This one is driving me nuts. Basically, I want to create a ViewPager
and add a few Fragment
s to it. Then, all I want to do, it set a value in one of the Fragment
's TextView
s. I can add the Fragment
s fine, and they attach, but when I go to findViewById()
for one of the TextView
s in the first Fragment
it throws a NullPointerException
. I, for the life of me, can't figure out why.
Here's my code so far, let me know if more is needed please.
public class SheetActivity extends FragmentActivity {
// /////////////////////////////////////////////////////////////////////////
// Variable Declaration
// /////////////////////////////////////////////////////////////////////////
private ViewPager viewPager;
private PagerTitleStrip titleStrip;
private String type;
private FragmentPagerAdapter fragmentPager; //UPDATE
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sheet);
viewPager = (ViewPager) findViewById(R.id.viewPager);
titleStrip = (PagerTitleStrip) findViewById(R.id.viewPagerTitleStrip);
// Determine which type of sheet to create
Intent intent = getIntent();
this.type = intent.getStringExtra("type");
FragmentManager manager = getSupportFragmentManager();
switch (type) {
case "1":
viewPager.setAdapter(new InstallAdapter(manager));
break;
case "2":
viewPager.setAdapter(new InstallAdapter(manager));
break;
}
fragmentPager = (FragmentPagerAdapter) viewPager.getAdapter(); //UPDATE
}
@Override
public void onResume() {
super.onResume();
fragmentPager.getItem(0).setText("something"); //UPDATE
}
class MyAdapter extends FragmentPagerAdapter {
private final String[] TITLES = { "Title1", "Title2" };
private final int PAGE_COUNT = TITLES.length;
private ArrayList<Fragment> FRAGMENTS = null;
public MyAdapter(FragmentManager fm) {
super(fm);
FRAGMENTS = new ArrayList<Fragment>();
FRAGMENTS.add(new FragmentA());
FRAGMENTS.add(new FragmentB());
}
@Override
public Fragment getItem(int pos) {
return FRAGMENTS.get(pos);
}
@Override
public int getCount() {
return PAGE_COUNT;
}
@Override
public CharSequence getPageTitle(int pos) {
return TITLES[pos];
}
}
}
All of Fragment
s I created only have the onCreateView()
method overridden so I can display the proper XML layout. Other than that they are 'stock'. Why can't I interact with elements in any of the Fragment
s?
UPDATE:
So do something like this?
public class FragmentA extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle inState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
public void setText(String text) {
TextView t = (TextView) getView().findViewById(R.id.someTextView); //UPDATE
t.setText(text);
}
}
XML LAYOUT FOR FRAGMENT A
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="@+id/someTextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:textSize="22sp" />
</LinearLayout>
The TextView
is located in the fragments layout, not in the ViewPagers
or the PagerAdapter
, that is causing the NPE. Now, you have 2 options.
Secondly, you could make the TextView
into FragmentA static, so it can be accessed by other classes. So your code would look something like this:
....
TextView myText;
@Override
public View onCreateView(....) {
myLayout = ....;
myText = myLayout.findViewById(yourID);
....
}
And then you would change the text from somewhere else (if it's really necessary):
FragmentA.myText.setText("new text");
Explaining method 2
Use the following in your Fragment.
public static void setText(String text) {
TextView t = (TextView) getView().findViewById(R.id.someTextView);
t.setText(text);
}
Then change the text like:
FragmentA.setText("Lulz");