                final String normalizedUrl = url.toExternalForm().substring(0, url.toExternalForm().lastIndexOf(aClass.getPackage().getName().replace(".", "/")));
                return new URL(normalizedUrl);
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
   }

Is it acceptable to aapt the apk first, and then parse the dex file? If this is acceptable in your case, I could write an answer. — StarPinkER, Mar 16 '13 at 06:52
Nah, I am trying to expose some methods to plugins dynamically and I wont know what classes are present before hand. — user210504, Mar 16 '13 at 14:08
I want to load classes from a package and make them available based on policy configuration as received from the server. But I want to do it in a generic way such that I dont have to know the classes which are part of the app. — user210504, Mar 17 '13 at 01:11

score 25 · Answer 1 · answered Apr 09 '13 at 01:56

25

Using DexFile to list all classes in your apk:

    try {
        DexFile df = new DexFile(context.getPackageCodePath());
        for (Enumeration<String> iter = df.entries(); iter.hasMoreElements();) {
            String s = iter.nextElement();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

the rest is using regexp or something else to filter out your desired class.

answered Apr 09 '13 at 01:56

tao

299
2
8

I used [this](http://mindtherobot.com/blog/737/android-hacks-scan-android-classpath/) as a starting point. – c0nstruct0r May 15 '14 at 09:40
5

It's not working properly since Android Gradle Plugin 2.0.0 – anavarroma Apr 13 '16 at 07:22
I've the same issue as @anavarroma this no longer seems to work, the code runs but doesn't bring back any of the classes – Peter Fox Jun 28 '16 at 09:16
1

@PeterFox, check out this answer to my post http://stackoverflow.com/a/36594966/1387138, it might be of help. – anavarroma Jun 28 '16 at 12:52
Can someone explain what are the results that include a `$` symbol? – Nathan H Sep 20 '16 at 11:10
1

Dollar sign means inner classes. See [This question](https://stackoverflow.com/questions/11388840/java-compiled-classes-contain-dollar-signs) – Tzlil Gavra Oct 08 '18 at 09:42

score 16 · Answer 2 · edited May 23 '17 at 12:02

16

Actually i found solution. Thanks for tao reply.

private String[] getClassesOfPackage(String packageName) {
    ArrayList<String> classes = new ArrayList<String>();
    try {
        String packageCodePath = getPackageCodePath();
        DexFile df = new DexFile(packageCodePath);
        for (Enumeration<String> iter = df.entries(); iter.hasMoreElements(); ) {
            String className = iter.nextElement();
            if (className.contains(packageName)) {
                classes.add(className.substring(className.lastIndexOf(".") + 1, className.length()));
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    return classes.toArray(new String[classes.size()]);
}

Tested on Android 5.0 Lolipop

edited May 23 '17 at 12:02

Community

1
1

answered Mar 17 '15 at 10:59

Sergey Shustikov

15,377
12
67
119

You should return the complete name of the class like `packagename.ClassName` because the person using this would want to use it in such ways `Class.forName(className)`. – lovesh Jul 19 '15 at 17:44
1

@lovesh it depends from your goal. Actually you can change code for your needs. – Sergey Shustikov Jul 19 '15 at 19:49
1

Holy cow. I wish I could find more ways to award points to this answer. I searched for **days** for this and only found it because someone linked to it from https://github.com/ronmamo/reflections/issues/115. And it's so easy! I'm thinking of going back to all the other SO posts and linking to here. By the way, for those who care, this method can return all of the classes for _all_ packages in the application if you set `packageName` to "com.myapp", assuming all packages start with that. It's also easy to modify to return fully qualified names and skip inner classes (for `Class.forName()`). – Mark Cramer Mar 15 '16 at 05:45
3

DexFile was deprecated: This API will be removed in a future Android release. https://developer.android.com/reference/dalvik/system/DexFile.html – hector6872 Aug 18 '17 at 09:57
Is there a modern solution that works for Gradle 2+? – Joshua Pinter Jul 04 '19 at 04:22

score 3 · Answer 3 · answered Jun 27 '15 at 11:08

Here's a solution that bring you not only the class name,
but also the Class<?> object.

