Flutter hybrid development BasicMessageChannel communicates with native android

• Three ways to mix communication
• Analysis of the
• The Android end
• The Flutter end

Said a thousand times I love you finally also arrived but a break up bar. This is love. Once how the imprint is engraved on my heart. once loved how dead and alive, finally still will be light, but everyone’s time transition is not the same.

Three ways to mix communication

• BasicMessageChannel: two-way communication with a return value and continuous communication
• MethodChannel: Two-way communication, with return values, one-time communication
• EventChannel: one-way communication. No return value is returned. The communication continues

Let’s take a look at today’s results:

As usual, first analyze the function:

Analysis of the

The Android end

The first step; Create BasicMessageChannel ()

(Don’t be so quick to copy, I’ll write tools below! Very good)

 private final BasicMessageChannel<String> messageChannel;
 
messageChannel = new BasicMessageChannel(messenger, "BasicMessageChannelPlugin", StringCodec.INSTANCE);
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BasicMessageChannel parameters:

• BinaryMessenger messenger – a tool for sending and receiving messages;
• String name– The name and unique identifier of a Channel corresponding to the Flutter end (andRendering (1.1)Corresponding)
• MessageCodec
  
  codec – the MessageCodec, which has the following table types
  

Rendering (1.1)

Step 2: Set up the message handler to process messages from Dart

 // Set up the message handler to process messages from Dart
        messageChannel.setMessageHandler(new BasicMessageChannel.MessageHandler<String>() {
            @Override
            public void onMessage(@Nullable String message, @NonNull BasicMessageChannel.Reply<String> reply) {
            // You can reply via reply
			 reply.reply("BasicMessageChannel received:"+ message); }});Copy the code

OnMessage parameters:

• Parameter one,String message, is the received parameter
• Argument 2: BasicMessageChannel. Reply < String > Reply, when received Flutter news, can Reply. Reply immediately () returns a data (andRendering (1.2)Corresponding)

Rendering (1.2)

Step three, send a message

 messageChannel.send(message, callback);
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Parameter Description:

• Parameter one: The message content to be sent (andRendering (1.3)Corresponding)
• Parameter 2: Feedback from Dart (I don’t think it’s going to help… )

Rendering (1.3)

BasicMessageChannel

import android.app.Activity;
import android.widget.Toast;

import io.flutter.Log;
import io.flutter.plugin.common.BasicMessageChannel;
import io.flutter.plugin.common.BinaryMessenger;
import io.flutter.plugin.common.StringCodec;

/ * * SZJ 2020/11/26 CSDN blog: https://blog.csdn.net/weixin_44819566/ WeChat public number: getting rich * / code
public class BasicMessageChannelPlugin implements BasicMessageChannel.MessageHandler<String> {
    private final Activity activity;
    private final BasicMessageChannel<String> messageChannel;

    public static BasicMessageChannelPlugin registerWith(BinaryMessenger messenger, Activity activity) {
        return new BasicMessageChannelPlugin(messenger, activity);
    }

    private BasicMessageChannelPlugin(BinaryMessenger messenger, Activity activity) {
        this.activity = activity;
        this.messageChannel = new BasicMessageChannel(messenger, "BasicMessageChannelPlugin", StringCodec.INSTANCE);
        // Set up the message handler to process messages from Dart
        messageChannel.setMessageHandler(this);

    }

    @Override// Process the Dart message
    public void onMessage(String s, BasicMessageChannel.Reply<String> reply) {
        reply.reply("BasicMessageChannel received:" + s);// You can reply via reply
        if (activity instanceofIShowMessage) { ((IShowMessage) activity).onShowMessage(s); Toast.makeText(activity, s, Toast.LENGTH_SHORT).show(); }}/** * Send a message to Dart and accept Dart's feedback **@paramMessage Indicates the content of the message to be sent to Dart@paramCallback from Dart feedback */
   public void send(String message, BasicMessageChannel.Reply<String> callback) { messageChannel.send(message, callback); }}Copy the code

The code is very simple, if you don’t understand, please leave a message in the comment section

Step 4: Write an interface that defines the data to fetch and send:

public interface IShowMessage {
    / * * * *@param message Flutter -> Android
     */
    void onShowMessage(String message);

    / * * * *@param message Android --> flutter
     */
    void sendMessage(String message);
}
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Step 5: Create click events to jump to the page and upload values

 EditText edit = findViewById(R.id.edit);

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FlutterAppActivity.start(BasicMsgChannelActivity.this,edit.getText().toString(),1); }});Copy the code

For those who are confused, please refer to the previous chapter :Flutter hybrid development transferring initialization data to Android(4.2)

Java code (FlutterAppActivity class);

public class FlutterAppActivity extends FlutterActivity  implements IShowMessage{
    private BasicMessageChannelPlugin basicMessageChannelPlugin;

    public final static String INIT_PARAMS = "initParams";
    /** * 0 passes initialization data to Flutter * 1 passes data to Flutter using BasicMsgChannel */
    private static int mtype ;

    public static void start(Context context, String initParams, int type) {
        mtype = type;
        Intent intent = new Intent(context, FlutterAppActivity.class);
        intent.putExtra(INIT_PARAMS, initParams);
        context.startActivity(intent);
    }

