Flutter 实现 App 内更新安装包

背景

目前flutter发展火热，生态越来越繁荣，但相比于原生开发，仍非常稚嫩，使用起来坑很多，最近做需求——app内完成安装包的更新，完成该功能踩了很多的坑，现在记录一下实现过程。

实现过程

1. 获取当前app的版本、平台信息

 static String _version; static String _flatform;

import 'package:package_info/package_info.dart';
/// 获取当前版本
   PackageInfo packageInfo = await PackageInfo.fromPlatform();
   _version = packageInfo.version;

import 'package:device_info/device_info.dart';
  /// 获取平台信息
  Future<String> getFlatForm() async {
    if (Platform.isAndroid) {
      _flatform = 'android';
    } else {
      _flatform = 'ios';
    }
    return _flatform;
  }

2. 从服务器拉取app版本的最新信息

Map _data = await _fetchVersionInfo();

 /// 拉取版本号信息
  Future<Map> _fetchVersionInfo() async {
    HttpResult res = await Api.get('/version-api/versions/latest', query: {
      'from': _flatform,
      'version': _version,
    });
    return res.code == 200 ? res.data : null;
  }

3. 与本地version信息比对，选择是否展示更新弹窗，我们采用的是event_bus触发

 if (localVersion == remoteVersion) return;eventManager.eventBus.fire(new UpdateAppEvent(versionInfo));

4. 进行版本升级，要注意区分Android与IOS （1） IOS更新app包

IOS的处理方式比较简单，直接跳转到appStore即可，我这里采用的urlLauncher直接跳转

urlLauncher.launch(_link);

（2） Android更新app包

需要开启存储权限，如果没有权限就申请

import 'package:permission_handler/permission_handler.dart';

  /// 检查是否有权限，用于安卓
  Future<bool> checkPermission() async {
    if (_flatform == 'android') {
      PermissionStatus permission = await PermissionHandler()
          .checkPermissionStatus(PermissionGroup.storage);
      if (permission != PermissionStatus.granted) {
        Map<PermissionGroup, PermissionStatus> permissions =
            await PermissionHandler()
                .requestPermissions([PermissionGroup.storage]);
        if (permissions[PermissionGroup.storage] == PermissionStatus.granted) {
          return true;
        }
      } else {
        return true;
      }
    } else {
      return true;
    }
    return false;
  }

需要在Android的 AndroidManifest.xml文件增加权限配置

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />

下载apk根据返回的下载链接，需要先把Android包文件下载到本地，这里需要对文件流进行操作，下载工具我是采用的HTTP请求工具库dio，这里也可以采用专业的下载插件flutter_downloader，这个插件支持Android、IOS下载，但是配置起来复杂，我折腾了好长时间，也没能配置成功，有玩转这个插件的可以给我推荐些文章。

import 'package:dio/dio.dart';
import 'package:path_provider/path_provider.dart';

/// 下载安卓更新包
Future<File> downloadAndroid(String url) async {
  /// 创建存储文件
  Directory storageDir = await getExternalStorageDirectory();
  String storagePath = storageDir.path;
  File file = new File('$storagePath/${Config.APP_NAME}v${_version}.apk');

  if (!file.existsSync()) {
    file.createSync();
  }

  try {
    /// 发起下载请求
    Response response = await Dio().get(url,
        onReceiveProgress: showDownloadProgress,
        options: Options(
          responseType: ResponseType.bytes,
          followRedirects: false,
        ));
    file.writeAsBytesSync(response.data);
    return file;
  } catch (e) {
    print(e);
  }
}

安装apk

import 'package:install_plugin/install_plugin.dart';

/// 安装apk
Future<Null> installApk(String url) async {
  File _apkFile = await downloadAndroid(url);
  String _apkFilePath = _apkFile.path;

  if (_apkFilePath.isEmpty) {
    print('make sure the apk file is set');
    return;
  }

  InstallPlugin.installApk(_apkFilePath, Config.APP_ID)
      .then((result) {
    print('install apk $result');
  }).catchError((error) {
    print('install apk error: $error');
  });
}

这里我用的是install_plugin: ^2.0.1，该插件在安卓上能正常运行，但是在Apple上先是报

[!] Unable to determine Swift version for the following pods:

install_plugin does not specify a Swift version and none of the targets (Runner) integrating it have the SWIFT_VERSION attribute set. Please contact the author or set the SWIFT_VERSION attribute in at least one of the targets that integrate this pod.
Xcode:
The sandbox is not in sync with the Podfile.lock. Run 'pod install' or update your CocoaPods installation.

手动添加了SWIFT_VERSION后，又报

fatal error: 'install_plugin/install_plugin-Swift.h' file not found
#import <install_plugin/install_plugin-Swift.h>

报错原因是iOS在构建的时候默认是objective-c，而这个插件使用的是swift

解决方法：

创建ios/File.swift

//
//  File.swift
//  Runner
//
//  Created by richer on 2019/11/22.
//  Copyright © 2019 The Chromium Authors. All rights reserved.
//

import Foundation

创建ios/Runner-Bridging-Header.h文件

//
//  Use this file to import your target's public headers that you would like to expose to Swift.
//

编辑ios/Podfile，在target 'Runner' do后面添加 use_frameworks!

target 'Runner' do
  use_frameworks!

5. 展示下载进度，dio提供下载进度的回调

 /// 展示下载进度
  void showDownloadProgress(num received, num total) {
    if (total != -1) {
      double _progress =
          double.parse('${(received / total).toStringAsFixed(2)}');
      eventManager.eventBus
          .fire(new UpdateAndroidProgressEvent(_progress));
    }
  }