OAuth authentication handling in a Android application

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="twetailer.console"
      android:versionName="0.1" android:versionCode="1">
    <uses-sdk android:minSdkVersion="8" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>

    <application android:label="@string/app_name" android:icon="@drawable/ase_men">
        <activity android:name=".Dashboard"
                  android:label="@string/app_name" android:launchMode="singleTop">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.intent.action.VIEW"/>
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.BROWSABLE"/>
                <data android:scheme="ase" android:host="oauthresponse"/>
            </intent-filter>
        </activity>
        <activity android:name="Preferences" android:label="@string/pref_name">
        </activity>

    </application>
</manifest>

Dashboard.java

package twetailer.console;

import oauth.signpost.commonshttp.CommonsHttpOAuthConsumer;
import oauth.signpost.commonshttp.CommonsHttpOAuthProvider;
import twetailer.oauth.OAuthDefs;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.CheckBox;
import android.widget.Toast;

public class Dashboard extends Activity {

    private static CommonsHttpOAuthConsumer consumer = null;
    private static CommonsHttpOAuthProvider provider = null;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        Preferences.setPreferenceContext(PreferenceManager.getDefaultSharedPreferences(getBaseContext()));

        boolean justAuthenticated = checkOAuthReturn(getIntent());
        
        if (!justAuthenticated && Preferences.get(Preferences.OAUTH_KEY, "").length() == 0) {
            // Display the pane with the warning message and the sign in button
            setContentView(R.layout.main_noauth);

            // Update the 'Remember me' checkbox with its last saved state, or the default one
            final String saveOAuthKeysPrefs = Preferences.get(Preferences.SAVE_OAUTH_KEYS, Preferences.SAVE_OAUTH_KEYS_DEFAULT);
            ((CheckBox) findViewById(R.id.app_noauth_keepmeconnected)).setChecked(Preferences.SAVE_OAUTH_KEYS_YES.equals(saveOAuthKeysPrefs));

            // Attach the event handler that will initiate the authorization process up to opening the browser with the authorization page
            findViewById(R.id.app_noauth_continue).setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    // Check if the 'Keep me connected' check box state changed and save its new state
                    boolean keepMeConnected = ((CheckBox) findViewById(R.id.app_noauth_keepmeconnected)).isChecked();
                    if (Preferences.SAVE_OAUTH_KEYS_YES.equals(saveOAuthKeysPrefs) != keepMeConnected) {
                        Preferences.set(Preferences.SAVE_OAUTH_KEYS, keepMeConnected ? Preferences.SAVE_OAUTH_KEYS_YES : Preferences.SAVE_OAUTH_KEYS_NO);
                    }
                    
                    // Set up the OAuth library
                    consumer = new CommonsHttpOAuthConsumer("<your_app_public_key>", "<your_app_secret_key>");

                    provider = new CommonsHttpOAuthProvider(
                            "https://<your_app_id>.appspot.com/_ah/OAuthGetRequestToken",
                            "https://<your_app_id>.appspot.com/_ah/OAuthAuthorizeToken",
                            "https://<your_app_id>.appspot.com/_ah/OAuthGetAccessToken");
                    
                    try {
                        // Steps 1 & 2:
                        // Get a request token from the application and prepare the URL for the authorization service
                        // Note: the response is going to be handled by the application <intent/> registered for that custom return URL
                        String requestTokenUrl = provider.retrieveRequestToken(consumer, "ase://oauthresponse");
                        
                        // Step 3:
                        // Invoke a browser intent where the user will be able to log in
                        startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(requestTokenUrl)));
                    }
                    catch(Exception ex) {
                        Toast.makeText(Dashboard.this, R.string.app_noauth_requesttoken_ex, Toast.LENGTH_LONG).show();
                        Log.e("Dashboard no auth", "Cannot initiate communication to get the request token\nException: " + ex.getClass().getName() + "\nMessage: " + ex.getMessage());
                    }
                }
            });
        }
        else {
            setContentView(R.layout.main);
        }
    }
    
