Android 导航抽屉回收器视图空指针异常
我正在根据材料设计教程与recycleView合作,我已经做了相应的工作,但我的日志显示:Android 导航抽屉回收器视图空指针异常,android,android-recyclerview,Android,Android Recyclerview,我正在根据材料设计教程与recycleView合作,我已经做了相应的工作,但我的日志显示: E/AndroidRuntime: FATAL EXCEPTION: main Process: com.portal.college.myapplication, PID: 6541 java.lang.NullPointerException at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerVie
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.portal.college.myapplication, PID: 6541 java.lang.NullPointerException
at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerView.java:5229)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4453)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4363)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1961)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1370)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1333)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:562)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2900)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3071)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1067)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1983)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1740)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:544)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
main_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:elevation="7dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<include
android:id="@+id/app_bar"
layout="@layout/app_bar_main" />
</LinearLayout>
<fragment
android:id="@+id/fragment_navigation_drawer"
android:layout_width="280dp"
android:layout_height="match_parent"
android:layout_gravity="start"
app:layout="@layout/fragment_navigation_drawer"
android:name="com.portal.college.myapplication.NavigationDrawerFragment"
tools:layout="@layout/fragment_navigation_drawer"
/>
</android.support.v4.widget.DrawerLayout>
NavigationDrawerFragment.java
package com.portal.college.myapplication;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.support.v7.widget.Toolbar;
import java.util.ArrayList;
import java.util.List;
public class NavigationDrawerFragment extends Fragment {
private ActionBarDrawerToggle mDrawerToggle;
private DrawerLayout mDrawerLayout;
private RecyclerView recyclerView;
private VivzAdapter adapter;
public NavigationDrawerFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View layout = inflater.inflate(R.layout.fragment_navigation_drawer,container,false);
recyclerView = (RecyclerView) layout.findViewById(R.id.drawerList);
adapter = new VivzAdapter(getActivity(),getData());
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
recyclerView.setAdapter(adapter);
return layout;
}
public static List<Information> getData(){
List<Information> data = new ArrayList<>();
int icons[] = {
R.drawable.ic_menu_camera,
R.drawable.ic_menu_gallery,
R.drawable.ic_menu_manage,
R.drawable.ic_menu_send};
String[] title = {"Camera","Gallery","Settings","Send"};
for(int i=0;i<title.length && i<icons.length;i++){
Information current = new Information();
current.iconId = icons[i];
current.title = title[i];
data.add(current);
}
return data;
}
public void setUp(DrawerLayout drawerLayout,Toolbar toolbar) {
mDrawerLayout = drawerLayout;
mDrawerToggle = new ActionBarDrawerToggle(getActivity(), drawerLayout, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close){
public void onDrawerOpened(View drawerView){
super.onDrawerOpened(drawerView);
}
public void onDrawerClosed(View drawerView){
super.onDrawerClosed(drawerView);
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
mDrawerLayout.post(new Runnable() {
@Override
public void run() {
mDrawerToggle.syncState();
}
});
/* containerView = getActivity().findViewById(fragment_id);
mDrawerLayout=drawerLayout;
mDrawerToggle = new ActionBarDrawerToggle(getActivity(), drawerLayout, toolbar, R.string.open_drawer,R.string.close_drawer){
@SuppressLint("NewApi")
public void onDrawerOpened(View drawerView){
super.onDrawerOpened(drawerView);
if(!mUserLearnedDrawer){
mUserLearnedDrawer = false;
saveToPreferences(getActivity(),KEY_USER_LEARNED_DRAWER, mUserLearnedDrawer+"");
}
getActivity().invalidateOptionsMenu();
*/
}
}
列表行布局为custom_Row.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/listIcon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_menu_camera"/>
<TextView
android:id="@+id/listText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Camera"
/>
</LinearLayout>
我已经讨论了stackoverflow的大部分解决方案,它们都是关于同一个问题的,但是我在这里失败了
有一件事我注意到,在VivzAdapter.java
中,获取数据Count
的函数名getItemCount()
返回data.size()
,当我将其更改为return0
时,它可以不使用recyclerView
,但当使用data.size()
返回时,它给出了NullPointerException
希望我已经详细解释了一切
如果您的
VivzAdapter.java
中有任何建议,将不胜感激,因为您将返回null而不是创建的ViewHolder
换成
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.custom_row,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
那么它应该可以工作了您的VivzAdapter.java正在返回null,因为它在运行时抛出了null指针异常
package com.portal.college.myapplication;
import android.content.Context;
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 java.util.Collections;
import java.util.List;
/**
* Created by admin on 08-Feb-16.
