最近一直在探索android flutter的混合开发，一路遇到了很多的坑，接下来便将这些记录下来，希望能帮助到大家的开发。

Android Flutter混合开发问题总结
 Android Flutter混合开发问题总结(二)

flutter常用指令

flutter help create
flutter创建项目的指令。我们可以指定创建module还是project，可以指定语言，如java、kotlin，同时可以指定是否生成androidx项目。

  -h, --help                     Print this usage information.
      --[no-]pub                 Whether to run "flutter pub get" after the project has been created.
                                 (defaults to on)
  
      --[no-]offline             When "flutter pub get" is run by the create command, this indicates whether to run it in offline mode or not. In offline mode, it will need to have all dependencies already available in the pub cache to succeed.
      --[no-]with-driver-test    Also add a flutter_driver dependency and generate a sample 'flutter drive' test.
  -t, --template=<type>          Specify the type of project to create.
  
            [app]                (default) Generate a Flutter application.
            [package]            Generate a shareable Flutter project containing modular Dart code.
            [plugin]             Generate a shareable Flutter project containing an API in Dart code with a platform-specific implementation for Android, for iOS code, or for both.
  
  -s, --sample=<id>              Specifies the Flutter code sample to use as the main.dart for an application. Implies --template=app. The value should be the sample ID of the desired sample from the API documentation website (http://docs.flutter.dev). An example can
                                 be found at https://master-api.flutter.dev/flutter/widgets/SingleChildScrollView-class.html
  
      --list-samples=<path>      Specifies a JSON output file for a listing of Flutter code samples that can created with --sample.
      --[no-]overwrite           When performing operations, overwrite existing files.
      --description              The description to use for your new Flutter project. This string ends up in the pubspec.yaml file.
                                 (defaults to "A new Flutter project.")
  
      --org                      The organization responsible for your new Flutter project, in reverse domain name notation. This string is used in Java package names and as prefix in the iOS bundle identifier.
                                 (defaults to "com.example")
  
      --project-name             The project name for this new Flutter project. This must be a valid dart package name.
  -i, --ios-language             [objc, swift (default)]
  -a, --android-language         [java, kotlin (default)]
      --[no-]androidx            Generate a project using the AndroidX support libraries

flutter channel

查看当前flutter分支

Flutter channels:
  beta
  dev
  master
* stable

flutter doctor

诊断当前flutter配置是否有问题

flutter doctor

诊断当前flutter配置是否有问题

flutter version --force 1.0.0

切换到指定flutter版本

flutter clean

clean当前工程

flutter run

运行当前工程

flutter analyze

分析当前项目dart代码

flutter assemble

构建资源

flutter attach

attach当前项目，通常用于调试

flutter bash-completion

Output command line shell completion setup scripts.

flutter build

编译flutter项目

flutter config

配置flutter设置

flutter devices

查看设备列表

flutter drive

为当前项目运行驱动测试

flutter emulators

查看模拟器列表以及运行

flutter format

格式化dart代码

flutter install

安装flutter项目

flutter logs

查看运行日志

flutter screenshot

对设备进行截图

flutter test

运行flutter单元测试

flutter upgrade

更新flutter 版本

flutter version

查看flutter 版本

flutter常见问题的解决

flutter工程无法进行依赖

可以查看一下.android/Flutter/build.gradle的buildTypes中是否包含app的build.gradle中所需的buildTypes

缺少libflutter.so

flutter项目默认支持的是armeabi-v7a,所以需要在app的gradle中加入如下配置：

    ndk {
        abiFilters "armeabi-v7a"
    }

如果还是提示这个错误，则需要在gradle.properties中华加入如下配置：

target-platform=android-arm

编译apk成功，但是运行flutter失败,例如：VM snapshot must be valid. /Check failed: vm. Must be able to initialize the VM.

