The 65K Dex Limit

Only 65.536 method can be invoked in the dex file of android apk. How can we work with it? See presentation at https://www.youtube.com/watch?v=5vEa9dihZEs

Transcript

2. 65K Dex Limit
3. The Good life in Android Land…
4. Unable to execute dex: method ID not in [0, 0xffff]: 65536 Conversion to Dalvik format failed: Unable to execute dex: method ID not in [0, 0xffff]: 65536 … becomes hell
6. FIGHT BACK
7. • What is this 65K DEX Limit • How to “solve” it • What we have been doing at QuizUp I will talk about..
9. • Android Manifests • Assets folder • Resources folder • Some other files • classes.dex Inside APK
10. The 65K Dex limit • Your app is too big, sorry mate! :( • Simple explanation: You have too many methods in the dex file • More specific explanation: You have too many methods (over 65.536 methods), that can being invoked, in the dex file
11. How to fight this animal Two things you can do:
 A. Cut down the code
 B. Creating multiple Dex files
12. A. Cut down the code 1. Analyze where the code is coming from
 - https://github.com/mihaip/dex-method- counts package com.stupid.dexlimit;
 
 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 
 public class MainActivity extends Activity
 {
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 helloPeople();
 }
 
 private void helloPeople()
 {
 Log.d(MainActivity.class.getSimpleName(),
 "How many methods are in this Application??");
 }
 }
13. A. Cut down the code package com.stupid.dexlimit;
 
 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 
 public class MainActivity extends Activity
 {
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 helloPeople();
 }
 
 private void helloPeople()
 {
 Log.d(MainActivity.class.getSimpleName(),
 "How many methods are in this Application??");
 }
 } Read in 60307 method IDs. <root>: 60307 : 6 android: 4842 [...] aurelienribon: 99 tweenengine: 99 equations: 22 paths: 5 bolts: 82 butterknife: 36 internal: 7 com: 46491 badlogic: 12414 gdx: 12414 [...] facebook: 3261 [...] [...]
14. A. Cut down the code 1. Analyze where the code is coming from
 - https://github.com/mihaip/dex-method- counts
 - https://github.com/siggijons/dex- methods 
 package com.stupid.dexlimit;
 
 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 
 public class MainActivity extends Activity
 {
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 helloPeople();
 }
 
 private void helloPeople()
 {
 Log.d(MainActivity.class.getSimpleName(),
 "How many methods are in this Application??");
 }
 }
15. A. Cut down the code 1. Analyze where the code is coming from
 - https://github.com/mihaip/dex-method- counts
 - https://github.com/siggijons/dex- methods 2. Use smaller libraries - Repack libraries with JarJar package com.stupid.dexlimit;
 
 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 
 public class MainActivity extends Activity
 {
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 helloPeople();
 }
 
 private void helloPeople()
 {
 Log.d(MainActivity.class.getSimpleName(),
 "How many methods are in this Application??");
 }
 }
16. package com.stupid.dexlimit;
 
 
 public class MainActivity extends Activity
 {
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 helloPeople();
 }
 
 private void helloPeople()
 {
 Log.d(MainActivity.class.getSimpleName(),
 "How many methods are in this Application??");
 }
 } How many methods are in this example? • 1 Activity w/ 2 methods • Compile the play service library • Question: How many methods are in the APK file? • Answer: ~20.000 methods (1/3 of 65K) • Solution: only compile what you need (e.g. com.google.android.gms:play- services-maps:7.8.0)
17. A. Cut down the code 1. Analyze where the code is coming from
 - https://github.com/mihaip/dex-method- counts
 - https://github.com/siggijons/dex- methods 2. Use smaller libraries - Repack libraries with JarJar 3. Proguard / Dexguard to shrink your code
 pros: Dexguard can shrink quite much
 cons: Increases your build time package com.stupid.dexlimit;
 
 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 
 public class MainActivity extends Activity
 {
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 helloPeople();
 }
 
 private void helloPeople()
 {
 Log.d(MainActivity.class.getSimpleName(),
 "How many methods are in this Application??");
 }
 }
18. How to fight this animal Two things you can do:
 A. Cut down the code
 B. Creating multiple Dex files
19. B. Creating multiple dex files • Normally you can only have 1 dex file • Get around this limit by using 3rd party libraries
 - pros: we can build the project
 - cons: longer building time • Mult-Dexing library from Google 
 - com.android.support:support-v4:21.0.0
 - Easy to use • Dexguard offers split dexing
 - splitdexfile com.facebook.**
 - More complex to use with the obfuscation • Today we use Dexguard
20. Multiple Dex files in QuizUp
21. Multiple Dex files in QuizUp
22. Multiple Dex files in QuizUp
23. Dalvik vs. ART • Difference regarding the dex limit? YES • ART (Android 5.0+) contains native support for multidexing • No native support in Dalvik
24. What we have learned • Dexguard -> Extra complexity level for split dexing • Choose what goes to the secondary dex file! • Build can break on run time when certain code is in secondary dex file • Avoid always being on the edge of the limit • Compile time increases, when split dexing :( • The tools for split dexing is becoming much better • Smile :)
25. QUESTIONS?