java - 如何从另一个类调用对象

在我的Android项目中，有一个MainActivity.java

MainActivity extends FragmentActivity{

    onCreate(Bundle savedInstanceState){

       BluetoothManager bluetoothManager =
                (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        mBluetoothAdapter = bluetoothManager.getAdapter();

    }
  }

如何在下面的类中使用mBluetoothAdapter对象

public class AvailableDevices extends ListFragment {

     // How to call mBluetoothAdapter here
  }

谢谢

最佳答案

将其作为参数传递给类的构造函数

public class AvailableDevices extends ListFragment {
   private BluetoothAdapter bluetoothAdapter;
   public AvailableDevices(BluetoothAdapter bluetoothAdapter) {
       this.bluetoothAdapter = bluetoothAdapter;
   }
}

或将其声明为静态公共数据成员

public class MainActivity extends FragmentActivity{

    public static BluetoothAdapter mBluetoothAdapter;

    ..
 }

然后在另一个类中使用MainActivity.mBluetoothAdapter

或将AvailableDevices用作内部类，然后将适配器声明为数据成员：

public class MainActivity extends FragmentActivity{

    private BluetoothAdapter mBluetoothAdapter;
    ..
    class AvailableDevices extends ListFragment {
         //can use mBluetoothAdapter
    }
}