How to reference a fragment's methods from an activity?

Question

I have a viewpager app that I am working on with 3 fragments. I am adding the fragments dynamically via the FragmentStatePagerAdapter like that:

public class ViewPagerAdapter extends FragmentStatePagerAdapter {

CharSequence Titles[]; // This will Store the Titles of the Tabs which are Going to be passed when ViewPagerAdapter is created
int NumbOfTabs; // Store the number of tabs, this will also be passed when the ViewPagerAdapter is created


// Build a Constructor and assign the passed Values to appropriate values in the class
public ViewPagerAdapter(FragmentManager fm,CharSequence mTitles[], int mNumbOfTabsumb) {
    super(fm);

    this.Titles = mTitles;
    this.NumbOfTabs = mNumbOfTabsumb;

}

//This method return the fragment for the every position in the View Pager
@Override
public Fragment getItem(int position) {

    if(position == 0) // if the position is 0 we are returning the First tab
    {
        Current_forecast_fragment current_forecast_fragment = new Current_forecast_fragment();
        return current_forecast_fragment;
    }
    else if (position == 1)            // As we are having 2 tabs if the position is now 0 it must be 1 so we are returning second tab
    {
        return new Hourly_forecast_fragment();
    }else {
        return new Daily_forecast_fragment();
    }

}

// This method return the titles for the Tabs in the Tab Strip

@Override
public CharSequence getPageTitle(int position) {
    return Titles[position];
}

// This method return the Number of tabs for the tabs Strip

@Override
public int getCount() {
    return NumbOfTabs;
}
}

How do I reference a fragment, lets say the current forecast one from my main activity? I tried something like that but I need the fragment id to reference it. Any suggestions?:

public class MainActivity extends AppCompatActivity {
ViewPager pager;
ViewPagerAdapter adapter;
SlidingTabLayout tabs;
CharSequence Titles[]={"Current","Hourly","Daily"};
int Numboftabs =3;
Current_forecast_fragment mCurrent_forecast_fragment;

public static final String TAG = MainActivity.class.getSimpleName();
public static final String LOCATION_KEY = "location_key";
public Forecast mForecast;
public static final String DAILY_FORECAST = "DAILY_FORECAST";
public static final String HOURLY_FORECAST = "HOURLY_FORECAST";
//default coordinates - Gotse Delchev, UK Lati:57.156866 ; Long:
private double latitude = 41.5667;
private double longitude = 23.7333;
private LocationManager locationManager;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //-----------MY CODE STARTS HERE-----------------

    mCurrent_forecast_fragment = (Current_forecast_fragment) getSupportFragmentManager().findFragmentById(R.id.??????);
    //Log.d("MainActivity",mCurrent_forecast_fragment.getTag() + "Georgi");
    getLocation();

    // Creating The ViewPagerAdapter and Passing Fragment Manager, Titles fot the Tabs and Number Of Tabs.
    adapter =  new ViewPagerAdapter(getSupportFragmentManager(),Titles,Numboftabs);

    // Assigning ViewPager View and setting the adapter
    pager = (ViewPager) findViewById(R.id.pager);
    pager.setAdapter(adapter);

    // Assiging the Sliding Tab Layout View
    tabs = (SlidingTabLayout) findViewById(R.id.tabs);
    tabs.setDistributeEvenly(true); // To make the Tabs Fixed set this true, This makes the tabs Space Evenly in Available width

    // Setting Custom Color for the Scroll bar indicator of the Tab View
    tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
        @Override
        public int getIndicatorColor(int position) {
            return getResources().getColor(R.color.tabsScrollColor);
        }
    });

    // Setting the ViewPager For the SlidingTabsLayout
    tabs.setViewPager(pager);




}
}

See http://stackoverflow.com/questions/8785221/retrieve-a-fragment-from-a-viewpager — QuantumTiger, Dec 14 '15 at 20:26
Possible XY problem. Why do you want to access the fragment? — Kevin Krumwiede, Dec 14 '15 at 20:29

score 0 · Accepted Answer · answered Dec 15 '15 at 00:41

After a lot of experimentation I came with a simple solution to my problem. Since I am adding the fragments dynamically (in the viewPagerAdapter) and not in XML I couldn't reference them weither by id or tag. My solution is to modify slightly the adapter so that it stores a reference of the fragment passed as a parameter. Then all of the methods of the fragment are accessible (if declired public) in the mainActivity:

MainActivity:

public class MainActivity extends AppCompatActivity {
ViewPager pager;
ViewPagerAdapter adapter;
SlidingTabLayout tabs;
CharSequence Titles[]={"Current","Hourly","Daily"};
int Numboftabs =3;
Current_forecast_fragment mCurrent_forecast_fragment;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //-----------MY CODE STARTS HERE-----------------
    this.mCurrent_forecast_fragment = new Current_forecast_fragment();

    // Creating The ViewPagerAdapter and Passing Fragment Manager, Titles fot the Tabs and Number Of Tabs.
    adapter =  new ViewPagerAdapter(getSupportFragmentManager(),Titles,Numboftabs,mCurrent_forecast_fragment);

    // Assigning ViewPager View and setting the adapter
    pager = (ViewPager) findViewById(R.id.pager);
    pager.setOffscreenPageLimit(3);
    pager.setAdapter(adapter);

    // Assiging the Sliding Tab Layout View
    tabs = (SlidingTabLayout) findViewById(R.id.tabs);
    tabs.setDistributeEvenly(true); // To make the Tabs Fixed set this true, This makes the tabs Space Evenly in Available width

    // Setting Custom Color for the Scroll bar indicator of the Tab View
    tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
        @Override
        public int getIndicatorColor(int position) {
            return getResources().getColor(R.color.tabsScrollColor);
        }
    });

    // Setting the ViewPager For the SlidingTabsLayout
    tabs.setViewPager(pager);
}

My Code in ViewPagerAdapter:

public class ViewPagerAdapter extends FragmentStatePagerAdapter {
private Current_forecast_fragment mCurrent_forecast_fragment;
CharSequence Titles[]; // This will Store the Titles of the Tabs which are Going to be passed when ViewPagerAdapter is created
int NumbOfTabs; // Store the number of tabs, this will also be passed when the ViewPagerAdapter is created


// Build a Constructor and assign the passed Values to appropriate values in the class
public ViewPagerAdapter(FragmentManager fm,CharSequence mTitles[], int mNumbOfTabsumb,Current_forecast_fragment current_fragment) {
    super(fm);
    this.mCurrent_forecast_fragment = current_fragment;
    this.Titles = mTitles;
    this.NumbOfTabs = mNumbOfTabsumb;

}

//This method return the fragment for the every position in the View Pager
@Override
public Fragment getItem(int position) {

    if(position == 0) // if the position is 0 we are returning the First tab
    {
        return this.mCurrent_forecast_fragment;
    }
    else if (position == 1)            // As we are having 2 tabs if the position is now 0 it must be 1 so we are returning second tab
    {
        return new Hourly_forecast_fragment();
    }else {
        return new Daily_forecast_fragment();
    }

}
}

How to reference a fragment's methods from an activity?

1 Answers1

Linked