Flutter 和 Android原生（Activity、Fragment）相互跳转、传参
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前言
本文主要讲解 Flutter 和 Android原生之间，页面相互跳转、传参，
但其中用到了两端相互通信的知识，非常建议先看完这篇 讲解通信的文章：
当前案例 Flutter SDK版本：3.13.2
Flutter使用多个轻量型引擎，进行混合开发，是从2.0开始的，大大的减轻了内存压力；
轻量型引擎开发-官方介绍视频：www.youtube.com/watch?v=p6c…
Flutter和原生端的关系
混合路由栈
如果是纯Flutter开发，只会有一个Flutter引擎，如果是混合开发，原生端 需要为每个从原生端跳转的Flutter页面创建独立的引擎 (也可以单例，但单例写法需要处理一些问题，这个到FlutterEngineGroup章节会讲解)；
比如：
1.0 从 Android_A页面 ==== 跳转到 ==== Flutter_A页面，Android端需要为Flutter_A页面，创建Flutter引擎；
1.1 紧接着，从 Flutter_A页面 ==== 跳转到 ==== Flutter_B页面，就不需要，它俩共用一个引擎；
1.2 每个Flutter引擎都有自己的路由栈，且这个路由栈只能管理Flutter页面；
1.3 使用Flutter提供的 Navigator.pop(context); 方法，可以从 Flutter_B页面 回退到 Flutter_A页面，但无法从 Flutter_A页面 回退到 Android_A，会黑屏，因为Flutter栈里面没有Android页面，可以使用 Navigator.canPop(context); 来检查Flutter路由栈中，是否还有其他路由；
1.4 如果不使用 Navigator.pop(context); 回退方法，使用手机自带的 Back按键 / 左滑屏幕 进行回退，是没有问题的，因为这种回退方式调用的是原生API，Android原生不光提供FlutterView渲染Flutter页面结果，还会创建FlutterActivity和FlutterView进行绑定；
1.5 看到这，大家应该理解，为什么说Flutter只是UI框架了吧；
Android 和 Flutter 跳转
Android 跳转 Flutter
Flutter 跳转 Android
效果图
Android代码
FlutterRouterManager.kt
package com.example.flutter_nav_android.util
import android.app.Activity
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.android.FlutterActivityLaunchConfigs
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.embedding.engine.FlutterEngineCache
import io.flutter.embedding.engine.dart.DartExecutor
class FlutterRouterManager(
val targetRoute: String,
val mEngineId: String,
val mContext: Activity
) {
var mEngine: FlutterEngine? = null
init {
createCachedEngine()
}
companion object {
/**
* 获取缓存中的 Flutter引擎
*/
@JvmStatic
fun getEngineCacheInstance(engineId: String): FlutterEngine? {
return FlutterEngineCache.getInstance().get(engineId)
}
}
/**
* 1、创建Flutter引擎
* 2、将初始命名路由，修改为目标页面路由
* 3、缓存Flutter引擎
*/
fun createCachedEngine(): FlutterEngine {
val flutterEngine = FlutterEngine(mContext) // 创建Flutter引擎
// 将初始命名路由，修改为目标页面路由
flutterEngine.navigationChannel.setInitialRoute(targetRoute)
// 这一步，是在执行相关Dart文件入口的 main函数，将Flutter页面渲染出结果
// 原生端获取结果，进行最终渲染上屏
flutterEngine.dartExecutor.executeDartEntrypoint(
DartExecutor.DartEntrypoint.createDefault()
)
// 将加载好的引擎，存储起来
FlutterEngineCache.getInstance().put(mEngineId, flutterEngine)
mEngine = flutterEngine
return flutterEngine
}
/**
* 根据引擎ID，前往指定的Flutter页面
*/
fun push() {
// 创建新的引擎（了解即可）
// mContext.startActivity(
// FlutterActivity
// .withNewEngine() // 创建引擎
// .backgroundMode(FlutterActivityLaunchConfigs.BackgroundMode.transparent) // 背景改为透明，不然切换页面时，会闪烁黑色
// .build(mContext))
// 使用缓存好的引擎（推荐）
mContext.startActivity(
FlutterActivity
.withCachedEngine(mEngineId) // 获取缓存好的引擎
.backgroundMode(FlutterActivityLaunchConfigs.BackgroundMode.transparent) // 背景改为透明，不然切换页面时，会闪烁黑色
.build(mContext)
)
}
/**
* 销毁当前Flutter引擎
*/
fun destroy() {
mEngine?.destroy()
}
}
PersonalActivity.kt
package com.example.flutter_nav_android.ui.activity
import android.graphics.Color
import android.os.Bundle
import android.text.SpannableString
import android.text.Spanned
import android.text.style.ForegroundColorSpan
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import com.example.flutter_nav_android.databinding.ActivityPersonalBinding
import com.example.flutter_nav_android.util.FlutterRouterManager
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
class PersonalActivity : AppCompatActivity(), MethodChannel.MethodCallHandler, View.OnClickListener {
private lateinit var bind: ActivityPersonalBinding
private lateinit var homeFlutterEngine: FlutterEngine
private lateinit var loginRouterManager: FlutterRouterManager
private lateinit var loginMethodChannel: MethodChannel
private lateinit var homeMethodChannel: MethodChannel
private val METHOD_CHANNEL_LOGIN = "com.example.flutter_nav_android/login/method"
