运行此代码时出现异常。我想解析一个json对象数组的url：
package com.example.compsci_734t;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
public class UoaCompsciActivity extends Activity {
private static String url = " http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";
//URL requestUrl = new URL(url);
JSONArray courses = null;
private static final String TAG_COURSES = "Courses";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_uoa_compsci);
new MyTask().execute();
}
private class MyTask extends AsyncTask<URL, Void, JSONObject> {
@Override
protected JSONObject doInBackground(URL... urls) {
loadJSON(url);
return null;
}
protected void onPostExecute(JSONObject json) {
try {
courses = json.getJSONArray(TAG_COURSES);
// looping through all courses
for (int i = 0; i < courses.length(); i++) {
JSONObject c = courses.getJSONObject(i);
// Storing each json item in variable
String course_id = c.getString("courseField:");
String course_name = c.getString("titleField:");
String course_semester = c.getString("semesterField:");
Log.v("--", "Course: \n" + " " + course_id + " " + course_name
+ " " + course_semester);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public JSONObject loadJSON(String url) {
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
return json;
}
}
这里也是我的logcat：
05-13 20:29:05.118: I/dalvikvm(770): threadid=3: reacting to signal 3
05-13 20:29:05.128: I/dalvikvm(770): Wrote stack traces to '/data/anr/traces.txt'
05-13 20:29:05.418: D/gralloc_goldfish(770): Emulator without GPU emulation detected.
05-13 20:31:46.128: I/dalvikvm(842): threadid=3: reacting to signal 3
05-13 20:31:46.218: I/dalvikvm(842): Wrote stack traces to '/data/anr/traces.txt'
05-13 20:31:46.408: D/gralloc_goldfish(842): Emulator without GPU emulation detected.
05-13 22:06:17.298: I/dalvikvm(918): threadid=3: reacting to signal 3
05-13 22:06:17.389: I/dalvikvm(918): Wrote stack traces to '/data/anr/traces.txt'
05-13 22:06:17.549: D/gralloc_goldfish(918): Emulator without GPU emulation detected.
05-13 22:06:17.829: W/dalvikvm(918): threadid=11: thread exiting with uncaught exception (group=0x409c01f8)
05-13 22:06:17.839: E/AndroidRuntime(918): FATAL EXCEPTION: AsyncTask #1
05-13 22:06:17.839: E/AndroidRuntime(918): java.lang.RuntimeException: An error occured while executing doInBackground()
05-13 22:06:17.839: E/AndroidRuntime(918): at android.os.AsyncTask$3.done(AsyncTask.java:278)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
05-13 22:06:17.839: E/AndroidRuntime(918): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.lang.Thread.run(Thread.java:856)
05-13 22:06:17.839: E/AndroidRuntime(918): Caused by: java.lang.IllegalArgumentException: Illegal character in scheme at index 0: http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses
05-13 22:06:17.839: E/AndroidRuntime(918): at java.net.URI.create(URI.java:727)
05-13 22:06:17.839: E/AndroidRuntime(918): at org.apache.http.client.methods.HttpPost.<init>(HttpPost.java:79)
05-13 22:06:17.839: E/AndroidRuntime(918): at com.example.compsci_734t.JSONParser.getJSONFromUrl(JSONParser.java:36)
05-13 22:06:17.839: E/AndroidRuntime(918): at com.example.compsci_734t.UoaCompsciActivity.loadJSON(UoaCompsciActivity.java:78)
05-13 22:06:17.839: E/AndroidRuntime(918): at com.example.compsci_734t.UoaCompsciActivity$MyTask.doInBackground(UoaCompsciActivity.java:42)
05-13 22:06:17.839: E/AndroidRuntime(918): at com.example.compsci_734t.UoaCompsciActivity$MyTask.doInBackground(UoaCompsciActivity.java:1)
05-13 22:06:17.839: E/AndroidRuntime(918): at android.os.AsyncTask$2.call(AsyncTask.java:264)
05-13 22:06:17.839: E/AndroidRuntime(918): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
05-13 22:06:17.839: E/AndroidRuntime(918): ... 5 more
更新了logcat：
05-13 22:15:01.438: I/dalvikvm(968): threadid=3: reacting to signal 3
05-13 22:15:01.598: I/dalvikvm(968): Wrote stack traces to '/data/anr/traces.txt'
05-13 22:15:01.718: D/gralloc_goldfish(968): Emulator without GPU emulation detected.
