This will demonstrate how to use twitter in Android

Twitter.java

public class TwitterShare extends Activity {
    /** Called when the activity is first created. */
    
	public static final String CONSUMER_KEY = "your consumer key";
	public static final String CONSUMER_SECRET = "your secret key";
	public static final String CALLBACK_URL = "http://localhost";
    
	public static final String requestTokenUrl="https://api.twitter.com/oauth/request_token";
    public static final String accessTokenUrl="https://api.twitter.com/oauth/access_token";
    public static final String authorizeUrl="https://api.twitter.com/oauth/authorize";

	private static final String tweet = "Your tweet here";
    
	CommonsHttpOAuthConsumer consumer;
	OAuthProvider provider;
	
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        
        try{
        	
        	createConsumerProvider();
        	authorize();
        	
        }catch(Exception e){e.printStackTrace();}
    }
    
    //===================================================================
    private void createConsumerProvider(){
    	
    	try{
    		
    		consumer = new CommonsHttpOAuthConsumer(CONSUMER_KEY, CONSUMER_SECRET);  
    		provider = new DefaultOAuthProvider(requestTokenUrl, accessTokenUrl, authorizeUrl);  
    		
    		HttpClient client = new DefaultHttpClient(); 
    		
    	}catch(Exception e){e.printStackTrace();}
    }
    
    //===================================================================
    private void authorize(){
    	
    	try{
    		
    		String authUrl = null;
    		boolean tokenRetrieved = false;
    		
    		try{
    			
    			authUrl = provider.retrieveRequestToken(consumer, CALLBACK_URL); 
    			tokenRetrieved = true;

    		}catch(Exception e){
    			
    			authUrl = provider.retrieveRequestToken(consumer, CALLBACK_URL); 
    			tokenRetrieved = true;
    		}
    		
    		final boolean tempToken = tokenRetrieved;
    		
    		final WebView webview = new WebView(this);
    		webview.getSettings().setJavaScriptEnabled(true);
    		webview.setWebViewClient(new WebViewClient(){
    			
    			@Override
    			public void onPageStarted(WebView webview, String authUrl, Bitmap favicon){
    				
    				 shouldOverrideUrlLoading(webview, authUrl);
    			}
    			
    			public boolean shouldOverrideUrlLoading(WebView view, final String url){
    			
    				try{
    					if (url.startsWith(TwitterShare.this.CALLBACK_URL)){
                            
    						provider.retrieveAccessToken(consumer,Uri.parse(url).getQueryParameter("oauth_verifier"));

                            Toast.makeText(TwitterShare.this,"Retrieving details, please wait..",Toast.LENGTH_LONG).show();
                            
                            webview.setVisibility(View.INVISIBLE);
                            webview.stopLoading();
                            webview.loadUrl("about:blank");
                            
                            if(tempToken)
                            	updateStatus();
                            else
                            	TwitterShare.this.finish();
    					}
    					
    				}catch(Exception e){e.printStackTrace();}
    				
    				return true;
    			}
    		});
    		webview.loadUrl(authUrl);
    		
    		this.setContentView(webview);
    		
    	}catch(Exception e){e.printStackTrace();}
    }
    
    //http://dev.bostone.us/2009/07/16/android-oauth-twitter-updates/#awp::2009/07/16/android-oauth-twitter-updates/
    
    //===================================================================
    private void updateStatus(){
    	
    	try{
    		
            // create a request that requires authentication
            HttpPost post = new HttpPost("http://twitter.com/statuses/update.xml");
            final List<NameValuePair> nvps = new ArrayList<NameValuePair>();
            // 'status' here is the update value you collect from UI
            nvps.add(new BasicNameValuePair("status", tweet));
            post.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));
            // set this to avoid 417 error (Expectation Failed)
            post.getParams().setBooleanParameter(CoreProtocolPNames.USE_EXPECT_CONTINUE, false);
            // sign the request
            consumer.sign(post);
            // send the request
            
            HttpClient client=new DefaultHttpClient();
            final org.apache.http.HttpResponse response = client.execute(post);
            // response status should be 200 OK
            int statusCode = response.getStatusLine().getStatusCode();
            final String reason = response.getStatusLine().getReasonPhrase();
            // release connection
            response.getEntity().consumeContent();
            if (statusCode != 200) {
              
            	Log.e("TwitterConnector", reason);
                throw new OAuthNotAuthorizedException();
            }
            
            this.finish();
    		
    	}catch(Exception e){e.printStackTrace();}
    }
}