Question

I have two fragments Fragment1 and Fragment2.When I start the application the functions defined inside both of the fragments gets executed.So it takes a long time on startup(Since XML parsing and population of list view are executed on both fragments).I need to reduce the startup time of the application.Is their any way to execute Fragment1 on startup, and execution of Fragment2 bring to background? So that the user can interact with Fragment1.And Fragment2 execute its functions without diturbing the user.

Here is my code,

Fragment1=>

    public class Fragment1 extends Fragment{


public static String feedurl="http://www.abcd.com/en/rssfeeds/1_2_3_5/latest/rss.xml";
static String URL = "";
static final String KEY_HEAD = "item"; // parent node
static final String KEY_DATE = "pubDate";
public static String headflag="";
int f=0;
GridView list;
HeadlinesAdapter adapter;
private TextView mMessageView;
private Button mClearButton;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View v = inflater.inflate(R.layout.first_fragment, container, false);


    return v;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);



    headlines.parse();
    populate_listview();

    }


 public void populate_listview()
 {


     URL="http://www.abcd.com/en/rssfeeds/1_2_3_5/latest/rss.xml";
     ArrayList<HashMap<String, String>> newsList = new ArrayList<HashMap<String, String>>();

    XMLParser parser = new XMLParser();
    String xml = parser.getXmlFromUrl(URL);
    Document doc = parser.getDomElement(xml);
    NodeList nl = doc.getElementsByTagName(KEY_HEAD);
    NodeList itemLst = doc.getElementsByTagName("item");
    String MarqueeStr="";

    for (int i = 0; i < nl.getLength(); i++) {
        HashMap<String, String> map = new HashMap<String, String>();
        Element e = (Element) nl.item(i);
                    newsList.add(map);


 }
    list=(GridView)getActivity().findViewById(R.id.grid);
    adapter=new Adapter1(getActivity(), newsList);        
            list.setAdapter(adapter);

  }

Fragment2=>

    public class Fragment2 extends Fragment{


public static String feedurl="http://www.abcd.com/en/rssfeeds/1_2_3_5/latest/rss.xml";
static String URL = "";
static final String KEY_HEAD = "item"; // parent node
static final String KEY_DATE = "pubDate";
public static String headflag="";
int f=0;
GridView list;
HeadlinesAdapter adapter;
private TextView mMessageView;
private Button mClearButton;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View v = inflater.inflate(R.layout.second_fragment, container, false);


    return v;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);



    sports.parse();
    populate_listview();

    }


 public void populate_listview()
 {


     URL="http://www.abcd.com/en/rssfeeds/1_2_3_5/latest/rss.xml";
     ArrayList<HashMap<String, String>> newsList = new ArrayList<HashMap<String, String>>();

    XMLParser parser = new XMLParser();
    String xml = parser.getXmlFromUrl(URL);
    Document doc = parser.getDomElement(xml);
    NodeList nl = doc.getElementsByTagName(KEY_HEAD);
    NodeList itemLst = doc.getElementsByTagName("item");
    String MarqueeStr="";

    for (int i = 0; i < nl.getLength(); i++) {
        HashMap<String, String> map = new HashMap<String, String>();
        Element e = (Element) nl.item(i);
                newsList.add(map);


 }
    list=(GridView)getActivity().findViewById(R.id.grid2);
    adapter=new HeadlinesAdapter(getActivity(), newsList);        
            list.setAdapter(adapter);

  }

MainActivity=>

 public class MainActivity extends FragmentActivity {

private ViewPager mViewPager;
private MessageLoader mLoader;
private Button mSenderButton, mReceiverButton;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    // We get UI references
    mViewPager = (ViewPager) findViewById(R.id.viewPager);
    mSenderButton = (Button) findViewById(R.id.sender_button);
    mReceiverButton = (Button) findViewById(R.id.receiver_button);
    // set pager adapter
    mViewPager.setAdapter(new MyAdapter(this));
    // set receiver button listener
    mReceiverButton.setOnClickListener(new OnClickListener() {          

        public void onClick(View v) {
            mViewPager.setCurrentItem(1);
        }
    });

    mSenderButton.setOnClickListener(new OnClickListener() {            

        public void onClick(View v) {
            mViewPager.setCurrentItem(0);
        }
    });
}


private class MyAdapter extends FragmentPagerAdapter{

    private Context mContext;
    private String[] frags = {Fragment1.class.getName(), Fragment2.class.getName()};

    public MyAdapter(FragmentActivity activity) {
        super(activity.getSupportFragmentManager());
        mContext = activity;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Fragment frag = (Fragment) super.instantiateItem(container, position);
        if(frag instanceof MessageLoader){
            mLoader = (MessageLoader) frag;
        }
        return frag;
    }

    @Override
    public Fragment getItem(int pos) {
        return Fragment.instantiate(mContext, frags[pos]);
    }

    @Override
    public int getCount() {
        return frags.length;
    }

}
}

Answer 1

This is related to your othewr questions:

Is their any way to stop execution of Fragment2 when application
startup.I have to start it only when I swipe to Fragment2

No and you shouldn’t try to do this in the first place. The ViewPager needs the second Fragment(which isn’t visible yet) to be in good shape so the user can immediately swipe to it if he chooses. If that Fragment wouldn’t be built then the user experience will be poor especially in your case as you parse some xml from an Url on the main UI thread. You should really look at doing that xml parsing on a background thread if you want to improve the speed of your app and avoid possible ANR’s.

I want to call ‘function1’ on startup and ‘function2’ only when I
swipe to Fragment2

Leave Fragment 1 as it is now(calling that method you wish to be called) and then use the OnPageChangeListener on the ViewPager. I assume that you use a custom FragmentPagerAdapter so you could get a reference to the second Fragment and directly call the populate_listview() method:

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
      Fragment2 = (Fragment2) getSupportFragmentManager()
                    .findFragmentByTag(
                            "android:switcher:" + R.id.viewPager + ":" + 1);
      if (fragment != null) {
        fragment.populate_listview();// remove the call from onViewCreated
      }
}

But this is just a hack. What you want to do is to use background threads(AysncTask or normal threads) for the long operation. Have a look at this blog entry.