Flutter系统交互插件shell的使用

在Flutter中，platform_channels 是实现与原生平台（Android 和 iOS）交互的一种常见方式。shell 通常不是直接用于描述这种交互的术语，但如果你指的是通过某种方式（例如，执行原生命令或脚本）与系统交互，你可以使用 Method Channels 或 Platform Channels 来实现。

以下是一个使用 Method Channel 在 Flutter 和原生平台（Android 和 iOS）之间通信的示例。这个示例展示了如何从 Flutter 调用原生平台的方法，并接收结果。

1. 设置 Flutter 项目

首先，确保你已经设置了一个 Flutter 项目。如果还没有，可以通过以下命令创建一个新的 Flutter 项目：

flutter create my_flutter_app
cd my_flutter_app

2. 在 Flutter 中定义 Method Channel

在 lib 目录下，打开 main.dart 文件，并定义一个 Method Channel：

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  static const platform = const MethodChannel('com.example.my_flutter_app/channel');

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Platform Channel Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text('Press the button to call the native platform code.'),
              ElevatedButton(
                onPressed: _invokeNativeFunction,
                child: Text('Invoke Native Function'),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Future<void> _invokeNativeFunction() async {
    try {
      final String result = await platform.invokeMethod('runShellCommand', 'echo Hello from Flutter');
      print(result); // This will print the result from the native code.
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Result: $result')));
    } on PlatformException catch (e) {
      print("Failed to invoke: '${e.message}'.");
    }
  }
}

3. 在 Android 中实现 Method Channel

在 android/app/src/main/kotlin/.../MainActivity.kt（或 MainActivity.java，如果你使用的是 Java）中，添加对 Method Channel 的处理：

Kotlin:

package com.example.my_flutter_app

import android.os.Bundle
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel

class MainActivity: FlutterActivity() {
    private val CHANNEL = "com.example.my_flutter_app/channel"

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
            if (call.method == "runShellCommand") {
                val command = call.argument<String>("command") ?: ""
                // Here you would run the shell command. For simplicity, we'll just return the command.
                result.success("Command executed: $command")
            } else {
                result.notImplemented()
            }
        }
    }
}

Java:

package com.example.my_flutter_app;

import android.os.Bundle;
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugin.common.MethodChannel;

public class MainActivity extends FlutterActivity {
    private static final String CHANNEL = "com.example.my_flutter_app/channel";

    @Override
    public void configureFlutterEngine(FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);
        new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
                .setMethodCallHandler(
                        (call, result) -> {
                            if (call.method.equals("runShellCommand")) {
                                String command = call.argument("command");
                                if (command == null) {
                                    command = "";
                                }
                                // Here you would run the shell command. For simplicity, we'll just return the command.
                                result.success("Command executed: " + command);
                            } else {
                                result.notImplemented();
                            }
                        }
                );
    }
}

4. 在 iOS 中实现 Method Channel

在 ios/Runner/AppDelegate.swift 中，添加对 Method Channel 的处理：

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    GeneratedPluginRegistrant.register(with: self)
    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    let channel = FlutterMethodChannel(name: "com.example.my_flutter_app/channel", binaryMessenger: controller)
    channel.setMethodCallHandler({
      (call: FlutterMethodCall, result: @escaping FlutterResult) in
      if call.method == "runShellCommand" {
        if let command = call.arguments as? String {
          // Here you would run the shell command. For simplicity, we'll just return the command.
          result("Command executed: \(command)")
        } else {
          result(FlutterError(code: "INVALID_ARGUMENT", message: "Expected a string argument for 'command'.", details: nil))
        }
      } else {
        result(FlutterMethodNotImplementedError(methodName: call.method))
      }
    })
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

总结

以上代码展示了如何在 Flutter 中通过 Method Channel 与原生平台（Android 和 iOS）进行交互。在这个例子中，Flutter 调用了一个名为 runShellCommand 的原生方法，并传递了一个简单的字符串参数。原生平台接收到调用后，执行了一些操作（在这个例子中是简单地返回了传递的命令），并将结果返回给 Flutter。

请注意，实际运行 shell 命令（特别是在 iOS 上）需要额外的权限和配置，并且出于安全考虑，通常不建议在移动应用中直接运行不受信任的 shell 命令。