我正在学习如何创建Flutter插件，所以我决定创建一个蓝牙插件，我知道有很多可用的，但在这里学习的目的。

我面临的错误如下

E/MethodChannel#flutterpluginbluetooth(22072): Failed to handle method call
E/MethodChannel#flutterpluginbluetooth(22072): java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Intent android.content.Context.registerReceiver(android.content.BroadcastReceiver, android.content.IntentFilter)' on a null object reference

我不是一个Java的开发者，我确信这不是一个漂亮的方法，所以现在就忽略这个方法。

这是我的OnMethodCall

  @Override
  public void onMethodCall(@NonNull MethodCall call, @NonNull Result result) {
    if (call.method.equals("getPlatformVersion")) {
      result.success("Android " + android.os.Build.VERSION.RELEASE);
    } else if (call.method.equals("getMessage")) {
      BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
      result.success("hello");


      System.out.println("DEBUG - Starting discovery");
      bluetoothAdapter.startDiscovery();
      final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
          System.out.println("DEBUG - inside onReceive");
          String action = intent.getAction();
          System.out.println("DEBUG - Action is: " + action);
          //Finding devices
          if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            System.out.println("Device Name: "  + device.getName());
          } else {
            System.out.println("DEBUG: Action did not match"  + BluetoothDevice.ACTION_FOUND);
          }
        }

      };
      IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
      System.out.println("DEBUG - About to registerReceiver");
      context.registerReceiver(mReceiver, filter);


    }
    else {
      result.notImplemented();
    }

  }

我的问题是为什么在这个上下文上出现错误。registerreceiver（mReceiver，filter）；

我也在阅读android文档，它在没有任何上下文的情况下调用RegisterReceiver，如果我尝试这种方法，我也会得到一个错误，如下所示，这在编译期间会发生。

error: cannot find symbol registerReceiver(mReceiver, filter);

这是OnAttachedToEngine

  @Override
  public void onAttachedToEngine(@NonNull FlutterPluginBinding flutterPluginBinding) {
    channel = new MethodChannel(flutterPluginBinding.getFlutterEngine().getDartExecutor(), "flutterpluginbluetooth");
    channel.setMethodCallHandler(this);
  }

关于上下文

我正在导入它

import android.content.Context;

在类内部，我声明了一个context变量

private Context context;

我真的很感激你帮我。