Call fragment function over activity

问题

I have a TabLayout with 3 tab.They are a fragment.

Test.java->PagerAdapter.java->TabFragment1+TabFragment2+TabFragment3

I want to call TabFragment1.helloworld() function. How can i call this function? Thanks.

Test.java created 3 tabs in below

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);

    tabLayout.addTab(tabLayout.newTab().setText("tab1"));

    tabLayout.addTab(tabLayout.newTab().setText("tab2"));                        

    tabLayout.addTab(tabLayout.newTab().setText("tab3"));

    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

    final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);

    viewPager.setOffscreenPageLimit(3);


final PagerAdapter adapter = new PagerAdapter
                                    (getSupportFragmentManager(), 
tabLayout.getTabCount());

viewPager.setAdapter(adapter);

PagerAdapter.java

public class PagerAdapter extends FragmentStatePagerAdapter {
    int mNumOfTabs;

    public PagerAdapter(FragmentManager fm, int NumOfTabs) {
        super(fm);
        this.mNumOfTabs = NumOfTabs;
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                TabFragment1 tab1 = new TabFragment1();
                return tab1;
            case 1:
                TabFragment2 tab2 = new TabFragment2();
                return tab2;
            case 2:
                TabFragment3 tab3 = new TabFragment3();
                return tab3;
            default:
                return null;
        }
    }

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

回答1:

You can access the desired fragment's method through your PagerAdapter:

((TabFragment1)adapter.getItem(0)).helloworld();

回答2:

It's a bit trickier than usual with ViewPagers, because you can't use the preferred findFragmentByTag() method. Here's something you could try - it's untested, but should be ok:

1. Create an interface, which all Fragments in your ViewPager implement:

   public interface ViewPagerFragmentBase {
   
       void callCommonMethod(int code);
   
   }
   

2. Implement it in all your ViewPager Fragments:

   public FragmentOne implements ViewPagerFragmentBase {
   
       @Override
       public void callCommonMethod(int code) {
   
           if (code == 1) {
               //Run code in this Fragment
           }
   
       }
   
   public FragmentTwo implements ViewPagerFragmentBase {
   
       @Override
       public void callCommonMethod(int code) {
   
           if (code == 2) {
               //Run code in this Fragment
           }
   
       }
   

3. Inside your Activity class, grab all Fragments currently in your Adapter, then cycle through each one, calling the callCommonMethod() along with a code which indicates the Fragment you are trying to reach:

   public class MainActivity extends AppCompatActivity {
   
       private void callCommonMethodInFragments(int code) {
   
           for (int i = 0; i < viewPagerAdapter.getCount(); i++) {
               ((ViewPagerFragmentBase)viewPagerAdapter.getItem(i)).callCommonMethod(code);
           }
   
       }
   
       //To call it...
       callCommonMethodInFragments(1); //This will run the method in FragmentOne only
   
   }
   

If the code matches the one in the Fragment you are trying to reach, then the method will run.

Something else you could also try though is an EventBus - this would allow you to achieve your goal more directly, and with less typing: https://github.com/greenrobot/EventBus

回答3:

To call fragment method from parent activity:

ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment);
fragment.callFunction(); 

回答4:

I had the same issue, and this worked for me: You have to add the fragments via your adapter and then you can access the fragment functions:

    myViewPager = (ViewPager) findViewById(R.id.viewpager);
    MyAdapterClass adapter = new MyAdapterClass(getSupportFragmentManager());
    adapter.addFragment(new TabOneFragment(), "");
    adapter.addFragment(new TabTwoFragment(), "");
    adapter.addFragment(new TabThreeFragment(), "");
    myViewPager.setAdapter(adapter);

    myTabLayout = (TabLayout) findViewById(R.id.tab_layout);

    myTabLayout.setupWithViewPager(myViewPager);

    // to access fragment functions:

    TabOneFragment tabOneFragment = (TabOneFragment) adapter.getItem(0);
    tabOneFragment.functionWhatSoEver();

来源：https://stackoverflow.com/questions/34182919/call-fragment-function-over-activity