Pass fragment as parameter?

Question

I have simple method where I want to pass fragment name as parameter. I have few fragments like

1) AddNewDatesFragment

2) AskFragment

3) DisclaimerFragment

I have below code that work properly as expected

FragmentManager fragmentManager = activity.getSupportFragmentManager();
    for (int entry = 0; entry < fragmentManager.getBackStackEntryCount();     entry++) {
    Fragment fragment = (Fragment)    fragmentManager.getBackStackEntryAt(entry);
        if (fragment instanceof AddNewDatesFragment) {
            Log.i("TAG", " Expected Fragment Found");
        }
    }

I want to write some code in method where I could call methods like this

        isExistFragment(AddNewDatesFragment);
        isExistFragment(AskFragment);
        isExistFragment(DisclaimerFragment);

etc...

I have tried code like this but not working gives compile time error at if condition.

    private boolean isExistFragment(Class<Fragment> expectedFragment) {
    FragmentManager fragmentManager = activity.getSupportFragmentManager();
    for (int entry = 0; entry < fragmentManager.getBackStackEntryCount(); entry++) {
        Fragment fragment = (Fragment) fragmentManager.getBackStackEntryAt(entry);
        if (fragment instanceof expectedFragment) {
            Log.i("TAG", " Expected Fragment Found");
            return true;
        }
    }
    return false;
}

I am curious about implementing such method. Thanks,

at if condition as : Multiple markers at this line - expectedFragment cannot be resolved to a type - Incompatible conditional operand types Fragment and expectedFragment — khurram, Jan 02 '15 at 13:11
Fragment Return null : in this line : Fragment fragment = (Fragment) fragmentManager .findFragmentById(fragmentManager.getBackStackEntryAt(entry) .getId()); — khurram, Jan 02 '15 at 13:40

Anand Tiwari · Answer 1 · 2015-01-02T13:33:44.680

1

getBackStackEntryAt(index)

does not return Fragment itself, it return BackStackEntry object for the respected fragment.

Please have a look http://developer.android.com/reference/android/app/FragmentManager.html#getBackStackEntryAt(int)

Use below snippet to retrieve Fragment from the stack:

   Fragment fragment = (Fragment) fragmentManager
            .findFragmentById(fragmentManager.getBackStackEntryAt(entry)
                    .getId());

Here, first you get BackStackEntry for the respected Fragement, by which you would get fragment id of fragment at perticular location. Then by id you easily can retrieve Fragment.

edited Jan 02 '15 at 13:33

answered Jan 02 '15 at 13:16

Anand Tiwari

1,583
10
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But I am getting compile time error, as you say that thing only comes at runtime. – khurram Jan 02 '15 at 13:25
use reflection : http://stackoverflow.com/questions/14846853/passing-a-class-as-an-argument-to-a-method-in-java – Anand Tiwari Jan 02 '15 at 13:40

score 0 · Answer 2 · answered Jan 02 '15 at 13:19

You could maybe use:

expectedFragment.isAssignableFVrom(fragment.getClass())

This will be true if the exceptedFragment class is an interface or superclass of the fragment class (see doc).

(PS: you can not use fragment instanceof expectedFragment on exceptedFragment because it is a class and not an object.)

score 0 · Answer 3 · answered Jan 02 '15 at 13:22

i think the problem with the import statements in the class extends FragmentActivity you imported supportv4 and in that expectedFragment you imported "import android.app.Fragment" once check import statements.

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;

or import android.app.Fragment;

hata · Accepted Answer · 2015-01-02T14:37:57.393

0

I don't know whether it is the best way or not. But I would use tag feature for the similar purpose.

When you add a fragment set a tag for later identification:

fragmentManager.beginTransaction()
               .replace(R.id.container, newlyAddFragment, TAG_FOR_THE_FRAGMENT)
               .commit();

And implement isExistFragment like this:

boolean isExistFragment(String tag) {
    Fragment targetFragment = fragmentManager.findFragmentByTag(tag);
    return targetFragment != null;
}

edited Jan 02 '15 at 14:37

answered Jan 02 '15 at 14:30

hata

11,633
6
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Yes its work for me too, At last I used the same strategy to solved theissue. – khurram Jan 06 '15 at 08:53

Pass fragment as parameter?

4 Answers4