扫描蓝牙设备传递至Adapter遇空指针问题及解决方法

我尝试把ScanActivity中发现的Bluetooth Device传递到其他类实现后续功能，但用构造方法传递时出现Bluetooth Device空指针异常。目前ScanActivity通过BroadcastReceiver发现蓝牙设备，将设备名称、地址存入BluetoothDeviceModel后传给RecyclerView的Bluetooth_adapter设置到ViewHolder中，现在需要把完整的BluetoothDevice对象传递到Adapter里。

步骤1：修改BluetoothDeviceModel，添加BluetoothDevice字段 #

在原有模型中新增字段存储完整的BluetoothDevice对象，确保Adapter能直接获取到设备实例：

public class BluetoothDeviceModel {
    private String name;
    private String address;
    private int imageResource;
    private BluetoothDevice device; // 新增存储完整设备的字段

    // 新增带BluetoothDevice的构造方法
    public BluetoothDeviceModel(String name, String address, int imageResource, BluetoothDevice device) {
        this.name = name;
        this.address = address;
        this.imageResource = imageResource;
        this.device = device;
    }

    // 新增设备对象的getter方法
    public BluetoothDevice getDevice() {
        return device;
    }

    // 保留原有getter方法
    public String getName() { return name; }
    public String getAddress() { return address; }
    public int getImageresouce() { return imageResource; }
}

步骤2：优化ScanActivity的设备发现逻辑 #

在BroadcastReceiver中传入完整的BluetoothDevice到模型，同时避免重复创建Adapter（原代码每次发现设备都new Adapter会引发性能问题）：

// 在ScanActivity的BroadcastReceiver的onReceive方法中
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
    BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
    // ... 权限检查和设备信息获取逻辑保持不变 ...

    // 传入完整的BluetoothDevice到模型
    data.add(new BluetoothDeviceModel(deviceName, deviceAddress, logoResourse, device));
    
    // 复用Adapter，仅在首次创建时初始化
    if (Adapter == null) {
        Adapter = new Bluetooth_adapter(data, ScanActivity.this, deviceClickListener);
        recyclerViewSD.setAdapter(Adapter);
    } else {
        Adapter.notifyDataSetChanged();
    }
}

步骤3：修改Bluetooth_adapter，添加点击回调并获取设备 #

先定义点击回调接口，再修改Adapter构造方法和绑定逻辑：

// 定义点击回调接口
public interface BluetoothDeviceClickListener {
    void onDeviceClicked(BluetoothDevice device);
}

// 修改Adapter类
public class Bluetooth_adapter extends RecyclerView.Adapter<BluetoothViewHolder> {

    private ArrayList<BluetoothDeviceModel> data;
    private Context context;
    private BluetoothDeviceClickListener clickListener;

    // 带回调的构造方法
    public Bluetooth_adapter(ArrayList<BluetoothDeviceModel> data, Context context, BluetoothDeviceClickListener clickListener) {
        this.data = data;
        this.context = context;
        this.clickListener = clickListener;
    }

    @NonNull
    @Override
    public BluetoothViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View view = inflater.inflate(R.layout.pair_devices, parent, false);
        return new BluetoothViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull BluetoothViewHolder holder, int position) {
        BluetoothDeviceModel deviceModel = data.get(position);
        BluetoothDevice device = deviceModel.getDevice(); // 获取完整设备对象

        // 原有UI绑定逻辑保持不变
        String name = deviceModel.getName();
        String address = deviceModel.getAddress();
        int imgresource = deviceModel.getImageresouce();
        holder.dropdownImgPD.setImageResource(imgresource);
        holder.deviceNamePD.setText(name != null ? name : address);

        // 设置点击事件，传递设备对象
        holder.cardViewPD.setOnClickListener(v -> {
            if (clickListener != null && device != null) {
                clickListener.onDeviceClicked(device);
            }
        });
    }

    @Override
    public int getItemCount() {
        return data.size();
    }
}

步骤4：在ScanActivity中初始化Adapter并处理回调 #

在onCreate方法中初始化Adapter，实现点击回调逻辑：

// 在ScanActivity的onCreate方法中，初始化data之后
BluetoothDeviceClickListener deviceClickListener = new BluetoothDeviceClickListener() {
    @Override
    public void onDeviceClicked(BluetoothDevice device) {
        // 这里处理设备点击后的逻辑，比如连接设备
        establishConnection(device);
    }
};

// 初始化Adapter
Adapter = new Bluetooth_adapter(data, this, deviceClickListener);
recyclerViewSD.setAdapter(Adapter);

同时修改ScanActivity的establishConnection方法，接收BluetoothDevice参数：

private void establishConnection(BluetoothDevice device) {
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED) {
        requestPermissions(new String[]{Manifest.permission.BLUETOOTH_CONNECT}, 1);
        return;
    }
    // 这里编写设备连接逻辑，比如创建BluetoothSocket
    Log.d(TAG, "准备连接设备: " + device.getName() + " (" + device.getAddress() + ")");
}

内容的提问来源于stack exchange，提问作者joash deoghare