在问这个问题之前，我经历了很多演示和 SO 线程，但没有一个对我有用。我正在尝试使用以下代码通过 USB 串行端口读取数据。
public class MainActivity extends Activity {
public final String ACTION_USB_PERMISSION = "com.myprject.usbex.USB_PERMISSION";
Button startButton, sendButton, clearButton, stopButton;
TextView textView;
EditText editText;
UsbManager usbManager;
UsbDevice device;
UsbSerialDevice serialPort;
UsbDeviceConnection connection;
UsbSerialInterface.UsbReadCallback mCallback = new UsbSerialInterface.UsbReadCallback() { //Defining a Callback which triggers whenever data is read.
@Override
public void onReceivedData(byte[] arg0) {
Toast.makeText(MainActivity.this, "Callback Received"+arg0, Toast.LENGTH_SHORT).show();
String data = null;
try {
data = new String(arg0, "UTF-8");
data.concat("/n");
tvAppend(textView, data);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
Toast.makeText(MainActivity.this, "Exception:"+e.getMessage(), Toast.LENGTH_SHORT).show();
}
}
};
private final BroadcastReceiver broadcastReceiver = new BroadcastReceiver() { //Broadcast Receiver to automatically start and stop the Serial connection.
@Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals(ACTION_USB_PERMISSION)) {
boolean granted = intent.getExtras().getBoolean(UsbManager.EXTRA_PERMISSION_GRANTED);
if (granted) {
connection = usbManager.openDevice(device);
serialPort = UsbSerialDevice.createUsbSerialDevice(device, connection);
if (serialPort != null) {
if (serialPort.open()) { //Set Serial Connection Parameters.
setUiEnabled(true);
serialPort.setBaudRate(9600);
serialPort.setDataBits(UsbSerialInterface.DATA_BITS_8);
serialPort.setStopBits(UsbSerialInterface.STOP_BITS_1);
serialPort.setParity(UsbSerialInterface.PARITY_NONE);
serialPort.setFlowControl(UsbSerialInterface.FLOW_CONTROL_OFF);
try {
serialPort.read(mCallback);
Toast.makeText(MainActivity.this, "Read"+serialPort.read(mCallback), Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(MainActivity.this, "Exception in read:"+e.getMessage(), Toast.LENGTH_SHORT).show();
}
tvAppend(textView, "Serial Connection Opened!\n");
Toast.makeText(MainActivity.this, "Serial port connected", Toast.LENGTH_SHORT).show();
} else {
Log.d("SERIAL", "PORT NOT OPEN");
}
} else {
Log.d("SERIAL", "PORT IS NULL");
}
} else {
Log.d("SERIAL", "PERM NOT GRANTED");
}
} else if (intent.getAction().equals(UsbManager.ACTION_USB_DEVICE_ATTACHED)) {
onClickStart(startButton);
} else if (intent.getAction().equals(UsbManager.ACTION_USB_DEVICE_DETACHED)) {
onClickStop(stopButton);
}
}
;
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
usbManager = (UsbManager) getSystemService(this.USB_SERVICE);
startButton = (Button) findViewById(R.id.buttonStart);
sendButton = (Button) findViewById(R.id.buttonSend);
clearButton = (Button) findViewById(R.id.buttonClear);
stopButton = (Button) findViewById(R.id.buttonStop);
editText = (EditText) findViewById(R.id.editText);
textView = (TextView) findViewById(R.id.textView);
setUiEnabled(false);
IntentFilter filter = new IntentFilter();
filter.addAction(ACTION_USB_PERMISSION);
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
registerReceiver(broadcastReceiver, filter);
}
public void setUiEnabled(boolean bool) {
startButton.setEnabled(!bool);
sendButton.setEnabled(bool);
stopButton.setEnabled(bool);
textView.setEnabled(bool);
}
public void onClickStart(View view) {
HashMap<String, UsbDevice> usbDevices = usbManager.getDeviceList();
if (!usbDevices.isEmpty()) {
boolean keep = true;
for (Map.Entry<String, UsbDevice> entry : usbDevices.entrySet()) {
device = entry.getValue();
int deviceVID = device.getVendorId();
if (deviceVID == 1659)//Arduino Vendor ID
{
PendingIntent pi = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
usbManager.requestPermission(device, pi);
keep = false;
} else {
connection = null;
device = null;
}
if (!keep)
break;
}
}
}
public void onClickSend(View view) {
String string = editText.getText().toString();
serialPort.write(string.getBytes());
tvAppend(textView, "\nData Sent : " + string + "\n");
}
public void onClickStop(View view) {
setUiEnabled(false);
serialPort.close();
tvAppend(textView,"\nSerial Connection Closed! \n");
}
public void onClickClear(View view) {
textView.setText(" ");
}
private void tvAppend(TextView tv, CharSequence text) {
final TextView ftv = tv;
final CharSequence ftext = text;
runOnUiThread(new Runnable() {
@Override
public void run() {
ftv.append(ftext);
}
});
}
}
我想从 USB 连续读取数据。使用上面的代码，我可以获得设备供应商 ID，并且serialPort.open()也可以正常工作。问题是我没有收到数据。
与此代码一起使用的库来自这里https://github.com/felHR85/SerialPortExample。
指出我哪里出错了。打开任何替代解决方案以在 Android 中通过 USB 读取数据。