我编写了小型测试应用程序来检查行为。
![enter image description here](https://i.stack.imgur.com/GylFN.gif)
让我们看一下示例,看看您的片段是否有问题(如您在上面看到的,具有不同菜单的 ViewPager 工作起来就像一个魅力)
Activity
's XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.TabLayout
android:id="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_below="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
Activity
班级。重要的部分是invalidateOptionsMenu()
每次ViewPager
有 PageSelected 事件。然后,我们设置setHasOptionsMenu
到所有片段和子片段(从嵌套的ViewPager
s) to false
如果他们走出屏幕。
public class MainActivity extends AppCompatActivity {
PagerAdapter pagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Fragment[] fragments = {
Fragment.instantiate(this, FragmentNoMenu.class.getName()),
Fragment.instantiate(this, FragmentA.class.getName()),
Fragment.instantiate(this, FragmentNoMenu.class.getName()),
Fragment.instantiate(this, FragmentB.class.getName()),
};
TabLayout tabLayout = (TabLayout)findViewById(R.id.tabLayout);
ViewPager viewPager = (ViewPager)findViewById(R.id.viewPager);
pagerAdapter = new PagerAdapter(getSupportFragmentManager(), fragments);
viewPager.setAdapter(pagerAdapter);
viewPager.setOffscreenPageLimit(0);
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}
@Override
public void onPageSelected(int position) {
invalidateOptionsMenu(position);
}
@Override
public void onPageScrollStateChanged(int state) {}
});
invalidateOptionsMenu(0);
tabLayout.setupWithViewPager(viewPager);
}
private void invalidateOptionsMenu(int position) {
for(int i = 0; i < pagerAdapter.getCount(); i++) {
Fragment fragment = pagerAdapter.getItem(i);
fragment.setHasOptionsMenu(i == position);
if (fragment instanceof FragmentWithViewPager) {
FragmentWithViewPager fragmentWithViewPager = (FragmentWithViewPager)fragment;
if (fragmentWithViewPager.pagerAdapter != null) {
for (int j = 0; j < fragmentWithViewPager.pagerAdapter.getCount(); j++) {
fragmentWithViewPager.pagerAdapter.getItem(j).setHasOptionsMenu(i == position);
}
}
}
}
invalidateOptionsMenu();
}
}
PagerAdapter
class:
public class PagerAdapter extends FragmentPagerAdapter {
private final Fragment[] fragments;
public PagerAdapter(FragmentManager fragmentManager, Fragment[] fragments) {
super(fragmentManager);
this.fragments = fragments;
}
@Override
public CharSequence getPageTitle(int position) {
return fragments[position].getClass().getSimpleName();
}
@Override
public Fragment getItem(int position) {
return fragments[position];
}
@Override
public int getCount() {
return fragments.length;
}
}
这是我使用的测试片段:
FragmentNoMenu
class:
public class FragmentNoMenu extends android.support.v4.app.Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_no_menu, container, false);
}
}
FragmentNoMenu
layout:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#0F0F50"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
FragmentA
类是一个带有嵌套 ViewPager 的 Fragment:
public class FragmentA extends FragmentWithViewPager {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_a, container, false);
Fragment[] fragments = {
Fragment.instantiate(getContext(), SubFragmentA.class.getName()),
Fragment.instantiate(getContext(), SubFragmentB.class.getName()),
Fragment.instantiate(getContext(), SubFragmentC.class.getName()),
};
if (pagerAdapter == null) {
pagerAdapter = new PagerAdapter(getChildFragmentManager(), fragments);
}
viewPager = (ViewPager)rootView.findViewById(R.id.viewPager);
viewPager.setAdapter(pagerAdapter);
return rootView;
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.fragment_a, menu);
super.onCreateOptionsMenu(menu, inflater);
}
}
FragmentA
的布局:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#B0B0B0"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_marginTop="80dp"
android:layout_width="match_parent"
android:layout_height="200dp"/>
</FrameLayout>
FragmentA
's menu:
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
android:id="@+id/action_item_1"
android:title="Item 1"
android:orderInCategory="250"
app:showAsAction="never" />
<item
android:id="@+id/action_item_2"
android:title="Item 2"
android:orderInCategory="300"
app:showAsAction="never" />
</menu>
NB! FragmentA
延伸FragmentWithViewPager
- 这是一个小的扩展Fragment
为了更容易区分 MainActivity 中嵌套片段的片段:
public class FragmentWithViewPager extends Fragment {
PagerAdapter pagerAdapter;
ViewPager viewPager;
}
FragmentB
:
public class FragmentB extends Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_b, container, false);
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.fragment_b, menu);
super.onCreateOptionsMenu(menu, inflater);
}
}
它的布局和菜单:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#999999"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
.....
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
android:id="@+id/action_item3"
android:title="Item 3"
android:icon="@drawable/ic_triage_star"
android:orderInCategory="250"
app:showAsAction="always" />
</menu>
子片段(从代码角度来看它们看起来都是一样的):
Layouts:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#AA0000"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:text="SubFragment C (with icon Menu)"
android:textSize="24sp"
android:textColor="#00BB00"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</FrameLayout>
Code:
public class SubFragmentB extends Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.subfragment_b, container, false);
}
}
就是这样!我已将项目上传到我的保管箱 -请随意查看!
我希望,它有帮助