如何将Android Open Accessory模式实现为服务? [英] How to implement Android Open Accessory mode as a service?

问题描述

我一直在玩Android Open Accessory Development Kit.遵循 Google提供的DemoKit示例，我没有遇到任何麻烦使解决方案适应我的应用程序.我可以很好地检测，通信和分离附件.

I've been playing around with the Android Open Accessory Development Kit. By following the DemoKit example provided by Google, I've had no trouble in adapting the solution to my application. I can detect, communicate, and detach the accessory just fine.

但是，我需要将整个事情作为服务运行.我有一个基本活动，该活动由USB_ACCESSORY_ATTACHED意图启动(即，在连接附件时)，并且工作正常.但是，与常规活动中的工作解决方案相比，启动服务并在其中运行相同的代码后，每当我尝试与附件进行通信时，我都会收到IOException(无此类设备")(监控arduino端显示USB连接成功).即使我在服务中指定了正确的BroadcastReceiver，并在onStartCommand回调方法中注册了它，并使用openAccessory()设置了通信端点，也会发生这种情况.相关代码如下.

However, I would need to run the whole thing as a service. I have a base activity which is launched by the USB_ACCESSORY_ATTACHED intent (that is, when the accessory is connected), and that works fine. But as soon as I start my service and run identical code in it compared to my working solution within a regular activity, I'm receiving an IOException ("no such device") whenever I'm trying to communicate with the accessory (monitoring arduino side shows a successful USB connection). This happens even though I've specified the correct BroadcastReceiver within the service, registered it in the onStartCommand callback method, and set up the communication endpoints with openAccessory(). Relevant code is as follows.

@Override
public void onCreate() {
    Log.d(TAG, "ONCREATE");

    manager = UsbManager.getInstance(this);
    mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(
            ACTION_USB_PERMISSION), 0);

    // Register broadcastreceiver for filtering accessory events
    IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
    filter.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);
    registerReceiver(mUsbReceiver,filter);
    super.onCreate();
}

public int onStartCommand(Intent intent, int flags, int startId) {
    Log.d(TAG, "ONSTARTCOMMAND METHOD ACCESSED");

    if (mInputStream != null && mOutputStream != null) {
        return START_NOT_STICKY;
    }

    UsbAccessory[] accessories = manager.getAccessoryList();
    mAccessory = (accessories == null ? null : accessories[0]);

    if (mAccessory != null) {
        if (manager.hasPermission(mAccessory)) {
            openAccessory();
        } else {
            synchronized (mUsbReceiver) {
                if (!mPermissionRequestPending) {
                    manager.requestPermission(mAccessory,
                            mPermissionIntent);
                    mPermissionRequestPending = true;
                }
            }
        }
    } else {
        Log.d(TAG, "mAccessory is null");
    }
    return START_NOT_STICKY;
}

openAccessory方法:

openAccessory method:

/**
 * Open the accessory
 */
private void openAccessory() {
    Log.d(TAG, "openAccessory: "+mAccessory);
    mFileDescriptor = manager.openAccessory(mAccessory);
    if (mFileDescriptor != null) {
        FileDescriptor fd = mFileDescriptor.getFileDescriptor();
        mInputStream = new FileInputStream(fd);
        mOutputStream = new FileOutputStream(fd);
        Thread thread = new Thread(null,this,"AccessoryThread");
        thread.start();
    }
}

有什么想法可以解决吗?

Any ideas for a possible solution?

推荐答案

解决方案很简单.

if (intent.getAction().equals(USB_ACCESSORY_ATTACHED)) {
    Intent i = new Intent(this, YourServiceName.class);
    i.putExtras(intent);
    startService(i);
}

基本上，复制在启动用于启动服务的活动时收到的意图，因为该意图包含ADK实现所需的附件的详细信息.

Basically, copy the intent that you received when starting your activity that you use to launch the service, because the intent contains the details of the accessory that the ADK implementation needs.

然后，在服务中继续完全像以前一样实现ADK的其余部分.

Then, in the service proceed to implement the rest of ADK exactly as before.

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