And while PathClassLoader.class.getDeclaredField("mDexs") fails frequently,
new DexFile(getContext().getPackageCodePath()) seems much more stable.

public abstract class ClassScanner {

    private static final String TAG = "ClassScanner"; 
    private Context mContext;

    public ClassScanner(Context context) {
        mContext = context;
    }

    public Context getContext() {
        return mContext;
    }

    void scan() throws IOException, ClassNotFoundException, NoSuchMethodException {
        long timeBegin = System.currentTimeMillis();

        PathClassLoader classLoader = (PathClassLoader) getContext().getClassLoader();
        //PathClassLoader classLoader = (PathClassLoader) Thread.currentThread().getContextClassLoader();//This also works good
        DexFile dexFile = new DexFile(getContext().getPackageCodePath());
        Enumeration<String> classNames = dexFile.entries();
        while (classNames.hasMoreElements()) {
            String className = classNames.nextElement();
            if (isTargetClassName(className)) {
                //Class<?> aClass = Class.forName(className);//java.lang.ExceptionInInitializerError
                //Class<?> aClass = Class.forName(className, false, classLoader);//tested on 魅蓝Note(M463C)_Android4.4.4 and Mi2s_Android5.1.1
                Class<?> aClass = classLoader.loadClass(className);//tested on 魅蓝Note(M463C)_Android4.4.4 and Mi2s_Android5.1.1
                if (isTargetClass(aClass)) {
                    onScanResult(aClass);
                }
            }
        }

        long timeEnd = System.currentTimeMillis();
        long timeElapsed = timeEnd - timeBegin;
        Log.d(TAG, "scan() cost " + timeElapsed + "ms");
    }

    protected abstract boolean isTargetClassName(String className);

    protected abstract boolean isTargetClass(Class clazz);

    protected abstract void onScanResult(Class clazz);
}

and this is a example how to use:

new ClassScanner(context) {

    @Override
    protected boolean isTargetClassName(String className) {
        return className.startsWith(getContext().getPackageName())//I want classes under my package
                && !className.contains("$");//I don't need none-static inner classes
    }

    @Override
    protected boolean isTargetClass(Class clazz) {
        return AbsFactory.class.isAssignableFrom(clazz)//I want subclasses of AbsFactory
                && !Modifier.isAbstract(clazz.getModifiers());//I don't want abstract classes
    }

    @Override
    protected void onScanResult(Class clazz) {
        Constructor constructor = null;
        try {
            constructor = clazz.getDeclaredConstructor();
            constructor.setAccessible(true);
            constructor.newInstance();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

}.scan();

score 2 · Answer 4 · answered Aug 29 '18 at 19:49

These approaches are generally outdated and don't work with multi dex apps. To support multidex you can get all of the DexFiles like this

internal fun getDexFiles(context: Context): Sequence<DexFile> {
    // Here we do some reflection to access the dex files from the class loader. These implementation details vary by platform version,
    // so we have to be a little careful, but not a huge deal since this is just for testing. It should work on 21+.
    // The source for reference is at:
    // https://android.googlesource.com/platform/libcore/+/oreo-release/dalvik/src/main/java/dalvik/system/BaseDexClassLoader.java
    val classLoader = context.classLoader as BaseDexClassLoader

    val pathListField = field("dalvik.system.BaseDexClassLoader", "pathList")
    val pathList = pathListField.get(classLoader) // Type is DexPathList

    val dexElementsField = field("dalvik.system.DexPathList", "dexElements")
    @Suppress("UNCHECKED_CAST")
    val dexElements = dexElementsField.get(pathList) as Array<Any> // Type is Array<DexPathList.Element>

    val dexFileField = field("dalvik.system.DexPathList\$Element", "dexFile")
    return dexElements.map {
        dexFileField.get(it) as DexFile
    }.asSequence()
}

private fun field(className: String, fieldName: String): Field {
    val clazz = Class.forName(className)
    val field = clazz.getDeclaredField(fieldName)
    field.isAccessible = true
    return field
}

From there you can use it like this to get all classes in a package

getDexFiles(context)
            .flatMap { it.entries().asSequence() }
            .filter { it.startsWith("my.package.name") }
            .map { context.classLoader.loadClass(it) }

score 1 · Answer 5 · answered Sep 19 '14 at 07:58

This is taken from http://mindtherobot.com/

Code example

Say we have an annotation called Foo and few classes decorated with it:

