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    【记录】Android中创建进程或线程去实现USB设备插入的状态检测

    Android crifan 3575浏览 0评论

    【背景】

    折腾：

    【已解决】Android设备作为Host希望实现可以检测到USB设备插入

    期间，需要尝试去通过，新建一个线程或进程，然后去动态检测USB设备的插入。

    【折腾过程】

    1.先去搞懂，android中如何新建线程。

    2.官网文档：

    https://developer.android.com/reference/java/lang/Thread.html

    3.看看：

    Android 线程 thread 两种实现方法！

    Android create new thread in service class

    去试试。

    4.期间出现：

    【已解决】android中switch中的case中不用使用enum枚举值：Type mismatch: cannot convert from xxx to int

    5.再去继续写代码测试。

    然后又遇到：

    【已解决】android中enum转换为int

    6.然后用了代码：

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    usbActionDetectThread =new Thread(
            new Runnable() { 
                @Override 
                public void run() 
                {
                    Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();
     
                    UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
                    HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
                    Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
                    while(deviceIterator.hasNext()){
                        UsbDevice device = deviceIterator.next();
                        int usbVid = device.getVendorId();
                        int usbPid = device.getProductId();
                        if((usbVid == ft232rUartVid) && (usbPid ==ft232rUartPid) ){
                            Toast.makeText(getApplicationContext(), "Found Usb device: FT232R UART", Toast.LENGTH_LONG).show();
                            Toast.makeText(getApplicationContext(), "Now send message USB_ACTION_ATTACH to activity ", Toast.LENGTH_LONG).show();
                             
                            Message foundUsbDeviceAttachMsg =new Message();
                            foundUsbDeviceAttachMsg.what=usb_action.USB_ACTION_ATTACH.getAction();
                            mHandler.sendMessage(foundUsbDeviceAttachMsg);
     
                            break;
                        }
                        else
                        {
                            Toast.makeText(getApplicationContext(), "Found USB VID="+usbVid+" PID=" + usbPid, Toast.LENGTH_LONG).show();
                        }
                    }
             
                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        //e.printStackTrace();
                    }
                }
    });
     
    usbActionDetectThread.start();

    结果都没指定到：

    run函数里面去。。。

    7.参考：

    How to Send the Current Thread to Sleep

    去改为：

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    usbActionDetectThread =new Thread()
            //new Runnable() {
    {
               // @Override 
                public void run()
                {
                    Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();
     
                    UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
                    HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
                    Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
                    while(deviceIterator.hasNext()){
                        UsbDevice device = deviceIterator.next();
                        int usbVid = device.getVendorId();
                        int usbPid = device.getProductId();
                        if((usbVid == ft232rUartVid) && (usbPid ==ft232rUartPid) ){
                            Toast.makeText(getApplicationContext(), "Found Usb device: FT232R UART", Toast.LENGTH_LONG).show();
                            Toast.makeText(getApplicationContext(), "Now send message USB_ACTION_ATTACH to activity ", Toast.LENGTH_LONG).show();
                             
                            Message foundUsbDeviceAttachMsg =new Message();
                            foundUsbDeviceAttachMsg.what=usb_action.USB_ACTION_ATTACH.getAction();
                            mHandler.sendMessage(foundUsbDeviceAttachMsg);
     
                            break;
                        }
                        else
                        {
                            Toast.makeText(getApplicationContext(), "Found USB VID="+usbVid+" PID=" + usbPid, Toast.LENGTH_LONG).show();
                        }
                    }
             
                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        //e.printStackTrace();
                    }
                }
    };
     
    usbActionDetectThread.start();

    再去试试是否能运行到。

    结果还是不行。

    8.再改为通过Handler：

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    //public class DeviceListActivity extends BaseActivity {
    public class DeviceListActivity extends BaseActivity implements Runnable {
     
        @Override
        public void run() {
            //0x0403 / 0x6001: FTDI FT232R UART
            final int ft232rUartVid = 0x0403; //1027
            final int ft232rUartPid = 0x6001; //24577
             
            Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();
     
            UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
            HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
            Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
            while(deviceIterator.hasNext()){
                UsbDevice device = deviceIterator.next();
                int usbVid = device.getVendorId();
                int usbPid = device.getProductId();
                if((usbVid == ft232rUartVid) && (usbPid ==ft232rUartPid) ){
                    Toast.makeText(getApplicationContext(), "Found Usb device: FT232R UART", Toast.LENGTH_LONG).show();
                    Toast.makeText(getApplicationContext(), "Now send message USB_ACTION_ATTACH to activity ", Toast.LENGTH_LONG).show();
                     
                    Message foundUsbDeviceAttachMsg =new Message();
                    foundUsbDeviceAttachMsg.what=usb_action.USB_ACTION_ATTACH.getAction();
                    mHandler.sendMessage(foundUsbDeviceAttachMsg);
     
                    break;
                }
                else
                {
                    Toast.makeText(getApplicationContext(), "Found USB VID="+usbVid+" PID=" + usbPid, Toast.LENGTH_LONG).show();
                }
            }
        }
         
        private void usbActionDetectViaHandler(){
            mHandler=new Handler()
            { 
                public void handleMessage(Message msg) 
                {
                    usb_action curUsbAction = usb_action.values()[msg.what]; //do your own bounds checking
                    switch(curUsbAction) 
                    {
                        case USB_ACTION_UNKNOWN:
                            Toast.makeText(getApplicationContext(), "Unkown USB action !", Toast.LENGTH_LONG).show();
                            break;
                        case USB_ACTION_ATTACH:
                            //TODO: do auto scan hart devices
                            Toast.makeText(getApplicationContext(), "Now should call the HART auto scan", Toast.LENGTH_LONG).show();
                            break;
                        case USB_ACTION_DETACH:
                            //stop auto detect usb action thread
                            Toast.makeText(getApplicationContext(), "Now destory the usb action detect thread", Toast.LENGTH_LONG).show();
                            usbActionDetectThread.destroy();
                            break;
                        default: 
                            break;       
                    } 
                    super.handleMessage(msg); 
                }
            };
             
            Thread curThread=new Thread(this); 
            curThread.start();
        }

    结果却会出错：

    jdi thread evaluations exception processing async thread queue

    参考：

    [Java:Eclipse]JDI thread evaluations:Exception processing async thread queue

    去关闭Expressions视图，

    重新debug，看看是否还会有该错误。

    果然没了该错误了。

    但是该运行的代码，还是没运行到。。。

    9.参考：

    Specifying the Code to Run on a Thread

    看到其中关键一句：

    Remember, though, that the Runnable won’t be running on the UI thread,

    所以，上述的代码，写在Runnable中的，是没法运行在：

    我当前的，本身就是出于UI线程中的。

    但是应该是：

    的确底层，去新建了线程，去执行对应的代码的。

    10.后来发现，上述代码出错了：

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    11-06 16:47:42.988: E/AndroidRuntime(3037): FATAL EXCEPTION: Thread-361
    11-06 16:47:42.988: E/AndroidRuntime(3037): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
    11-06 16:47:42.988: E/AndroidRuntime(3037):     at android.os.Handler.<init>(Handler.java:121)
    11-06 16:47:42.988: E/AndroidRuntime(3037):     at android.widget.Toast$TN.<init>(Toast.java:347)
    11-06 16:47:42.988: E/AndroidRuntime(3037):     at android.widget.Toast.<init>(Toast.java:93)
    11-06 16:47:42.988: E/AndroidRuntime(3037):     at android.widget.Toast.makeText(Toast.java:240)
    11-06 16:47:42.988: E/AndroidRuntime(3037):     at com.yy.xxx.activities.DeviceListActivity.run(DeviceListActivity.java:298)
    11-06 16:47:42.988: E/AndroidRuntime(3037):     at java.lang.Thread.run(Thread.java:856)
    11-06 16:47:43.386: D/dalvikvm(3037): threadid=1: still suspended after undo (sc=1 dc=1)

    看代码中的：

    ?
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    public void run() {

    很明显是：

    第一句就是：

    298行的：

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    Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();

    结果导致了上面的

    at com.yy.xxx.activities.DeviceListActivity.run(DeviceListActivity.java:298)

    调用makeText出错：

    at android.widget.Toast.makeText(Toast.java:240)

