Navigation in Navigation Drawer

Question

I have a Navigation Drawer which has 5 items. If user selects an Item, I'm loading respective Fragment in FrameLayout Now, if user pulls out the Navigation Drawer and selects the same Item as previous, I should not load the same Fragment again, so I'm saving the selected position and if previous selected position equals current selection I'm just closing the Navigation Drawer as follows:

    String title = null;
    invalidateOptionsMenu();
    android.support.v4.app.Fragment fragment = null;
    if (position == getPrevSelectedItem()) {
        // Already selected fragment is being displayed
    } else {
        switch (position) {
            case Numerics.ZERO:
                fragment = new DashBoardFragment();
                title = fragment.getClass().getSimpleName();
                break;
            case Numerics.ONE:
                break;
            case Numerics.TWO:
                break;
            case Numerics.THREE:
                break;
            case Numerics.FOUR:
                break;
            default:
                break;
        }
        if (fragment != null) {
            showFragment(fragment, title);
        }
        setSelectedItem(position);
    }

I'm adding fragments by adding to backstack in order to provide back navigation to previous fragment as follows :

    if (fragment != null) {
        String backStateName = fragment.getClass().getName();
        mFragmentManager = getSupportFragmentManager();
        mFragmentTransaction = mFragmentManager.beginTransaction();
        mFragmentTransaction.replace(R.id.dashboard_container, fragment);
        mFragmentTransaction.addToBackStack(backStateName);
        mFragmentTransaction.commit();
    }

The problem is: If I select Item no:3 and then select Item:4, if I navigate back the previous selection is still 4, but I'm displaying Fragment with no:3. So, if I select Item no:3 again from Navigation Drawer the Fragment loads again. How to solve this ??

EDIT:

public int getPrevSelectedItem() {
    return selectedItem;
}

public void setSelectedItem(int selectedItem) {
    this.selectedItem = selectedItem;
}

Answer 1

try this

Fragment currentFragment = getActivity().getFragmentManager().findFragmentById(R.id.dashboard_container);
if(currentFragment instanceof YouFragmentName)
    return

Answer 2

you can check the instance of loaded fragment on clicking the menu

Fragment loadedFragment= getFragmentManager().findFragmentById(R.id.fragmentLoadingSpace);

  if( !(loadedFragment instanceof  FragmentName1)){

// load fragment

        }

Answer 3

I think there is no need of else statement or you can use else only for closing drawer

public int prevPosition=-1;    

if (getPrevSelectedItem() != prevPosition) {
        // Already selected fragment is being displayed
        prevPosition =getPrevSelectedItem();  
        callFragment(position);
 } 
private void callFragment(int position) {
    // TODO Auto-generated method stub
    switch (position) {
    case Numerics.ZERO:
        fragment = new DashBoardFragment();
        title = fragment.getClass().getSimpleName();
        break;
    case Numerics.ONE:
        break;
    case Numerics.TWO:
        break;
    case Numerics.THREE:
        break;
    case Numerics.FOUR:
        break;
    default:
        break;
    }
    if (fragment != null) {
        showFragment(fragment, title);
    }
    setSelectedItem(position);

}

Answer 4

From my comment:

The drawer does not get updated when you press back - so you need to add some code to onBackPressed() in the activity , where you update the position according to the popped BackstackEntry .

@Override
public void onBackPressed(){

    String backStackEntryName = fragmentManager.getBackStackEntryAt(backCount - 2).getName(); 
     int id =  R.id.my_main_frag; //default option
     if (MyMainFrag.class.getName().equals(backStackEntryName)){
         id =  R.id.my_main_frag;
         selectedItem = 0;
     } else if (MySecondFrag.class.getName().equals(backStackEntryName)){
         id = R.id.my_second_frag;
         selectedItem = 1;
     }
      ...

     navigation.setCheckedItem(id);
     super.onBackPressed();
}