Java Question How to use code with lambda?

[DonManfred]

I was asked to help creating a wrapper for TapKey Securitykeys.

They provide sample Androidapplication in which they are using lambda.

https://developers.tapkey.io/mobile/android/getting_started/

The Example app can be found here: https://github.com/tapkey/android-s...src/main/java/net/tpky/demoapp/authentication

In the mainactivity it starts with a check.
https://github.com/tapkey/android-s.../main/java/net/tpky/demoapp/MainActivity.java

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    private static final String TAG = MainActivity.class.getSimpleName();

    private UserManager userManager;
    private Auth0PasswordIdentityProvider passwordIdentityProvider;

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

        /*
         * Retrieve the TapkeyServiceFactory singleton.
         */
        App app = (App) getApplication();
        TapkeyServiceFactory tapkeyServiceFactory = app.getTapkeyServiceFactory();

        ConfigManager configManager = tapkeyServiceFactory.getConfigManager();
        userManager = tapkeyServiceFactory.getUserManager();
        passwordIdentityProvider = app.getPasswordIdentityProvider();

        /*
         * When no user is signed in, redirect to login LoginActivity
         */
        if(!userManager.hasUsers()){
            Intent intent = new Intent(this, LoginActivity.class);
            startActivity(intent);
            finish();
            return;
        }

        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        View headerView = navigationView.getHeaderView(0);
        TextView usernameTextView = (TextView) headerView.findViewById(R.id.nav_header__username);

        /*
         * Get the username of first user and display it in side menu. The first user is used here,
         * because we don't support multi-user yet anyways.
         */
        User firstUser = userManager.getFirstUser();
        if(firstUser != null){
            usernameTextView.setText(firstUser.getIpUserName());
        }

        /*
         * Verify, that app is compatible
         */
        configManager.getAppState(CancellationTokens.None)

                // asynchronously receive the operation result on the UI thread
                .continueOnUi((Func1<ConfigManager.AppState, Void, Exception>) appState -> {

                    // some time might have passed and maybe the activity is already finishing.
                    if (isFinishing())
                        return null;


                    switch (appState) {

                        // SDK Version is not supported anymore
                        case CLIENT_TOO_OLD:

                            new AlertDialog.Builder(MainActivity.this)
                                    .setMessage(R.string.main_app_too_old)
                                    .setPositiveButton(R.string.app_too_old_button, new DialogInterface.OnClickListener() {
                                        public void onClick(DialogInterface dialog, int id) {
                                            finish();
                                        }
                                    })
                                    .setOnDismissListener(dialogInterface -> {

                                        // TODO: Redirect to the app store, to let the user
                                        // download the latest app version.

                                        finish();
                                    })
                                    .create()
                                    .show();

                            break;

                        // This version of the SDK is still supported but is short before expiring and should be updated.
                        case CLIENT_UPDATE_SUGGESTED:

                            new AlertDialog.Builder(MainActivity.this)
                                    .setMessage(R.string.newer_app_available)
                                    .setPositiveButton(R.string.newer_app_available_button, null)
                                    .create()
                                    .show();

                            break;

                        case CLIENT_VERSION_OK:
                        default:
                    }

                    return null;
                })

                // Handle exceptions raised in async code.
                .catchOnUi(e -> {

                    // Handle error
                    Log.e(TAG, "failed to fetch app state: ", e);
                    return null;
                })

                // Make sure, no exceptions get lost.
                .conclude();
    }

How can i use such code in my wrapper?

Do i need to develop the library with Android Studio? As of now i am using Eclipse for syntaxhelp and SLC to compile.

I can into an error in SLC for sure

E:\B4ALibs.workspace\TapKeySDK\src\de\donmanfred\TapKeyAppwrapper.java:60: error: lambda expressions are not supported in -source 7
AsyncSchedulers.setSchedulerInterceptor((x, name) -> AsyncSchedulerUtils.applyLogging(x, name, 500, 10000));
^
(use -source 8 or higher to enable lambda expressions)
1 error

javac 11.0.1

Error.

Any suggestions/hints?

PD: The Device used is using Android 7+

 

[moster67]

I am not at home now but you should be able to replace the Lamda with an Anonymous class. After that you can compile with SLC.

 

[moster67]

Try the modified MainActivity.java class I have attached.

As a general note, I think it is much easier to work and wrap libs with Android Studio.
In this case, in Android Studio, you can simply highlight the "->" sign and then type ALT + ENTER and you get an option to automatically convert Lamda into an Anonymous class. Now you can compile with SLC.

 

[DonManfred]

As a general note, I think it is much easier to work and wrap libs with Android Studio.

I tried to follow the Tutorial about Android Studio and i failed. I was using a recent AS though.
Can you upload a AS-Project with a small example wrapper? Or help me configuring AS or the build scripts using a Remotedesktopconnection (would like to donate for a bit help to get started)?

In this case, in Android Studio, you can simply highlight the "->" sign and then type ALT + ENTER and you get an option to automatically convert Lamda into an Anonymous class.

in the beginning i was not sure that i understand what a anonymous class is. But after using this "trick" i know better. Thank you for this tip! At least i could use AS now to convert the code to not use lamda
The code in the example main was just an example. It was more important to adapt the Authproviderclass.

I now converted the java files in AS to use anonymous classes and then i copied over the files to my Eclipse project. And, hopefully, i do come futher now. I´ll inform you...

Many thanks for this - really useful - hint

 

[DonManfred]

After i now learned that i need to replace the Lamda starting from the most inner methods i now was able to convert all of the Lamda from the authentificationclasses.