Live Streaming radio application - NullPointerException

Question

I have created a simple live streaming radio application. Here a .pls file is parsing for the streaming of the audio from the url . I am getting a NullPointerException.

Giving my logcat below :

02-04 04:54:54.409: E/AndroidRuntime(1603): FATAL EXCEPTION: main
02-04 04:54:54.409: E/AndroidRuntime(1603): Process: com.rad, PID: 1603
02-04 04:54:54.409: E/AndroidRuntime(1603): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rad/com.rad.MainActivity}: java.lang.NullPointerException
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.os.Handler.dispatchMessage(Handler.java:102)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.os.Looper.loop(Looper.java:136)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at android.app.ActivityThread.main(ActivityThread.java:5017)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at java.lang.reflect.Method.invokeNative(Native Method)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at java.lang.reflect.Method.invoke(Method.java:515)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-04 04:54:54.409: E/AndroidRuntime(1603):     at dalvik.system.NativeStart.main(Native Method)
02-04 04:54:54.409: E/AndroidRuntime(1603): Caused by: java.lang.NullPointerException
02-04 04:54:54.409: E/AndroidRuntime(1603):     at com.rad.MainActivity.initializeMediaPlayer(MainActivity.java:133)

Giving my mainactivity class :

        import java.io.IOException;
    import java.util.LinkedList;

    import android.app.Activity;
    import android.media.MediaPlayer;
    import android.media.MediaPlayer.OnBufferingUpdateListener;
    import android.media.MediaPlayer.OnPreparedListener;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.ProgressBar;

    public class MainActivity extends Activity implements OnClickListener {

        private ProgressBar playSeekBar;

        private Button buttonPlay;

        private Button buttonStopPlay;

        private MediaPlayer player;

        LinkedList<String> urls;

        public String mPls="//.pls uri here";

        /*StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();

        StrictMode.setThreadPolicy(policy); */

        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            initializeUIElements();



            Thread thread = new Thread(new Runnable(){
                @Override
                public void run() {

                     fGetPlayableUrl(mPls);
 try {
                initializeMediaPlayer();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }                   
                                 }
            });

            thread.start(); 


        } 




        private LinkedList<String> fGetPlayableUrl( String mPls) {
            GetStreamingUrl oGetStreamingUrl = new GetStreamingUrl(MainActivity.this);
            urls = oGetStreamingUrl.getStreamingUrl(mPls);
            return urls;
        }
        private void initializeUIElements() {

            playSeekBar = (ProgressBar) findViewById(R.id.progressBar1);
            playSeekBar.setMax(100);
            playSeekBar.setVisibility(View.INVISIBLE);

            buttonPlay = (Button) findViewById(R.id.button1);
            buttonPlay.setOnClickListener(this);

            buttonStopPlay = (Button) findViewById(R.id.button2);
            buttonStopPlay.setEnabled(false);
            buttonStopPlay.setOnClickListener(this);

        }

        public void onClick(View v) {
            if (v == buttonPlay) {
                startPlaying();
            } else if (v == buttonStopPlay) {
                stopPlaying();
            }
        }

        private void startPlaying() {
            buttonStopPlay.setEnabled(true);
            buttonPlay.setEnabled(false);

            playSeekBar.setVisibility(View.VISIBLE);

            player.prepareAsync();
            player.setOnPreparedListener(new OnPreparedListener() {

                public void onPrepared(MediaPlayer mp) {
                    player.start();
                }
        });

        }

        private void stopPlaying() {
            if (player.isPlaying()) {
                player.stop();
                player.release();
                try {
                    initializeMediaPlayer();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

            buttonPlay.setEnabled(true);
            buttonStopPlay.setEnabled(false);
            playSeekBar.setVisibility(View.INVISIBLE);
        }

        private void initializeMediaPlayer() throws IOException {
            player = new MediaPlayer();
            try {
            //player=MediaPlayer.create(this,Uri.parse("http://198.27.80.37:5412/listen.pls?sid=2"));

                player.setDataSource(urls.toString());
                //player.prepareAsync();
                //player.start();

            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalStateException e) {
                e.printStackTrace();
            }

            player.setOnBufferingUpdateListener(new OnBufferingUpdateListener() {

                public void onBufferingUpdate(MediaPlayer mp, int percent) {
                    playSeekBar.setSecondaryProgress(percent);
                    Log.i("Buffering", "" + percent);
                }
            });
        }

        @Override
        protected void onPause() {
            super.onPause();
            if (player.isPlaying()) {
                player.stop();
            }
        }
    }

GetStreamingUrl.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.LinkedList;
import android.content.Context;
import android.util.Log;

public class GetStreamingUrl {

private static String LOGTAG = "GetStreamingUrl";
private Context mContext;

public GetStreamingUrl(Context context) {
    Log.i(LOGTAG, "call to constructor");
    this.mContext = context;

}

public LinkedList<String> getStreamingUrl(String url) {

    Log.i(LOGTAG, "get streaming url");
    final BufferedReader br;
    String murl = null;
    LinkedList<String> murls = null;
    try {
        URLConnection mUrl = new URL(url).openConnection();
        br = new BufferedReader(
                new InputStreamReader(mUrl.getInputStream()));
        murls = new LinkedList<String>();
        while (true) {
            try {
                String line = br.readLine();

                if (line == null) {
                    break;
                }
                murl = parseLine(line);
                if (murl != null && !murl.equals("")) {
                    murls.add(murl);

                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    Log.i(LOGTAG, "url to stream :" + murl);
    return murls;
}

private String parseLine(String line) {
    if (line == null) {
        return null;
    }
    String trimmed = line.trim();
    if (trimmed.indexOf("http") >= 0) {
        return trimmed.substring(trimmed.indexOf("http"));
    }
    return "";
        }
  } 

Answer 1

You're referencing the urls variable in your initializeMediaPlayer() method before urls is ever initialized.

Answer 2

Your LinkedList<String> urls; is being initialized in fGetPlayableUrl(mPls); but you are calling initializeMediaPlayer(); before fGetPlayableUrl(mPls); where you do player.setDataSource(urls.toString()); but urls is still null and you are trying to get an object from it. As a result it is giving you a NullPointerException