Question

当前，我正在使用流在我的应用程序中实现SQlite db备份功能。当我备份数据库时，它可以正常工作，并且文件中的数据已经通过“ SQlite的Db浏览器”进行了验证。但是，当尝试通过FilOuputStream从我的应用程序的数据库路径还原，并通过android SAF（存储访问框架）从返回的UrI还原到InputStream时，指向我放置了数据库备份的外部存储，我得到了损坏的数据库文件并且连接也关闭了。

以下是我为此目的使用的两种方法

进行备份

   //back db to a URI
public synchronized static boolean backupDb(Context context, Uri uri, String dbNam) throws IOException {
    File dbFile = new File(context.getDatabasePath(dbNam).getPath());
    FileInputStream inFilStream = new FileInputStream(dbFile);
    OutputStream outFilStream = context.getContentResolver().openOutputStream(uri);//new FileOutputStream(backupFile);
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inFilStream.read(buffer)) > 0) {
        outFilStream.write(buffer, 0, length);
    }
    outFilStream.flush();
    outFilStream.close();
    inFilStream.close();
    return true;
}

还原备份

  //restore db from a URI
public static synchronized boolean restoreBackup(Context context, Uri uri, String dbNam) {
    try {
        InputStream inFilStream = context.getContentResolver().openInputStream(uri);
        File dbFile = new File(context.getDatabasePath(dbNam).getPath());
        FileOutputStream outFilStream = new FileOutputStream(dbFile);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inFilStream.read(buffer)) > 0) {
            outFilStream.write(buffer, 0, length);
            Log.wtf("db", "restoring backup up");
        }
        outFilStream.flush(); 
     // using outFilStream.getFD().sync(); also not working
        outFilStream.close();
        inFilStream.close();
        return true;
    } catch (IOException e) {
        return false;
    }
}

日志

我不明白为什么这样做，因为当我调试并将断点放入其有效的还原方法中时，这很奇怪，请帮忙找出那里出了什么问题。

Answer 1

循环丢失了一些字节，所以我像那样使用 filechannel

    public synchronized static boolean saveDbBackup(Context context, Uri uri, String dbNam) throws IOException {
    File dbFile = new File(context.getDatabasePath(dbNam).getPath());
    FileChannel inFilChannel = new FileInputStream(dbFile).getChannel();
    FileChannel outFilChannel = ((FileOutputStream)context.getContentResolver().openOutputStream(uri)).getChannel();//new FileOutputStream(backupFile);
    outFilChannel.transferFrom(inFilChannel,0,inFilChannel.size());
    outFilChannel.close();
    inFilChannel.close();
    return true;
}

public static synchronized boolean restoreDbBackup(Context context, Uri uri, String dbNam) {
    try {
        FileChannel inFileChannel= ((FileInputStream) context.getContentResolver().openInputStream(uri)).getChannel();
        FileChannel outFileChannel= new FileOutputStream(new File(context.getDatabasePath(dbNam).getPath())).getChannel();
        outFileChannel.transferFrom(inFileChannel,0,inFileChannel.size());
        outFilChannel.close();
        inFilChannel.close();
        return true;
    } catch (IOException e) {
        return false;
    }
}

损坏的文件是使用FileInputStream和outstream生成的：java，android

1 个答案: