Question

I want to sync the local database file in the Android app with the users’ DropBox or SkyDrive account. Anything would do.
I am not able to get a running code.
Please help.

Here is the code I got from the official DropBox site, but it says error at
“final static private AccessType ACCESS_TYPE = AccessType.APP_FOLDER;” as NoClassDefFoundError

public class DBRoulette extends Activity {
private static final String TAG = "DBRoulette";

///////////////////////////////////////////////////////////////////////////
//                      Your app-specific settings.                      //
///////////////////////////////////////////////////////////////////////////

// Replace this with your app key and secret assigned by Dropbox.
// Note that this is a really insecure way to do this, and you shouldn't
// ship code which contains your key & secret in such an obvious way.
// Obfuscation is good.
final static private String APP_KEY = "5gqlcpeirbe9kju";
final static private String APP_SECRET = "zs9bi3nwqf4arn2";

// If you'd like to change the access type to the full Dropbox instead of
// an app folder, change this value.
final static private AccessType ACCESS_TYPE = AccessType.APP_FOLDER;

///////////////////////////////////////////////////////////////////////////
//                      End app-specific settings.                       //
///////////////////////////////////////////////////////////////////////////

// You don't need to change these, leave them alone.
final static private String ACCOUNT_PREFS_NAME = "prefs";
final static private String ACCESS_KEY_NAME = "ACCESS_KEY";
final static private String ACCESS_SECRET_NAME = "ACCESS_SECRET";


DropboxAPI<AndroidAuthSession> mApi;

private boolean mLoggedIn;

// Android widgets
private Button mSubmit;
private LinearLayout mDisplay;
private Button mPhoto;
private Button mRoulette;

private ImageView mImage;

private final String PHOTO_DIR = "/Photos/";

final static private int NEW_PICTURE = 1;
private String mCameraFileName;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if (savedInstanceState != null) {
        mCameraFileName = savedInstanceState.getString("mCameraFileName");
    }

    // We create a new AuthSession so that we can use the Dropbox API.
    AndroidAuthSession session = buildSession();
    mApi = new DropboxAPI<AndroidAuthSession>(session);

    // Basic Android widgets
    setContentView(R.layout.main);

    checkAppKeySetup();

    mSubmit = (Button)findViewById(R.id.auth_button);

    mSubmit.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            // This logs you out if you're logged in, or vice versa
            if (mLoggedIn) {
                logOut();
            } else {
                // Start the remote authentication
                mApi.getSession().startAuthentication(DBRoulette.this);
            }
        }
    });

    mDisplay = (LinearLayout)findViewById(R.id.logged_in_display);

    // This is where a photo is displayed
    mImage = (ImageView)findViewById(R.id.image_view);

    // This is the button to take a photo
    mPhoto = (Button)findViewById(R.id.photo_button);

    mPhoto.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent();
            // Picture from camera
            intent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);

            // This is not the right way to do this, but for some reason, having
            // it store it in
            // MediaStore.Images.Media.EXTERNAL_CONTENT_URI isn't working right.

            Date date = new Date();
            DateFormat df = new SimpleDateFormat("yyyy-MM-dd-kk-mm-ss");

            String newPicFile = df.format(date) + ".jpg";
            String outPath = "/sdcard/" + newPicFile;
            File outFile = new File(outPath);

            mCameraFileName = outFile.toString();
            Uri outuri = Uri.fromFile(outFile);
            intent.putExtra(MediaStore.EXTRA_OUTPUT, outuri);
            Log.i(TAG, "Importing New Picture: " + mCameraFileName);
            try {
                startActivityForResult(intent, NEW_PICTURE);
            } catch (ActivityNotFoundException e) {
                showToast("There doesn't seem to be a camera.");
            }
        }
    });


    // This is the button to take a photo
    mRoulette = (Button)findViewById(R.id.roulette_button);

    mRoulette.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            DownloadRandomPicture download = new DownloadRandomPicture(DBRoulette.this, mApi, PHOTO_DIR, mImage);
            download.execute();
        }
    });

    // Display the proper UI state if logged in or not
    setLoggedIn(mApi.getSession().isLinked());

}

@Override
protected void onSaveInstanceState(Bundle outState) {
    outState.putString("mCameraFileName", mCameraFileName);
    super.onSaveInstanceState(outState);
}

@Override
protected void onResume() {
    super.onResume();
    AndroidAuthSession session = mApi.getSession();

    // The next part must be inserted in the onResume() method of the
    // activity from which session.startAuthentication() was called, so
    // that Dropbox authentication completes properly.
    if (session.authenticationSuccessful()) {
        try {
            // Mandatory call to complete the auth
            session.finishAuthentication();

