我的 Android 应用程序出现错误，该应用程序从本地主机提取 json 数据并使用 RecycleView 在 homefragment 中查看它。我对此有点陌生，我不确定我做错了什么。请帮忙
HomeFragment.java
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
/**
* A simple {@link Fragment} subclass.
*/
public class HomeFragment extends Fragment {
public static final int CONNECTION_TIMEOUT = 10000;
public static final int READ_TIMEOUT = 15000;
private RecyclerView mRVFishPrice;
private AdapterFish mAdapter;
ArrayList<listMovie> movieList;
AdapterFish adapter;
public HomeFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
final View rootView = inflater.inflate(R.layout.fragment_home, container, false);
RecyclerView mRecyclerView = (RecyclerView) rootView.findViewById(R.id.fishPriceList);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(mLayoutManager);
new AsyncFetch().execute();
return rootView;
}
private class AsyncFetch extends AsyncTask<String, String, String> {
ProgressDialog pdLoading = new ProgressDialog(getActivity());
HttpURLConnection conn;
URL url = null;
@Override
protected void onPreExecute() {
super.onPreExecute();
pdLoading.setMessage("\tLoading...");
pdLoading.setCancelable(false);
pdLoading.show();
}
@Override
protected String doInBackground(String... params) {
try {
url = new URL("http://100.74.245.14/finalproject/select_images.php");
} catch (MalformedURLException e) {
e.printStackTrace();
return e.toString();
}
try {
conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(READ_TIMEOUT);
conn.setConnectTimeout(CONNECTION_TIMEOUT);
conn.setRequestMethod("GET");
conn.setDoOutput(true);
} catch (IOException e1) {
e1.printStackTrace();
}
try {
int response_code = conn.getResponseCode();
if(response_code == HttpURLConnection.HTTP_OK) {
InputStream input = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(input));
StringBuilder result = new StringBuilder();
String line;
while((line = reader.readLine()) != null) {
result.append(line);
}
return (result.toString());
}
else {
return ("Unsucessful");
}
} catch (IOException e) {
e.printStackTrace();
return e.toString();
}finally {
conn.disconnect();
}
}
@Override
protected void onPostExecute(String result) {
pdLoading.dismiss();
List<listMovie> data = new ArrayList<>();
pdLoading.dismiss();
try {
JSONObject jsonObj = new JSONObject(result);
JSONArray jArray = jsonObj.getJSONArray("test");
//Log.d("json", result);
for(int i = 0; i < jArray.length(); i++) {
Log.d("json", "test");
JSONObject json_data = jArray.getJSONObject(i);
listMovie movieData = new listMovie();
movieData.movieId = json_data.getString("movie_id");
movieData.movieName = json_data.getString("name");
movieData.movieImage = json_data.getString("imageurl");
data.add(movieData);
}
mRVFishPrice = (RecyclerView) getView().findViewById(R.id.fishPriceList);
mAdapter = new AdapterFish(getActivity(), data);
mRVFishPrice.setAdapter(mAdapter);
mRVFishPrice.setLayoutManager(new LinearLayoutManager(getActivity()));
} catch (JSONException e) {
Toast.makeText(getActivity(), e.toString(), Toast.LENGTH_LONG).show();
}
}
}
}
AdapterFish.java
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import com.bumptech.glide.Glide;
import java.util.Collections;
import java.util.List;
public class AdapterFish extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private Context context;
private LayoutInflater inflater;
List<listMovie> data = Collections.emptyList();
listMovie current;
int currentPos = 0;
public AdapterFish(Context context, List<listMovie> data) {
this.context = context;
inflater = LayoutInflater.from(context);
this.data = data;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.fragment_home, parent, false);
MyHolder holder = new MyHolder(view);
return holder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
MyHolder myHolder = (MyHolder) holder;
listMovie current = data.get(position);
Log.d("movie", current.movieName);
myHolder.textMovieName.setText(current.movieName);
myHolder.textMovieId.setText(current.movieId);
Glide.with(context).load(current.movieImage)
.placeholder(R.drawable.placeholder)
.error(R.drawable.ic_menu_camera)
.into(myHolder.ivMovie);
}
@Override
public int getItemCount() {
return data.size();
}
class MyHolder extends RecyclerView.ViewHolder {
