BackupDataInput

open class BackupDataInput

Provides the structured interface through which a BackupAgent reads information from the backup data set, via its onRestore() method. The data is presented as a set of "entities," each representing one named record as previously stored by the agent's android.app.backup.BackupAgent#onBackup(ParcelFileDescriptor,android.app.backup.BackupDataOutput,ParcelFileDescriptor) implementation. An entity is composed of a descriptive header plus a byte array that holds the raw data saved in the remote backup.

The agent must consume every entity in the data stream, otherwise the restored state of the application will be incomplete.

Example

A typical android.app.backup.BackupAgent#onRestore(android.app.backup.BackupDataInput,int,ParcelFileDescriptor) implementation might be structured something like this:

public void onRestore(BackupDataInput data, int appVersionCode,
                        ParcelFileDescriptor newState) {
      while (data.readNextHeader()) {
          String key = data.getKey();
          int dataSize = data.getDataSize();
 
          if (key.equals(MY_BACKUP_KEY_ONE)) {
              // process this kind of record here
              byte[] buffer = new byte[dataSize];
              data.readEntityData(buffer, 0, dataSize); // reads the entire entity at once
 
              // now 'buffer' holds the raw data and can be processed however
              // the agent wishes
              processBackupKeyOne(buffer);
          } else if (key.equals(MY_BACKUP_KEY_TO_IGNORE) {
              // a key we recognize but wish to discard
              data.skipEntityData();
          } // ... etc.
     }
  }

Summary

Public methods

open fun getDataSize(): Int

open fun getKey(): String!

open fun readEntityData(
    data: ByteArray!, 
    offset: Int, 
    size: Int
): Int

open fun readNextHeader(): Boolean

open fun skipEntityData(): Unit