一、Windows环境下Flutter引擎源码下载

1、下载depot_tools及配置环境变量

git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

下载完成后配置环境变量

path中添加

注意环境变量要放到python环境变量之前

C:\depot_tools\depot_tools

新增一个系统变量

名为“DEPOT_TOOLS_WIN_TOOLCHAIN“，值为”0“。该变量的作用是告诉depot_tools使用本地安装的 Visual Studio版本（depot_tools默认是使用google内部版本）。

在cmd中运行gclient命令，此时无任何提示，会下载部分资源，可以观察depot_tools文件夹

D:\MyData\ningzhen>gclient`
WARNING: Your metrics.cfg file was invalid or nonexistent. A new one will be created.
Usage: gclient.py <command> [options]

Meta checkout dependency manager for Git.

Commands are:
  config   creates a .gclient file in the current directory
  diff     displays local diff for every dependencies
  fetch    fetches upstream commits for all modules
  flatten  flattens the solutions into a single DEPS file
  getdep   gets revision information and variable values from a DEPS file
  grep     greps through git repos managed by gclient
  help     prints list of commands or help for a specific command
  metrics  reports, and optionally modifies, the status of metric collection`
  pack     generates a patch which can be applied at the root of the tree`
  recurse  operates [command args ...] on all the dependencies`
  revert   reverts all modifications in every dependencies`
  revinfo  outputs revision info mapping for the client and its dependencies`
  root     outputs the solution root (or current dir if there isn't one)`
  runhooks runs hooks for files that have been modified in the local working copy`
  setdep   modifies dependency revisions and variable values in a DEPS file`
  status   shows modification status for every dependencies`
  sync     checkout/update all modules`
  validate validates the .gclient and DEPS syntax`
  verify   verifies the DEPS file deps are only from allowed_hosts`

Options:
  --version             show program's version number and exit`
  -h, --help            show this help message and exit`
  -j JOBS, --jobs=JOBS  Specify how many SCM commands can run in parallel;`
                        `defaults to 8 on this machine`
  -v, --verbose         Produces additional output for diagnostics. Can be`
                        `used up to three times for more logging info.`
  --gclientfile=CONFIG_FILENAME`
                        `Specify an alternate .gclient file`
  --spec=SPEC           create a gclient file containing the provided string.`
                        `Due to Cygwin/Python brokenness, it can't contain any`
                        `newlines.`
  --no-nag-max          Ignored for backwards compatibility.

2、下载Flutter Engine源码

第一次下载可以使用fetch flutter命令，

后面更新使用gclient sync命令

会在目录下创建.gclient文件

solutions = [
  {
    "custom_deps": {},
    "deps_file": "DEPS",
    "managed": False,
    "name": "src/flutter",
    "safesync_url": "",
    "url": "https://github.com/flutter/engine.git",
  },
]

开始下载

C:\Flutter_Engine>gclient sync
1>________ running 'git -c core.deltaBaseCacheLimit=2g clone --no-checkout --progress https://github.com/flutter/engine.git C:\Flutter_Engine\src\_gclient_flutter_8wjc56ou' in 'C:\Flutter_Engine'`
1>Cloning into 'C:\Flutter_Engine\src\_gclient_flutter_8wjc56ou'...`
1>remote: Enumerating objects: 252166, done.`
1>remote: Counting objects: 100% (113/113), done.`
1>remote: Compressing objects: 100% (71/71), done.`
1>Receiving objects:  12% (31628/252166), 51.84 MiB | 383.00 KiB/s

二、MAC/Linux 下载编译FlutterEngine

1、下载depot_tools及配置环境变量

git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
配置环境变量
export PATH="$PATH:/path/to/depot_tools"

2、设置代理

• 在~/.bash_profile 文件中，添加如下代码：

function proxy_off(){
        unset http_proxy
        unset https_proxy
        unset ftp_proxy
        unset rsync_proxy
        echo -e "已关闭代理"
}
#注意，根据自己的配置设置有可能会是1080或1086
function proxy_on() {
        export no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com"
        export http_proxy="http://127.0.0.1:1087"
        export https_proxy=$http_proxy
        export ftp_proxy=$http_proxy
        export rsync_proxy=$http_proxy
        export HTTP_PROXY=$http_proxy
        export HTTPS_PROXY=$http_proxy
        export FTP_PROXY=$http_proxy
        export RSYNC_PROXY=$http_proxy
        echo -e "已开启代理"
}

• 执行source ~/.bash_profile，使其立刻生效。

• 需要使用代理时开启ss全局模式，然后打开终端，输入proxy_on就会启动。如果需要关闭，只需要输入proxy_off。

• 判断终端是否走了代理服务器

  curl cip.cc
  

• 该设置仅对当前终端窗口生效，关闭窗口，下次需要在设置一次proxy_on

3、第一次执行gclient下载对应的资源

gclient 

执行此命令，没有任何提示，可以关注depot_tools文件夹大小

4、fetch flutter开始下载

mkdir FlutterEngine
fetch flutter //会创建.gclient文件后会开始同步

5、下载完成后，开始编译

我们使用到的构建参数主要有以下几种
--android 指定android平台
--ios 指定ios平台
--runtime-mode debug,profile,release,jit_release 前三个大家应该都熟，第四个jit_release猜测应该是支持hot_reload的release ([Flutter's modes](https://github.com/flutter/flutter/wiki/Flutter%27s-modes)官网里没看到说明呀 )
--unoptimized 默认是optimized优化过的
--android-cpu {arm,x64,x86,arm64} 默认是arm(对应arm-v7)
--ios --ios-cpu {arm,arm64}

构建Android产物

Android的arm的debug优化版
cd src/
./flutter/tools/gn --android 
ninja -C out/android_debug -j 8
./flutter/tools/gn 
ninja -C out/host_debug -j 8

Android arm64的release优化版
cd src/
./flutter/tools/gn --android --android-cpu arm64 --runtime-mode=release
ninja -C out/android_release_arm64 -j 8
./flutter/tools/gn --android-cpu arm64 --runtime-mode=release
ninja -C out/host_release_arm64 -j 8

Android x64的profile非优化版
cd src/
./flutter/tools/gn --android --android-cpu x64 --unoptimized --runtime-mode=profile
ninja -C out/android_profile_unopt_x64 -j 8
./flutter/tools/gn --android-cpu x64 --unoptimized --runtime-mode=profile
ninja -C out/host_profile_unopt_x64 -j 8

Android使用本地引擎

终端命令行参数传入
gradlew clean assembleDebug -PlocalEngineOut=engine/src/out/android_debug_unopt

或者

在gradle.properties文件中加入如下内容
localEngineOut=engine/src/out/android_debug_unopt

或者直接使用flutter的build方式

flutter build apk --local-engine=android_debug_unopt --local-engine-src-path=/engine/src

6、Flutter Engine 离线包下载

链接：https://pan.baidu.com/s/1ytKrnxW9QqKF9oxIjFj5DA
提取码：4wsm