Flutter开发(二十八)：Flutter_1.12与Android混合开发_flutterengine 预热

1. Android 页面跳转到 Flutter 页面两种方式及传值

上一节看到无论跳转还是嵌入，速度都要一秒多，肉眼可见的慢，没有原生快很多。为了优化这个问题，flutter 提供了 FlutterEngine 来进行预热/缓存，需要跳转的时候直接找到对应 id 进行跳转即可。

1. Android 页面跳转到 Flutter 页面两种方式及传值

前面一节说了两种方式：

第一种作为 fragment 嵌入到原生页面中；

第二种是作为一个新的页面 activity 跳转进入；

下面讲的是用两种方法跳转到 flutter 然后传值。先看效果图：

 对比上一节，跳转的速度快了很多，因为用到了 FlutterEngine ，它的简单使用：设置路由和传参，使用dart executor来预热，给它一个id并且缓存；

原生 Android 项目下具体代码如下：

import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
 
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.android.FlutterFragment;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.embedding.engine.FlutterEngineCache;
import io.flutter.embedding.engine.dart.DartExecutor;
 
public class MainActivity extends AppCompatActivity {
    Button tv_test,btn_test1;
    FrameLayout frameFlutter;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        setFlutterEngine();
 
        tv_test = findViewById(R.id.btn_test);
        btn_test1 = findViewById(R.id.btn_test1);
        frameFlutter = findViewById(R.id.frameFlutter);
        tv_test.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //跳转activity
                startActivity(
                        FlutterActivity
                                .withCachedEngine("my_engine_id")
                                .build(MainActivity.this)
                );
            }
        });
        btn_test1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //fragment嵌入
                FlutterFragment flutterFragment = FlutterFragment.withCachedEngine("my_engine_id")
                        .build();
                getSupportFragmentManager()
                        .beginTransaction()
                        .add(R.id.frameFlutter, flutterFragment)
                        .commit();
            }
        });
    }
 
    private void setFlutterEngine() {
        // 初始化FlutterEngine.
        FlutterEngine flutterEngine = new FlutterEngine(this);
        //设置传参
        flutterEngine.getNavigationChannel().setInitialRoute("route1?{\"name\":\"" + "张三" + "\"}");
        // 使用dart executor来预热FlutterEngine.
        flutterEngine.getDartExecutor().executeDartEntrypoint(
                DartExecutor.DartEntrypoint.createDefault()
        );
 
        // 缓存FlutterEngine，并且给一个id，方便后面获取
        FlutterEngineCache
                .getInstance()
                .put("my_engine_id", flutterEngine);
    }
}

flutter module 中 main.dart ，取出对应路由，并且拿到传来的参数并且显示出来，具体代码：

import 'dart:ui';
 
import 'package:flutter/material.dart';
import 'dart:convert';
 
void main() => runApp(const MyApp());
 
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
 
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}
 
class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);
 
  final String title;
 
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}
 
class _MyHomePageState extends State<MyHomePage> {
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: _widgetForRoute(),// This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}
 
Widget _widgetForRoute() {
  String route = _getRouteName(window.defaultRouteName);
  Map<String, dynamic> params = _getParamsStr(window.defaultRouteName);
  switch (route) {
    case 'route1':
      return Center(
        child: Text(params['name']),
      );
    default:
      return
        Center(
          child: Text(params['name']),
        );
  }
}
 
// 获取路由名称
String _getRouteName(String s) {
  if (s.indexOf('?') == -1) {
    return s;
  } else {
    return s.substring(0, s.indexOf('?'));
  }
}
 
// 获取参数
Map<String, dynamic> _getParamsStr(String s) {
  if (s.indexOf('?') == -1) {
    return Map();
  } else {
    return json.decode(s.substring(s.indexOf('?') + 1));
  }
}

这样就完成了跳转以及传参。