我对Android环境很新。我正在徘徊从网页中检索JSON内容，所以我发现本教程从网址（Tutorial Link）获取JSON内容，并且它也适用于我的数据。
现在，我想要做的事情一个Tab应用程序，其中一个选项卡使用该代码来检索JSON数据。我已经使用了片段，我试图修改代码以便与片段兼容，无论如何，当我启动相关选项卡时，应用程序崩溃。
由于前一个教程正常，我很确定问题出在我的新手代码上。
FragmentTab1.Java
package com.alessandrobocci.fenice;
import java.util.ArrayList;
import java.util.HashMap;
import com.alessandrobocci.fenice.library.JSONParser;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Fragment;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
public class FragmentTab1 extends Fragment {
ListView list;
TextView title;
TextView name;
TextView api;
Button Btngetdata;
ArrayList<HashMap<String, String>> oslist = new ArrayList<HashMap<String, String>>();
//URL to get JSON Array
private static String url = "http://10.0.2.2/test/read.php";
//JSON Node Names
private static final String TAG_OS = "todo";
private static final String TAG_VER = "title";
JSONArray arr = null;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
//Inflate the layout for this fragment
//This layout contains your list view
View view = inflater.inflate(R.layout.fragmenttab1, container, false);
title = (TextView)getView().findViewById(R.id.vers);
//now you must initialize your list view
list =(ListView)view.findViewById(R.id.listnews);
new JSONParse().execute();
return view;
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONObject json = jParser.getJSONFromUrl(url);
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
// Getting JSON Array from URL
arr = json.getJSONArray(TAG_OS);
for(int i = 0; i < arr.length(); i++){
JSONObject c = arr.getJSONObject(i);
// Storing JSON item in a Variable
String ver = c.getString(TAG_VER);
// Adding value HashMap key => value
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_VER, ver);
oslist.add(map);
//list=(ListView) getView().findViewById(R.id.list);
ListAdapter adapter = new SimpleAdapter(getActivity(), oslist,
R.layout.list_v,
new String[] { TAG_VER }, new int[] {
R.id.vers});
list.setAdapter(adapter);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(getActivity(), "You Clicked at "+oslist.get(+position).get("title"), Toast.LENGTH_SHORT).show();
}
});
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
logcat的：
07-04 14:59:36.250: D/gralloc_goldfish(1081): Emulator without GPU emulation detected.
07-04 14:59:38.350: D/dalvikvm(1081): GC_CONCURRENT freed 154K, 10% free 6030K/6663K, paused 11ms+8ms
07-04 14:59:38.690: W/System.err(1081): org.apache.http.conn.HttpHostConnectException: Connection to http://10.0.2.2 refused
07-04 14:59:38.741: W/System.err(1081): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:183)
07-04 14:59:38.741: W/System.err(1081): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
07-04 14:59:38.881: W/System.err(1081): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
07-04 14:59:38.910: W/System.err(1081): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
07-04 14:59:38.910: W/System.err(1081): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
07-04 14:59:39.100: W/System.err(1081): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
07-04 14:59:39.150: W/System.err(1081): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
07-04 14:59:39.150: W/System.err(1081): at com.alessandrobocci.fenice.library.JSONParser.getJSONFromUrl(JSONParser.java:38)
07-04 14:59:39.200: W/System.err(1081): at com.alessandrobocci.fenice.FragmentTab1$JSONParse.doInBackground(FragmentTab1.java:72)
07-04 14:59:39.310: W/System.err(1081): at com.alessandrobocci.fenice.FragmentTab1$JSONParse.doInBackground(FragmentTab1.java:1)
07-04 14:59:39.330: W/System.err(1081): at android.os.AsyncTask$2.call(AsyncTask.java:264)
07-04 14:59:39.330: W/System.err(1081): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-04 14:59:39.390: W/System.err(1081): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-04 14:59:39.440: W/System.err(1081): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
