Android设备与外接U盘实现数据读取操作的示例

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
  //输入的内容
  private EditText u_disk_edt;
  //写入到U盘
  private Button u_disk_write;
  //从U盘读取
  private Button u_disk_read;
  //显示读取的内容
  private TextView u_disk_show;
  //自定义U盘读写权限
  private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
  //当前处接U盘列表
  private UsbMassStorageDevice[] storageDevices;
  //当前U盘所在文件目录
  private UsbFile cFolder;
  private final static String U_DISK_FILE_NAME = "u_disk.txt";
  private Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      switch (msg.what) {
        case 100:
          showToastMsg("保存成功");
          break;
        case 101:
          String txt = msg.obj.toString();
          if (!TextUtils.isEmpty(txt))
            u_disk_show.setText("读取到的数据是：" + txt);
          break;
      }
    }
  };

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initViews();
  }

  private void initViews() {
    u_disk_edt = (EditText) findViewById(R.id.u_disk_edt);
    u_disk_write = (Button) findViewById(R.id.u_disk_write);
    u_disk_read = (Button) findViewById(R.id.u_disk_read);
    u_disk_show = (TextView) findViewById(R.id.u_disk_show);
    u_disk_write.setOnClickListener(this);
    u_disk_read.setOnClickListener(this);
  }

  @Override
  public void onClick(View view) {
    switch (view.getId()) {
      case R.id.u_disk_write:
        final String content = u_disk_edt.getText().toString().trim();
        mHandler.post(new Runnable() {
          @Override
          public void run() {
            saveText2UDisk(content);
          }
        });

        break;
      case R.id.u_disk_read:
        mHandler.post(new Runnable() {
          @Override
          public void run() {
            readFromUDisk();
          }
        });

        break;
    }
  }

  private void readFromUDisk() {
    UsbFile[] usbFiles = new UsbFile[0];
    try {
      usbFiles = cFolder.listFiles();
    } catch (IOException e) {
      e.printStackTrace();
    }
    if (null != usbFiles && usbFiles.length > 0) {
      for (UsbFile usbFile : usbFiles) {
        if (usbFile.getName().equals(U_DISK_FILE_NAME)) {
          readTxtFromUDisk(usbFile);
        }
      }
    }
  }

  /**
   * @description 保存数据到U盘，目前是保存到根目录的
   * @author ldm
   * @time 2017/9/1 17:17
   */
  private void saveText2UDisk(String content) {
    //项目中也把文件保存在了SD卡，其实可以直接把文本读取到U盘指定文件
    File file = FileUtil.getSaveFile(getPackageName()
            + File.separator + FileUtil.DEFAULT_BIN_DIR,
        U_DISK_FILE_NAME);
    try {
      FileWriter fw = new FileWriter(file);
      fw.write(content);
      fw.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
    if (null != cFolder) {
      FileUtil.saveSDFile2OTG(file, cFolder);
      mHandler.sendEmptyMessage(100);
    }
  }

  /**
   * @description OTG广播注册
   * @author ldm
   * @time 2017/9/1 17:19
   */
  private void registerUDiskReceiver() {
    //监听otg插入 拔出
    IntentFilter usbDeviceStateFilter = new IntentFilter();
    usbDeviceStateFilter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
    usbDeviceStateFilter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
    registerReceiver(mOtgReceiver, usbDeviceStateFilter);
    //注册监听自定义广播
    IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
    registerReceiver(mOtgReceiver, filter);
  }

  /**
   * @description OTG广播，监听U盘的插入及拔出
   * @author ldm
   * @time 2017/9/1 17:20
   * @param
   */
  private BroadcastReceiver mOtgReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
      String action = intent.getAction();
      switch (action) {
        case ACTION_USB_PERMISSION://接受到自定义广播
          UsbDevice usbDevice = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
          //允许权限申请
          if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
            if (usbDevice != null) {
              //用户已授权，可以进行读取操作
              readDevice(getUsbMass(usbDevice));
            } else {
              showToastMsg("没有插入U盘");
            }
          } else {
            showToastMsg("未获取到U盘权限");
          }
          break;
        case UsbManager.ACTION_USB_DEVICE_ATTACHED://接收到U盘设备插入广播
          UsbDevice device_add = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
          if (device_add != null) {
            //接收到U盘插入广播，尝试读取U盘设备数据
            redUDiskDevsList();
          }
          break;
        case UsbManager.ACTION_USB_DEVICE_DETACHED://接收到U盘设设备拔出广播
          showToastMsg("U盘已拔出");
          break;
      }
    }
  };