TextView textMovieName;
TextView textMovieId;
ImageView ivMovie;
public MyHolder(View itemView) {
super(itemView);
Log.d("myholder", "test");
textMovieName = (TextView) itemView.findViewById(R.id.textMovieName);
textMovieId = (TextView) itemView.findViewById(R.id.textMovieId);
ivMovie = (ImageView) itemView.findViewById(R.id.ivMovie);
}
}
}
listMovies.java
public class listMovie {
public String movieId;
public String movieName;
public String movieImage;
public String getMovieId() {
return movieId;
}
public void setMovieId(String movieId) {
this.movieId = movieId;
}
public String getMovieName() {
return movieName;
}
public void setMovieName(String movieName) {
this.movieName = movieName;
}
public String getMovieImage() {
return movieImage;
}
public void setMovieImage(String movieImage) {
this.movieImage = movieImage;
}
}
fragment_home.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.fyp.HomeFragment">
<!-- TODO: Update blank fragment layout -->
<android.support.v7.widget.RecyclerView
android:id="@+id/fishPriceList"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="10dp"
android:layout_weight="1" />
</FrameLayout>
container_fish.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:clickable="true"
android:padding="10dp" >
<ImageView
android:layout_width="60dp"
android:layout_height="40dp"
android:scaleType="fitXY"
android:id="@+id/ivMovie"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="fish name"
android:id="@+id/textMovieName"
android:layout_marginLeft="5dp"
android:layout_toRightOf="@id/ivMovie"
android:layout_toLeftOf="@+id/textMovieId"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="price"
android:id="@+id/textMovieId"
android:textColor="@color/colorAccent"
android:layout_alignParentEnd="true"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp" />
</LinearLayout>
JSON 文件
{"test":[{"movie_id":"1","name":"Movie 1","imageurl":"http:\/\/10.0.2.2\/finalproject\/images\/AJ2-2.png"},{"movie_id":"2","name":"Movie 2","imageurl":"http:\/\/10.0.2.2\/finalproject\/images\/aj.png"},{"movie_id":"3","name":"Movie 3","imageurl":"http:\/\/10.0.2.2\/finalproject\/images\/gameover.png"},{"movie_id":"4","name":"Movie 4","imageurl":"http:\/\/10.0.2.2\/finalproject\/images\/tar.jpg"}]}
错误出来了
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.arshadjailani.fyp, PID: 2582
java.lang.NullPointerException
at com.example.arshadjailani.fyp.AdapterFish.onBindViewHolder(AdapterFish.java:50)
at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5825)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5858)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5094)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4970)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2029)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1414)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1377)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:578)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3315)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3124)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3568)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:131)
at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1364)
at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:846)
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:1197)
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:1987)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1744)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCa
错误指向这一行
myHolder.textMovieName.setText(current.movieName);
myHolder.textMovieId.setText(current.movieId);
最佳答案
您在 onCreateViewHolder 中夸大了错误的布局文件
View view = inflater.inflate(R.layout.fragment_home, parent, false);
应该是
View view = inflater.inflate(R.layout.container_fish, parent, false);
第二个错误!
public class HomeFragment extends Fragment {
...
RecyclerView mRecyclerView;
...
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.fishPriceList);
}
}
在执行后
mAdapter = new AdapterFish(getActivity(), data);
mRecyclerView .setAdapter(mAdapter);
mRecyclerView .setLayoutManager(new LinearLayoutManager(getActivity()));
关于java - Fragment 中的 RecyclerView 错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42991364/