StreamHandler.java

/*
 * Copyright 2010 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.facebook.stream;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.MalformedURLException;

import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

import com.facebook.android.AsyncFacebookRunner;
import com.facebook.android.Facebook;
import com.facebook.android.FacebookError;
import com.facebook.android.Util;
import com.facebook.android.AsyncFacebookRunner.RequestListener;

/**
 * A handler for the stream page. It's responsible for
 * fetching the stream data from the API and storing it
 * in a local file based cache. It uses the helper class
 * StreamRenderer to render the stream.
 *  
 * @author yariv
 */
public class StreamHandler extends Handler {

    private static final String CACHE_FILE = "cache.txt";

    /**
     * Called by the dispatcher to render the stream page.
     */
    public void go() {
        dispatcher.getWebView().addJavascriptInterface(
                new StreamJsHandler(this), "app");

        // first try to load the cached data
        try {
            String cached = FileIO.read(getActivity(), CACHE_FILE);
            if (cached != null) {
                JSONObject obj = new JSONObject(cached);
                dispatcher.loadData(StreamRenderer.render(obj));
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        }

        Facebook fb = Session.restore(getActivity()).getFb();
        new AsyncFacebookRunner(fb).request("me/home", 
                new StreamRequestListener());
    }

    public class StreamRequestListener implements RequestListener {

        public void onComplete(String response, final Object state) {
            try {
                JSONObject obj = Util.parseJson(response);
                // try to cache the result
                try {
                    FileIO.write(getActivity(), response, CACHE_FILE);
                } catch (IOException e) {
                    e.printStackTrace();
                }

                // Convert the result into an HTML string and then load it
                // into the WebView in the UI thread.
                final String html = StreamRenderer.render(obj);
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        dispatcher.loadData(html);
                    }
                });

            } catch (JSONException e) {
                Log.e("stream", "JSON Error:" + e.getMessage());
            } catch (FacebookError e) {
                Log.e("stream", "Facebook Error:" + e.getMessage());
            }
        }

        public void onFacebookError(FacebookError e, final Object state) {
            Log.e("stream", "Facebook Error:" + e.getMessage());
        }

        public void onFileNotFoundException(FileNotFoundException e,
                                            final Object state) {
            Log.e("stream", "Resource not found:" + e.getMessage());      
        }

        public void onIOException(IOException e, final Object state) {
            Log.e("stream", "Network Error:" + e.getMessage());      
        }

        public void onMalformedURLException(MalformedURLException e,
                                            final Object state) {
            Log.e("stream", "Invalid URL:" + e.getMessage());            
        }

    }
}