將手機中的文件復(fù)制到u盤中，需要u盤讀取權(quán)限和文件讀寫權(quán)限

1.添加權(quán)限

    <uses-permission android:name="android.permission.READ_PHONE_STATE" /> 
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />

2.添加第三方依賴庫

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

3.編寫界面

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Android盒子外接U盤文件讀寫測試DEMO"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        />

    <EditText
        android:id="@+id/u_disk_edt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:hint="輸入要保存到U盤中的文字內(nèi)容"/>


    <Button
        android:id="@+id/u_disk_write"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:gravity="center"
        android:text="往U盤中寫入數(shù)據(jù)"/>

    <Button
        android:id="@+id/u_disk_read"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:gravity="center"
        android:text="從U盤中讀取數(shù)據(jù)"/>

    <TextView
        android:id="@+id/u_disk_show"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginLeft="10dp"
        />
</LinearLayout>

4.在activity中編寫功能

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

//輸入的內(nèi)容
private EditText u_disk_edt;
//寫入到U盤
private Button u_disk_write;
//從U盤讀取
private Button u_disk_read;
//顯示讀取的內(nèi)容
private TextView u_disk_show;
//自定義U盤讀寫權(quán)限
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
//當(dāng)前處接U盤列表
private UsbMassStorageDevice[] storageDevices;
//當(dāng)前U盤所在文件目錄
private UsbFile cFolder;
private final static String U_DISK_FILE_NAME = "u_disk.txt";
@SuppressLint("HandlerLeak")
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("讀取到的數(shù)據(jù)是：" + txt);
                break;
        }
    }
};

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

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 保存數(shù)據(jù)到U盤，目前是保存到根目錄的
 * @author ldm
 * @time 2017/9/1 17:17
 */
private void saveText2UDisk(String content) {
    //項目中也把文件保存在了SD卡，其實可以直接把文本讀取到U盤指定文件
    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廣播注冊
 * @author ldm
 * @time 2017/9/1 17:19
 */
private void registerUDiskReceiver() {
    //監(jiān)聽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);
    //注冊監(jiān)聽自定義廣播
    IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
    registerReceiver(mOtgReceiver, filter);
}

/**
 * @description OTG廣播，監(jiān)聽U盤的插入及拔出
 * @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://接受到自定義廣播
                UsbDevice usbDevice = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                //允許權(quán)限申請
                if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                    if (usbDevice != null) {
                        //用戶已授權(quán)，可以進(jìn)行讀取操作
                        readDevice(getUsbMass(usbDevice));
                    } else {
                        showToastMsg("沒有插入U盤");
                    }
                } else {
                    showToastMsg("未獲取到U盤權(quán)限");
                }
                break;
            case UsbManager.ACTION_USB_DEVICE_ATTACHED://接收到U盤設(shè)備插入廣播
                UsbDevice device_add = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                if (device_add != null) {
                    //接收到U盤插入廣播，嘗試讀取U盤設(shè)備數(shù)據(jù)
                    redUDiskDevsList();
                }
                break;
            case UsbManager.ACTION_USB_DEVICE_DETACHED://接收到U盤設(shè)設(shè)備拔出廣播
                showToastMsg("U盤已拔出");
                break;
        }
    }
};

/**
 * @description U盤設(shè)備讀取
 * @author ldm
 * @time 2017/9/1 17:20
 */
private void redUDiskDevsList() {
    //設(shè)備管理器
    UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
    //獲取U盤存儲設(shè)備
    storageDevices = UsbMassStorageDevice.getMassStorageDevices(this);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
    //一般手機只有1個OTG插口
    for (UsbMassStorageDevice device : storageDevices) {
        //讀取設(shè)備是否有權(quán)限
        if (usbManager.hasPermission(device.getUsbDevice())) {
            readDevice(device);
        } else {
            //沒有權(quán)限，進(jìn)行申請
            usbManager.requestPermission(device.getUsbDevice(), pendingIntent);
        }
    }
    if (storageDevices.length == 0) {
        showToastMsg("請插入可用的U盤");
    }
}

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
        //設(shè)備分區(qū)
        Partition partition = device.getPartitions().get(0);
        //文件系統(tǒng)
        FileSystem currentFs = partition.getFileSystem();
        currentFs.getVolumeLabel();//可以獲取到設(shè)備的標(biāo)識
        //通過FileSystem可以獲取當(dāng)前U盤的一些存儲信息，包括剩余空間大小，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();//設(shè)置當(dāng)前文件對象為根目錄
    } 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;
    //讀取文件內(nèi)容
    InputStream is = new UsbFileInputStream(descFile);
    //讀取秘鑰中的數(shù)據(jù)進(jìn)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();
          }
        }
    }
  }

5.添加文件處理工具類

     public class FileUtil {
             public static final String DEFAULT_BIN_DIR = "usb";
        /**
         * 檢測SD卡是否存在
         */
        public static boolean checkSDcard() {
            return Environment.MEDIA_MOUNTED.equals(Environment
                    .getExternalStorageState());
        }
    
        /**
         * 從指定文件夾獲取文件
         *
         * @return 如果文件不存在則創(chuàng)建, 如果如果無法創(chuàng)建文件或文件名為空則返回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;
        }
    
        /**
         * 獲取SD卡下指定文件夾的絕對路徑
         *
         * @return 返回SD卡下的指定文件夾的絕對路徑
         */
        public static String getSavePath(String folderName) {
            return getSaveFolder(folderName).getAbsolutePath();
        }
    
        /**
         * 獲取文件夾對象
         *
         * @return 返回SD卡下的指定文件夾對象，若文件夾不存在則創(chuàng)建
         */
        public static File getSaveFolder(String folderName) {
            File file = new File(getExternalStorageDirectory()
                    .getAbsoluteFile()
                    + File.separator
                    + folderName
                    + File.separator);
            file.mkdirs();
            return file;
        }
    
        /**
         * 關(guān)閉流
         */
        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 把本地文件寫入到U盤中
         * @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 {//開始寫入
                fis = new FileInputStream(f);//讀取選擇的文件的
                if (usbFile.isDirectory()) {//如果選擇是個文件夾
                    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();
            }
        }
    }

6.提示下，要先打開界面，然后把u盤插上手機上，手機才能授權(quán)獲取到讀取u盤的usb讀取權(quán)限