Question

Hi i have been working through my first android app and it’s starting to become a Little slow and laggy. I have done iPhone apps before and i know that i have to release stuff. so i suppose my question is what are best practices for coding for android in terms of avoiding memory leaks. loading data from a JSON feed and just generally streamline my code to make it more efficient to improve user experience?

any help you can provide would be appreciated and passionate about android but just want to make sure i’m doing it right

heres a sample of my code so far

public class HomeActivity extends ListActivity {

    private MergeAdapter adapter=null;
    private ArrayAdapter<String> arrayAdapter=null;
    private ArrayAdapter<String> arrayAdapter2=null;
    private ArrayAdapter<String> arrayAdapter3=null;
    private static final String apiKey = "46fhr636gdbc737hjd92932dd"; 
    private static final String apiUser = "android-app-v1";
    private static final String ChosenTeam = null;
    private static String ChosenMethod = null; 
    public String fulldata = null;
    public String chosenLeagueId = "40";
    public List<String> newsList = null;
    public List<String> newsList2 = null;
    public List<String> newsList3 = null;

    public int newsAmount = 0;


    long unixTimeStamp = System.currentTimeMillis() / 1000L;

    //add Time Stamp to URL


    //public String chosenMethod; 


    String newsFeedRequest = "1.0/website/" + chosenLeagueId + "/news?timestamp=" + unixTimeStamp;
    String fixturesFeedURL = "https://website.com/_services/api/" + newsFeedRequest;
    private int container;


    private static String buildHmacSignature(String pKey, String pStringToSign)
    {
      String lSignature = "None";
      try
      {
        Mac lMac = Mac.getInstance("HmacSHA256");
        SecretKeySpec lSecret = new SecretKeySpec(pKey.getBytes(), "HmacSHA256");
        lMac.init(lSecret);

        byte[] lDigest = lMac.doFinal(pStringToSign.getBytes());
        BigInteger lHash = new BigInteger(1, lDigest);
        lSignature = lHash.toString(16);
        if ((lSignature.length() % 2) != 0) {
          lSignature = "0" + lSignature;
        }
      }
      catch (NoSuchAlgorithmException lEx)
      {
        throw new RuntimeException("Problems calculating HMAC", lEx);
      }
      catch (InvalidKeyException lEx)
      {
        throw new RuntimeException("Problems calculating HMAC", lEx);
      }

      return lSignature;
    }


    public void checkPreferences(){


        SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
        final String ChosenMethodPref = preferences.getString("ChosenMethod", ChosenMethod);
        Log.v("myapp", "ChosenMethod Home = " + ChosenMethodPref);

         if (ChosenMethodPref.equals("Team")) {
             setContentView(R.layout.homeactteam2);
             newsAmount = 5;

         } else {
             setContentView(R.layout.homeact);
             newsAmount = 10;
         }
}

    public void loadData(){String myhash = buildHmacSignature(apiKey, fixturesFeedURL);


    HttpClient client = new DefaultHttpClient();
    HttpPost post = new HttpPost(fixturesFeedURL);

    List<NameValuePair> pairs = new ArrayList<NameValuePair>();
    pairs.add(new BasicNameValuePair("requestToken", myhash));
    pairs.add(new BasicNameValuePair("apiUser", apiUser));

    try {
        post.setEntity (new UrlEncodedFormEntity(pairs));
        HttpResponse response = client.execute(post);
        BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
        String json = reader.readLine();
        fulldata = String.valueOf(json);
        Log.v("myApp","newsdata" + fulldata);

        newsList = new ArrayList<String>();
        newsList2 = new ArrayList<String>();
        newsList3 = new ArrayList<String>();

        JSONObject obj = new JSONObject(json);    
        JSONObject objData = obj.getJSONObject("data");
        JSONArray jArray = objData.getJSONArray("news");


           for(int t = 0; t < newsAmount; t++){
               JSONObject newsTitleDict = jArray.getJSONObject(t);

             newsList3.add(newsTitleDict.getString("title"));

           }

           for(int t = 0; t < 1; t++){
               JSONObject newsTitleDict = jArray.getJSONObject(t);

             newsList.add(newsTitleDict.getString("title"));
             newsList2.add(newsTitleDict.getString("title"));

           }



    } catch (ClientProtocolException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


    arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);
    arrayAdapter2 = new ArrayAdapter<String>(this, R.layout.single_item, newsList2);
    arrayAdapter3 = new ArrayAdapter<String>(this, R.layout.single_item, newsList3);

        ListView list = getListView();
           list.setTextFilterEnabled(true);

           LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
            View header = inflater.inflate( R.layout.homeheader, list, false);
            View header2 = inflater.inflate( R.layout.homeheader2, list, false);
            View header3 = inflater.inflate( R.layout.homeheader3, list, false);


    //setListAdapter (arrayAdapter);


        adapter = new MergeAdapter();
        adapter.addView(header);
        adapter.addAdapter(arrayAdapter);
        adapter.addView(header2);
        adapter.addAdapter(arrayAdapter2);
        adapter.addView(header3);
        adapter.addAdapter(arrayAdapter3);
        setListAdapter(adapter);

    }   
@Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        checkPreferences();
        loadData();


        Button backbtn = (Button) findViewById(R.id.backbtn);

        //Listening to button event
        backbtn.setOnClickListener(new View.OnClickListener() {

            public void onClick(View arg0) {
                //Starting a new Intent
                Intent previousScreen = new Intent(getApplicationContext(), ChooseTeamActivity.class);
                ChosenMethod = "null";
                SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
                SharedPreferences.Editor editor = preferences.edit();
                editor.putString("ChosenMethod", ChosenMethod);            
                editor.commit();
                previousScreen.putExtra("FullData", fulldata);
                startActivity(previousScreen);


            }
        });

    }


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    if (item.getItemId() == R.id.home) {

        startActivity(new Intent(HomeActivity.this, HomeActivity.class));

        return(true);
  }


    if (item.getItemId() == R.id.match) {

        startActivity(new Intent(HomeActivity.this, MatchActivity.class));

        return(true);
  }



    if (item.getItemId() == R.id.teams) {

        startActivity(new Intent(HomeActivity.this, TeamsActivity.class));

        return(true);
  }



    if (item.getItemId() == R.id.twitter) {

        startActivity(new Intent(HomeActivity.this, TwitterActivity.class));

        return(true);
  }

    if (item.getItemId() == R.id.info) {

        startActivity(new Intent(HomeActivity.this, InfoActivity.class));

        return(true);
  }


    return(super.onOptionsItemSelected(item));


}

}

Answer 1

You should take a look at this awesome presentation by Romain Guy.

It will give you an inside view of the things you are looking for, and you will also get a bunch of handy tips 🙂

E.g. besides using AsyncTasks and Handlers to avoid overloading the gui thread, you could declare the most of your variables as final. Custom itemrenderer implementations will significantly speed up your gui (scrolling), and -though it’s not a good Java practice-, using direct references instead of getters and setters will also improve somewhat the performance.