Call method in MainActivty from Fragment

Question

I have MainActivty class with DrawerLayout, so I add Fragments dynamically.

public void selectDrawerItem(MenuItem menuItem) {
    Fragment fragment = null;
    Class fragmentClass;
    switch(menuItem.getItemId()) {
        case R.id.nav_websites:
            fragmentClass = ScreenOne.class;
            break;
        case R.id.nav_commands:
            fragmentClass = ScreenTwo.class;
            break;
        case R.id.nav_help:
            fragmentClass = ScreenThree.class;
            break;
        default:
            fragmentClass = ScreenOne.class;
    }
    try {
        fragment = (Fragment) fragmentClass.newInstance();
    } catch (Exception e) {
        e.printStackTrace();
    }
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();
    setTitle(menuItem.getTitle());
    mDrawerLayout.closeDrawers();
}

In first fragment

public class ScreenOne extends Fragment implements  Button.OnClickListener

I have a function

public void loadText() {
    SharedPreferences myPrefs;
    myPrefs = getActivity().getSharedPreferences("myPrefs", MODE_WORLD_READABLE);

    siteName1.setText(myPrefs.getString("siteName1_txt", "").toString());
    siteURL1.setText(myPrefs.getString("siteURL1_txt", "").toString());

}

In my mainActivity class, in onCreate method, I want to call loadText() method, I tried

ScreenOne fragment = new ScreenOne();
fragment.loadText();

But that didn't work. I can't find fragment by ID or Tag, because they don't havy any. Please, any help or advice woild by much appreciated.

You can do it easily using this answer: http://stackoverflow.com/a/40714641/4862126 — Er. Kaushik Kajavadara, Mar 10 '17 at 12:41
first u have to check which fragment is currently visible,bcz u can call the function from ScreenOne only if that fragment is currently active — darwin, Mar 10 '17 at 12:57

score 1 · Accepted Answer · edited May 23 '17 at 12:00

There are several big problems with your code, these are the problems I see:

You really need to get an understanding of How Fragments work
You don't know which Fragment you have, but always try to access ScreenOne
You want to use a fragment method in onCreate without caring about fragment lifecycle
You try to create a Fragment instance, then use it even if it fails
You create a fragment with a constructor when you should use newInstance and Arguments
Your activity is coupled to your Fragment because you call concrete methods

That being said, the easiest fix for this particular problem is to only call the loadText method when you are guaranteed that is the current screen (ie. do it when you change it OR keep a reference to the current item and use instanceOf)

public void selectDrawerItem(MenuItem menuItem) {
    ...
    try {
        fragment = (Fragment) fragmentClass.newInstance();
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();
        ...
        if (ScreenOne.class.equals(fragmentClass)) {
            fragment.loadText();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

However I want to make clear, this is not the cleanest solution and I recommend you stick with single responsibility and have the fragment be responsible for loading its own text, while the activity is responsible for passing in the value from shared preferences as an argument (or via an interface callback pattern). This avoids any change of loadText being called before the fragment is ready.

score 0 · Answer 2 · answered Mar 10 '17 at 12:54

0

You can access any public method of YourActivity by using like

((YourActivity) getActivity()).nameofmethod

only whom is attached to YourActivity

answered Mar 10 '17 at 12:54

Rajesh

2,618
19
25

As Darwin mentioned on the other answer - He is looking to call a function whiche lies in fragment from the activity and not vice versa – Nick Cardoso Mar 10 '17 at 13:15

score -1 · Answer 3 · answered Mar 10 '17 at 13:03

-1

You can call your Activity method by using context of that activity such as:

((MainActivity)context).updateWishlistCount();

Hope this helps you!

answered Mar 10 '17 at 13:03

Kunal Dudka

467
1
6
14

1

He is looking to call a function lies in fragment from the activity and not vice versa – darwin Mar 10 '17 at 13:06
Also in a fragment you would use getActivity. Also to decouple a fragment (it's entire point) you'd use an interface here. Also someone posted this identical answer a long time before you. – Nick Cardoso Mar 10 '17 at 13:31

Call method in MainActivty from Fragment

3 Answers3