Flutter How to Start Android Activity from Flutter View

Flutter and Dart is an excellent combination for creating the UI, but for accessing the platform-specific service we need to open platform-specific activity. So lets in this article we will explore how to start an android activity and access the service from Flutter View.

Create a Project for this Android Activity Flutter View Demo

Create a Project

1. From File menu select the New Flutter Project
2. Enter the project name
3. Select the AndroidX support and click on next
   
4. After the above, we step click on Finish
   We will have the following project structure created.

Create the Second Activity in Android

Just go to the android folder and open it in separate windows. We will have the following project structure.

Create the Activity

Just right-click
on the Kotlin folder and create a blank activity from the menu. If you create the activity then you may be required to upgrade the Gradle and do some import. So Just click on update and wait for the project sync completed.

Update the project build config build.gradle file

Due to some problem, it may happen that we have some error in the build.gradle file.

   ext.kotlin_version = '1.3.41' '1.2.71'

Now, remove the '1.2.71' from the ext.kolin_version and start the sync again. If all these issues resolved then the sync will be completed successfully;

Go to ou newly created activity and add the dependency by clicking on Alt+Enter key. Or alternatively, you can add the appcompat dependency directly into your build.gradle files like below.

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
    implementation 'androidx.appcompat:appcompat:1.1.0'
}

Create the Theme for our activity

Now, we need to create an AppCompat Theme for our activity. So go to res->value->style.xml files and add the theme.

<style name="MyTheme" parent="@style/Theme.AppCompat.Light.DarkActionBar">
        <item name="colorPrimary">#7B1FA2</item>
        <item name="colorPrimaryDark">#4A148C</item>
        <item name="colorAccent">@android:color/holo_blue_light</item>
        <item name="android:windowBackground">@drawable/launch_background</item>
    </style>

Set the theme to Android Activity

Open the file AndroidMenifest.xml file and set the theme like below.

 <activity android:name=".KotlinActivity"
            android:theme="@style/MyTheme">  
 </activity>

Create the method to start the second Activity

Go to the main activity again and add the required method as like below.

package com.nplix.android_activity_demo

import android.content.Intent
import android.os.Bundle

import io.flutter.app.FlutterActivity
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugins.GeneratedPluginRegistrant

class MainActivity: FlutterActivity() {
  private val CHANNEL = "com.startActivity/testChannel"
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    GeneratedPluginRegistrant.registerWith(this)

    MethodChannel(flutterView,CHANNEL).setMethodCallHandler{ call,result ->
      if(call.method.equals("StartSecondActivity")){
        val intent=Intent(this,KotlinActivity::class.java)
        startActivity(intent)
        result.success("ActivityStarted")
      }
      else{
        result.notImplemented()
      }
    }
  }
}

So what we are doing here?

• First of all, we are defining a channel using the line private val CHANNEL = "com.startActivity/testChannel" we will use this to create the platform from the flutter view.
• Create a method handler in the line

MethodChannel(flutterView,CHANNEL).setMethodCallHandler{ call,result ->
      if(call.method.equals("StartSecondActivity")){
        val intent=Intent(this,KotlinActivity::class.java)
        startActivity(intent)
        result.success("ActivityStarted")
      }
      else{
        result.notImplemented()
      }
    }

• Third, we are comparing the called method using the if condition and starting the activity.
• In the case method not match then we will throw the method not implemented the method using the below line.

 else{
        result.notImplemented()
      }

Call the Android Method from Flutter View

Now time call the android method to start the activity from Flutter View. So let's create a button to start the activity.

 RaisedButton(
              color: Colors.blue,
              onPressed: (){
                _startActivity();
              },
              child: Padding(
                padding: const EdgeInsets.all(16.0),
                child: Text(
                  'Start Android Activity',
                  style: TextStyle(color: Colors.white,fontSize: 24),
                ),
              ),
            ),

Create the _startActivity()

Future<void> _startActivity() async {
    try {
      final String result = await platform.invokeMethod('StartSecondActivity');
      debugPrint('Result: $result ');
    } on PlatformException catch (e) {
      debugPrint("Error: '${e.message}'.");
    }
  }

So before that, we need to create the platform as well using the below code.

 static const platform = const MethodChannel('com.startActivity/testChannel');

Run and Test the App

Let's test the application. If you run it it will be like below.

Wrapping Up

This is just a very basic demo of how to call the platform-specific method, service or function from flutter view. In short, we can say that using this you can perform anything that you can do in normal android application written in Kotlin or Java.

• Check out getting started with flutter.
• Check Flutter.dev