可以尝试flutter clean, 然后flutter run一下项目，再去运行主工程

flutter混淆配置

  -keep class io.flutter.app.** {*;}
  -keep class io.flutter.plugin.** {*;}
  -keep class io.flutter.util.** {*;}
  -keep class io.flutter.view.** {*;}
  -keep class io.flutter.** {*;}
  -keep class io.flutter.plugins.** {*;}
  -dontwarn io.flutter.**

跳转flutter所在activity黑屏

  val flutterView = Flutter.createView(this, lifecycle, Gson().toJson(map))
  val layout = findViewById<FrameLayout>(R.id.flutter_container)
  layout.visibility = View.INVISIBLE
  layout.addView(flutterView)
  val listeners = arrayOfNulls<FlutterView.FirstFrameListener>(1)
  listeners[0] = FlutterView.FirstFrameListener {
      layout.visibility = View.VISIBLE
      loadingDialog.dismiss()
  }
  flutterView.addFirstFrameListener(listeners[0])

或者设置当前主题

flutter的activity进入加载较慢

debug包这种情况比较明显，但是release加载很快，可以仿照一下闲鱼，在进入FlutterActivity的时候提供一个加载loading

Activity中加载flutter几种方式

直接加载flutter的main.dart

GeneratedPluginRegistrant.registerWith即可

public class MainActivity extends FlutterActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    GeneratedPluginRegistrant.registerWith(this);
  }
}

继承FlutterActivity

class TestFlutterActivity : FlutterActivity() {

    private lateinit var flutterFragment: FlutterFragment

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
//        setContentView(R.layout.activity_flutter_test)
        GeneratedPluginRegistrant.registerWith(this)
    }


    override fun createFlutterView(context: Context?): FlutterView {
        val matchParent = WindowManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
        val nativeView = this.createFlutterNativeView()
        val flutterView = FlutterView(this, null, nativeView)
        flutterView.setInitialRoute("web_view_page")
        flutterView.layoutParams = matchParent
//        flutterView.enableTransparentBackground()
        val layout = findViewById<FrameLayout>(R.id.flutter_container)
        val listeners = arrayOfNulls<FlutterView.FirstFrameListener>(1)
        listeners[0] = FlutterView.FirstFrameListener {
            layout.visibility = View.VISIBLE
        }
        flutterView.addFirstFrameListener(listeners[0])
        this.addContentView(flutterView, matchParent)
        return flutterView
    }

    override fun onBackPressed() {
        if (flutterView != null) {
            flutterView.popRoute()
        } else {
            super.onBackPressed()
        }
    }
}

addContentView直接加载FlutterView

class MainFlutterActivity : FlutterFragmentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main_flutter)
        val mFlutterView: View = Flutter.createView(this, lifecycle, "main_flutter")
        val mParams = FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT,
                FrameLayout.LayoutParams.MATCH_PARENT)
        addContentView(mFlutterView, mParams)
    }
}

通过FlutterFragment

class FlutterActivity : AppCompatActivity() {

    private lateinit var flutterFragment: FlutterFragment

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_helper_center)
        flutterFragment = Flutter.createFragment("web_view_page")
        supportFragmentManager.beginTransaction().replace(R.id.flutter_container, flutterFragment).commitAllowingStateLoss()
    }
}

Android原生与Flutter间的通信、传值

可以通过flutter_boost，但是目前有适配问题，不支持flutter1.7、1.9

Flutter传值->Android

有点类似于Eventbus的方式：

flutter.dart中发送事件：

  static const platform = const MethodChannel("webview");

  void _finish() {
    platform.invokeMethod("finish");
  }

android接收并处理：

    MethodChannel(flutterView, "webview").setMethodCallHandler { methodCall, result ->
        if(methodCall.method == "finish"){
            finish()
        }
    }

Android传值->Flutter

android跳转flutter的时候可以通过路由名字直接传入值。

dart:

import 'dart:ui' as ui;

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  static const String HELP_URL =
      'https://xxxx';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in a Flutter IDE). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: _widgetRouter(ui.window.defaultRouteName)
    );
  }
}

Widget _widgetRouter(String json) {
  return RouterManager.getInstance().getPageByRouter(json);
}


class RouterManager {
  static RouterManager mInstance = new RouterManager();

  static RouterManager getInstance() {
    return mInstance;
  }

  /*
    根据传入的route名  找到对应跳转的路径
   */
  StatefulWidget getPageByRouter(String jsonStr) {
    String path = "";
    String param = "";
    if (jsonStr != null && jsonStr.isNotEmpty && jsonStr != "/") {
      var jsonResponse = jsonDecode(jsonStr);
      path = jsonResponse["path"];
      print("==== router === path = $path");
      param = jsonResponse["param"];
      print("==== router === param = $param");
      path = path != null && path.isNotEmpty ? path : RouterPath.HOME_PAGE;
      param = param != null && param.isNotEmpty ? param : "[]";
    }
    Map<String, dynamic> map = json.decode(param);
    Widget widget = _getWidgetPage(path, map);

    if (widget == null) {
      debugPrint('==== 找不到widget =====');
    }
    return widget;
  }

