我用于我的Android应用PagerSlidingTabStrip和Material Navigation Drawer库。我正在观看ViewPager的奇怪行为 - 当我第一次打开它时，它正常工作，但我再次打开它，ViewPager是空的，没有适配器。
MainActivity：
public class MainActivity extends AppCompatActivity {
private Drawer drawer;
private int lastSelection;
private BroadcastReceiver mRegistrationBroadcastReceiver;
private boolean isClickedByUser = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
drawer = new DrawerBuilder().withActivity(MainActivity.this)
.withToolbar(toolbar).addDrawerItems(
new PrimaryDrawerItem().withName(R.string.name1)
.withIcon(R.drawable.icon1),
new PrimaryDrawerItem()
.withName(R.string.name2)
.withIcon(R.drawable.icon2))
.withOnDrawerItemClickListener(
new Drawer.OnDrawerItemClickListener() {
@Override
public boolean onItemClick(AdapterView<?> adapterView, View view,
int position, long id,
IDrawerItem iDrawerItem) {
switch (position) {
case 0:
setTitle(R.string.title1);
break;
case 1:
setTitle(R.string.title2);
break;
}
FragmentManager fManager = getSupportFragmentManager();
FragmentTransaction transaction = fManager.beginTransaction();
transaction.replace(R.id.container, PlaceholderFragment.newInstance(
position)).commitAllowingStateLoss();
lastSelection = position;
return false;
}
})
.build();
drawer.setSelection(0);
}
@Override
public void onBackPressed() {
if (drawer != null && drawer.isDrawerOpen()) {
drawer.closeDrawer();
} else {
super.onBackPressed();
}
}
@Override
public void onConfigurationChanged(Configuration newConfig){
super.onConfigurationChanged(newConfig);
drawer.setSelection(lastSelection);
}
}
PlaceholderFragment，在ViewPager中完成：
public class PlaceholderFragment extends Fragment {
private static final String ID = "id";
private int id;
public static PlaceholderFragment newInstance(int id) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ID, id);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
id = getArguments().getInt(ID);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = null;
switch (id) {
case 0:
rootView = inflater.inflate(R.layout.view1, container, false);
break;
case 1:
rootView = inflater.inflate(R.layout.tabs, container, false);
ViewPager pager = (ViewPager) rootView.findViewById(R.id.viewPager);
pager.setAdapter(new PagerAdapter(getActivity().getSupportFragmentManager()));
PagerSlidingTabStrip tabs = (PagerSlidingTabStrip) rootView.findViewById(R.id.tabs);
tabs.setViewPager(pager);
tabs.setShouldExpand(true);
tabs.setIndicatorColorResource(R.color.tab_indicator_color);
tabs.setTextColorResource(R.color.tab_text_color);
break;
default:
break;
}
return rootView;
}
private class PagerAdapter extends FragmentPagerAdapter {
private int[] titlesResIds = { R.string.title1, R.string.title2 };
public PagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public CharSequence getPageTitle(int position) {
return getString(titlesResIds[position]);
}
@Override
public int getCount() {
return titlesResIds.length;
}
@Override
public Fragment getItem(int position) {
return TabFragment.newInstance(position);
}
}
}
TabFragment：
public class TabFragment extends ListFragment {
private static final String ID = "id";
private int id;
public static TabFragment newInstance(int id) {
TabFragment fragment = new TabFragment();
Bundle args = new Bundle();
args.putInt(ID, id);
fragment.setArguments(args);
return fragment;
}
public TabFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
id = getArguments().getInt(ID);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
AsyncTask<String, String, String> asyncTask = new AsyncTask<String, String, String>() {
@Override
protected String doInBackground(String... params) {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url("http://host/")
.build();
String result = null;
try {
Response response = client.newCall(request).execute();
result = response.body().string();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
@Override
protected void onPostExecute(String response) {
super.onPostExecute(response);
Gson gson = new Gson();
JsonReader reader = new JsonReader(new StringReader(response));
reader.setLenient(true);
ArrayList<Message> messages = gson.fromJson(reader,
new TypeToken<ArrayList<Message>>(){}.getType());
int i = messages.size() - 1;
while (i != -1) {
if (messages.get(i).getType() != id)
messages.remove(i);
i--;
}
ArrayAdapter adapter = new MyListAdapter(messages);
setListAdapter(adapter);
}
};
asyncTask.execute();
return inflater.inflate(R.layout.fragment, container, false);
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Intent messageIntent = new Intent(getActivity(), MessageActivity.class);
startActivity(messageIntent);
}
private class MyListAdapter extends ArrayAdapter {
private Context context = getActivity();
private ArrayList<Message> messages;
public MyListAdapter(ArrayList<Message> messages) {
super(getActivity(), R.layout.list_adapter);
this.messages = messages;
}
@Override
public int getCount() {
return messages.size();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
LayoutInflater inflater = LayoutInflater.from(context);
convertView = inflater.inflate(R.layout.list_adapter, parent, false);
holder = new ViewHolder();
holder.imageIcon = (ImageView) convertView.findViewById(R.id.list_icon);
holder.textDatetime = (TextView) convertView.findViewById(R.id.list_text_datetime);
holder.textPrimary = (TextView) convertView.findViewById(R.id.list_text_primary);
holder.textSecondary = (TextView) convertView.findViewById(R.id.list_text_secondary);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
Message message = messages.get(position);
long timestamp = message.getTimestamp() * 1000;
Date date = new Date(timestamp);
String datetime = new SimpleDateFormat("dd.MM.yyyy hh:mm", Locale.US).format(date);
holder.imageIcon.setImageResource(message.getIcon() == 0 ?
R.drawable.icon1 :
R.drawable.icon2);
holder.textDatetime.setText(datetime);
holder.textPrimary.setText(message.getTitle());
holder.textSecondary.setText(message.getMessage());
return convertView;
}
private class ViewHolder {
ImageView imageIcon;
TextView textDatetime;
TextView textPrimary;
TextView textSecondary;
}
}
}
答案 0 :(得分：1)
我已经决定了我的问题。我在我的getChildFragmentManager()中插入方法PlaceholderFragment，就像在这个答案中一样 - How set ViewPager inside a Fragment。