Question

我正在开发一个使用数据库的Android。我想在使用真机运行时将数据库复制到SD卡。但它并不总能成功。我的程序没有说明原因，只是说它无法复制数据库。我将数据库存储在res\raw\mobilephone1.db;它是10 MB。我设置了允许将数据写入SD卡的权限。

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

这是对的吗？

private final String DATABASE_PATH = android.os.Environment  
                .getExternalStorageDirectory().getAbsolutePath()  
                + "/mobilephone";  
    private final String DATABASE_FILENAME = "mobilephone.db"; 


private SQLiteDatabase openDatabase()  
    {  
        try  
        {  
            // obtain absolute path of mobilephone.db  
            String databaseFilename = DATABASE_PATH + "/" + DATABASE_FILENAME;  
            File dir = new File(DATABASE_PATH);          
            // if/sdcard/mobilephone exist，crtate this list 
            if (!dir.exists()) {  
                dir.mkdir();  
                }
            // if  mobilephone.db file did not exist in/sdcard/mobilephone then copy this filt to SD card list（/sdcard/mobilephone） from res\raw
            if (!(new File(databaseFilename)).exists())  
            {  

                // obtain the InputStream object that encapsulate mobilephone.db
                InputStream is = getResources().openRawResource(R.raw.mobilephone1);  
                FileOutputStream fos = new FileOutputStream(databaseFilename);  

                int count = 0;
                while (count == 0) {
                 count = is.available();
                }
                byte[] buffer = new byte[count];

                int readCount = 0; // the number of bytes that has successfully readen
                while (readCount < count) {
                 readCount += is.read(buffer, readCount, count - readCount);
                }

                fos.write(buffer, 0, count); 
                fos.close();  
                is.close();  
            }  
            // go to mobilephone.db in /sdcard/mobilephone  
            SQLiteDatabase database = SQLiteDatabase.openOrCreateDatabase(  
                   databaseFilename, null);  
            return database;  
        }  
        catch (Exception e)  
        {  
        }  
        return null;  
    }

Answer 1

试试这个::

File sd = Environment.getExternalStorageDirectory();

File src = new File("YOUR_SOURCE_PATH");

File dest = new File(sd +  "/" +DATABASE_NAME);

      try 
      {
          if (Environment.getExternalStorageDirectory().canWrite()) 
          {                 
              if (srcdb.exists()) 
              {
                  FileChannel src = new FileInputStream(srcdb).getChannel();
                  FileChannel dst = new FileOutputStream(destdb).getChannel();
                  dst.transferFrom(src, 0, src.size());
                  src.close();
                  dst.close();  
                  flag=0; 

              }
              else
              {
                  Toast.makeText(getApplicationContext(), "ERROR: File not found in Database " , Toast.LENGTH_LONG).show();                    
              }
          }
          else
          {
              Toast.makeText(getApplicationContext(), "ERROR: Cannot write to file" , Toast.LENGTH_LONG).show();
          }
      }
      catch (Exception e) 
      {
          Log.e("Movedb", "Error in Copying" + e.toString());

      }

此外，您只需要一个权限：

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

无法将数据库复制到SD卡

1 个答案: