追逐,探索,永不停歇~
前言
還記得剛入坑 Flutter 打包時,被深深震驚了一番,臥槽,這包好大!
- ✓ Built build/app/outputs/apk/release/app-release.apk (23.8MB).
足足將近 24 MB,第一反應真的懵逼了。
當然直接提交市場後,也是被人各種 diss,原因還是沒什麼功能,包賊大,使用者下載賊不舒服。
強烈要求優化 Apk 大小。
既然是探索,前提我還是個剛入 Flutter 坑的小白白,所以嘛,難免不全面,歡迎各位大佬拍磚、指點~
探索之路 一部曲
首先,我首次打包的方式如下:
雷同使用下面的命令(預設帶有 --release):
- flutter build apk
一、熊貓壓縮法(減少 0.7 MB)
首先第一想法,圖片我沒做壓縮,同樣經過檢視後,發現圖片在 apk 佔比為 4.1% :
- 2.3 % Flutter 引用到的資原始檔;
- 1.8% Android 啟動頁的背景圖。
最後,我們通過國寶之手試試最後能減少多少?
這裡分別針對 Flutter 下圖片資源、Android/iOS 啟動頁進行壓縮。
再次執行 build apk 後,完成輸出如下日誌:
- ✓ Built build/app/outputs/apk/release/app-release.apk (23.1MB).
再來看 Apk 中圖片的佔比以及降低到 1%:
最終 Apk 大小直接減少了 0.7 MB,還是比較爽的。
二、so 優化大法(減少 14 MB)
做 Android 的小夥伴知道,對於我們這些小廠沒能力搞動態下發 so 的小渣渣而言,只能默默逆向大廠 Apk,看看人家是怎麼做的,然後借(抄)鑑(襲)。
針對 Flutter 打出的 Apk 包,排在第一位的便是 lib,佔比 86.4%,足足有 19.6 MB:
這裡看到將我們編寫的 Dart 程式碼轉化為不同架構下的 so 庫,以供原生呼叫(我是這麼猜測的哈)。
針對不同 CPU 架構所代表含義,尤其 Flutter 打包 Apk 生成的三種 CPU 架構分別對應什麼含義:
- x86_64: Intel 64 位,一般用於平板或者模擬器,支援 x86 以及 x86_64 CPU 架構裝置。
- arm64-v8a: 第 8 代 64 位,包含 AArch32、AArch64 兩個執行狀態,且對應 32 、64 bit,並且支援 armeabi、armeabi-v7a 以及 arm64-v8a。
- armeabi-v7a: 第 7 代 arm v7,使用硬體浮點運算,具有高階擴充功能,相容 armeabi 以及 armeabi-v7a,而且目前大部分手機都是這個架構。
其實我們第一次通過 flutter build apk 命令生成 apk 時,Google 這裡已經為我們提示了:
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter build apk
You are building a fat APK that includes binaries for android-arm, android-arm64, android-x64.
If you are deploying the app to the Play Store, it's recommended to use app bundles or split the APK to reduce the APK size.
To generate an app bundle, run:
flutter build appbundle --target-platform android-arm,android-arm64,android-x64
Learn more on: https://developer.android.com/guide/app-bundle
To split the APKs per ABI, run:
flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Learn more on: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 13.8s
✓ Built build/app/outputs/apk/release/app-release.apk (23.1MB).
複製程式碼
接下來通過以下命令進行分別打包(構建指定 CPU 架構型別 Apk 包):
- flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi
這裡解釋下這個命令的含義:
- 首先 flutter build apk 表示當前構建 release 包;
- 後面 android-arm,android-arm64,android-x64 則是指定生成對應架構的 release 包;
- 最後的 --split-per-abi 則表示告知需要按照我們指定的型別分別打包,如果移除則直接構建包含所有 CPU 架構的 Apk 包。
所以這個命令的含義就是告訴編譯器,我需要你為我針對我指定的三種不同架構分別生成對應的 Apk 包。
有的小夥伴就說了,你這空口無憑,沒證據啊。
好,我給你執行一波~
- 驗證:flutter build apk --target-platform android-arm,android-arm64,android-x64 結果
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter build apk --target-platform android-arm,android-arm64,android-x64
You are building a fat APK that includes binaries for android-arm, android-arm64, android-x64.
If you are deploying the app to the Play Store, it's recommended to use app bundles or split the APK to reduce the APK size.
To generate an app bundle, run:
flutter build appbundle --target-platform android-arm,android-arm64,android-x64
Learn more on: https://developer.android.com/guide/app-bundle
To split the APKs per ABI, run:
flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Learn more on: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split
Removed unused resources: Binary resource data reduced from 817KB to 815KB: Removed 0%
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 115.8s
✓ Built build/app/outputs/apk/release/app-release.apk (23.1MB).
