我正在开发应用程序，它打印用户在安装了Android设备和OTG线缆的打印机上定义的文本。当我运行应用程序并单击打印按钮时，打印机省略打印声音然后什么也不做，我收到的响应是
Log.i("Info", "Bulk transfer started");
Log.i("Info", ??);
Log.i("Info", "Amount of data transferred : " + 5);
Log.i("Info", "Interface released");
Log.i("Info", "Usb connection closed");
Log.i("Info", "Brodcast reciever unregistered");
请帮助我，我错在这里是源代码。
activity_main
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<TextView
android:id="@+id/usbDevice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<Button
android:id="@+id/buttonPrint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Print" />
</LinearLayout>
xml / device_filter
<resources>
<usb-device vendor-id="65535" product-id="7176" />
</resources>
MainActivity
package com.example.hp.printviausb;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.hardware.usb.UsbConstants;
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbEndpoint;
import android.hardware.usb.UsbInterface;
import android.hardware.usb.UsbManager;
import android.hardware.usb.UsbRequest;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Iterator;
public class MainActivity extends ActionBarActivity
{
private UsbManager mUsbManager;
private UsbDevice mDevice;
private UsbDeviceConnection mConnection;
private UsbInterface mInterface;
private UsbEndpoint mEndPoint;
private PendingIntent mPermissionIntent;
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
private static Boolean forceCLaim = true;
HashMap<String, UsbDevice> mDeviceList;
Iterator<UsbDevice> mDeviceIterator;
int protocol;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
mDeviceList = mUsbManager.getDeviceList();
mDeviceIterator = mDeviceList.values().iterator();
Button print = (Button) findViewById(R.id.buttonPrint);
Toast.makeText(this, "Device List Size: " + String.valueOf(mDeviceList.size()), Toast.LENGTH_SHORT).show();
TextView textView = (TextView) findViewById(R.id.usbDevice);
String usbDevice = "";
// This is just testing what devices are connected
while (mDeviceIterator.hasNext())
{
UsbDevice usbDevice1 = mDeviceIterator.next();
usbDevice += "\n" + "DeviceID: " + usbDevice1.getDeviceId() + "\n" + "DeviceName: " + usbDevice1.getDeviceName() + "\n" + "DeviceClass: " + usbDevice1.getDeviceClass() + " - "
+ translateDeviceClass(usbDevice1.getDeviceClass()) + "\n" + "DeviceSubClass: " + usbDevice1.getDeviceSubclass() + "\n" + "VendorID: " + usbDevice1.getVendorId() + "\n" + "ProductID: " + usbDevice1.getProductId()
+ "\n";
protocol = usbDevice1.getDeviceProtocol();
int interfaceCount = usbDevice1.getInterfaceCount();
Toast.makeText(this, "INTERFACE COUNT: " + String.valueOf(interfaceCount), Toast.LENGTH_SHORT).show();
mDevice = usbDevice1;
if (mDevice == null)
{
Toast.makeText(this, "mDevice is null", Toast.LENGTH_SHORT).show();
}
else
{
// Toast.makeText(this, "mDevice is not null", Toast.LENGTH_SHORT).show();
}
textView.setText(usbDevice);
}
if (mDevice == null)
{
Toast.makeText(this, "mDevice is null", Toast.LENGTH_SHORT).show();
}
else
{
// Toast.makeText(this, "mDevice is not null", Toast.LENGTH_SHORT).show();
}
print.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
mPermissionIntent = PendingIntent.getBroadcast(MainActivity.this, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver(mUsbReceiver, filter);
if (mDevice != null)
mUsbManager.requestPermission(mDevice, mPermissionIntent);
// else
// Toast.makeText(this, "USB ", Toast.LENGTH_SHORT).show();
// print(mConnection, mInterface);
}
});
}
private String translateDeviceClass(int deviceClass)
{
switch (deviceClass)
{
case UsbConstants.USB_CLASS_APP_SPEC:
return "Application specific USB class";
case UsbConstants.USB_CLASS_AUDIO:
return "USB class for audio devices";
case UsbConstants.USB_CLASS_CDC_DATA:
return "USB class for CDC devices (communications device class)";
case UsbConstants.USB_CLASS_COMM:
return "USB class for communication devices";
case UsbConstants.USB_CLASS_CONTENT_SEC:
return "USB class for content security devices";
case UsbConstants.USB_CLASS_CSCID:
return "USB class for content smart card devices";
case UsbConstants.USB_CLASS_HID:
