目录

Launching a Jetpack Compose activity from your Flutter application

目录

Native Android activities allow you to launch fullscreen UIs that are entirely run by and on the Android platform. You will only write Kotlin code in those views (though they might pass messages to and receive messages from your Dart code) and you will have access to the full breadth of native Android functionality.

Adding this functionality requires making several changes to your Flutter app and its internal, generated Android app. On the Flutter side, you will need to create a new platform method channel and call its invokeMethod method. On the Android side, you will need to register a matching native MethodChannel to receive the signal from Dart and then launch a new activity. Recall that all Flutter apps (when running on Android) exist within an Android activity that is completely consumed by the Flutter app. Thus, as you will see in the code sample, the job of the native MethodChannel callback is to launch a second activity.

Not all Android activities use Jetpack Compose, but this tutorial assumes you want to use Compose.

On the Dart side

#

On the Dart side, create a method channel and invoke it from a specific user interaction, like tapping a button.

dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

// SECTION 1: START COPYING HERE
const platformMethodChannel = MethodChannel(
  // Note: You can change this string value, but it must match
  // the `CHANNEL` attribute in the next step.
  'com.example.flutter_android_activity',
);
// SECTION 1: END COPYING HERE

void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  // SECTION 2: START COPYING HERE
  void _launchAndroidActivity() {
    platformMethodChannel.invokeMethod(
      // Note: You can change this value, but it must match
      // the `call.method` value in the next section.
      'launchActivity',

      // Note: You can pass any primitive data types you like.
      // To pass complex types, use package:pigeon to generate
      // matching Dart and Kotlin classes that share serialization logic.
      {'message': 'Hello from Flutter'},
    );
  }
  // SECTION 2: END COPYING HERE

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: const Center(
          child: Text('Hello World!'),
        ),
        floatingActionButton: FloatingActionButton(
          // SECTION 3: Call `_launchAndroidActivity` somewhere.
          onPressed: _launchAndroidActivity,
          // SECTION 3: End

          tooltip: 'Launch Android activity',
          child: const Icon(Icons.launch),
        ),
      ),
    );
  }
}

There are 3 important values that must match across your Dart and Kotlin code:

  1. The channel name (in this sample, the value is "com.example.flutter_android_activity").
  2. The method name (in this sample, the value is "launchActivity").
  3. The structure of the data which Dart passes and the structure of the data which Kotlin expects to receive. In this case, the data is a map with a single "message" key.

On the Android side

#

You must make changes to 4 files in the generated Android app to ready it for launching fresh Compose activities.

The first file requiring modifications is android/app/build.gradle.

  1. Add the following to the existing android block:

    android/app/build.gradle
    groovy
    android {
  // Begin adding here
  buildFeatures {
    compose true
  }
  composeOptions {
    // https://developer.android.com/jetpack/androidx/releases/compose-kotlin
    kotlinCompilerExtensionVersion = "1.4.8"
  }
  // End adding here
}

    Visit the developer.android.com link in the code snippet and adjust kotlinCompilerExtensionVersion, as necessary. You should only need to do this if you receive errors during flutter run and those errors tell you which versions are installed on your machine.

  2. Next, add the following block at the bottom of the file, at the root level:

    android/app/build.gradle
    groovy
    dependencies {
    implementation("androidx.core:core-ktx:1.10.1")
    implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.6.1")
    implementation("androidx.activity:activity-compose")
    implementation(platform("androidx.compose:compose-bom:2024.06.00"))
    implementation("androidx.compose.ui:ui")
    implementation("androidx.compose.ui:ui-graphics")
    implementation("androidx.compose.ui:ui-tooling-preview")
    implementation("androidx.compose.material:material")
    implementation("androidx.compose.material3:material3")
    testImplementation("junit:junit:4.13.2")
    androidTestImplementation("androidx.test.ext:junit:1.1.5")
    androidTestImplementation("androidx.test.espresso:espresso-core:3.5.1")
    androidTestImplementation(platform("androidx.compose:compose-bom:2023.08.00"))
    androidTestImplementation("androidx.compose.ui:ui-test-junit4")
    debugImplementation("androidx.compose.ui:ui-tooling")
    debugImplementation("androidx.compose.ui:ui-test-manifest")
}

    The second file requiring modifications is android/build.gradle.

  3. Add the following buildscript block at the top of the file:

    android/build.gradle
    groovy
    buildscript {
    dependencies {
        // Replace with the latest version.
        classpath 'com.android.tools.build:gradle:8.1.1'
    }
    repositories {
        google()
        mavenCentral()
    }
}

    The third file requiring modifications is android/app/src/main/AndroidManifest.xml.

  4. In the root application block, add the following <activity> declaration:

    android/app/src/main/AndroidManifest.xml
    xml
    <manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <application
        android:label="flutter_android_activity"
        android:name="${applicationName}"
        android:icon="@mipmap/ic_launcher">

       // START COPYING HERE
        <activity android:name=".SecondActivity" android:exported="true" android:theme="@style/LaunchTheme"></activity>
       // END COPYING HERE

       <activity android:name=".MainActivity" …></activity>
      …
</manifest>

    The fourth and final code requiring modifications is android/app/src/main/kotlin/com/example/flutter_android_activity/MainActivity.kt. Here you'll write Kotlin code for your desired Android functionality.

  5. Add the necessary imports at the top of the file:

    MainActivity.kt
    kotlin
    package com.example.flutter_android_activity

import android.content.Intent
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.Button
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.ui.Modifier
import androidx.core.app.ActivityCompat
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugins.GeneratedPluginRegistrant

  6. Modify the generated MainActivity class by adding a CHANNEL field and a configureFlutterEngine method:

    MainActivity.kt
    kotlin
    class MainActivity: FlutterActivity() {
    // This value must match the `MethodChannel` name in your Dart code.
    private val CHANNEL = "com.example.flutter_android_activity"

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        GeneratedPluginRegistrant.registerWith(flutterEngine)

        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler {
            call: MethodCall, result: MethodChannel.Result ->
                when (call.method) {
                    // Note: This must match the first parameter passed to
                    // `platformMethodChannel.invokeMethod` in your Dart code.
                    "launchActivity" -> {
                        try {
                            // Takes an object, in this case a String.
                            val message = call.arguments
                            val intent = Intent(this@MainActivity, SecondActivity::class.java)
                            intent.putExtra("message", message.toString())
                            startActivity(intent)
                        } catch (e: Exception){}
                            result.success(true)
                        }
                        else -> {}
                }
        }
    }
}

  7. Add a second Activity to the bottom of the file, which you referenced in the previous changes to AndroidManifest.xml:

    MainActivity.kt
    kotlin
    class SecondActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
                Column {
                    Text(text = "Second Activity")
                    // Note: This must match the shape of the data passed from your Dart code.
                    Text("" + getIntent()?.getExtras()?.getString("message"))
                    Button(onClick = {  finish() }) {
                        Text("Exit")
                    }
                }
            }
        }
    }
}

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