@Retention(RetentionPolicy.RUNTIME)
public @interface Foo {
  String value();
}

@Foo("person")
public class Person {

}

@Foo("order")
public class Order {

}

Here’s a simple class that goes over all classes in your app in runtime, finds those marked with @Foo and get the value of the annotation. Do not copy and paste this code into your app – it has a lot to be fixed and added, as described below the code.

public class ClasspathScanner {
  private static final String TAG = ClasspathScanner.class.getSimpleName();

  private static Field dexField;

  static {
    try {
      dexField = PathClassLoader.class.getDeclaredField("mDexs");
      dexField.setAccessible(true);
    } catch (Exception e) {
      // TODO (1): handle this case gracefully - nobody promised that this field will always be there
      Log.e(TAG, "Failed to get mDexs field");
    } 
  }

  public void run() {
    try {
      // TODO (2): check here - in theory, the class loader is not required to be a PathClassLoader
      PathClassLoader classLoader = (PathClassLoader) Thread.currentThread().getContextClassLoader();

      DexFile[] dexs = (DexFile[]) dexField.get(classLoader);
      for (DexFile dex : dexs) {
        Enumeration<String> entries = dex.entries();
        while (entries.hasMoreElements()) {
          // (3) Each entry is a class name, like "foo.bar.MyClass"
          String entry = entries.nextElement();
          Log.d(TAG, "Entry: " + entry);

          // (4) Load the class
          Class<?> entryClass = dex.loadClass(entry, classLoader);
          if (entryClass != null) {
            Foo annotation = entryClass.getAnnotation(Foo.class);
            if (annotation != null) {
              Log.d(TAG, entry + ": " + annotation.value());
            }
          }
        }
      }
    } catch (Exception e) {
      // TODO (5): more precise error handling
      Log.e(TAG, "Error", e);
    }
  }
}

Stefano Liboni · Answer 6 · 2016-06-10T20:56:10.447

I found the same solution of Sergey Shustikov, with the package name derived form the context and handles inner classes. Unfortunally while it's working on Galaxy Nexus, it's not working on Nexus 6 and Nexus 6p (not tested on other devices).

Here's the code:

private HashMap<String, String> loadClassFullnames() {
    final HashMap<String, String> ret = new HashMap<>();
    try {
        final String thisPackage = context.getPackageName();
        final DexFile tmp = new DexFile(context.getPackageCodePath());
        for (Enumeration<String> iter = tmp.entries(); iter.hasMoreElements(); ) {
            final String classFullname = iter.nextElement();
            if (classFullname.startsWith(thisPackage)) {
                // TODO filter out also anonymous classes (es Class1$51)
                final int index = classFullname.lastIndexOf(".");
                final String c = (index >= 0) ? classFullname.substring(index + 1) : classFullname;
                ret.put(c.replace('$', '.'), classFullname);
            }
        }
    } catch (Throwable ex) {
        Debug.w("Unable to collect class fullnames. Reason: " + ex.getCause() + "\n\rStack Trace:\n\r" + ((ex.getCause() != null)? ex.getCause().getStackTrace(): "none"));
    }

    return ret;
}

It seams that on Galaxy Nexus, the DexFile contains also the application packages (the one we are trying to find!), while on Nexus 6[p] no package from matching thisPackage are found while some other packages are there... Does anybody have the same problem?

score -1 · Answer 7 · edited Mar 16 '13 at 19:36

-1

try this..

   Reflections reflections = new Reflections("my.project.prefix");

   Set<Class<? extends Object>> allClasses 
                        = reflections.getSubTypesOf(Object.class);

edited Mar 16 '13 at 19:36

stinepike

54,068
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answered Mar 16 '13 at 07:57

Mahi

1,754
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14

This does not work in Android, relections library crashes with unsupported dex class error – user210504 Mar 16 '13 at 22:43
The issue with approach is – user210504 Mar 17 '13 at 01:11
@user210504 Yes ! Not work in android – linjiejun Mar 17 '22 at 06:36

Find all classes in a package in Android

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