Java 片段中的ViewPager和TableLayout。空对象引用上的setAdapter
我正在尝试在片段中添加viewPager。但当我启动应用程序时,我会收到以下信息: java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)” 我的主要片段:Java 片段中的ViewPager和TableLayout。空对象引用上的setAdapter,java,android,android-fragments,android-viewpager,Java,Android,Android Fragments,Android Viewpager,我正在尝试在片段中添加viewPager。但当我启动应用程序时,我会收到以下信息: java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)” 我的主要片段: public class YourTasksFragment extends Fragment { @Bind(R.id.vi
public class YourTasksFragment extends Fragment {
@Bind(R.id.viewpager)
ViewPager viewPager;
@Bind(R.id.tabs)
TabLayout tabLayout;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_your_tasks, container, false);
return v;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
setupViewPager(viewPager);
tabLayout.setupWithViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getChildFragmentManager());
adapter.addFragment(new OneFragment(), "ONE");
adapter.addFragment(new TwoFragment(), "TWO");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> fragmentList = new ArrayList<>();
private final List<String> fragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager childFragmentManager) {
super(childFragmentManager);
}
@Override
public Fragment getItem(int position) {
return fragmentList.get(position);
}
@Override
public int getCount() {
return fragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
fragmentList.add(fragment);
fragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return fragmentTitleList.get(position);
}
}
}
public类YourTasksFragment扩展了片段{
@绑定(R.id.viewpager)
查看页面查看页面;
@绑定(R.id.tabs)
表格布局;
@可空
@凌驾
CreateView上的公共视图(布局、充气机、视图组容器、捆绑包保存状态){
视图v=充气机。充气(R.layout.fragment\u您的任务,容器,false);
返回v;
}
@凌驾
已创建视图上的公共void(视图,捆绑保存状态){
super.onViewCreated(视图,savedInstanceState);
设置viewPager(viewPager);
tabLayout.setupWithViewPager(viewPager);
}
专用无效设置ViewPager(ViewPager ViewPager){
ViewPagerAdapter适配器=新的ViewPagerAdapter(getChildFragmentManager());
addFragment(新的OneFragment(),“一”);
addFragment(新的TwoFragment(),“TWO”);
viewPager.setAdapter(适配器);
}
类ViewPagerAdapter扩展了FragmentPagerAdapter{
private final List fragmentList=new ArrayList();
私有最终列表fragmentTitleList=新ArrayList();
公共视图页面编辑器(碎片管理器子碎片管理器){
超级(儿童碎片管理器);
}
@凌驾
公共片段getItem(int位置){
返回碎片列表。获取(位置);
}
@凌驾
public int getCount(){
返回fragmentList.size();
}
public void addFragment(片段片段,字符串标题){
碎片列表。添加(碎片);
碎片标题列表。添加(标题);
}
@凌驾
公共字符序列getPageTitle(int位置){
返回碎片标题列表。获取(位置);
}
}
}
布局:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"
app:tabGravity="fill"/>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />
您忘记在方法onCreateView上添加Butterknife.bind(this,v)。 它是绑定视图所必需的
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_your_tasks, container, false);
Butterknife.bind(this,v);
return v;
}
您忘记在方法onCreateView上添加Butterknife.bind(this,v)。 它是绑定视图所必需的
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_your_tasks, container, false);
Butterknife.bind(this,v);
return v;
}
您忘记在onCreateView()中设置Butterknife,因此该变量从未初始化 这样做:
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_your_tasks, container, false);
Butterknife.bind(this,v);
return v;
}
希望有帮助 您忘记在onCreateView()中设置Butterknife,因此变量从未初始化 这样做:
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_your_tasks, container, false);
Butterknife.bind(this,v);
return v;
}
希望有帮助 尝试手动链接viewpager,并验证其布局是否正确。尝试手动链接viewpager,并验证其布局是否正确。真是个错误!我真瞎:)谢谢。问题解决了。真是个错误!我真瞎:)谢谢。问题解决了。