原有Android项目中体验Flutter

1. 手动整合Flutter到Android项目

1. Flutter支持x86_64,armeabi-v7a,arm64-v8a

   android {
     //...
     defaultConfig {
       ndk {
         // Filter for architectures supported by Flutter.
         // 如果使用Android模拟器测试请添加'x86'平台
         abiFilters 'armeabi-v7a', 'arm64-v8a', 'x86_64'
       }
     }
   }

2. java8支持

   android {
     //...
     compileOptions {
       sourceCompatibility 1.8
       targetCompatibility 1.8
     }
   }

3. 在现有Android项目的同级目录执行创建Flutter项目的命令flutter create -t module --org cn.it200 my_flutter

4. 配置settings.gradle

   // Include the host app project.
   include ':app'                                    // assumed existing content
   setBinding(new Binding([gradle: this]))                                // new
   evaluate(new File(                                                     // new
     settingsDir.parentFile,                                              // new
     'my_flutter/.android/include_flutter.groovy'                         // new
   ))                                                                     // new
    

5. 为Android项目依赖Flutter模块

   dependencies {
     implementation project(':flutter')
   }

6. 在Java代码中可以正常导入Flutter相关包,编译项目无异常

2. 在Activity中启动Flutter页面

1. 注册FlutterActivity到清单文件

   <activity
     android:name="io.flutter.embedding.android.FlutterActivity"
     android:theme="@style/LaunchTheme"
     android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
     android:hardwareAccelerated="true"
     android:windowSoftInputMode="adjustResize"
   />

2. 启动FlutterActivity

   //打开首页
   startActivity(
     FlutterActivity.createDefaultIntent(currentActivity)
   );
    
   //根据路由打开指定页面
   startActivity(
           FlutterActivity
                   .withNewEngine()
                   .initialRoute("/other")
                   .build(MainActivity.this)
   );

3. 引入FlutterEngine加快启动

   //初始化FlutterEngine并进行缓存
   FlutterEngine flutterEngine = new FlutterEngine(this);
   flutterEngine.getDartExecutor().executeDartEntrypoint(
           DartExecutor.DartEntrypoint.createDefault()
   );
   FlutterEngineCache.getInstance().put("my_engine_id", flutterEngine);

   //改变启动方式
   startActivity(
       FlutterActivity.withCachedEngine("my_engine_id").build(MainActivity.this);
   );

4. 引入FlutterEngine时初始化路由

   在创建flutterEngine对象后插入如下内容:
   flutterEngine.getNavigationChannel().setInitialRoute("/other");

3. 在Activity中加载Flutter页面

1. 布局文件添加代码

   <FrameLayout
       android:layout_weight="1"
       android:id="@+id/fragment_container"
       android:layout_width="match_parent"
       android:layout_height="match_parent" />

2. 在Activity中添加代码

   // Define a tag String to represent the FlutterFragment within this
   // Activity's FragmentManager. This value can be whatever you'd like.
   private static final String TAG_FLUTTER_FRAGMENT = "flutter_fragment";
    
   // Declare a local variable to reference the FlutterFragment so that you
   // can forward calls to it later.
   private FlutterFragment flutterFragment;

   // Get a reference to the Activity's FragmentManager to add a new
       // FlutterFragment, or find an existing one.
       FragmentManager fragmentManager = getSupportFragmentManager();
    
       // Attempt to find an existing FlutterFragment,
       // in case this is not the first time that onCreate() was run.
       flutterFragment = (FlutterFragment) fragmentManager
               .findFragmentByTag(TAG_FLUTTER_FRAGMENT);
    
       // Create and attach a FlutterFragment if one does not exist.
       if (flutterFragment == null) {
           flutterFragment = FlutterFragment.createDefault();
    
           fragmentManager
                   .beginTransaction()
                   .add(
                           R.id.fragment_container,
                           flutterFragment,
                           TAG_FLUTTER_FRAGMENT
                   )
                   .commit();
       }
    
    

   @Override
   public void onPostResume() {
       super.onPostResume();
       flutterFragment.onPostResume();
   }
    
   @Override
   protected void onNewIntent(@NonNull Intent intent) {
       super.onNewIntent(intent);
       flutterFragment.onNewIntent(intent);
   }
    
   @Override
   public void onBackPressed() {
       flutterFragment.onBackPressed();
   }
    
   @Override
   public void onRequestPermissionsResult(
           int requestCode,
           @NonNull String[] permissions,
           @NonNull int[] grantResults
   ) {
       flutterFragment.onRequestPermissionsResult(
               requestCode,
               permissions,
               grantResults
       );
   }
    
   @Override
   public void onUserLeaveHint() {
       flutterFragment.onUserLeaveHint();
   }
    
   @Override
   public void onTrimMemory(int level) {
       super.onTrimMemory(level);
       flutterFragment.onTrimMemory(level);
   }

3. 使用FlutterFragment.withCachedEngine("my_engine_id").build();加速启动

   if (flutterFragment == null) {
       flutterFragment = FlutterFragment.withCachedEngine("my_engine_id").build();
       fragmentManager
               .beginTransaction()
               .add(
                       R.id.fragment_container,
                       flutterFragment,
                       TAG_FLUTTER_FRAGMENT
               )
               .commit();
   }