i am having problems trying to update/replace Fragments in a
ViewPager. the problem is that the old fragments simply won't get
replaced by the new ones. i have read a couple of solutions on
stackoverflow, and tried them, but it still doesn't work. anyone have
any ideas why? i will explain what i am trying to do below.
i have a Pojo class
public class Pojo {
public String text;
public Pojo(String text) { this.text = text; }
}
i have a group class, PojoGroup
public class PojoGroup {
public String title;
public List<Pojo> pojos;
public PojoGroup(String title, List<Pojo> pojos) {
this.title = title;
this.pojos = pojos;
}
}
the idea is that i will bind the PojoGroup to a Fragment. the XML of
the fragment, pojogroup_frag.xml, looks like the following. as you can
see, i will set the tvTitle to PojoGroup.title and bind the list of
Pojo to the ListView.
<LinearLayout xmlns:android="..."
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TextView android:id="@+id/tvTitle" android:layout_width="..."
android_layout_height="..."/>
<ListView android:id="@+id/listView" android:layout_width="..."
android_layout_height="..."/>
</LinearLayout>
for completeness, here is my pojo adapter to bind the list of pojos to
the ListView.
public class PojoAdapter extends ArrayAdapter<Pojo> {
public PojoAdapter(Context ctx, int resId, List<Pojo> objects) {
super(ctx, resId, objects);
}
public View getView(int pos, View convertView, ViewGroup parent) {
View v = convertView;
if(null == v) {
Context ctx = getContext();
LayoutInflater vi =
(LayoutInflater)ctx.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflat(R.layout.pojo_row, null);
}
TextView tv = (TextView)v.findViewById(R.id.tvText);
Pojo pojo = getItem(pos);
tv.setText(pojo.text);
}
}
my pojo_row.xml file looks like the following.
<LinearLayout xmlns:android="..."
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TextView android:id="@+id/tvText" android:layout_width="..."
android_layout_height="..."/>
</LinearLayout>
my main.xml has a Button and a ViewPager. my MainActivity class looks
like the following.
public class MainActivity extends FragmentActivity {
PojoGroupPagerAdapter pagerAdapter;
ViewPager viewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button b = (Button)findViewById(R.id.bReplace);
b.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) { generateAndReplaceFrags(); }
});
pagerAdapter = new
PojoGroupPagerAdapter(getSupportFragmentManager());
viewPager = (ViewPager)findViewById(R.id.pager);
viewPager.setAdapter(pagerAdapter);
}
void generateAndReplaceFrags() {
//PojoGroupFactory just generates a random List of PojoGroups
List<PojoGroup> groups = PojoGroupFactory.getPojoGroups();
pagerAdater.setPojoGroups(groups);
}
}
my pojo fragment, PojoFrag, looks like the following.
public class PojoFrag extends Fragment {
PojoGroup pojoGroup;
View view;
TextView tvTitle;
ListView listView;
public PojoFrag(PojoGroup group) { pojoGroup = group; }
public View onCreateView(LayoutInflater inflater, ViewGroup
container, Bundle savedInstanceState) {
view = inflater.inflate(R.layout.pojogroup_frag, null);
listView = (ListView)view.findViewById(R.id.listView);
tvTitle = (TextView)view.findViewById(R.id.tvTitle);
List<Pojo> objects = pojoGroup.getPojos();
listView.setAdapter(new PojoAdapter(getActivity(), R.id.tvText,
objects));
tvTitle.setText(pojoGroup.title);
return view;
}
}
the PojoGroupPagerAdapter class is not too complex, and this class is
where some of the suggestions on stackoverflow previously suggested
modifications be made. however, it is still not working. i can provide
the full project source code if needed.
public class PojoGroupPagerAdapter extends FragmentPagerAdapter {
List<PojoGroup> pojoGroups;
Map<Integer, Fragment> fragments;
public PojoGroupPagerAdapter(FragmentManager fm) {
super(fm);
fragments = new HashMap<Integer, Fragment>();
}
public Fragment getItem(int position) {
Integer key = new Integer(position);
if(fragments.containsKey(key)) {
return fragments.get(key);
}
PojoGroup group = pojoGroups.get(position);
PojoFrag frag = new PojoFrag(group);
fragments.put(key, frag);
return frag;
}
public int getCount() {
return (null == pojoGroups) ? 0 : pojoGroups.size();
}
public int getItemPosition(Object object) {
if(!fragments.containsKey(object))
return POSITION_NONE;
return POSITION_UNCHANGED;
}
public void setPojoGroups(List<PojoGroup> pojoGroups) {
this.pojoGroups = pojoGroups;
fragments.clear();
int total = pojoGroups.size();
for(int i=0; i < total; i++) {
Integer key = new Integer(i);
PojoGroup group = pojoGroups.get(i);
PojoFrag frag = new PojoFrag(group);
fragments.put(key, frag);
}
notifyDataSetChanged();
}
}
as you can see, i have overridden the getItemPosition(Object) method,
but this still does not help to replace the old view with the new one.
i also played around with FragmentTransaction, but this doesn't work
either. i am attempting to create a new ViewPager object and add it to
the main view. however, i am getting some weird exception (probably
because i have no idea how to construct AttributeSet).
any help with this problem is appreciated.
here is the link to the demo project: http://www.box.com/s/xbtm3amtkj7f13j2llm4
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