我正在我的 Android 应用程序中实现备份/恢复系统。

每隔几分钟自动备份一次。 在卸载并重新安装我的应用程序后，我正在尝试从我的 SD 卡恢复我的数据库备份文件。

备份有效，但问题在于:
每当用户再次安装我的应用程序时，都会出现文件未找到异常，但是，如果用户关闭该应用程序，然后再次打开它，恢复就可以了。不知何故，当应用程序首次启动时，恢复会遇到问题。

恢复必须在第一次启动时发生。

注意:backupExists 函数返回 true。

@Override
public void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if(backUpExists()){

        restoreDB();
      }
}
     private boolean backUpExists()
  {
    try{
        File sd = Environment.getExternalStorageDirectory();
        if (sd.canRead()){
            String backupDBPath = "myDB";
             File backupedDB = new File(sd, backupDBPath);
             if(backupedDB.exists()){
                 return true;
             }
        }
    } catch(Exception ex) {
         Toast.makeText(getBaseContext(), ex.toString(), Toast.LENGTH_LONG).show();
    }
        return false;
  }
  private void restoreDB()
  {
    try{
        File sd = Environment.getExternalStorageDirectory();
        File data = Environment.getDataDirectory();

        if (sd.canWrite()) {
            String restroredDBPath = "//data//myPackage//databases//myDB";
            String backupDBPath = "myDB";
            File restoredDB = new File(data, restroredDBPath);
            File backupedDB = new File(sd, backupDBPath);
                FileChannel src = new FileInputStream(backupedDB).getChannel();
                FileChannel dst = new FileOutputStream(restoredDB).getChannel();
                dst.transferFrom(src, 0, src.size());
                src.close();
                dst.close();
                Toast.makeText(getBaseContext(), restoredDB.toString(), Toast.LENGTH_LONG).show();

        }
    } catch (Exception e) {

        Toast.makeText(getBaseContext(), e.toString(), Toast.LENGTH_LONG).show();
    }
  }

回溯

09-09 22:49:50.931: I/Database(23206): sqlite returned: error code = 26, msg = statement aborts at 14: [SELECT COUNT(*) FROM Photos WHERE AlbumId=0] file is encrypted or is not a database
09-09 22:49:50.931: D/AndroidRuntime(23206): Shutting down VM
09-09 22:49:50.931: W/dalvikvm(23206): threadid=1: thread exiting with uncaught exception (group=0x4151c700)
09-09 22:49:50.931: E/AndroidRuntime(23206): FATAL EXCEPTION: main
09-09 22:49:50.931: E/AndroidRuntime(23206): net.sqlcipher.database.SQLiteException: file is encrypted or is not a database
09-09 22:49:50.931: E/AndroidRuntime(23206):    at     net.sqlcipher.database.SQLiteQuery.native_fill_window(Native Method)
09-09 22:49:50.931: E/AndroidRuntime(23206):    at net.sqlcipher.database.SQLiteQuery.fillWindow(SQLiteQuery.java:73)
09-09 22:49:50.931: E/AndroidRuntime(23206):    at net.sqlcipher.database.SQLiteCursor.fillWindow(SQLiteCursor.java:290)
[snipped]

最佳答案

请使用这段代码，它可能会对你有所帮助......我已经用这种方式做了同样的事情

用于备份

try {
    File sd = Environment.getExternalStorageDirectory();
    File data = Environment.getDataDirectory();

    if (sd.canWrite()) {
        String currentDBPath = "//data/package name/databases/database_name";
        String backupDBPath = "database_name";
        File currentDB = new File(data, currentDBPath);
        File backupDB = new File(sd, backupDBPath);

        if (currentDB.exists()) {
            FileChannel src = new FileInputStream(currentDB).getChannel();
            FileChannel dst = new FileOutputStream(backupDB).getChannel();
            dst.transferFrom(src, 0, src.size());
            src.close();
            dst.close();
            Toast.makeText(getApplicationContext(), "Backup is successful to SD card", Toast.LENGTH_SHORT).show();
        }
    }
} catch (Exception e) {
}

用于恢复

try {
    File sd = Environment.getExternalStorageDirectory();
    File data = Environment.getDataDirectory();

    if (sd.canWrite()) {
    String currentDBPath = "//data/package name/databases/database_name";
        String backupDBPath = "database_name";
        File currentDB = new File(data, currentDBPath);
        File backupDB = new File(sd, backupDBPath);

        if (currentDB.exists()) {
            FileChannel src = new FileInputStream(backupDB).getChannel();
            FileChannel dst = new FileOutputStream(currentDB).getChannel();
            dst.transferFrom(src, 0, src.size());
            src.close();
            dst.close();
            Toast.makeText(getApplicationContext(), "Database Restored successfully", Toast.LENGTH_SHORT).show();
        }
    }
} catch (Exception e) {
}

你可以在 if 条件下的文件 channel 中看到两者之间的一点差异。

关于android - 恢复 SQLite 数据库文件，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18635412/