我无法让它正常工作。基本应用程序的功能正常，但一个布局文件上的ViewPager根本不显示任何片段。我多次检查了代码，但找不到错误。当我尝试调试它时，我注意到它甚至没有初始化片段类，而你选择选项卡时应该这样做。
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
new GetData(this).execute();
TabLayout tab_layout = (TabLayout) findViewById(R.id.tab_layout);
tab_layout.addTab(tab_layout.newTab().setText("CASUAL"));
tab_layout.addTab(tab_layout.newTab().setText("RANKED"));
tab_layout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tab_layout.getTabCount());
viewPager.setAdapter(adapter);
tab_layout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_stats) {
// Handle the camera action
} else if (id == R.id.nav_about) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
我的PagerAdapter：
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
CasualStats tab1 = new CasualStats();
return tab1;
case 1:
RankedStats tab2 = new RankedStats();
return tab2;
default:
return null;
}
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
使用ViewPager进行布局：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"><![CDATA[
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:layout_below="@id/tab_layout"/>
]]>
<android.support.design.widget.TabLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:id="@+id/tab_layout">
</android.support.design.widget.TabLayout>
<view
android:layout_width="wrap_content"
android:layout_height="wrap_content"
class="android.support.v4.view.ViewPager"
android:layout_alignParentStart="true"
android:id="@+id/view_pager"
android:layout_below="@+id/tab_layout" />
</RelativeLayout>
用于在ViewPager中显示的选项卡片段的类只是普通的自动生成的Android Studio片段类。
其中一个片段：
public class CasualStats extends Fragment{
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public CasualStats() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment CasualStats.
*/
// TODO: Rename and change types and number of parameters
public static CasualStats newInstance(String param1, String param2) {
CasualStats fragment = new CasualStats();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_casual_stats, container, false);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
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"
tools:context="com.app.anzel.r6s.CasualStats">
<!-- TODO: Update blank fragment layout -->
<TextView
android:text="1st fragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:layout_marginStart="28dp"
android:layout_marginTop="22dp"
android:id="@+id/textView"
android:visibility="visible" />
</RelativeLayout>
- 为您的viewpager创建适配器。
- 在您的viewpager上设置适配器。
- 使用tabLayout.setupWithViewPager(your_viewpager);
- 如果viewpager在Activity中或在另一个片段内部，请确保使用getSupportFragmentManager或getchildFragmentManager()。
- 您的适配器必须覆盖public CharSequence getPageTitle(int position)以为选项卡布局提供每个片段的标题。
- Rahul Shukla