private val METHOD_CHANNEL_HOME = "com.example.flutter_nav_android/home/method"
private val NAV_FLUTTER_LOGIN_NOTICE = "navFlutterLoginNotice"
private val POP_NOTICE = "popNotice"
private val PERSONAL_POP_NOTICE = "personalPopNotice"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
bind = ActivityPersonalBinding.inflate(layoutInflater)
setContentView(bind.root)
initView()
loginRouterManager = FlutterRouterManager("/login", "login_engine", this)
// 两端建立通信
loginMethodChannel = MethodChannel(loginRouterManager.mEngine!!.dartExecutor, METHOD_CHANNEL_LOGIN)
loginMethodChannel.setMethodCallHandler(this)
// 获取 Flutter Home页面的引擎，并且建立通信
homeFlutterEngine = FlutterRouterManager.getEngineCacheInstance("home_engine")!!
homeMethodChannel = MethodChannel(homeFlutterEngine.dartExecutor,METHOD_CHANNEL_HOME)
}
/**
* 监听来自 Flutter端 的消息通道
*
* call： Android端 接收到 Flutter端 发来的 数据对象
* result：Android端 给 Flutter端 执行回调的接口对象
*/
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
val methodName: String = call.method
when (methodName) { // 销毁 Flutter Login 页面
POP_NOTICE -> {
val age = call.argument<Int>("age")
getResult(age.toString())
loginRouterManager.mEngine!!.navigationChannel.popRoute()
}
else -> {
result.notImplemented()
}
}
}
override fun onClick(v: View?) {
when (v) {
bind.toFlutter -> { // 前往 Flutter Login 页面
val map: MutableMap<String, String> = mutableMapOf<String, String>()
map["name"] = "老王"
loginMethodChannel.invokeMethod(NAV_FLUTTER_LOGIN_NOTICE,map)
loginRouterManager.push()
}
bind.pop -> { // 销毁 Android Personal 页面
val map: MutableMap<String, Int> = mutableMapOf<String, Int>()
map["age"] = 18
homeMethodChannel.invokeMethod(PERSONAL_POP_NOTICE,map)
finish()
}
}
}
/**
* 初始化页面
*/
private fun initView() {
bind.toFlutter.setOnClickListener(this)
bind.pop.setOnClickListener(this)
var name = intent.getStringExtra("name")
val title = "接收初始化参数："
val msg = title + name
val ss = SpannableString(msg)
ss.setSpan(
ForegroundColorSpan(Color.RED),
title.length,
msg.length,
Spanned.SPAN_INCLUSIVE_EXCLUSIVE
)
bind.initV.text = ss
}
/**
* 获取上一页的返回参数
*/
private fun getResult(age: String) {
val title = "接收上一页返回参数："
val msg = title + age
val ss = SpannableString(msg)
ss.setSpan(
ForegroundColorSpan(Color.RED),
title.length,
msg.length,
Spanned.SPAN_INCLUSIVE_EXCLUSIVE
)
bind.resultV.text = ss
}
override fun onDestroy() {
super.onDestroy()
loginRouterManager.destroy()
}
}
SchoolActivity.kt
package com.example.flutter_nav_android.ui.activity
import android.content.Intent
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.example.flutter_nav_android.databinding.ActivitySchoolBinding
import com.example.flutter_nav_android.util.FlutterRouterManager
import io.flutter.embedding.android.FlutterFragment
import io.flutter.embedding.android.TransparencyMode
import io.flutter.embedding.engine.FlutterEngineCache
import io.flutter.plugin.common.MethodChannel
class SchoolActivity : AppCompatActivity() {
private lateinit var bind: ActivitySchoolBinding
private lateinit var bookFragment: FlutterFragment
private lateinit var studentFragment: FlutterFragment
private val METHOD_CHANNEL_BOOK = "com.example.flutter_nav_android/book/method"
private val METHOD_CHANNEL_STUDENT = "com.example.flutter_nav_android/student/method"
private val NAV_FLUTTER_BOOK_NOTICE = "navFlutterBookNotice"
private val NAV_FLUTTER_STUDENT_NOTICE = "navFlutterStudentNotice"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
bind = ActivitySchoolBinding.inflate(layoutInflater)
setContentView(bind.root)
initView()
initChannel()
}
/**
* 建立通信
*/
private fun initChannel() {
val bookEngine = FlutterRouterManager.getEngineCacheInstance("book_engine")
val bookChannel = MethodChannel(bookEngine!!.dartExecutor,METHOD_CHANNEL_BOOK)
val map: MutableMap<String, String> = mutableMapOf<String, String>()
map["title"] = "Book"
bookChannel.invokeMethod(NAV_FLUTTER_BOOK_NOTICE,map)
val studentEngine = FlutterRouterManager.getEngineCacheInstance("student_engine")
val studentChannel = MethodChannel(studentEngine!!.dartExecutor,METHOD_CHANNEL_STUDENT)
val map2: MutableMap<String, String> = mutableMapOf<String, String>()
map2["title"] = "Student"
studentChannel.invokeMethod(NAV_FLUTTER_STUDENT_NOTICE,map2)
}
/**
* 初始化页面
*/
private fun initView() {
bookFragment = FlutterFragment.withCachedEngine("book_engine")
.transparencyMode(TransparencyMode.transparent) // 背景透明，避免切换页面，出现闪烁
.shouldAttachEngineToActivity(false) // 是否让Flutter控制Activity，true：可以 false：不可以，默认值 true
.build()
supportFragmentManager
.beginTransaction()
.add(bind.bookFragment.id, bookFragment)
.commit()
studentFragment = FlutterFragment.withCachedEngine("student_engine")
.transparencyMode(TransparencyMode.transparent) // 背景透明，避免切换页面，出现闪烁
.shouldAttachEngineToActivity(false) // 是否让Flutter控制Activity，true：可以 false：不可以，默认值 true
.build()
supportFragmentManager
.beginTransaction()
.add(bind.studentFragment.id, studentFragment)
.commit()
}
// ================================ 这些是固定写法，Flutter需要这些回调 ================================
override fun onPostResume() {
super.onPostResume()
bookFragment.onPostResume()
studentFragment.onPostResume()
}
override fun onNewIntent(intent: Intent) {
super.onNewIntent(intent)
bookFragment.onNewIntent(intent)
studentFragment.onNewIntent(intent)
}
override fun onBackPressed() {
bookFragment.onBackPressed()
studentFragment.onBackPressed()
}
override fun onRequestPermissionsResult(
requestCode: Int,
permissions: Array<String?>,
grantResults: IntArray
) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
bookFragment.onRequestPermissionsResult(
requestCode,
permissions,
grantResults
)
studentFragment.onRequestPermissionsResult(
requestCode,
permissions,
grantResults
)
}
override fun onUserLeaveHint() {
bookFragment.onUserLeaveHint()
studentFragment.onUserLeaveHint()
}
override fun onTrimMemory(level: Int) {
super.onTrimMemory(level)
bookFragment.onTrimMemory(level)
studentFragment.onTrimMemory(level)
}
}
MainActivity.kt
package com.example.flutter_nav_android.ui.activity
import android.content.Intent
import android.graphics.Color
import android.text.SpannableString
import android.text.Spanned
import android.text.style.ForegroundColorSpan
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import com.example.flutter_nav_android.databinding.ActivityMainBinding
import com.example.flutter_nav_android.util.FlutterRouterManager
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
class MainActivity : AppCompatActivity(), MethodChannel.MethodCallHandler, View.OnClickListener {
private lateinit var bind: ActivityMainBinding
private lateinit var homeMethodChannel: MethodChannel
private val METHOD_CHANNEL_HOME = "com.example.flutter_nav_android/home/method"
private val NAV_ANDROID_PERSONAL_NOTICE = "navAndroidPersonalNotice"
private val NAV_FLUTTER_HOME_NOTICE = "navFlutterHomeNotice"
private val POP_NOTICE = "popNotice"
private lateinit var homeRouterManager: FlutterRouterManager
private lateinit var bookRouterManager: FlutterRouterManager
private lateinit var studentRouterManager: FlutterRouterManager
override fun onCreate(savedInstanceState: android.os.Bundle?) {
super.onCreate(savedInstanceState)
bind = ActivityMainBinding.inflate(layoutInflater)
setContentView(bind.root)
bind.toFlutter.setOnClickListener(this)
bind.toFlutterFragment.setOnClickListener(this)
homeRouterManager = FlutterRouterManager("/home", "home_engine", this)
// 两端建立通信
homeMethodChannel = MethodChannel(homeRouterManager.mEngine!!.dartExecutor,METHOD_CHANNEL_HOME)
homeMethodChannel.setMethodCallHandler(this)
// 这里Fragment案例的
bookRouterManager = FlutterRouterManager("/book", "book_engine", this)
studentRouterManager = FlutterRouterManager("/student", "student_engine", this)
}
/**
* 监听来自 Flutter端 的消息通道
*
* call： Android端 接收到 Flutter端 发来的 数据对象
* result：Android端 给 Flutter端 执行回调的接口对象
*/
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
val methodName: String = call.method
when (methodName) {
NAV_ANDROID_PERSONAL_NOTICE -> { // Flutter Home 页面 前往 Android Personal 页面
val intent = Intent(this, PersonalActivity::class.java)
intent.putExtra("name",call.argument<String>("name"))
startActivity(intent)
}
POP_NOTICE -> { // 销毁 Flutter Home 页面
val age = call.argument<Int>("age")
getResult(age.toString())
homeRouterManager.mEngine!!.navigationChannel.popRoute()
}
else -> {
result.notImplemented()
}
}
}
override fun onClick(v: View?) {
when (v) {
bind.toFlutter -> { // 前往 Flutter Home 页面
val map: MutableMap<String, String> = mutableMapOf<String, String>()
map["name"] = "张三"
homeMethodChannel.invokeMethod(NAV_FLUTTER_HOME_NOTICE,map)
homeRouterManager.push()
}
bind.toFlutterFragment -> {
val intent = Intent(this, SchoolActivity::class.java)
startActivity(intent)
}
}
}
/**
* 获取上一页的返回参数
*/
private fun getResult(age: String) {
val title = "接收上一页返回参数："
val msg = title + age
val ss = SpannableString(msg)
ss.setSpan(
ForegroundColorSpan(Color.RED),
title.length,
msg.length,
Spanned.SPAN_INCLUSIVE_EXCLUSIVE
)
bind.resultV.text = ss
}
override fun onDestroy() {
super.onDestroy()
homeRouterManager.destroy()
bookRouterManager.destroy()
studentRouterManager.destroy()
}
}
activity_personal.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="60dp"
android:layout_marginBottom="16dp"
android:background="@color/cardview_shadow_start_color"
android:gravity="center_vertical"
android:paddingStart="16dp"
android:text="Android Personal"
android:textColor="@color/material_dynamic_primary60"
android:textSize="26sp"
android:textStyle="bold"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/init_v"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:text="接收初始化参数："
android:textColor="@color/material_dynamic_primary60"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/result_v"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="接收上一页返回参数："
android:textColor="@color/material_dynamic_primary60"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@id/init_v" />
<Button
android:id="@+id/to_flutter"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="前往 Flutter Login"
android:textSize="20sp"
android:textAllCaps="false"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@id/result_v" />
<Button
android:id="@+id/pop"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:text="返回 上一页"
android:textSize="20sp"
android:textAllCaps="false"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@id/to_flutter" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
activity_school.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="20dp"
android:orientation="vertical">
<TextView
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="@color/cardview_shadow_start_color"
android:gravity="center_vertical"
android:paddingStart="16dp"
android:text="Android School"
android:textColor="@color/material_dynamic_primary60"
android:textSize="26sp"
android:textStyle="bold" />
<FrameLayout
android:id="@+id/book_fragment"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="0dp" />
<FrameLayout
android:id="@+id/student_fragment"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="0dp" />
</LinearLayout>
</layout>
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="60dp"
android:layout_marginBottom="16dp"
android:background="@color/cardview_shadow_start_color"
android:gravity="center_vertical"
android:paddingStart="16dp"
android:text="Android Main"
android:textColor="@color/material_dynamic_primary60"
android:textSize="26sp"
android:textStyle="bold"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/result_v"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:text="接收上一页返回参数："