return "USB class for human interface devices (for example, mice and keyboards)";
case UsbConstants.USB_CLASS_HUB:
return "USB class for USB hubs";
case UsbConstants.USB_CLASS_MASS_STORAGE:
return "USB class for mass storage devices";
case UsbConstants.USB_CLASS_MISC:
return "USB class for wireless miscellaneous devices";
case UsbConstants.USB_CLASS_PER_INTERFACE:
return "USB class indicating that the class is determined on a per-interface basis";
case UsbConstants.USB_CLASS_PHYSICA:
return "USB class for physical devices";
case UsbConstants.USB_CLASS_PRINTER:
return "USB class for printers";
case UsbConstants.USB_CLASS_STILL_IMAGE:
return "USB class for still image devices (digital cameras)";
case UsbConstants.USB_CLASS_VENDOR_SPEC:
return "Vendor specific USB class";
case UsbConstants.USB_CLASS_VIDEO:
return "USB class for video devices";
case UsbConstants.USB_CLASS_WIRELESS_CONTROLLER:
return "USB class for wireless controller devices";
default:
return "Unknown USB class!";
}
}
// Broadcast receiver to obtain permission from user for connection
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver()
{
public void onReceive(Context context, Intent intent)
{
String action = intent.getAction();
if (ACTION_USB_PERMISSION.equals(action))
{
synchronized (this)
{
UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false))
{
if (device != null)
{
// call method to set up device communication
mInterface = device.getInterface(0);
mEndPoint = mInterface.getEndpoint(0);
mConnection = mUsbManager.openDevice(device);
startPrinting(device);
// setup();
}
}
else
{
// Log.d("SUB", "permission denied for device " + device);
Toast.makeText(context, "PERMISSION DENIED FOR THIS DEVICE", Toast.LENGTH_SHORT).show();
}
}
}
}
};
public void startPrinting(final UsbDevice printerDevice)
{
Handler handler = new Handler();
handler.post(new Runnable()
{
UsbDeviceConnection conn;
UsbInterface usbInterface;
@Override
public void run()
{
try
{
Log.i("Info", "Bulk transfer started");
// usbInterface = printerDevice.getInterface(0);
for (int i = 0; i < printerDevice.getInterfaceCount(); i++)
{
usbInterface = printerDevice.getInterface(i);
if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_PRINTER)
{
// usbInterface = mDevice;
}
}
UsbEndpoint endPoint = usbInterface.getEndpoint(0);
conn = mUsbManager.openDevice(mDevice);
conn.claimInterface(usbInterface, true);
String myStringData = "TEXT";
myStringData += "\n";
byte[] array = myStringData.getBytes();
ByteBuffer output_buffer = ByteBuffer.allocate(array.length);
UsbRequest request = new UsbRequest();
request.initialize(conn, endPoint);
request.queue(output_buffer, array.length);
if (conn.requestWait() == request)
{
Log.i("Info", output_buffer.getChar(0) + "");
Message m = new Message();
m.obj = output_buffer.array();
output_buffer.clear();
}
else
{
Log.i("Info", "No request recieved");
}
int transfered = conn.bulkTransfer(endPoint, myStringData.getBytes(), myStringData.getBytes().length, 5000);
Log.i("Info", "Amount of data transferred : " + transfered);
}
catch (Exception e)
{
Log.e("Exception", "Unable to transfer bulk data");
e.printStackTrace();
}
finally
{
try
{
conn.releaseInterface(usbInterface);
Log.i("Info", "Interface released");
conn.close();
Log.i("Info", "Usb connection closed");
unregisterReceiver(mUsbReceiver);
Log.i("Info", "Brodcast reciever unregistered");
}
catch (Exception e)
{
Log.e("Exception", "Unable to release resources because : " + e.getMessage());
e.printStackTrace();
}
}
}
});
}
}
Manifest_file
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.hp.printviausb">
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-feature android:name="android.hardware.usb.host" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme">
<activity
android:name=".MainActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
<action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
<action android:name="android.hardware.usb.action.USB_DEVICE_DETACHED" />
<meta-data
android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
android:resource="@xml/device_filter" />
</intent-filter>
</activity>
</application>
</manifest>