*/
public class VivzAdapter extends RecyclerView.Adapter<VivzAdapter.MyViewHolder>{
private final LayoutInflater inflater;
List<Information> data = Collections.emptyList();
public VivzAdapter(Context context,List<Information> data){
inflater=LayoutInflater.from(context);
this.data=data;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.custom_row,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
Information current = data.get(position);
holder.title.setText(current.title);
holder.id.setImageResource(current.iconId);
}
@Override
public int getItemCount() {
return data.size();
}
class MyViewHolder extends RecyclerView.ViewHolder{
TextView title;
ImageView id;
public MyViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.listText);
id = (ImageView) itemView.findViewById(R.id.listIcon);
}
}
}
package com.portal.college.myapplication;
导入android.content.Context;
导入android.support.v7.widget.RecyclerView;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.ImageView;
导入android.widget.TextView;
导入java.util.Collections;
导入java.util.List;
/**
*由管理员于2016年2月8日创建。
*/
公共类VivzAdapter扩展了RecyclerView.Adapter{
私人充气机;
List data=Collections.emptyList();
公共VivzAdapter(上下文、列表数据){
充气器=充气器。从(上下文);
这个。数据=数据;
}
@凌驾
公共MyViewHolder onCreateViewHolder(视图组父级,int-viewType){
视图=充气机。充气(右布局。自定义行,父项,false);
MyViewHolder=新的MyViewHolder(视图);
报税表持有人;
}
@凌驾
公共无效onBindViewHolder(MyViewHolder,int位置){
信息当前=数据获取(位置);
holder.title.setText(当前.title);
holder.id.setImageResource(当前的.iconId);
}
@凌驾
public int getItemCount(){
返回data.size();
}
类MyViewHolder扩展了RecyclerView.ViewHolder{
文本视图标题;
图像视图id;
公共MyViewHolder(查看项目视图){
超级(项目视图);
title=(TextView)itemView.findViewById(R.id.listText);
id=(ImageView)itemView.findViewById(R.id.listIcon);
}
}
}
上面的代码可能会解决这个问题。是的,我不知道这个愚蠢的错误是怎么发生的,几乎浪费了4个小时,首先我想知道你上面的句子是什么意思。第二,我想知道你的答案和我的有什么不同。我确实指出了同样的错误,并说明了如何更改代码。你甚至没有解释这个问题。
package com.portal.college.myapplication;
/**
* Created by admin on 08-Feb-16.
*/
public class Information {
int iconId;
String title;
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/listIcon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_menu_camera"/>
<TextView
android:id="@+id/listText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Camera"
/>
</LinearLayout>
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.custom_row,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
package com.portal.college.myapplication;
import android.content.Context;
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 java.util.Collections;
import java.util.List;
/**
* Created by admin on 08-Feb-16.
*/
public class VivzAdapter extends RecyclerView.Adapter<VivzAdapter.MyViewHolder>{
private final LayoutInflater inflater;
List<Information> data = Collections.emptyList();
public VivzAdapter(Context context,List<Information> data){
inflater=LayoutInflater.from(context);
this.data=data;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.custom_row,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
Information current = data.get(position);
holder.title.setText(current.title);
holder.id.setImageResource(current.iconId);
}
@Override
public int getItemCount() {
return data.size();
}
class MyViewHolder extends RecyclerView.ViewHolder{
TextView title;
ImageView id;
public MyViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.listText);
id = (ImageView) itemView.findViewById(R.id.listIcon);
}
}
}