如果有一个为什么说“ RecyclerView没有LayoutManager”。请查看详细信息
沈国安
问题内容：
问题答案：
我recyclerview在我的应用程序中做了一个
问题是，java.lang.IllegalStateException: RecyclerView has no LayoutManager即使定义了错误，我也会收到以下错误：
这是ListContentAAR.java文件的代码：
class ListContentAAR {
String picTag;
ListContentAAR( String picTag) {
this.picTag = picTag;
}
}
这是RVAdapterAAR.java文件的代码：
public class RVAdapterAAR extends RecyclerView.Adapter<RVAdapterAAR.PersonViewHolder> {
public static class PersonViewHolder extends RecyclerView.ViewHolder {
CardView cardView;
TextView pic;
PersonViewHolder(View itemView) {
super(itemView);
cardView = (CardView) itemView.findViewById(R.id.card_accept_request);
homelessPic = (TextView) itemView.findViewById(R.id.pic_tag);
}
}
List<ListContentAAR> listContentAARs;
RVAdapterAAR(List<ListContentAAR> listContentAARs) {
this.listContentAARs = listContentAARs;
}
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
}
public PersonViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.fragment_accept_a_request, viewGroup, false);
PersonViewHolder personViewHolder = new PersonViewHolder(view);
return personViewHolder;
}
public void onBindViewHolder (PersonViewHolder personViewHolder, int i) {
personViewHolder.pic.setText(listContentAARs.get(i).homelessPicTag);
}
public int getItemCount() {
return listContentAARs.size();
}
}
这是AcceptARequest.java文件的代码：
public class AcceptARequest 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;
private List<ListContentAAR> listContentAARs;
private RecyclerView recyclerView;
public AcceptARequest() {
// 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 AcceptARequest.
*/
// TODO: Rename and change types and number of parameters
public static AcceptARequest newInstance(String param1, String param2) {
AcceptARequest fragment = new AcceptARequest();
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
View rootView = inflater.inflate(R.layout.fragment_accept_a_request, container, false);
RecyclerView recyclerView = (RecyclerView) rootView.findViewById(R.id.accept_request_list);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setHasFixedSize(true);
initializeData();
initializeAdapter();
return rootView;
}
private void initializeData(){
listContentAARs = new ArrayList<>();
listContentAARs.add(new ListContentAAR("Emma Wilson"));
}
private void initializeAdapter(){
RVAdapterAAR adapter = new RVAdapterAAR(listContentAARs);
recyclerView.setAdapter(adapter);
}
// 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);
}
}
这是fragment_accept_a_request.xml文件的代码：
<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="wrap_content"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context="com.abc.xyz.AcceptARequest">
<android.support.v7.widget.RecyclerView
android:id="@+id/accept_request_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<android.support.v7.widget.CardView
android:id="@+id/card_accept_request"
android:layout_width="match_parent"
android:layout_height="@dimen/card_accept_request"
app:cardElevation="2dp"
app:cardUseCompatPadding="true"
app:contentPadding="10dp">
<!--<ImageView
android:id="@+id/pic_accept"
android:layout_width="match_parent"
android:layout_height="@dimen/pic_dimen_accept"
android:layout_gravity="center_horizontal|center_vertical"
android:layout_alignParentTop="true"/> -->
<TextView
android:id="@+id/pic_tag"
android:layout_width="match_parent"
android:layout_height="@dimen/pic_dimen_accept"
android:text="@string/image_view_tag_accept"
android:gravity="center_horizontal|center_vertical"/>
</android.support.v7.widget.CardView>
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
这是MainActivity.java文件的代码：
public class MainActivity extends AppCompatActivity {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
public SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Typeface typeFace = Typeface.createFromAsset(getAssets(),"fonts/Pacifico.ttf");
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
TextView mTitle = (TextView) toolbar.findViewById(R.id.toolbar_title);
mTitle.setTypeface(typeFace);
toolbar.setTitle(mTitle.getText().toString());
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowTitleEnabled(false);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(this, getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
/*FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});*/
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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) {
Intent settingsIntent = new Intent(MainActivity.this, SettingsActivity.class);
startActivity(settingsIntent);
} else if (id == R.id.action_profile) {
Intent profileIntent = new Intent(MainActivity.this, ProfileActivity.class);
startActivity(profileIntent);
} else if (id == R.id.action_send_feedback) {
Intent sendFeedbackIntent = new Intent(MainActivity.this, SendFeedback.class);
startActivity(sendFeedbackIntent);
} else if (id == R.id.action_help) {
Intent helpIntent = new Intent(MainActivity.this, HelpActivity.class);
startActivity(helpIntent);
}
return super.onOptionsItemSelected(item);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
protected Context mContext;
public SectionsPagerAdapter(Context context, FragmentManager fm) {
super(fm);
mContext = context;
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
// return MainActivity.PlaceholderFragment.newInstance(position + 1);
switch (position) {
case 0:
return new AcceptARequest();
case 1:
return new PostARequest();
default:
return new AcceptARequest(); // return AcceptARequest() actually
}
}
@Override
public int getCount() {
// Show 2 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return "Accept A Request";
case 1:
return "Post A Request";
}
return null;
}
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
/**
* Returns a new instance of this fragment for the given 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);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
}
这是stacktrace：
FATAL EXCEPTION: main
java.lang.IllegalStateException: RecyclerView has no LayoutManager
at android.support.v7.widget.RecyclerView.generateLayoutParams(RecyclerView.java:3182)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:748)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:749)
at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
at com.humanehelper.humanehelper.AcceptARequest.onCreateView(AcceptARequest.java:75)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1106)
at android.support.v4.view.ViewPager.populate(ViewPager.java:952)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)
at android.view.View.measure(View.java:15172)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:610)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:677)
at android.view.View.measure(View.java:15172)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:15172)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
at android.view.View.measure(View.java:15172)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:15172)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
at android.view.View.measure(View.java:15172)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2148)
at android.view.View.measure(View.java:15172)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1848)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1100)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1273)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
at android.view.Choreographer.doCallbacks(Choreographer.java:555)
at android.view.Choreographer.doFrame(Choreographer.java:525)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com
由于我是初学者，所以无法弄清楚为什么会出现以下错误。
请告诉我。
提前致谢。
问题答案：
我知道了！
问题出在两个文件中。
劳拉托所说的第一个问题是fragment_accept_a_request.xml。从XML元素中删除XML元素recyclerView并将其放置在其下方，但使用相同的父布局完成了这项工作。
第二个问题是AcceptARequest.java。在这里我声明了两个RecyclerView一个是initialiseData()方法和另一个用于声明recyclerView。
我所做的更改fragment_accept_a_request.xml是：
<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="wrap_content"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context="com.abc.xyz.AcceptARequest">
<android.support.v7.widget.RecyclerView
android:id="@+id/accept_request_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
</android.support.v7.widget.RecyclerView>
<android.support.v7.widget.CardView
android:id="@+id/card_accept_request"
android:layout_width="match_parent"
android:layout_height="@dimen/card_accept_request"
app:cardElevation="2dp"
app:cardUseCompatPadding="true"
app:contentPadding="10dp">
<!--<ImageView
android:id="@+id/pic_accept"
android:layout_width="match_parent"
android:layout_height="@dimen/pic_dimen_accept"
android:layout_gravity="center_horizontal|center_vertical"
android:layout_alignParentTop="true"/> -->
<TextView
android:id="@+id/pic_tag"
android:layout_width="match_parent"
android:layout_height="@dimen/pic_dimen_accept"
android:text="@string/image_view_tag_accept"
android:gravity="center_horizontal|center_vertical"/>
</android.support.v7.widget.CardView>
</RelativeLayout>
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