通过USB从Android应用程序将数据发送到PC

我想创建一个应用程序来通过USB从Android应用程序发送数据到PC。我的code如下：

I would like to create an App to send data through USB from Android App to PC. My Code as follows :

    package com.sample.dummy.app.senddatathoughserialport;

    import java.io.UnsupportedEncodingException;
    import android.os.Bundle;
    import android.app.Activity;
    import android.content.Context;
    import android.content.Intent;
    import android.hardware.usb.UsbConstants;
    import android.hardware.usb.UsbDeviceConnection;
    import android.hardware.usb.UsbEndpoint;
    import android.hardware.usb.UsbInterface;
    import android.hardware.usb.UsbManager;
    import android.hardware.usb.UsbDevice;
    import android.util.Log;
    import android.view.Menu;
    import android.view.View;
    import android.widget.Button;
    import android.widget.TextView;
    import android.widget.Toast;

public class MainActivity extends Activity 
{


@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final TextView tv = (TextView)findViewById(R.id.multiAutoCompleteTextView1);
    Button sButton = (Button) findViewById(R.id.button1);
    final UsbManager manager = (UsbManager) this.getSystemService(Context.USB_SERVICE);
    Toaster(""+manager);

    // -- register click event with first button ---
    sButton.setOnClickListener(new View.OnClickListener() 
    {
       @SuppressWarnings({ "unused" })
       public void onClick(View v) 
       {         
            try
            {
                Intent intent = new Intent("android.hardware.usb.action.USB_DEVICE_ATTACHED");
                UsbDevice mDevice = (UsbDevice) intent.getParcelableExtra(UsbManager.ACTION_USB_DEVICE_ATTACHED);
                Toaster(""+mDevice);
                final UsbDeviceConnection connection = manager.openDevice(mDevice); 

                UsbInterface usbIf = null;
                Toaster("Its ok here 1");
                int count = mDevice.getInterfaceCount();
                Toaster("Its ok here 1");
                for(int i=0; i< count; i++)
                {
                    usbIf = mDevice.getInterface(i);
                }

                UsbEndpoint epIN = null;
                UsbEndpoint epOUT = null;
                Toaster("It's ok here 2");
                for (int i = 0; i < usbIf.getEndpointCount(); i++) 
                {            
                   if (usbIf.getEndpoint(i).getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)
                   {                 
                        if (usbIf.getEndpoint(i).getDirection() == UsbConstants.USB_DIR_IN)                         
                        epIN = usbIf.getEndpoint(i);
                        else
                        epOUT = usbIf.getEndpoint(i);
                   } 
                   else 
                   {
                        Log.d("USB","Not Bulk");
                        Toaster("Thedaa log daggara");
                   }
                }

                String get = tv.getText().toString();
                try
                {
                    byte[] str = get.getBytes(get);
                    connection.bulkTransfer(epOUT, str, str.length, 500);
                } 
                catch (UnsupportedEncodingException e) 
                {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    Toaster("Data sending failed!");
                }
                finally
                {
                    Toaster("Data sent through USB !");
                }
            }
            catch(Exception e)
            {
                Log.d("Failed", e.toString());  
                Toaster("Attempt Failed !!");
            }
       }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) 
{
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
public void Toaster(String string)
{
    Toast.makeText(this, string,Toast.LENGTH_LONG).show();
}}

和我的Andr​​oid清单XML文件如下：

And my Android Manifest Xml file is as follows:

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 package="com.sample.dummy.app.senddatathoughserialport"
                                 android:versionCode="1"
                                android:versionName="1.0" >
 <uses-feature android:name="android.hardware.usb.host" />
 <uses-sdk android:minSdkVersion="12" />
 <application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.sample.dummy.app.senddatathoughserialport.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>  
        <intent-filter>
            <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
            <action android:name="android.hardware.usb.action.USB_DEVICE_DETACHED" />
        </intent-filter>

        <meta-data
            android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
            android:resource="@xml/device_filter" />
        <meta-data
            android:name="android.hardware.usb.action.USB_DEVICE_DETACHED"
            android:resource="@xml/device_filter" />        
    </activity>        
</application></manifest>

我得到的问题UsbDevice mDevice;它总是显示为空值 请给我的助手，使之成为成功的应用程序。

i'm getting problem with UsbDevice mDevice; which always shows value of null Please give me assistant to make it a successful app.