    @Override
    protected void onNewIntent(Intent intent) {
        checkOAuthReturn(intent);
    }
    
    private boolean checkOAuthReturn(Intent intent) {
        boolean returnFromAuth = false;
        Uri uri = intent.getData();

        if (uri != null && uri.toString().startsWith("ase://oauthresponse")) {
            // Step 4:
            // Get the request token from the Authentication log in page
            String code = uri.getQueryParameter("oauth_verifier");

            try {
                // Step 5:
                // Get directly the access tokens
                provider.retrieveAccessToken(consumer, code);
                Log.e("Dashboard no auth", "User authenticated");
                returnFromAuth = true;
                
                // Persist the tokens
                if (Preferences.SAVE_OAUTH_KEYS_YES.equals(Preferences.get(Preferences.SAVE_OAUTH_KEYS, Preferences.SAVE_OAUTH_KEYS_DEFAULT))) {
                    Preferences.set(Preferences.OAUTH_KEY, consumer.getToken());
                    Preferences.set(Preferences.OAUTH_SECRET, consumer.getTokenSecret());
                    Log.e("Dashboard no auth", "User tokens persisted as preferences");
                }
            }
            catch(Exception ex) {
                Toast.makeText(Dashboard.this, R.string.app_noauth_accesstoken_ex, Toast.LENGTH_LONG).show();
                Log.e("Dashboard no auth", "Cannot complete communication to get the request token\nException: " + ex.getClass().getName() + "\nMessage: " + ex.getMessage());
            }
        }
        
        return returnFromAuth;
    }
}

main_noauth.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical"
>
    <LinearLayout 
        android:layout_height="wrap_content" 
        android:layout_width="match_parent" 
        android:orientation="horizontal"
    >
        <ImageView 
            android:layout_height="wrap_content" 
            android:layout_width="wrap_content" 
            android:src="@drawable/ase_network" 
            android:layout_margin="5dip"
            android:layout_gravity="top"
        ></ImageView>
        <TextView 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" 
            android:text="@string/app_noauth_warning" 
            android:layout_marginRight="5dip"
            android:layout_marginTop="5dip" 
            android:layout_marginBottom="5dip"
        ></TextView>
    </LinearLayout>
    <CheckBox 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:checked="true" 
        android:text="@string/app_noauth_keepmeconnected"
        android:layout_gravity="center_horizontal" 
        android:id="@+id/app_noauth_keepmeconnected"
    ></CheckBox>
    <Button 
        android:text="@string/btn_continue" 
        android:layout_height="wrap_content" 
        android:layout_width="wrap_content" 
        android:id="@+id/app_noauth_continue"
        android:layout_gravity="center_horizontal"
    ></Button>
</LinearLayout>

Preferences.java

package twetailer.console;

import android.content.SharedPreferences;
import android.preference.PreferenceActivity;
import android.util.Log;

public class Preferences extends PreferenceActivity {

    protected static SharedPreferences appPrefs;
    
    protected static final String OAUTH_KEY = "oauthKey";
    protected static final String OAUTH_SECRET = "oauthSecret";
    protected static final String SAVE_OAUTH_KEYS = "saveOAuthKeys";
    protected static final String SAVE_OAUTH_KEYS_YES = "Y";
    protected static final String SAVE_OAUTH_KEYS_NO = "N";
    protected static final String SAVE_OAUTH_KEYS_DEFAULT = SAVE_OAUTH_KEYS_NO;
    
    protected static void setPreferenceContext(SharedPreferences preferences) {
        appPrefs = preferences;
    }
    
    protected static String get(String key, String defaultValue) {
        try {
            return appPrefs.getString(key, defaultValue);
        }
        catch(Exception ex) {
            return set(key, defaultValue);
        }
    }

    public static String set(String key, String value) {
        SharedPreferences.Editor editor = appPrefs.edit();
        editor.putString(key, value);
        editor.commit();
        return value;
    }
}