今天我们尝试使用 facebook redex 库来优化我们的安装包。

不过个人感觉 redex 太过于复杂了，内部还耦合着很多 Facebook 特有的逻辑。

个人更加建议掌握原理之后，自己实现一套轻量简单的。

安装 redex

在 github checkout redex的源码，

根据 readme 完成编译：

git clone https://github.com/facebook/redex.git
cd redex

autoreconf -ivf && ./configure && make -j4
sudo make install

编译 RedexSample

RedexSample 通过引入一大堆开源库，尝试把 dex 数量变多一些。直接编译即可

assembleDebug

通过 redex 命令优化

1. 为了可以更加清楚流程，可以输出 redex 的日志

   export TRACE=2
   

2. 去除 debuginfo 的方法 ``` redex --sign -s ReDexSample/keystore/debug.keystore -a androiddebugkey -p android -c redex-test/stripdebuginfo.config -P ReDexSample/proguard-rules.pro -o redex-test/strip_output.apk ReDexSample/build/outputs/apk/debug/ReDexSample-debug.apk

可以看到这样的日志

Running StripDebugInfoPass... matched on 105417 methods. Removed 0 dbg line entries, 103172 dbg local var entries, 0 dbg prologue start entries, 0 epilogue end entries and 14107 empty dbg tables. StripDebugInfoPass (run) completed in 0.1 seconds

再次安装查看是否堆栈行号还存在

2019-02-08 23:52:20.763 13117-13117/com.sample.redex E/test: java.lang.Throwable at com.sample.redex.MainActivity.onCreate(MainActivity.java:20) at android.app.Activity.performCreate(Activity.java:7436) at android.app.Activity.performCreate(Activity.java:7426) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1286) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3279) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3484) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:86) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2123) at android.os.Handler.dispatchMessage(Handler.java:109) at android.os.Looper.loop(Looper.java:207) at android.app.ActivityThread.main(ActivityThread.java:7470) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:958)

3. Dex 重分包的方法

redex --sign -s ReDexSample/keystore/debug.keystore -a androiddebugkey -p android -c redex-test/interdex.config -P ReDexSample/proguard-rules.pro -o redex-test/interdex_output.apk ReDexSample/build/outputs/apk/debug/ReDexSample-debug.apk

需要注意的是，redex 不会处理第一个 dex，因为第一个 dex 是需要 maindex pattern 来指定的。会有以下的日志：

Running InterDexPass... [primary dex]: 0 out of 228 classes in primary dex from interdex list. [primary dex]: 0 out of 228 classes in primary dex skipped from interdex list. Writing out primary dex with 228 classes. No interdex classes passed. [dex ordering] Cross-dex-ref-minimizer active with method ref weight 100, field ref weight 90, type ref weight 100, string ref weight 90. Writing out secondary dex number 1, which is not part of of coldstart, not part of of extended set, doesn't have scroll classes and has 6511 classes. Writing out secondary dex number 2, which is not part of of coldstart, not part of of extended set, doesn't have scroll classes and has 7566 classes. Writing out secondary dex number 3, which is not part of of coldstart, not part of of extended set, doesn't have scroll classes and has 19 classes.

```

然后查看原包与生成的 interdex_output.apk 的分包差异，个人认为 redex 的分包计算方法写的也是有那么一点问题，但是我们可以参考这个思路。