Twitter4j

To send the tweets, we use the excellent Twitter4j library available here. The twitter-4j-core-android... jar is added to our projects /lib folder. Using this library vastly simplifies the code needed to connect to the Twitter service - heres our TwitterWidgetActivity in full:

/*
 * Copyright (c) 2011 OTAMate Technology Ltd. All Rights Reserved.
 * http://www.androidacademy.com
 */

package com.androidacademy.tutorials.twitterwidget;

import twitter4j.Twitter;
import twitter4j.TwitterFactory;
import twitter4j.auth.AccessToken;
import android.app.Activity;
import android.appwidget.AppWidgetManager;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RemoteViews;
import android.widget.TextView;
import android.widget.Toast;

public class TwitterWidgetActivity extends Activity {
    private int mAppWidgetId = AppWidgetManager.INVALID_APPWIDGET_ID;
    private EditText mTwitterEditText;
    private TextView mTwitterDialogMessage;
    private Button mSendButton;
    private Button mCancelButton;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        // If the user backs out of the widget placement, tell the widget host
        setResult(RESULT_CANCELED);
        
        LayoutInflater factory = LayoutInflater.from( this );
        View mainView = factory.inflate( R.layout.send_tweet, null );
           
        mTwitterEditText = (EditText) mainView.findViewById (R.id.twitterText );
        mTwitterDialogMessage = (TextView) mainView.findViewById (R.id.twitterDialogMessage );
        mSendButton = (Button) mainView.findViewById( R.id.button_send);
        mCancelButton = (Button) mainView.findViewById( R.id.button_cancel);

        setContentView(mainView);
        
        mSendButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                if (!"".equals(mTwitterEditText.getText().toString())) {
                    final SharedPreferences settings = 
                        getSharedPreferences(Constants.SHARED_PREF_CONFIG, Context.MODE_PRIVATE);
                    SharedPreferences.Editor editor = settings.edit();
                    editor.putString(Constants.KEY_LAST_TWEET_TEXT, 
                        mTwitterEditText.getText().toString());
                    editor.commit();

                    final Twitter twitter = new TwitterFactory().getInstance();
                    twitter.setOAuthConsumer(Constants.CONSUMER_KEY, Constants.CONSUMER_SECRET);

                    // If we've got here with no Twitter auth token we need to get one
                    if ("".equals(settings.getString(Constants.KEY_ACCESS_TOKEN, ""))) {
                        TwitterWidgetActivity.this.startActivity(
                            new Intent(TwitterWidgetActivity.this, AuthoriseTwitterActivity.class));
                    } else {
                        new Thread(
                            new Runnable() {
                                public void run() {
                                    AccessToken accessToken = new AccessToken(
                                        settings.getString(Constants.KEY_ACCESS_TOKEN, ""), 
                                        settings.getString(Constants.KEY_ACCESS_TOKEN_SECRET, ""));
                                                
                                    twitter.setOAuthAccessToken(accessToken);
                                    try {
                                        Intent update = new Intent(TwitterWidgetActivity.this, 
                                            TwitterWidgetProvider.class);
                                        update.setAction(Constants.UPDATE);
                                        sendBroadcast(update);
                                        twitter.updateStatus(settings.getString(
                                            Constants.KEY_LAST_TWEET_TEXT, ""));
                                        finish();
                                    } catch (Exception e) {}
                                }
                            }
                        ).start();
                    }
                } else {
                    Toast.makeText(getApplicationContext(), 
                        getString(R.string.toast_no_text_entered), Toast.LENGTH_SHORT).show();
                }
            }
        });
        
        mCancelButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                finish();
            }
        });     
    }
    
    @Override
    protected void onResume() {
        super.onResume();
        
        SharedPreferences settings = 
            getSharedPreferences(Constants.SHARED_PREF_CONFIG, Context.MODE_PRIVATE);

        // If we've been added as a widget we don't need to  explain how to do it 
        if (!"".equals(settings.getString(Constants.KEY_ACCESS_TOKEN, ""))) {
            mTwitterDialogMessage.setVisibility(View.GONE);
        }
            
        Intent intent = getIntent();
        Bundle extras = intent.getExtras();
        if (extras != null) {
            mAppWidgetId = extras.getInt(
                AppWidgetManager.EXTRA_APPWIDGET_ID, 
                AppWidgetManager.INVALID_APPWIDGET_ID);
            
            AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this);
            RemoteViews views = new RemoteViews(this.getPackageName(), R.layout.widget);
            appWidgetManager.updateAppWidget(mAppWidgetId, views);
            
            Intent resultValue = new Intent();
            resultValue.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, mAppWidgetId);
            setResult(RESULT_OK, resultValue);
        }
    }           
}

Notice how we retrieve the consumer key and secret we stored earlier and use it to set authorisation on the Twitter object we ultimately call updateStatus() on - that's the call that actually sends the tweet. Notice also this is done in its own thread to keep the UI snappy.

That's about it for this one - I'd suggest you download the source and run it in Eclipse, setting breakpoints at the various points in the code I highlighted. As usual, this tutorial is intended just to get the basics across. If you were to implement a fuller Twitter client you'd have to deal with the history, the timeline, following and retweeting etc - all of which are available using appropriate API calls.

The app is available in the market here.