    的。

    11.所以，去参考：

    Communicating with the UI Thread

    看看如何打印toast。

    算了，暂时不打印toast了，改为log算了：

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    @Override
    public void run() {
        //0x0403 / 0x6001: FTDI FT232R UART
        final int ft232rUartVid = 0x0403; //1027
        final int ft232rUartPid = 0x6001; //24577
         
        //Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();
        gLogger.debug("Begin check usb action");
     
        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
        HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
        while(deviceIterator.hasNext()){
            UsbDevice device = deviceIterator.next();
            int usbVid = device.getVendorId();
            int usbPid = device.getProductId();
            if((usbVid == ft232rUartVid) && (usbPid ==ft232rUartPid) ){
                //Toast.makeText(getApplicationContext(), "Found Usb device: FT232R UART", Toast.LENGTH_LONG).show();
                //Toast.makeText(getApplicationContext(), "Now send message USB_ACTION_ATTACH to activity ", Toast.LENGTH_LONG).show();
                gLogger.debug("Found Usb device: FT232R UART");
                gLogger.debug("Now send message USB_ACTION_ATTACH to activit");
                 
                Message foundUsbDeviceAttachMsg =new Message();
                foundUsbDeviceAttachMsg.what=usb_action.USB_ACTION_ATTACH.getAction();
                mHandler.sendMessage(foundUsbDeviceAttachMsg);
     
                break;
            }
            else
            {
                //Toast.makeText(getApplicationContext(), "Found USB VID="+usbVid+" PID=" + usbPid, Toast.LENGTH_LONG).show();
                gLogger.debug("Found USB VID="+usbVid+" PID=" + usbPid);
            }
        }
    }

    然后继续调试。

    然后的确可以运行到这个run函数了。

    12.但是又有问题：

    代码：

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    @Override
    public void run() {
        //0x0403 / 0x6001: FTDI FT232R UART
        final int ft232rUartVid = 0x0403; //1027
        final int ft232rUartPid = 0x6001; //24577
         
        //Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();
        gLogger.debug("Begin check usb action");
     
        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
        HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
        while(deviceIterator.hasNext()){
            UsbDevice device = deviceIterator.next();
            int usbVid = device.getVendorId();
            int usbPid = device.getProductId();
            if((usbVid == ft232rUartVid) && (usbPid ==ft232rUartPid) ){
                //Toast.makeText(getApplicationContext(), "Found Usb device: FT232R UART", Toast.LENGTH_LONG).show();
                //Toast.makeText(getApplicationContext(), "Now send message USB_ACTION_ATTACH to activity ", Toast.LENGTH_LONG).show();
                gLogger.debug("Found Usb device: FT232R UART");
                gLogger.debug("Now send message USB_ACTION_ATTACH to activit");
                 
                Message foundUsbDeviceAttachMsg =new Message();
                foundUsbDeviceAttachMsg.what=usb_action.USB_ACTION_ATTACH.getAction();
                mHandler.sendMessage(foundUsbDeviceAttachMsg);
     
                break;
            }
            else
            {
                //Toast.makeText(getApplicationContext(), "Found USB VID="+usbVid+" PID=" + usbPid, Toast.LENGTH_LONG).show();
                gLogger.debug("Found USB VID="+usbVid+" PID=" + usbPid);
            }
        }
         
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    只运行了一次，只执行了一次的sleep的200毫秒后，结果就不再执行了。

    所以需要去解决：

    【已解决】为何android中实现了Runnable的进程只运行了一次

    然后就可以正常检测usb的状态了。

     

    【总结】

    此处，相关代码为：

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    public class DeviceListActivity extends BaseActivity implements Runnable {
     
        private Thread usbActionDetectThread = null;
         public Handler mHandler;
     
     
        @Override
        public void run() {
            // set to lower priority
            android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_BACKGROUND);
     
            //0x0403 / 0x6001: FTDI FT232R UART
            final int ft232rUartVid = 0x0403; //1027
            final int ft232rUartPid = 0x6001; //24577
     
            boolean bNotFoundUsb = true;
            while(bNotFoundUsb)
            {
                //Toast.makeText(getApplicationContext(), "Begin check usb action", 1000).show();
                gLogger.debug("Begin check usb action");
         
                UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
                HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
                Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
                while(deviceIterator.hasNext()){
                    UsbDevice device = deviceIterator.next();
                    int usbVid = device.getVendorId();
                    int usbPid = device.getProductId();
                    if((usbVid == ft232rUartVid) && (usbPid ==ft232rUartPid) ){
                        //Toast.makeText(getApplicationContext(), "Found Usb device: FT232R UART", Toast.LENGTH_LONG).show();
                        //Toast.makeText(getApplicationContext(), "Now send message USB_ACTION_ATTACH to activity ", Toast.LENGTH_LONG).show();
                        gLogger.debug("Found Usb device: FT232R UART");
                        gLogger.debug("Now send message USB_ACTION_ATTACH to activit");
                         
                        Message foundUsbDeviceAttachMsg =new Message();
                        foundUsbDeviceAttachMsg.what=usb_action.USB_ACTION_ATTACH.getAction();
                        mHandler.sendMessage(foundUsbDeviceAttachMsg);
                         
                        bNotFoundUsb = false;
         
                        break;
                    }
                    else
                    {
                        //Toast.makeText(getApplicationContext(), "Found USB VID="+usbVid+" PID=" + usbPid, Toast.LENGTH_LONG).show();
                        gLogger.debug("Found USB VID="+usbVid+" PID=" + usbPid);
                    }
                }//while(deviceIterator.hasNext()){
                 
                if(bNotFoundUsb)
                {
                    try {
                        int sleepTimeInMs = 200;
                        gLogger.debug("Sleep milliseconds: " + sleepTimeInMs);
                        Thread.sleep(sleepTimeInMs);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        //e.printStackTrace();
                    }
                }
     
                }//while(bNotFoundUsb)
            }//public void run()
        }
         
        public enum usb_action{
            USB_ACTION_UNKNOWN(0), USB_ACTION_ATTACH(1), USB_ACTION_DETACH(2);
             
            usb_action (int action)
            {
                this.action = action;
            }
             
            private final int action;
     
            public int getAction() {
                return action;
            }
        }
     
        private void usbActionDetectViaHandler(){
            mHandler=new Handler()
            { 
                public void handleMessage(Message msg) 
                {
                    usb_action curUsbAction = usb_action.values()[msg.what]; //do your own bounds checking
                    switch(curUsbAction) 
                    {
                        case USB_ACTION_UNKNOWN:
                            Toast.makeText(getApplicationContext(), "Unkown USB action !", Toast.LENGTH_LONG).show();
                            break;
                        case USB_ACTION_ATTACH:
                            //TODO: do auto scan hart devices
                            Toast.makeText(getApplicationContext(), "Now should call the HART auto scan", Toast.LENGTH_LONG).show();
                            break;
                        case USB_ACTION_DETACH:
                            //stop auto detect usb action thread
                            Toast.makeText(getApplicationContext(), "Now destory the usb action detect thread", Toast.LENGTH_LONG).show();
                            usbActionDetectThread.destroy();
                            usbActionDetectThread = null;
                            break;
                        default: 
                            break;       
                    }
                    super.handleMessage(msg); 
                }
            };
     
            Thread curThread=new Thread(this); 
            curThread.start();
        }
     
        private void detectUsbDeviceAttach(){
            //Method1: this should work, but due to android usb manager bug:
            //can not get intert usb attach action
            //so here can not use this method
            //usbActionDetectViaFilter();
     
            //Method2: use thread + handler to do usb detect
            usbActionDetectViaHandler();
        }
     
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            //...
             
            detectUsbDeviceAttach();
        }
     
        @SuppressWarnings("deprecation")
        @Override
        public void onDestroy() {
            //...
     
            super.onDestroy();
            //usbOnDestroy();
             
            //TODO: release current resources? thread? ...
            if(null != usbActionDetectThread){
                if(usbActionDetectThread.isAlive()){
                    usbActionDetectThread.destroy();
                }
            }
        }
     
    }

    可以实现：

    循环执行，检测usb的插入

    发送都应的message给handler去处理。

    然后后续就可以去执行自己要的动作了。

    转载请注明：在路上 » 【记录】Android中创建进程或线程去实现USB设备插入的状态检测

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