Android – Fragment内部的RecyclerView – NullPointerException
我正在尝试在Fragment使用RecyclerView （在ViewPager使用它）但是当我尝试执行时我得到了NullPointerException ：
Process: com.yomansk8.birthdaysoundboard, PID: 4448 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$LayoutManager.onMeasure(android.support.v7.widget.RecyclerView$Recycler, android.support.v7.widget.RecyclerView$State, int, int)' on a null object reference at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1456) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560) at android.view.View.measure(View.java:17430) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) at android.view.Choreographer.doCallbacks(Choreographer.java:580) at android.view.Choreographer.doFrame(Choreographer.java:550) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
首先，这是我的片段的布局，它只包含RecyclerView ：
这是我的片段：
package com.yomansk8.birthdaysoundboard.Fragments; import android.app.Activity; import android.media.MediaPlayer; import android.os.Bundle; import android.support.annotation.Nullable; import android.support.v4.app.Fragment; import android.support.v7.app.ActionBar; import android.support.v7.widget.GridLayoutManager; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.support.v7.widget.Toolbar; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import com.yomansk8.birthdaysoundboard.Adapters.RecyclerViewAdapter; import com.yomansk8.birthdaysoundboard.GenerateDatas; import com.yomansk8.birthdaysoundboard.MainActivity; import com.yomansk8.birthdaysoundboard.Models.ViewModel; import com.yomansk8.birthdaysoundboard.R; import com.yomansk8.birthdaysoundboard.ScrollManager; import java.util.List; /** * Created by Yohann on 09/03/2015. */ public class DiversFragment extends Fragment implements RecyclerViewAdapter.OnItemClickListener { private MediaPlayer mPlayer = null; private Toolbar toolbar; private RecyclerView recyclerView; private GridLayoutManager mLayoutManager; private RecyclerViewAdapter adapter; private List items; @Override public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View v = inflater.inflate(R.layout.fragment_divers, container, false); toolbar = ((MainActivity)getActivity()).getToolbar(); recyclerView = (RecyclerView) v.findViewById(R.id.recyclerDivers); recyclerView.setHasFixedSize(true); items = GenerateDatas.getAmbianceList(); adapter = new RecyclerViewAdapter(items); /*toolbar.post(new Runnable() { @Override public void run() { ScrollManager manager = new ScrollManager(); manager.attach(recyclerView); manager.addView(toolbar, ScrollManager.Direction.UP); manager.setInitialOffset(toolbar.getHeight()); } });*/ Log.v("TEST", "onCreateView()"); return v; } @Override public void onViewCreated(View view , Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); Log.v("TEST", "onViewCreated()"); mLayoutManager = new GridLayoutManager(getActivity(), 3); recyclerView.setLayoutManager(mLayoutManager); adapter.setOnItemClickListener(this); recyclerView.setAdapter(adapter); } @Override public void onItemClick(View view, ViewModel viewModel) { // Lire le son ici Integer sound = getResources().getIdentifier(viewModel.getSound(), "raw", getActivity().getPackageName()); playSound(sound); } private void playSound(int resId) { if(mPlayer != null) { mPlayer.stop(); mPlayer.release(); } mPlayer = MediaPlayer.create(getActivity(), resId); mPlayer.start(); } @Override public void onPause() { super.onPause(); if(mPlayer != null) { mPlayer.stop(); mPlayer.release(); } } }
我还尝试将我的RecyclerView初始化在onCreateView和onViewCreated ，但没有成功。
任何想法？
编辑：
这是我的Adapter的代码：
package com.yomansk8.birthdaysoundboard.Adapters; import android.os.Handler; import android.support.v7.widget.RecyclerView; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ImageView; import android.widget.TextView; import com.squareup.picasso.Picasso; import com.yomansk8.birthdaysoundboard.R; import com.yomansk8.birthdaysoundboard.Models.ViewModel; import java.util.List; /** * Created by Yohann on 19/02/2015. */ public class RecyclerViewAdapter extends RecyclerView.Adapter implements View.OnClickListener { private List items; private OnItemClickListener onItemClickListener; public RecyclerViewAdapter(List items) { this.items = items; } public void setOnItemClickListener(OnItemClickListener onItemClickListener) { this.onItemClickListener = onItemClickListener; } @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler, parent, false); v.setOnClickListener(this); return new ViewHolder(v); } @Override public void onBindViewHolder(ViewHolder holder, int position) { ViewModel item = items.get(position); holder.text.setText(item.getText()); holder.image.setImageBitmap(null); Integer mImage = holder.image.getResources().getIdentifier(item.getImage(), "drawable", holder.image.getContext().getPackageName()); Picasso.with(holder.image.getContext()).load(mImage).into(holder.image); holder.itemView.setTag(item); } @Override public int getItemCount() { return items.size(); } @Override public void onClick(final View v) { // Give some time to the ripple to finish the effect if (onItemClickListener != null) { new Handler().postDelayed(new Runnable() { @Override public void run() { onItemClickListener.onItemClick(v, (ViewModel) v.getTag()); } }, 200); } } protected static class ViewHolder extends RecyclerView.ViewHolder { public ImageView image; public TextView text; public ViewHolder(View itemView) { super(itemView); image = (ImageView) itemView.findViewById(R.id.image); text = (TextView) itemView.findViewById(R.id.text); } } public interface OnItemClickListener { void onItemClick(View view, ViewModel viewModel); } }
我觉得你像我一样使用了旧版的recyclerview。 我采用了版本recyclerview-20.0.0的第一个版本，当然还有例外。 所以我升级我的android sdk，然后将最新版本22.1.1 （support-v4和recyclerview-v7 jar）复制到我的项目的libs中，然后我的项目工作。
为了防止我的团队的后续人员混淆版本，我将两个jar子命名为包含修订信息：
我项目的libs目录中的jar：
Android的支持，v4-22.1.1.jar
Android的支持-V7-recyclerview-22.1.1.jar
在此之前，我还在修订版20.0.0中找到了一个解决方案，我创建了一个名为MyRecyclerView的小部件，它从RecyclerView扩展，然后在构造函数中新建一个粗略的LayoutManager。
public class MyRecyclerView extends RecyclerView { public MyRecyclerView(Context context) { this(context, null); } public MyRecyclerView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public MyRecyclerView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); setLayoutManager(new LayoutManager() { @Override public LayoutParams generateDefaultLayoutParams() { return null; } }); } }
它可以工作，但不是完美的方法。
BTW，正如@yigit在他的回答中所说，这是缺乏与IDE的集成，并且将来会有更好的集成 。
为您的片段尝试此布局：