rick rick - 5 months ago 95
Android Question

Getting the current Fragment instance in the viewpager

Below is my code which has

3 Fragment classes
each embedded with each of the 3 tabs on
ViewPager
. I have a menu option. As shown in the
onOptionsItemSelected()
, by selecting an option, I need to update the fragment that is currently visible. To update that I have to call a method which is in the fragment class. Can someone please suggest how to call that method?

public class MainActivity extends ActionBarActivity {

ViewPager ViewPager;
TabsAdapter TabsAdapter;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

ViewPager = new ViewPager(this);
ViewPager.setId(R.id.pager);
setContentView(ViewPager);

final ActionBar bar = getSupportActionBar();

bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

//Attaching the Tabs to the fragment classes and setting the tab title.
TabsAdapter = new TabsAdapter(this, ViewPager);
TabsAdapter.addTab(bar.newTab().setText("FragmentClass1"),
FragmentClass1.class, null);
TabsAdapter.addTab(bar.newTab().setText("FragmentClass2"),
FragmentClass2.class, null);
TabsAdapter.addTab(bar.newTab().setText("FragmentClass3"),
FragmentClass3.class, null);


if (savedInstanceState != null) {
bar.setSelectedNavigationItem(savedInstanceState.getInt("tab", 0));
}

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.addText:

**// Here I need to call the method which exists in the currently visible Fragment class**

return true;

}

return super.onOptionsItemSelected(item);
}


@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("tab", getSupportActionBar().getSelectedNavigationIndex());

}

public static class TabsAdapter extends FragmentPagerAdapter
implements ActionBar.TabListener, ViewPager.OnPageChangeListener {

private final Context mContext;
private final ActionBar mActionBar;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();

static final class TabInfo {
private final Class<?> clss;
private final Bundle args;

TabInfo(Class<?> _class, Bundle _args) {
clss = _class;
args = _args;
}
}

public TabsAdapter(ActionBarActivity activity, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mActionBar = activity.getSupportActionBar();
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}

public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) {
TabInfo info = new TabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
mActionBar.addTab(tab);
notifyDataSetChanged();

}

@Override
public void onPageScrollStateChanged(int state) {
// TODO Auto-generated method stub

}

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// TODO Auto-generated method stub

}

@Override
public void onPageSelected(int position) {
// TODO Auto-generated method stub
mActionBar.setSelectedNavigationItem(position);
}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub

}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
Object tag = tab.getTag();
for (int i=0; i<mTabs.size(); i++) {
if (mTabs.get(i) == tag) {
mViewPager.setCurrentItem(i);

}
}

tabPosition = tab.getPosition();
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub

}

@Override
public Fragment getItem(int position) {
TabInfo info = mTabs.get(position);
return Fragment.instantiate(mContext, info.clss.getName(), info.args);
}

@Override
public int getCount() {
return mTabs.size();
}

}

}


Suppose below is the fragment class with the method
updateList()
I want to call:

public class FragmentClass1{

ArrayList<String> originalData;


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

View fragmentView = inflater.inflate(R.layout.frag1, container, false);

originalData = getOriginalDataFromDB();

return fragmentView;

}


public void updateList(String text)
{
originalData.add(text);
//Here I could do other UI part that need to added
}
}

Answer

by selecting an option, I need to update the fragment that is currently visible.

A simple way of doing this is using a trick related to the FragmentPagerAdapter implementation:

case R.id.addText:
     Fragment page = getSupportFragmentManager().findFragmentByTag("android:switcher:" + R.id.pager + ":" + ViewPager.getCurrentItem());
     // based on the current position you can then cast the page to the correct 
     // class and call the method:
     if (ViewPager.getCurrentItem() == 0 && page != null) {
          ((FragmentClass1)page).updateList("new item");     
     } 
return true;

Please rethink your variable naming convention, using as the variable name the name of the class is very confusing(so no ViewPager ViewPager, use ViewPager mPager for example).

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