While developing apps we tend to think about dexs, jars, apks and classes as build/run time abstractions that just work. Most of the time this is true, however, when trying to debug runtime issues in large apps, things can sometimes get tricky.

With ClassyShark analyzing dependencies is a breeze. ClassyShark is fast and shows the right info (dependency classes, packages, methods and AndroidManifest) in no time. If your app is crashing or misbehaving at runtime and you’re not sure why then ClassyShark may be able to help you.

Grab the latest release from [here] (https://github.com/googlesamples/android-classyshark/releases).

Let's examine the following simplified scenario. What if we have a main method that calls a FancyLibrary (simulated dependency). FancyLibrary is a simple Reader/Writer implementation, where a field is written once and accessed many times. Our app is using FancyLibrary, as a 3-rd party dependency. Here is our app's main code:

final FancyLibrary fancyLibrary = new FancyLibrary();

for (int i = 0; i < 50; i++) {
   new Thread(new Runnable() {
       @Override
       public void run() {
           fancyLibrary.changeNumber();
       }
   }, "T" + i).start();
}

The full example is here.

When running this code we have a race condition, in FancyLibrary more than one thread changes the value:

• thread T0 ==> wrote value
• thread T1 ==> wrote value
• thread T2 ==> read value
• thread T3 ==> read value
• thread T4 ==> read value
• thread T5 ==> read value
• thread T6 ==> read value

Let's say FancyLibrary is a popular open source project, so to find the problem we need to research the code and make sure we have an understanding, which code made its way to the jar in our Android project.

Let's use ClassyShark, first let's fire up ClassyShark

Double Click, opening the FancyLib.jar

We see, all the classes exactly as our app sees them. Let's head into FancyLibrary.class, as this is the class from our code that does the trouble (either in command line or double click)

Now we see the problem, this class is not thread safe because of the variable declaration. One way to solve this is to wrap the access to the FancyLibrary inside synchronized block.

final FancyLibrary fancyLibrary = new FancyLibrary();

   for (int i = 0; i < 50; i++) {
       new Thread(new Runnable() {
           @Override
           public void run() {
          
               wrapLibrary(fancyLibrary);
           }
       }, "T" + i).start();
   }

private static synchronized void wrapLibrary(FancyLibrary fLib) {
   fLib.changeNumber();
}

Bottom line the FancyLib is not thread safe, however it was not documented anywhere.

Clone this repository and import the ClassySharkWS folder in your favorite IDE.

• Multi tabbed interface
• Apk/Dex/Jar/Class formats
• Android manifest
• Incremental/Camel/Fuzzy searches

• dexlib2 by jesusfreke
• guava by Google
• ASM by OW2

If you've found an error, please file an issue:

https://github.com/googlesamples/android-classyshark/issues

Patches are encouraged, and may be submitted by forking this project and submitting a pull request through GitHub.

Copyright 2015 Google, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.