  /**
   * @description U盘设备读取
   * @author ldm
   * @time 2017/9/1 17:20
   */
  private void redUDiskDevsList() {
    //设备管理器
    UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
    //获取U盘存储设备
    storageDevices = UsbMassStorageDevice.getMassStorageDevices(this);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
    //一般手机只有1个OTG插口
    for (UsbMassStorageDevice device : storageDevices) {
      //读取设备是否有权限
      if (usbManager.hasPermission(device.getUsbDevice())) {
        readDevice(device);
      } else {
        //没有权限，进行申请
        usbManager.requestPermission(device.getUsbDevice(), pendingIntent);
      }
    }
    if (storageDevices.length == 0) {
      showToastMsg("请插入可用的U盘");
    }
  }

  private UsbMassStorageDevice getUsbMass(UsbDevice usbDevice) {
    for (UsbMassStorageDevice device : storageDevices) {
      if (usbDevice.equals(device.getUsbDevice())) {
        return device;
      }
    }
    return null;
  }

  private void readDevice(UsbMassStorageDevice device) {
    try {
      device.init();//初始化
      //设备分区
      Partition partition = device.getPartitions().get(0);
      //文件系统
      FileSystem currentFs = partition.getFileSystem();
      currentFs.getVolumeLabel();//可以获取到设备的标识
      //通过FileSystem可以获取当前U盘的一些存储信息，包括剩余空间大小，容量等等
      Log.e("Capacity: ", currentFs.getCapacity() + "");
      Log.e("Occupied Space: ", currentFs.getOccupiedSpace() + "");
      Log.e("Free Space: ", currentFs.getFreeSpace() + "");
      Log.e("Chunk size: ", currentFs.getChunkSize() + "");
      cFolder = currentFs.getRootDirectory();//设置当前文件对象为根目录
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  private void showToastMsg(String msg) {
    Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
  }

  private void readTxtFromUDisk(UsbFile usbFile) {
    UsbFile descFile = usbFile;
    //读取文件内容
    InputStream is = new UsbFileInputStream(descFile);
    //读取秘钥中的数据进行匹配
    StringBuilder sb = new StringBuilder();
    BufferedReader bufferedReader = null;
    try {
      bufferedReader = new BufferedReader(new InputStreamReader(is));
      String read;
      while ((read = bufferedReader.readLine()) != null) {
        sb.append(read);
      }
      Message msg = mHandler.obtainMessage();
      msg.what = 101;
      msg.obj = read;
      mHandler.sendMessage(msg);
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      try {
        if (bufferedReader != null) {
          bufferedReader.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }
}

<?xml version="1.0" encoding="utf-8"?>


  

  


  

  

  

package com.ldm.androidudisk.utils;

import android.os.Environment;

import com.github.mjdev.libaums.fs.UsbFile;
import com.github.mjdev.libaums.fs.UsbFileOutputStream;

import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import static android.os.Environment.getExternalStorageDirectory;

/**
 * 文件操作工具类
 *
 * @author ldm
 * @description：
 * @date 2016-4-28 下午3:17:10
 */
public final class FileUtil {
  public static final String DEFAULT_BIN_DIR = "usb";

  /**
   * 检测SD卡是否存在
   */
  public static boolean checkSDcard() {
    return Environment.MEDIA_MOUNTED.equals(Environment
        .getExternalStorageState());
  }

  /**
   * 从指定文件夹获取文件
   *
   * @return 如果文件不存在则创建, 如果如果无法创建文件或文件名为空则返回null
   */
  public static File getSaveFile(String folderPath, String fileNmae) {
    File file = new File(getSavePath(folderPath) + File.separator
        + fileNmae);
    try {
      file.createNewFile();
    } catch (IOException e) {
      e.printStackTrace();
    }
    return file;
  }

  /**
   * 获取SD卡下指定文件夹的绝对路径
   *
   * @return 返回SD卡下的指定文件夹的绝对路径
   */
  public static String getSavePath(String folderName) {
    return getSaveFolder(folderName).getAbsolutePath();
  }

  /**
   * 获取文件夹对象
   *
   * @return 返回SD卡下的指定文件夹对象，若文件夹不存在则创建
   */
  public static File getSaveFolder(String folderName) {
    File file = new File(getExternalStorageDirectory()
        .getAbsoluteFile()
        + File.separator
        + folderName
        + File.separator);
    file.mkdirs();
    return file;
  }

  /**
   * 关闭流
   */
  public static void closeIO(Closeable... closeables) {
    if (null == closeables || closeables.length <= 0) {
      return;
    }
    for (Closeable cb : closeables) {
      try {
        if (null == cb) {
          continue;
        }
        cb.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

  private static void redFileStream(OutputStream os, InputStream is) throws IOException {
    int bytesRead = 0;
    byte[] buffer = new byte[1024 * 8];
    while ((bytesRead = is.read(buffer)) != -1) {
      os.write(buffer, 0, bytesRead);
    }
    os.flush();
    os.close();
    is.close();
  }

  /**
   * @description 把本地文件写入到U盘中
   * @author ldm
   * @time 2017/8/22 10:22
   */
  public static void saveSDFile2OTG(final File f, final UsbFile usbFile) {
    UsbFile uFile = null;
    FileInputStream fis = null;
    try {//开始写入
      fis = new FileInputStream(f);//读取选择的文件的
      if (usbFile.isDirectory()) {//如果选择是个文件夹
        UsbFile[] usbFiles = usbFile.listFiles();
        if (usbFiles != null && usbFiles.length > 0) {
          for (UsbFile file : usbFiles) {
            if (file.getName().equals(f.getName())) {
              file.delete();
            }
          }
        }
        uFile = usbFile.createFile(f.getName());
        UsbFileOutputStream uos = new UsbFileOutputStream(uFile);
        try {
          redFileStream(uos, fis);
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    } catch (final Exception e) {
      e.printStackTrace();
    }
  }
}

compile 'com.github.mjdev:libaums:0.5.5'