Android - Getting context of a fragment in a pager

Question

I have a android application using a pager as navigation. For the tabs I have 3 layouts as content. On one of the fragments is a gallery and I want to add images to it. For that I have to set an ImageAdapter but I need to know how to access the context of a fragment.

final LayoutInflater factory = getLayoutInflater();
final View view = factory.inflate(R.layout.pictures, null);
Gallery g = (Gallery) view.findViewById(R.id.gallery1);
g.setAdapter(new ImageAdapter(view.getContext()));

I use this code above in the onCreate method to get the gallery from a layout that is not the contentview. I have to give a Context to the ImageAdapter. But what context do I have to set there?

EDIT: This is my complete code:

package com.bw2801.uwelugemediathek;

import java.util.Locale;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Context;
import android.database.DataSetObserver;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.SpinnerAdapter;
import android.widget.Toast;

public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener {

SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
PicturesSectionFragment ps = new PicturesSectionFragment();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Set up the action bar.
    final ActionBar actionBar = getActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    // Create the adapter that will return a fragment for each of the three
    // primary sections of the app.
    mSectionsPagerAdapter = new SectionsPagerAdapter(
            getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    // When swiping between different sections, select the corresponding
    // tab. We can also use ActionBar.Tab#select() to do this if we have
    // a reference to the Tab.
    mViewPager
            .setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
                @Override
                public void onPageSelected(int position) {
                    actionBar.setSelectedNavigationItem(position);
                }
            });

    // For each of the sections in the app, add a tab to the action bar.
    for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
        // Create a tab with text corresponding to the page title defined by
        // the adapter. Also specify this Activity object, which implements
        // the TabListener interface, as the callback (listener) for when
        // this tab is selected.
        actionBar.addTab(actionBar.newTab()
                .setText(mSectionsPagerAdapter.getPageTitle(i))
                .setTabListener(this));
    }

    final LayoutInflater factory = getLayoutInflater();
    final View view = factory.inflate(R.layout.pictures, null);
    Gallery g = (Gallery) view.findViewById(R.id.gallery1);
    g.setAdapter(new ImageAdapter(ps.getActivity()));
}

public class ImageAdapter extends BaseAdapter { 
    private Context mContext;

    private Integer[] mImageIds = {
            R.drawable.image01,
            R.drawable.image02,
            R.drawable.image03,
            R.drawable.image04,
            R.drawable.image05,
            R.drawable.image06,
            R.drawable.image07,
            R.drawable.image08,
    };

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return mImageIds.length;
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView i = new ImageView(mContext);

        i.setImageResource(mImageIds[position]);
        i.setLayoutParams(new Gallery.LayoutParams(150, 100));
        i.setScaleType(ImageView.ScaleType.FIT_XY);

        return i;
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public void onTabSelected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
    // When the given tab is selected, switch to the corresponding page in
    // the ViewPager.
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabReselected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
}

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
 * one of the sections/tabs/pages.
 */
public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch(position) {
            case 0:
                return new DummySectionFragment();
            case 1:
                return new SoundSectionFragment();
            case 2:
                return ps;
        }
        return new DummySectionFragment();
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
        case 0:
            return "Informationen";
        case 1:
            return "Soundboard";
        case 2:
            return "Galerie";
        }
        return null;
    }
}

public static class DummySectionFragment extends Fragment {

    public DummySectionFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.info, container, false);
    }
}

public static class PicturesSectionFragment extends Fragment {

    public PicturesSectionFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.pictures, container, false);
    }
}

public static class SoundSectionFragment extends Fragment {

    public SoundSectionFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.sounds, container, false);
    }
}
}

Answer 1

Fragments don't have their own Context, they use parent Activity.

• To get parent Activity Context, use getActivity()
• To use Application Context, use getActivity().getApplicationContext()

Prefer Application Context wherever possible.

UPDATE:

getActivity() of a Fragment returns an Activity instance if and only if, the said Fragment is currently attached to an Activity.

---

So,

Fragment f = new MyFragment();  

creates a fragment, but it is not attached to an activity yet. Hence f.getActivity() returns null.

---

After its added to an activity:

getFragmentManager().beginTransaction().add(f,"fragment").commit();

Now, getActivity() will return an Activity instance.

---

Again, if we detach the fragment from Activity:

getFragmentManager().beginTransaction().detach(f).commit()

getActivity() will again return a null value.

---

So, we should not use getActivity() outside the Fragment class, because we can't be sure of attached status. Thus I'll advice you to used getActivity() inside the fragment's own class in its methods: onAttach(), onCreate() or onActivityCreated().