是否可以从不是其所有者的Android设备读取记录？

Question

I'm developing an app which should be able to synchronize datastores between several devices.

I cannot figure out why I cannot read a record from a device which is not the owner of the datastore. Whereas the owner device of the datastore can read this same record. I have to precise that the datastore has been created with the EDITOR permission (see below).

try {
    datastoreTitle = mDatastoreManager.createDatastore();
    datastoreTitle.setRole(DbxPrincipal.PUBLIC, DbxDatastore.Role.EDITOR);  
    } catch (DbxException e) {
        e.printStackTrace();
    }

Someone has him been confronted to the same problem? The code raising this issue is below :

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);



    /**
     * Opening of the database
     */
    db = new SQliteHelper( this ) ;



    /**
     * Connection to dropbox API
     */
    mAccountManager = DbxAccountManager.getInstance(getApplicationContext(), APP_KEY, APP_SECRET);   


    // Set up the datastore manager
    if (mAccountManager.hasLinkedAccount()) {
        try {
            // Use Dropbox datastores
            mDatastoreManager = DbxDatastoreManager.forAccount(mAccountManager.getLinkedAccount());

        } catch (DbxException.Unauthorized e) {
            System.out.println("Account was unlinked remotely");
        }


    }
    if (mDatastoreManager == null) {
        // Account isn't linked yet, use local datastores
        mDatastoreManager = DbxDatastoreManager.localManager(mAccountManager);              

        AlertDialog.Builder alert = new AlertDialog.Builder(MainActivity.this);
        alert.setTitle("Connection à Dropbox");
        alert.setMessage("L'initialisation de l'application sert à vous synchroniser avec l'espace de données partagées.\r\n"
                + "Souhaitez-vous synchroniser votre application?");

        alert.setPositiveButton("Oui", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {

            mAccountManager.startLink((Activity)MainActivity.this, REQUEST_LINK_TO_DBX);

          }
        });

        alert.setNegativeButton("Non", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton) {

              Intent returnIntent = new Intent();
              setResult(RESULT_CANCELED, returnIntent);
              finish();


          }
        });


        alert.show();
    }

/**
 * Listener
 */

mDatastoreManager.addListListener(new DbxDatastoreManager.ListListener() {
    @Override
    public void onDatastoreListChange(DbxDatastoreManager dbxDatastoreManager) {

List<TitleList> listInBDD = db.getTitleSQliteHelper(); 
Set<DbxDatastoreInfo> datastorePresent = null;
try {
    datastorePresent = mDatastoreManager.listDatastores();
} catch (DbxException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}
Iterator<DbxDatastoreInfo> mdbxDatastoreInfoIterator = datastorePresent.iterator() ;

while (mdbxDatastoreInfoIterator.hasNext()){

    DbxDatastoreInfo mdbxDatastoreInfo = mdbxDatastoreInfoIterator.next();
    boolean find = false ;
    Log.d("Test 1 - delete Datastore =>  mdbxDatastoreInfo.id :" , mdbxDatastoreInfo.id ) ;

    for (TitleList titleFound : listInBDD){
        if (titleFound.idDbx.equals(mdbxDatastoreInfo.id)){
            Log.d("Test 2 - delete Datastore =>  TitleList :" , titleFound.nom.toString() ) ;

            find = true ;
        }
    }

    /**
     * Problem comes below
     */


    if ( !find ){
        Log.d("Delete absent datastore inside of the BDD : " , mdbxDatastoreInfo.id ) ;
        try {

            DbxDatastore dbxStore = mDatastoreManager.openDatastore(mdbxDatastoreInfo.id);
            // Toast to check that the datastores have been found
            Toast.makeText(MainActivity.this, dbxStore.getId(), Toast.LENGTH_LONG).show();
            DbxTable tab = dbxStore.getTable("table_de_courses"); // All is fine up to here, "tab" seems empty for a device which is not the owner of the database
            QueryResult mResults = tab.query(); 
            Iterator<DbxRecord> mRecord = mResults.iterator();

            // When the device is not the owner of the database, the code stops at this while condition
            while (mRecord.hasNext()){

                DbxRecord tmpRecord = mRecord.next(); 
                Set<String> fieldList = tmpRecord.fieldNames();
                Iterator<String> fieldNameList = fieldList.iterator();

                while (fieldNameList.hasNext()){

                    String str = fieldNameList.next();

                    if ( str.equalsIgnoreCase("titre") ){
                            TitleList tit = new TitleList(tab.get("titre").getString("titre"));
                            tit.setConnectDropbox();
                            tit.setIdDbx(mdbxDatastoreInfo.id);
                            db.addLists(tit);
                        }

                }

            }


        } catch (DbxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

UPDATE

I want to bring further explanation on my issue. I take a pratical case to describe how my app should work:

• A user opens the app from his device
  • He connects to the dropbox API (He's connecting with an "APP_KEY and APP_SERVICE"),
  • He creates a datastore inside of the dropbox app,
  • And then he creates records (with one of them containing a field called "titre" ),

• B user opens the app from another device,

  • He connects to the same dropbox API (He's connecting with the same couple of "APP_KEY and APP_SERVICE"),

  • Thanks to the listener, his app is syncing to diplay on his screen the new datastore created by the A user (I'm sure that the listener makes its job because I watch the datastore's IDs thanks to a Toast [see the code]),

    • Problem: the datastore will never be displayed because the field called "titre" is not found out inside of the listener (see the code content).

In debug mode I can see the code skipping this part of the code (see below). Whereas there are records with one of them containing the "titre" field!

while (mRecord.hasNext()){ 
...

I hope my details will be clearer, don't hesitate to ask me further information. Thank you if you can help me!

PS: one more detail, users have to connect to dropbox with a same mail and password to share their datastores. Otherwise they cannot shared their datastores (nevertheless it is what I have understood). Am I doing a mistake here?.

Answer 1

I'm not following completely what you're trying to do here, but some suggestions:

• If the same user is logged in to both devices, you don't need to set the role. You are the owner on each device. Just give the network time to sync.

• In general, another device will have to wait a certain time before it is visible in your list of datastores; then you open it, and then you have to wait again until the contents will appear.

Using listeners is a good way to watch for these events.

UPDATE: I think you're almost there. It's expected that right after the datastore appears in the list, when you open it, it is empty. The act of opening it temms the library to start downloading the contents in the background. When that download is complete (and sometimes when it is only partially complete) your listener will be called again. So your listener should just give up if it doesn't find the expected "titre" record and a later call will find it.

UPDATE TOO: If you want different users (using different Dropbox accounts) to share a datastore, you do have to set the public role, but you have to do something else too: the owner (creator) of the datastore must somehow transmit the datastore ID of the datastore to the other users, and (this is the important part!) their instance of the app must call openDatastore() with that ID. Until a user calls openDatastore() that datastore will not show in that user's listDatastores().

Good luck!