android:textColor="@color/material_dynamic_primary60"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintBottom_toBottomOf="parent"/>
<Button
android:id="@+id/to_flutter"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="前往 Flutter Home"
android:textSize="20sp"
android:textAllCaps="false"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toBottomOf="@id/result_v"
app:layout_constraintRight_toRightOf="parent" />
<Button
android:id="@+id/to_flutter_fragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:text="前往 Flutter Fragment"
android:textSize="20sp"
android:textAllCaps="false"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toBottomOf="@id/to_flutter"
app:layout_constraintRight_toRightOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<application
android:name="${applicationName}"
android:icon="@mipmap/ic_launcher"
android:label="flutter_nav_android"
android:theme="@style/AppTheme">
<activity
android:name="io.flutter.embedding.android.FlutterActivity"
android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
android:hardwareAccelerated="true"
android:windowSoftInputMode="adjustResize" />
<activity android:name=".ui.activity.SchoolActivity" android:exported="true"/>
<activity android:name=".ui.activity.PersonalActivity" android:exported="true"/>
<activity
android:name=".ui.activity.MainActivity"
android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
android:exported="true"
android:hardwareAccelerated="true"
android:launchMode="singleTop"
android:windowSoftInputMode="adjustResize">
<!-- Specifies an Android theme to apply to this Activity as soon as
the Android process has started. This theme is visible to the user
while the Flutter UI initializes. After that, this theme continues
to determine the Window background behind the Flutter UI. -->
<meta-data
android:name="io.flutter.embedding.android.NormalTheme"
android:resource="@style/NormalTheme" />
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- Don't delete the meta-data below.
This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
<meta-data
android:name="flutterEmbedding"
android:value="2" />
</application>
<!-- Required to query activities that can process text, see:
https://developer.android.com/training/package-visibility?hl=en and
https://developer.android.com/reference/android/content/Intent#ACTION_PROCESS_TEXT.
In particular, this is used by the Flutter engine in io.flutter.plugin.text.ProcessTextPlugin. -->
<queries>
<intent>
<action android:name="android.intent.action.PROCESS_TEXT" />
<data android:mimeType="text/plain" />
</intent>
</queries>
</manifest>
Flutter代码
book.dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class Book extends StatefulWidget {
const Book({super.key});
@override
State<Book> createState() => _BookState();
}
class _BookState extends State<Book> {
String title = '';
static const String METHOD_CHANNEL_BOOK = 'com.example.flutter_nav_android/book/method';
static const String NAV_FLUTTER_BOOK_NOTICE = 'navFlutterBookNotice';
@override
void initState() {
super.initState();
MethodChannel bookMethodChannel = const MethodChannel(METHOD_CHANNEL_BOOK);
bookMethodChannel.setMethodCallHandler(methodHandler);
}
/// 监听来自 Android端 的消息通道
/// Android端调用了函数，这个handler函数就会被触发
Future<dynamic> methodHandler(MethodCall call) async {
final String methodName = call.method;
switch (methodName) {
case NAV_FLUTTER_BOOK_NOTICE: // 进入当前页面
{
title = call.arguments['title'];
setState(() {});
return 0;
}
default:
{
return PlatformException(
code: '-1',
message: '未找到Flutter端具体实现函数',
details: '具体描述'); // 返回给Android端
}
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.amberAccent,
body: Container(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
alignment: Alignment.center,
child: Text(
'Flutter $title',
style: const TextStyle(
fontWeight: FontWeight.bold,
color: Colors.red,
fontSize: 20,
),
),
),
);
}
}
home.dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class Home extends StatefulWidget {
const Home({super.key});
@override
State<Home> createState() => _HomeState();
}
class _HomeState extends State<Home> {
late MethodChannel homeMethodChannel;
String name = '';
String age = '';
static const String METHOD_CHANNEL_HOME = 'com.example.flutter_nav_android/home/method';
static const String NAV_ANDROID_PERSONAL_NOTICE = 'navAndroidPersonalNotice';
static const String NAV_FLUTTER_HOME_NOTICE = 'navFlutterHomeNotice';
static const String POP_NOTICE = 'popNotice';
static const String PERSONAL_POP_NOTICE = 'personalPopNotice';
@override
void initState() {
super.initState();
homeMethodChannel = const MethodChannel(METHOD_CHANNEL_HOME);
homeMethodChannel.setMethodCallHandler(methodHandler);
}
/// 监听来自 Android端 的消息通道
/// Android端调用了函数，这个handler函数就会被触发
Future<dynamic> methodHandler(MethodCall call) async {
final String methodName = call.method;
switch (methodName) {
case NAV_FLUTTER_HOME_NOTICE: // 进入当前页面
{
name = call.arguments['name'];
setState(() {});
return 0;
}
case PERSONAL_POP_NOTICE: // Android Personal 页面 销毁了
{
age = '${call.arguments['age']}';
setState(() {});
return 0;
}
default:
{
return PlatformException(
code: '-1',
message: '未找到Flutter端具体实现函数',
details: '具体描述'); // 返回给Android端
}
}
}
/// 销毁当前页面
popPage() {
if (Navigator.canPop(context)) { // 检查Flutter路由栈中，是否还有其他路由
Navigator.pop(context);
} else {
Map<String, int> map = {'age': 12};
homeMethodChannel.invokeMethod(POP_NOTICE, map);
}
}
/// 前往 Android Personal 页面
navAndroidPersonal() {
Map<String, String> map = {'name': '李四'};
homeMethodChannel.invokeMethod(NAV_ANDROID_PERSONAL_NOTICE, map);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: const Text(
'Flutter Home',
style: TextStyle(
fontWeight: FontWeight.w500,
fontSize: 26,
color: Colors.yellow),
)),
body: SizedBox(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Padding(
padding: const EdgeInsets.only(bottom: 16),
child: RichText(
text: TextSpan(
text: '接收初始化参数：',
style: const TextStyle(color: Colors.black, fontSize: 20),
children: [
TextSpan(
text: name,
style: const TextStyle(color: Colors.red,fontWeight: FontWeight.bold),
)
])),
),
Padding(
padding: const EdgeInsets.only(bottom: 16),
child: RichText(
text: TextSpan(
text: '接收上一页返回参数：',
style: const TextStyle(color: Colors.black, fontSize: 20),
children: [
TextSpan(
text: age,
style: const TextStyle(color: Colors.red,fontWeight: FontWeight.bold),
)
])),
),
Padding(
padding: const EdgeInsets.only(bottom: 8),
child: ElevatedButton(
onPressed: navAndroidPersonal,
child: const Text(
'前往 Android Personal',
style: TextStyle(fontSize: 20),
),
),
),
ElevatedButton(
onPressed: popPage,
child: const Text(
'返回 上一页',
style: TextStyle(fontSize: 20),
),
),
],
),
),
);
}
}
login.dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class Login extends StatefulWidget {
const Login({super.key});
@override
State<Login> createState() => _LoginState();
}
class _LoginState extends State<Login> {
late MethodChannel loginMethodChannel;
String name = '';
final String METHOD_CHANNEL_LOGIN = 'com.example.flutter_nav_android/login/method';
static const String NAV_FLUTTER_LOGIN_NOTICE = 'navFlutterLoginNotice';
final String POP_NOTICE = 'popNotice';
@override
void initState() {
super.initState();
loginMethodChannel = MethodChannel(METHOD_CHANNEL_LOGIN);
loginMethodChannel.setMethodCallHandler(methodHandler);
}
/// 监听来自 Android端 的消息通道
/// Android端调用了函数，这个handler函数就会被触发
Future<dynamic> methodHandler(MethodCall call) async {
final String methodName = call.method;
switch (methodName) {
case NAV_FLUTTER_LOGIN_NOTICE: // 进入当前页面
{
name = call.arguments['name'];
setState(() {});
return 0;
}
default:
{
return PlatformException(code: '-1', message: '未找到Flutter端具体实现函数', details: '具体描述'); // 返回给Android端
}
}
}
/// 销毁当前页面
popPage() {
if (Navigator.canPop(context)) { // 检查Flutter路由栈中，是否还有其他路由
Navigator.pop(context);
} else {
Map<String, int> map = {'age': 28};
loginMethodChannel.invokeMethod(POP_NOTICE, map);
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: const Text(
'Flutter Login',
style: TextStyle(
fontWeight: FontWeight.w500,
fontSize: 26,
color: Colors.yellow),
)),
body: SizedBox(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Padding(
padding: const EdgeInsets.only(bottom: 16),
child: RichText(
text: TextSpan(
text: '接收初始化参数：',
style: const TextStyle(color: Colors.black, fontSize: 20),
children: [
TextSpan(
text: name,
style: const TextStyle(color: Colors.red,fontWeight: FontWeight.bold),
)
])),
),
ElevatedButton(
onPressed: popPage,
child: const Text(
'返回 上一页',
style: TextStyle(fontSize: 20),
),
),
],
),
),
);
}
}
student.dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class Student extends StatefulWidget {
const Student({super.key});
@override
State<Student> createState() => _StudentState();
}
class _StudentState extends State<Student> {
String title = '';
static const String METHOD_CHANNEL_STUDENT = 'com.example.flutter_nav_android/student/method';
static const String NAV_FLUTTER_STUDENT_NOTICE = 'navFlutterStudentNotice';
@override
void initState() {
super.initState();
MethodChannel bookMethodChannel = const MethodChannel(METHOD_CHANNEL_STUDENT);
bookMethodChannel.setMethodCallHandler(methodHandler);
}
/// 监听来自 Android端 的消息通道
/// Android端调用了函数，这个handler函数就会被触发
Future<dynamic> methodHandler(MethodCall call) async {
final String methodName = call.method;
switch (methodName) {
case NAV_FLUTTER_STUDENT_NOTICE: // 进入当前页面
{
title = call.arguments['title'];
setState(() {});
return 0;
}
default:
{
return PlatformException(
code: '-1',
message: '未找到Flutter端具体实现函数',
details: '具体描述'); // 返回给Android端
}
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.cyan,
body: Container(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
alignment: Alignment.center,
child: Text(
'Flutter $title',
style: const TextStyle(
fontWeight: FontWeight.bold,
color: Colors.white,
fontSize: 20,
),
),
),
);
}
}
main.dart
import 'package:flutter/material.dart';
import 'package:flutter_nav_android/book.dart';
import 'package:flutter_nav_android/student.dart';
import 'home.dart';
import 'login.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
colorScheme: ColorScheme.fromSeed(
seedColor: Colors.deepPurple,
),
useMaterial3: true,
),
routes: {
'/home': (context) => const Home(),
'/login': (context) => const Login(),
'/book': (context) => const Book(),
'/student': (context) => const Student(),
},
initialRoute: '/home',
);
}
}
踩坑
- 一个路由坑，Flutter 加载 根命名路由标识，默认是
" / "，如果你在Flutter端使用了" / "作为根路由页面，有时候，从Android 跳转 Flutter页面时，它会将 根路由页面 先push进栈，再push你的目标页面进栈，会多出一个页面； - 所有我直接不用
" / "标识，而使用页面对应的路由标识字符串，来指定根路由。
// 原来带坑的写法
// routes: {
// '/': (context) => const Home(),
// '/login': (context) => const Login(),
// '/personal': (context) => const Personal()
// },
// initialRoute: '/',
// 解决方式的写法
routes: {
'/home': (context) => const Home(),
'/login': (context) => const Login(),
'/personal': (context) => const Personal()
},
initialRoute: '/home',
奇技淫巧
在案例中，我使用的是 命名路由 和 Channel方式 进行 页面跳转、传参，下面直接使用引擎进行 页面跳转、传参，但实用价值不高，因为弊端太大；
比如：
- 只提供了
List<String>类型，进行传参； - 目标Flutter页面内的widget，默认参数会全部失效；
- Flutter的Widget默认参数，是由主文件内的
MaterialApp组件提供的，一个Flutter应用，一般只会使用一个MaterialApp，它代表返回一个App，如果将目标Flutter页面套上MaterialApp，可以解决这个默认参数问题，但会引发 路由问题； - 不过也有适用场景：让每个Flutter页面完全独立，之间没有任何交互，比如跳转、数据共享等等，这样路由就不需要了，让每个Flutter页面都使用
MaterialApp，当作App和原生交互；
综上所述，大家将这种方式当作 扩展知识 就好了。
Android 代码
class MainActivity : AppCompatActivity(), View.OnClickListener {
... ...