  Widget _getWidgetPage(String path, Map<String, dynamic> map) {
    Widget widget;
    switch (path) {
      case RouterPath.HOME_PAGE:
        widget = MyHomePage(title: 'Flutter Demo Home Page');
        break;
      case RouterPath.WEB_VIEW_PAGE:
        widget = WebViewPage(map["title"], map["url"]);
        break;
    }
    return widget;
  }
}

class RouterPath {
  static const String HOME_PAGE = 'home_page';
  static const String WEB_VIEW_PAGE = 'web_view_page';
}

在_getWidgetPage内配置路由跳转的值及对应界面。

android

与之前主要的区别在于参数通过hashmap转换成json形式放入路由名称中，然后把路由名连同参数一起传给main.dart

    val map = HashMap<String, String>()
    val params = HashMap<String, String>()
    params.put("title", "帮助中心")
    params.put("url", WebUrlConfig.HELP_URL)
    map.put("path", "web_view_page")
    map.put("param", Gson().toJson(params))
    val matchParent = WindowManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
    val nativeView = this.createFlutterNativeView()
    val flutterView = FlutterView(this, null, nativeView)
    flutterView.setInitialRoute(Gson().toJson(map))
    flutterView.layoutParams = matchParent
    val layout = findViewById<FrameLayout>(R.id.flutter_container)
    val listeners = arrayOfNulls<FlutterView.FirstFrameListener>(1)
    listeners[0] = FlutterView.FirstFrameListener {
        layout.visibility = View.VISIBLE
    }
    flutterView.addFirstFrameListener(listeners[0])
    this.addContentView(flutterView, matchParent)

android部分的封装

我这里对其android部分进行了封装，需要使用的话直接拷贝代码即可：

BaseFlutterActivity：

abstract class BaseFlutterActivity : AppCompatActivity() {

    lateinit var flutterView: FlutterView

    private val loadingDialog: LoadingDialog by lazy {
        LoadingDialog(this, "加载中")
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_flutter_activity)
        loadingDialog.show()
        val map = HashMap<String, String>()
        map["path"] = routeUrl()
        map["param"] = Gson().toJson(routeParams())
        flutterView = Flutter.createView(this, lifecycle, Gson().toJson(map))
        val layout = findViewById<FrameLayout>(R.id.flutter_container)
        layout.addView(flutterView)
        val listeners = arrayOfNulls<FlutterView.FirstFrameListener>(1)
        listeners[0] = FlutterView.FirstFrameListener {
            layout.visibility = View.VISIBLE
            loadingDialog.dismiss()
        }
        flutterView.addFirstFrameListener(listeners[0])

        if (setChannel().isNotEmpty()) {
            setFlutterMessageHandler()?.let {
                MethodChannel(flutterView, setChannel()).setMethodCallHandler(it)
            }
        }

    }

    open fun setChannel(): String {
        return ""
    }

    open fun setFlutterMessageHandler(): MethodChannel.MethodCallHandler? {
        return null
    }


    abstract fun routeUrl(): String

    abstract fun routeParams(): HashMap<String, String>
}

使用：
下面代码是跳转一个webview并且传入url：

class FlutterWebActivity : BaseAegisFlutterActivity() {

    private val title: String by lazy { intent.getStringExtra(TITLE) }
    private val url: String by lazy { intent.getStringExtra(URL) }

    companion object {
        const val TITLE = "title"
        const val URL = "url"

        fun buildIntent(context: Context?, title: String, url: String): Intent {
            val intent = Intent(context, FlutterWebActivity::class.java)
            intent.putExtra(TITLE, title)
            intent.putExtra(URL, url)
            return intent
        }
    }

    override fun routeUrl(): String = "web_view_page"

    override fun routeParams(): HashMap<String, String> {
        val params = HashMap<String, String>()
        params["title"] = title
        params["url"] = url
        return params
    }

    override fun setChannel(): String = "webview"

    override fun setFlutterMessageHandler(): MethodChannel.MethodCallHandler? {
        return MethodChannel.MethodCallHandler { methodCall, _ ->
            if (methodCall.method == "finish") {
                finish()
            }
        }
    }
}

总结

Android Flutter的混合开发基础先总结到这里，希望能帮助到大家。后续内容我会再进行补充。