CODEWITHSUNDEEP
android
user971741
user971741

Reputation:

getItem in FragmentPagerAdapter not working as expected

I have the below code in my app.

From my understanding I expect that after Main activity is loaded getItem from Tab Adapter should be called with index: 1 as it is set as tab-1 .setTabListener(this), 1,true);

But instead of it getItem gets called twice first with index: 0 and then index: 1. Why is that can anyone explain?

//Main activity code:
    @Override
    protected void onCreate(final Bundle savedInstanceState) {

        …
        // Tabs Initilization
        viewPager = (ViewPager) findViewById(R.id.TabHandler);
        actionBar = getActionBar();
        mAdapter = new TabsAdapter(getSupportFragmentManager());

        actionBar.addTab(actionBar.newTab().setText(tabs[0])
                .setTabListener(this), 0, false);
        actionBar.addTab(actionBar.newTab().setText(tabs[1])
                .setTabListener(this), 1,true);
        actionBar.addTab(actionBar.newTab().setText(tabs[2])
                .setTabListener(this), 2, false);
}

//And this inside the `Tab Adapter`
public class TabsAdapter extends FragmentPagerAdapter {

    public TabsAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int index) {

        switch (index) {
            case 0:
                return new ZeroViewFragment();
            case 1:
                return new OneViewFragment();
            case 2:
                return new TwoViewFragment();
        }

        return null;
    }

    @Override
    public int getCount() {
        return 3;
    }

}

Upvotes: 1

Views: 527

Answers (1)

Kiril Aleksandrov
Kiril Aleksandrov

Reputation: 2591

This is beacause the ViewPager loads not only the visible fragment but the left and right fragments too. So in your case the visible fragment is #0, there is not left fragment and the right fragment is #1. The result is that fragments #0 and #1 are loaded. This behavior is implemented for performance reasons because this way the ViewPager has the next fragment prepared and ready to be shown and there will be no lag when swiping between pages.

Upvotes: 0

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