    String mInitParam;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i("szjonCreate",mtype+"");
        if (mtype == 0) {
           // Pass initialization data to Flutter
            mInitParam = getIntent().getStringExtra(INIT_PARAMS);

        }else if(mtype == 1) {// Use BasicMsgChannel to pass data
            basicMessageChannelPlugin = BasicMessageChannelPlugin.registerWith(getFlutterEngine().getDartExecutor(), this); }}@Override
    protected void onStart(a) {
        super.onStart();
        if (mtype == 1) {
            String initParam = getIntent().getStringExtra(INIT_PARAMS);
            this.sendMessage(initParam); }}/** * Pass initialization parameters to Flutter *@return* /
    @NonNull
    @Override
    public String getInitialRoute(a) {
        return mInitParam == null ? super.getInitialRoute() : mInitParam;
    }

// Use the Flutter engine pre-initialized in MyApplication to increase the Flutter page opening speed.
// Note: in this mode, getInitialRoute will not be called so initialization parameters cannot be set
// @Override
// public String getCachedEngineId() {
// return App.ENG_INED;
/ /}


    @Override
    public void onShowMessage(String message) {
        Log.i("szjonShowMessage",message);
    }

    @Override
    public void sendMessage(String message) {
        Log.i("szjsendMessage",message);
        if (basicMessageChannelPlugin == null) {
            return;
        }
        basicMessageChannelPlugin.send(getIntent().getStringExtra(INIT_PARAMS),this::onShowMessage); }}Copy the code

My sendMessage() method is written in onStart()

 @Override
    protected void onStart(a) {
        super.onStart();
        if (mtype == 1) {
            String initParam = getIntent().getStringExtra(INIT_PARAMS);
            this.sendMessage(initParam); }}Copy the code

The mType in the code is a variable used to distinguish the Flutter from the variable used in the previous chapter :Flutter hybrid development to pass initialization data to Android(4.2)!

The initialization of the Android terminal is complete, in a simple analysis:

• The BasicMsgChannelActivity page has a button and a text box. Clicking the button invoks the method to jump to the FlutterAppActivity page FlutterAppActivity is a Flutter page because FlutterAppActivity inherits from FlutterActivity. In the onCreate method of FlutterAppActivity then use tools BasicMessageChannelPlugin, this utility class is initialized BasicMessageChannel (). The send method is called in the onStart() method to pass the dart value.

The Flutter end

BasicMessageChannel()
BasicMessageChannel<String> _basicMessageChannel =
      BasicMessageChannel('BasicMessageChannelPlugin', StringCodec());
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  String showMessage;

  @override
  void initState(a) {
    // Use BasicMessageChannel to receive messages from Native and reply to Native
    _basicMessageChannel
        .setMessageHandler((String message) => Future<String>(() {
              setState(() {
                showMessage = 'BasicMessageChannel:' + message;
              });
              return "BasicMessageChannel receives message from Android:" + message;
            }));
    super.initState();
  }
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 RaisedButton(
      onPressed: () {
      _basicMessageChannel.send("I am data of Flutter!!");
      },
      child: Text("Send a message to native"),
      ),
     TextField(
        onChanged: _onTextChange,
        decoration: InputDecoration(
        hintText: "Please enter a message to native send",
          ),
    ),
    Text(BasicMessageChannel receives android native data as: ${showMessage}),
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  void _onTextChange(value) async {
    String response;
    /** * on Android the equivalent is reply.reply() */
    response = await _basicMessageChannel.send(value);
    setState(() {
      showMessage =  response ;
    });
  }
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BasicMessageChannel messageChannel = BasicMessageChannel(parameter 1, parameter 2, parameter 3); messageChannel.send(message, callback);Copy the code

 @Override// Process the Dart message
  messageChannel.setMessageHandler(new BasicMessageChannel.MessageHandler<String>() {
            @Override
            public void onMessage(@Nullable String message, @NonNull BasicMessageChannel.Reply<String> reply) {
             reply.reply("I'm android code reply:" + s);// You can reply via replyToast.makeText(activity, message, Toast.LENGTH_SHORT).show(); }});Copy the code

// Initialize BasicMessageChannel
 BasicMessageChannel<String> _basicMessageChannel =
      BasicMessageChannel('BasicMessageChannelPlugin', StringCodec());

_basicMessageChannel
        .setMessageHandler((String message) => Future<String>(() {
              setState(() {
                //Android --> Flutter
                showMessage = 'BasicMessageChannel:' + message;
              });
              return "BasicMessageChannel receives message from Android:" + message;
            }));
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String response = _basicMessageChannel.send(value);
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  @Override
        public String getCachedEngineId(a) {
            return App.ENG_INED;
        }
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