複製程式碼
看見沒,事實論證結果。
最後,我們採取告知編譯器為我們生成指定 CPU 架構的 Apk 的方式,並檢視對應輸出日誌資訊:
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 36.0s
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.8MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (10.1MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (10.2MB).
複製程式碼
看看 app-armeabi-v7a-release.apk 包大小,結果是不是賊喜人?由 23.8 MB 直接減少到 9.8 MB。
隨後我們看下對應的 apk 內容:
lib 佔比也從原來的 86.4%,19.6 MB 直接減少為 67.2%,大小 6.3 MB。
三、混淆大法好(減少 0.4 MB)
還記得 Android 混淆的魅力嗎?
- 增加逆向難度;
- 減少 Apk 大小;
- 。。。
對此 Flutter 也為我們提供了混淆命令:
- flutter build apk --obfuscate --split-debug-info=//
簡單說下我個人對於此命令的理解:
- --obfuscate:開啟混淆操作;
- --split-debug-info=:將因混淆生成的 map 符號表快取到此位置。
這裡我們先測試下,直接構建完整包,並新增混淆操作,輸出的 apk 大小有多少:
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter build apk --obfuscate --split-debug-info=HLQ_Struggle
You are building a fat APK that includes binaries for android-arm, android-arm64, android-x64.
If you are deploying the app to the Play Store, it's recommended to use app bundles or split the APK to reduce the APK size.
To generate an app bundle, run:
flutter build appbundle --target-platform android-arm,android-arm64,android-x64
Learn more on: https://developer.android.com/guide/app-bundle
To split the APKs per ABI, run:
flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Learn more on: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 60.3s
✓ Built build/app/outputs/apk/release/app-release.apk (21.9MB).
複製程式碼
同樣也在專案根目錄下生成了符號檔案:
相比一開始的 23.8 MB,減少了 1.9 MB。那麼我們直接針對不同 CPU 生成對應的 Apk 並新增混淆結果又是怎樣呢?
➜ xxx_app git:(master) ✗ flutter build apk --obfuscate --split-debug-info=debugInfo --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 39.3s
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.4MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (9.7MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (9.8MB).
複製程式碼
未混淆的 v7a 大小與開啟混淆相比,開啟混淆減少了 0.4 MB。
還不錯。
對於混淆的檔案,出問題怎麼除錯呢?
莫慌,Flutter 同樣提供了 symbolize 神器,當然這個不在涉獵範圍內,就不詳細解釋了,知道就好:
heliquan@Mac ~/CodePro/FlutterPro/haozhuan_app master ● flutter symbolize -h
Symbolize a stack trace from an AOT compiled flutter application.
Usage: flutter symbolize [arguments]
-h, --help Print this usage information.
-d, --debug-info=</out/android/app.arm64.symbols> A path to the symbols file generated with "--split-debug-info".
-i, --input=</crashes/stack_trace.err> A file path containing a Dart stack trace.
-o, --output=<A file path for a symbolicated stack trace to be written to.>
Run "flutter help" to see global options.
複製程式碼
End
上面叨叨半天,總結一個比較有用的命令:
- flutter build apk --obfuscate --split-debug-info=HLQ_Struggle --target-platform android-arm,android-arm64,android-x64 --split-per-abi
含義就是,哥,幫我針對不同 CPU 架構分別打包,別忘記混淆哈,生成的符號表檔案記得幫我放在 HLQ_Struggle 目錄下。
詳細日誌如下:
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter build apk --obfuscate --split-debug-info=HLQ_Struggle --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 36.9s
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.4MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (9.7MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (9.8MB).
複製程式碼
當然也有小夥伴說了,打包前 clean 下,生成的包會小,實際測試一下:
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter clean
Cleaning Xcode workspace... 3.3s
Deleting build... 2,774ms (!)
Deleting .dart_tool... 41ms
Deleting Generated.xcconfig... 0ms
Deleting flutter_export_environment.sh... 0ms
Deleting App.framework... 9ms
heliquan@Mac ~/CodePro/FlutterPro/xxx_app master ● flutter build apk --obfuscate --split-debug-info=HLQ_Struggle --target-platform android-arm,android-arm64,android-x64 --split-per-abi
Running Gradle task 'assembleRelease'... Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Removed unused resources: Binary resource data reduced from 816KB to 814KB: Removed 0%
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 215.3s (!)
✓ Built build/app/outputs/apk/release/app-armeabi-v7a-release.apk (9.4MB).
✓ Built build/app/outputs/apk/release/app-arm64-v8a-release.apk (9.7MB).
✓ Built build/app/outputs/apk/release/app-x86_64-release.apk (9.8MB).
複製程式碼
根據以上輸出結果,並沒發現減少了哪兒。
一點小經歷分享,當然肯定會有更好的操作方法,但是目前僅次於此,歡迎各位大佬交流~