07-04 14:59:39.440: W/System.err(1081): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
07-04 14:59:39.500: W/System.err(1081): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
07-04 14:59:39.510: W/System.err(1081): at java.lang.Thread.run(Thread.java:856)
07-04 14:59:39.510: W/System.err(1081): Caused by: java.net.ConnectException: socket failed: EACCES (Permission denied)
07-04 14:59:39.611: W/System.err(1081): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:181)
07-04 14:59:39.710: W/System.err(1081): ... 16 more
07-04 14:59:39.710: W/System.err(1081): Caused by: java.net.SocketException: socket failed: EACCES (Permission denied)
07-04 14:59:39.870: W/System.err(1081): at libcore.io.IoBridge.socket(IoBridge.java:573)
07-04 14:59:39.870: W/System.err(1081): at java.net.PlainSocketImpl.create(PlainSocketImpl.java:201)
07-04 14:59:39.870: W/System.err(1081): at java.net.Socket.checkOpenAndCreate(Socket.java:663)
07-04 14:59:39.921: W/System.err(1081): at java.net.Socket.connect(Socket.java:807)
07-04 14:59:39.979: W/System.err(1081): at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
07-04 14:59:39.979: W/System.err(1081): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
07-04 14:59:40.051: W/System.err(1081): ... 16 more
07-04 14:59:40.091: W/System.err(1081): Caused by: libcore.io.ErrnoException: socket failed: EACCES (Permission denied)
07-04 14:59:40.210: W/System.err(1081): at libcore.io.Posix.socket(Native Method)
07-04 14:59:40.240: W/System.err(1081): at libcore.io.BlockGuardOs.socket(BlockGuardOs.java:169)
07-04 14:59:40.260: W/System.err(1081): at libcore.io.IoBridge.socket(IoBridge.java:558)
07-04 14:59:40.310: W/System.err(1081): ... 21 more
07-04 14:59:40.370: E/Buffer Error(1081): Error converting result java.lang.NullPointerException
07-04 14:59:40.380: E/JSON Parser(1081): Error parsing data org.json.JSONException: End of input at character 0 of
07-04 14:59:40.390: D/AndroidRuntime(1081): Shutting down VM
07-04 14:59:40.403: W/dalvikvm(1081): threadid=1: thread exiting with uncaught exception (group=0x409951f8)
07-04 14:59:40.452: E/AndroidRuntime(1081): FATAL EXCEPTION: main
07-04 14:59:40.452: E/AndroidRuntime(1081): java.lang.NullPointerException
07-04 14:59:40.452: E/AndroidRuntime(1081): at com.alessandrobocci.fenice.FragmentTab1$JSONParse.onPostExecute(FragmentTab1.java:80)
07-04 14:59:40.452: E/AndroidRuntime(1081): at com.alessandrobocci.fenice.FragmentTab1$JSONParse.onPostExecute(FragmentTab1.java:1)
07-04 14:59:40.452: E/AndroidRuntime(1081): at android.os.AsyncTask.finish(AsyncTask.java:602)
07-04 14:59:40.452: E/AndroidRuntime(1081): at android.os.AsyncTask.access$600(AsyncTask.java:156)
07-04 14:59:40.452: E/AndroidRuntime(1081): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
07-04 14:59:40.452: E/AndroidRuntime(1081): at android.os.Handler.dispatchMessage(Handler.java:99)
07-04 14:59:40.452: E/AndroidRuntime(1081): at android.os.Looper.loop(Looper.java:137)
07-04 14:59:40.452: E/AndroidRuntime(1081): at android.app.ActivityThread.main(ActivityThread.java:4340)
07-04 14:59:40.452: E/AndroidRuntime(1081): at java.lang.reflect.Method.invokeNative(Native Method)
07-04 14:59:40.452: E/AndroidRuntime(1081): at java.lang.reflect.Method.invoke(Method.java:511)
07-04 14:59:40.452: E/AndroidRuntime(1081): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-04 14:59:40.452: E/AndroidRuntime(1081): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-04 14:59:40.452: E/AndroidRuntime(1081): at dalvik.system.NativeStart.main(Native Method)
如果有必要，我还会发布其他代码，我认为无论如何它都很有用，例如MainActivity.Java（包含Tabs）可以使用简单的FragmenTab代码来检索一些文本。 希望我很清楚，谢谢。
答案 0 :(得分：1)
更改此
title = (TextView)getView().findViewById(R.id.vers);
到
title = (TextView)view.findViewById(R.id.vers);
title可能为空，导致NullPointerException，如果您发布堆栈跟踪，则可以确认。
您还可以在for循环中设置适配器。没必要那样做。添加项目到列表并将适配器设置为listview一次