            // Store it locally in our app for later use
            TokenPair tokens = session.getAccessTokenPair();
            storeKeys(tokens.key, tokens.secret);
            setLoggedIn(true);
        } catch (IllegalStateException e) {
            showToast("Couldn't authenticate with Dropbox:" + e.getLocalizedMessage());
            Log.i(TAG, "Error authenticating", e);
        }
    }
}

// This is what gets called on finishing a media piece to import
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == NEW_PICTURE) {
        // return from file upload
        if (resultCode == Activity.RESULT_OK) {
            Uri uri = null;
            if (data != null) {
                uri = data.getData();
            }
            if (uri == null && mCameraFileName != null) {
                uri = Uri.fromFile(new File(mCameraFileName));
            }
            File file = new File(mCameraFileName);

            if (uri != null) {
                UploadPicture upload = new UploadPicture(this, mApi, PHOTO_DIR, file);
                upload.execute();
            }
        } else {
            Log.w(TAG, "Unknown Activity Result from mediaImport: "
                    + resultCode);
        }
    }
}

private void logOut() {
    // Remove credentials from the session
    mApi.getSession().unlink();

    // Clear our stored keys
    clearKeys();
    // Change UI state to display logged out version
    setLoggedIn(false);
}

/**
 * Convenience function to change UI state based on being logged in
 */
private void setLoggedIn(boolean loggedIn) {
    mLoggedIn = loggedIn;
    if (loggedIn) {
        mSubmit.setText("Unlink from Dropbox");
        mDisplay.setVisibility(View.VISIBLE);
    } else {
        mSubmit.setText("Link with Dropbox");
        mDisplay.setVisibility(View.GONE);
        mImage.setImageDrawable(null);
    }
}

private void checkAppKeySetup() {
    // Check to make sure that we have a valid app key
    if (APP_KEY.startsWith("CHANGE") ||
            APP_SECRET.startsWith("CHANGE")) {
        showToast("You must apply for an app key and secret from developers.dropbox.com, and add them to the DBRoulette ap before trying it.");
        finish();
        return;
    }

    // Check if the app has set up its manifest properly.
    Intent testIntent = new Intent(Intent.ACTION_VIEW);
    String scheme = "db-" + APP_KEY;
    String uri = scheme + "://" + AuthActivity.AUTH_VERSION + "/test";
    testIntent.setData(Uri.parse(uri));
    PackageManager pm = getPackageManager();
    if (0 == pm.queryIntentActivities(testIntent, 0).size()) {
        showToast("URL scheme in your app's " +
                "manifest is not set up correctly. You should have a " +
                "com.dropbox.client2.android.AuthActivity with the " +
                "scheme: " + scheme);
        finish();
    }
}

private void showToast(String msg) {
    Toast error = Toast.makeText(this, msg, Toast.LENGTH_LONG);
    error.show();
}

/**
 * Shows keeping the access keys returned from Trusted Authenticator in a local
 * store, rather than storing user name & password, and re-authenticating each
 * time (which is not to be done, ever).
 *
 * @return Array of [access_key, access_secret], or null if none stored
 */
private String[] getKeys() {
    SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
    String key = prefs.getString(ACCESS_KEY_NAME, null);
    String secret = prefs.getString(ACCESS_SECRET_NAME, null);
    if (key != null && secret != null) {
        String[] ret = new String[2];
        ret[0] = key;
        ret[1] = secret;
        return ret;
    } else {
        return null;
    }
}

/**
 * Shows keeping the access keys returned from Trusted Authenticator in a local
 * store, rather than storing user name & password, and re-authenticating each
 * time (which is not to be done, ever).
 */
private void storeKeys(String key, String secret) {
    // Save the access key for later
    SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
    Editor edit = prefs.edit();
    edit.putString(ACCESS_KEY_NAME, key);
    edit.putString(ACCESS_SECRET_NAME, secret);
    edit.commit();
}

private void clearKeys() {
    SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
    Editor edit = prefs.edit();
    edit.clear();
    edit.commit();
}

private AndroidAuthSession buildSession() {
    AppKeyPair appKeyPair = new AppKeyPair(APP_KEY, APP_SECRET);
    AndroidAuthSession session;

    String[] stored = getKeys();
    if (stored != null) {
        AccessTokenPair accessToken = new AccessTokenPair(stored[0], stored[1]);
        session = new AndroidAuthSession(appKeyPair, ACCESS_TYPE, accessToken);
    } else {
        session = new AndroidAuthSession(appKeyPair, ACCESS_TYPE);
    }

    return session;
}

}

Answer 1

Do you add the dropbox-android-sdk.jar in your buildPath and in a correct way ?

The DropboxAPI JAR file should be in the libs/ folder, not lib/.

Try this and tell me if it works now …

PS: I’m working with DropboxAPI for android, and their code works very well for me and their documentation is really good to do your own application.