尝试从字段'android.view.View android.support.v7.widget.RecyclerView $ ViewHolder.itemView'中读取 [英] Attempt to read from field 'android.view.View android.support.v7.widget.RecyclerView$ViewHolder.itemView'
问题描述
我试图延迟随机选择recyclerview项.我需要在片段加载后启动随机选择方法,而无需任何用户交互,但是会出现以下错误.之后,将其放在ImageView上单击以进行检查,但再次出现相同的异常.这里有人会告诉我我在哪里犯错,或者还有什么可能是实现此目的的更好的方法.下面是我的代码
I am trying to select recyclerview item randomly with delay.I need to start random selection method after fragment load without any user interaction,But getting the following error. Afterward I put it on ImageView click to check but again I am getting same exception.Will anybody here tell me where I am making a mistake,or what else could be better way to achieve this.Below is my code
package com.apponative.bjja.fragments;
import android.os.Bundle;
import android.os.Handler;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.apponative.bjja.R;
import com.apponative.bjja.adapters.AttackGridAdapter;
import java.util.Random;
public class Fragment_AttackGrid extends Fragment {
View v;
RecyclerView grid_attack;
AttackGridAdapter attackGridAdapter;
Bundle b;
int itemCount;
Handler randomHandler;
Runnable randomRunnable;
Random rand;
int randomNum = 0;
long emptyTime;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
v = inflater.inflate(R.layout.fragment_attack_grid, container, false);
setUpViews();
return v;
}
void setUpViews() {
b = getArguments();
itemCount = b.getInt(getString(R.string.item_count));
rand = new Random();
randomHandler = new Handler();
grid_attack = (RecyclerView) v.findViewById(R.id.attack_grid);
RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getActivity(), 4);
grid_attack.setLayoutManager(layoutManager);
attackGridAdapter = new AttackGridAdapter(getActivity(), itemCount);
grid_attack.setAdapter(attackGridAdapter);
v.findViewById(R.id.belt_black).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
selectRandomly();
}
});
}
void selectRandomly() {
for (int i = 0; i < itemCount; i++) {
emptyTime = emptyTime+1000;
randomRunnable = new Runnable() {
@Override
public void run() {
grid_attack.findViewHolderForAdapterPosition(randomNum).itemView.setSelected(false);
randomNum = rand.nextInt((itemCount - 0) + 1) + 0;
grid_attack.findViewHolderForAdapterPosition(randomNum).itemView.setSelected(true);
}
};
randomHandler.postDelayed(randomRunnable, emptyTime);
}
emptyTime = emptyTime+2000;
randomRunnable = new Runnable() {
@Override
public void run() {
grid_attack.findViewHolderForAdapterPosition(randomNum).itemView.performClick();
}
};
randomHandler.postDelayed(randomRunnable, emptyTime);
}
@Override
public void onResume() {
super.onResume();
// selectRandomly();
}
}
一开始我放
selectRandomly()
selectRandomly()
在
onResume()
onResume()
方法,我得到一个例外:
method and I was getting an exception:
01-27 18:28:44.969 19041-19041/com.apponative.bjja E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.apponative.bjja, PID: 19041
java.lang.NullPointerException: Attempt to read from field 'android.view.View android.support.v7.widget.RecyclerView$ViewHolder.itemView' on a null object reference at com.apponative.bjja.fragments.Fragment_AttackGrid$2.run(Fragment_AttackGrid.java:77)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:155)
at android.app.ActivityThread.main(ActivityThread.java:5696)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)
根据片段生命周期,网址为片段生命周期 onResume()和onStart()创建视图后将调用方法.我也尝试将方法放在那里,但没有成功.
According to fragment lifecycle at Fragment LifeCycle onResume() and onStart() methods are called after view has been created. I tried putting my method there too, But no success.
推荐答案
如果您的onCreateViewHolder方法返回null,则可能会发生这种情况
This may happen if your onCreateViewHolder method returns null
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