override fun onCreate(savedInstanceState: android.os.Bundle?) {
super.onCreate(savedInstanceState)
... ...
val flutterEngine = FlutterEngine(this)
// 定义参数
val dartEntrypointArgs = mutableListOf<String>()
dartEntrypointArgs.add("张三")
// 这种方式传参数，会导致这个Flutter页面中的Widget默认参数，全部失效，
// 这种只有 Dart主入口文件，比如main.dart的 main函数才能接收到参数
// void main(List<String args>) {}
// flutterEngine.dartExecutor.executeDartEntrypoint(
// DartExecutor.DartEntrypoint.createDefault(),
// dartEntrypointArgs
// )
// 这种可以指定页面接收，但需要在主入口文件里先声明
// void showPersonal(List<String> args) {}
flutterEngine.dartExecutor.executeDartEntrypoint(
DartExecutor.DartEntrypoint(
FlutterInjector.instance().flutterLoader().findAppBundlePath(),
"showPersonal"), // 找到目标Flutter页面提供的 暴露函数
dartEntrypointArgs)
FlutterEngineCache.getInstance().put("personal_engine", flutterEngine)
}
override fun onClick(v: View?) {
... ...
val map: MutableMap<String, String> = mutableMapOf<String, String>()
map["name"] = "张三"
startActivity(
FlutterActivity
.withCachedEngine("personal_engine") // 获取缓存好的引擎
.backgroundMode(FlutterActivityLaunchConfigs.BackgroundMode.transparent) // 背景改为透明，不然切换页面时，会闪烁黑色
.build(this))
}
}
Flutter代码
main.dart（主文件）
import 'package:flutter/material.dart';
import 'package:flutter_nav_android/personal.dart';
void main(List<String> args) {
debugPrint('args：$args');
runApp(const MyApp());
}
/// 注解说明文档：https://mrale.ph/dartvm/compiler/aot/entry_point_pragma.html
/// 注解：表明它可以在 AOT 模式下直接从本机或 VM 代码解析、分配或调用
@pragma("vm:entry-point")
void showPersonal(List<String> args) { // 在主文件入口暴露出来
debugPrint('args：$args');
runApp(Personal(title: args.first));
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
colorScheme: ColorScheme.fromSeed(
seedColor: Colors.deepPurple,
),
useMaterial3: true,
),
);
}
}
personal.dart（目标页面）
import 'package:flutter/material.dart';
class Personal extends StatefulWidget {
final String? title;
const Personal({super.key,this.title});
@override
State<Personal> createState() => _PersonalState();
}
class _PersonalState extends State<Personal> {
/// 在这个页面中，使用的Widget 默认参数全部失效，外层套上 Material组件 也无效
@override
Widget build(BuildContext context) {
return Container(
color: Colors.white,
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
alignment: Alignment.center,
child: Directionality(
textDirection: TextDirection.ltr,
child: Text(
widget.title ?? '',
style: const TextStyle(
color: Colors.lightBlue,
fontSize: 30,
),
)),
);
}
}
FlutterEngineGroup
-
如果你接受以上缺点，可以使用
FlutterEngineGroup，这个东西就是换成了单例写法，我们自己写单例，需要处理一个问题，比如这个需求：同时获取两个Flutter引擎，这里就要通过判空新建一个Flutter引擎； -
而
FlutterEngineGroup已经处理了这个问题，自首个Flutter引擎起，后面多出的Flutter引擎，都是其子类，如果只剩下最后一个，那么这个Flutter引擎将和首个Flutter引擎性能特征相同； -
FlutterEngineGroup官方文档：flutter.cn/docs/develo…
-
从我个人体验上来说，不使用单例，性能也足够了，如果有很多混合的Flutter页面，那当我没说😐。
-
我没找到创建子类Flutter引擎的相关代码，是从注解中发现的
Debug 和 Release
我用真机做测试，发现在Debug模式下，第一次从 Android 跳转 Flutter 会出现黑屏现象，但 打完包 或在 Release模式 就看不出来了；
我们默认的运行模式就是 Debug模式，可以通过 修改IDE运行命令 --release，切换为 Release模式；
