我试图重现此问题,但是用下面的代码我看到container.getChildCount()总是3或更低:
MainActivity.java
public class MainActivity extends AppCompatActivity {
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
private String TAG = SectionsPagerAdapter.class.getSimpleName();
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
Log.v(TAG, "container.getChildCount:" + container.getChildCount());
return super.instantiateItem(container, position);
}
@Override
public int getCount() {
return 10;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
return String.format(l, "Section %d", position);
}
}
public static class PlaceholderFragment extends Fragment {
private static final String ARG_SECTION_NUMBER = "section_number";
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
ListView listView = (ListView) rootView.findViewById(R.id.listView);
ArrayAdapter<String> listAdapter = new ArrayAdapter<>(getActivity(), android.R.layout.simple_list_item_1);
listAdapter.add("Fragment Body " + getArguments().getInt(ARG_SECTION_NUMBER));
listAdapter.add("one");
listAdapter.add("two");
listAdapter.add("three");
listView.setAdapter(listAdapter);
return rootView;
}
}
}
activity_main.xml中
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"/>
fragment_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity$PlaceholderFragment">
<ListView
android:id="@+id/listView"
android:layout_height="match_parent"
android:layout_width="wrap_content" />
“有2页保留,两侧” - 你怎么知道这是真的吗?你在看什么变量或对象?谢谢! –
在空闲状态,我检查了container.getChildCount()(在PagerAdapter的instantiateItem方法中使用),它给出了5.这意味着有两页保留在任何一方。 –
我试图用包含ListView的简单片段来重现此行为,使用android.support.v4.app.FragmentPagerAdapter和android.support.v4.view.ViewPager,但container.getChildCount在我的测试应用程序中始终保持3或更低。你使用的是我使用的ViewPager类吗? –