CODEWITHSUNDEEP
androidandroid-layoutandroid-viewpagerandroid-buttonandroid-pageradapter
PhDeOliveira
PhDeOliveira

Reputation: 2333

onClickListener inside of PagerAdapter

So I've been struggling with this for a while. I'm a pretty new android developer, so understanding some concepts to me are still very difficult.

In my layout I'm using a PagerAdapter to swipe horizontally between pages. I want to have a button in the landing layout, when clicked, to scroll to an adjacent layout.

Now my problem is that I'm getting a NPE once I click that button. So I see the problem, but don't know how to write it to make it do actually what it's supposed to.

Here's my code.

public class CustomPageAdapter extends PagerAdapter {

ViewPager mPager;

public Object instantiateItem(View collection, int position) {

    LayoutInflater inflater = (LayoutInflater) collection.getContext()
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    int resId = 0;
    switch (position) {
        case 0: {
            resId = R.layout.field01;
            break;
        }
        case 1: {
            resId = R.layout.add_site;
            break;
        }
        case 2: {
            resId = R.layout.main;
            break;
        }
    }

    View view = inflater.inflate(resId, null);
    if (position == 1) {
        Button addSiteButton = (Button) view.findViewById(R.id.addSiteButton);
        addSiteButton.setOnClickListener(new OnClickListener() {


            public void onClick(View v) {
             mPager.setCurrentItem(2); //NPE happens here.
            }
        });
    }


    ((ViewPager) collection).addView(view, 0);

    return view;
}

@Override
public void destroyItem(View arg0, int arg1, Object arg2) {
    ((ViewPager) arg0).removeView((View) arg2);
}

@Override
public boolean isViewFromObject(View arg0, Object arg1) {
    return arg0 == ((View) arg1);

}

@Override
public Parcelable saveState() {
    return null;
}

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

Thanks in advance!

Upvotes: 1

Views: 1160

Answers (1)

andro
andro

Reputation: 977

The NPE is occurring because you are trying to access mPager which is just a reference and not pointing to anything, created by line: ViewPager mPager;

You will need to retrieve the viewPager from layout in mPager reference as:

ViewPager mPager = (ViewPager) findViewById(R.id.pager);

Upvotes: 1

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