05-13 22:15:02.288: E/JSON Parser(968): Error parsing data org.json.JSONException: Value <?xml of type java.lang.String cannot be converted to JSONObject
05-13 22:15:02.288: D/AndroidRuntime(968): Shutting down VM
05-13 22:15:02.288: W/dalvikvm(968): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
05-13 22:15:02.298: E/AndroidRuntime(968): FATAL EXCEPTION: main
05-13 22:15:02.298: E/AndroidRuntime(968): java.lang.NullPointerException
05-13 22:15:02.298: E/AndroidRuntime(968): at com.example.compsci_734t.UoaCompsciActivity$MyTask.onPostExecute(UoaCompsciActivity.java:49)
05-13 22:15:02.298: E/AndroidRuntime(968): at com.example.compsci_734t.UoaCompsciActivity$MyTask.onPostExecute(UoaCompsciActivity.java:1)
05-13 22:15:02.298: E/AndroidRuntime(968): at android.os.AsyncTask.finish(AsyncTask.java:602)
05-13 22:15:02.298: E/AndroidRuntime(968): at android.os.AsyncTask.access$600(AsyncTask.java:156)
05-13 22:15:02.298: E/AndroidRuntime(968): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
05-13 22:15:02.298: E/AndroidRuntime(968): at android.os.Handler.dispatchMessage(Handler.java:99)
05-13 22:15:02.298: E/AndroidRuntime(968): at android.os.Looper.loop(Looper.java:137)
05-13 22:15:02.298: E/AndroidRuntime(968): at android.app.ActivityThread.main(ActivityThread.java:4424)
05-13 22:15:02.298: E/AndroidRuntime(968): at java.lang.reflect.Method.invokeNative(Native Method)
05-13 22:15:02.298: E/AndroidRuntime(968): at java.lang.reflect.Method.invoke(Method.java:511)
05-13 22:15:02.298: E/AndroidRuntime(968): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-13 22:15:02.298: E/AndroidRuntime(968): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-13 22:15:02.298: E/AndroidRuntime(968): at dalvik.system.NativeStart.main(Native Method)
05-13 22:15:02.889: I/dalvikvm(968): threadid=3: reacting to signal 3
05-13 22:15:02.919: I/dalvikvm(968): Wrote stack traces to '/data/anr/traces.txt'
完整的logcat： 05-13 22：15：01.438：I / dalvikvm（968）：threadid = 3：对信号3作出反应 05-13 22：15：01.598：I / dalvikvm（968）：将堆栈跟踪写入'/data/anr/traces.txt' 05-13 22：15：01.718：D / gralloc_goldfish（968）：未检测到GPU仿真的仿真器。 05-13 22：15：02.288：E / JSON Parser（968）：解析数据时出错org.json.JSONException：Value
答案 0 :(得分：1)
错误本身就是解释性的：
java.lang.IllegalArgumentException：scheme中的非法字符 索引0
您需要删除网址中的起始空格字符：
private static String url = "http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";
<强>更新
在您更新了问题之后，现在问题出现在这一行：
courses = json.getJSONArray(TAG_COURSES);
因为您尚未初始化或设置courses的值，这就是导致NullPointerException错误的原因。
答案 1 :(得分：0)
它与JSON解析无关。
private static String url = " http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";
你必须从网址字符串
中删除初始空格答案 2 :(得分：0)
嗨，由于网络服务中的一些问题可能是由于编码问题而不是你的或者android的问题。正如你在该字符串中得到响应一样，只需用“”替换你得到的字符。
response = response.replace（“”，“”）;
然后在此之后进行解析。它对我有用。我希望它对你也有用.....
答案 3 :(得分：0)
我已经解决了。感谢你的帮助。我还将解析后的内容转换为列表视图。这是我的工作代码：
package com.example.compsci_734t;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.util.ArrayList;
import java.util.zip.GZIPInputStream;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ListActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class People extends Activity{
ArrayList<String> items = new ArrayList<String>();
static InputStream is = null;
//private static String url = "";
//private static String url = "http:...";
private static String url = "http....";
//URL requestUrl = new URL(url);
JSONArray people = null;
private static final String TAG_COURSES = "Courses";
static JSONObject jObj = null;
static String json = "";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.people);
new MyTasks().execute();
}
private class MyTasks extends AsyncTask<URL, Void, JSONObject> {
@Override
protected JSONObject doInBackground(URL... urls) {
// return loadJSON(url);
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
//HttpPost httpPost = new HttpPost(url);
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
/*BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "UTF-8"), 8);*/
InputStream inputStream = is;
GZIPInputStream input = new GZIPInputStream(inputStream);
InputStreamReader reader = new InputStreamReader(input);
BufferedReader in = new BufferedReader(reader);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = in.readLine()) != null) {
sb.append(line);
//System.out.println(line);
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
JSONArray people = new JSONArray(json);
//JSONArray people = new JSONArray(json);
for (int i = 0; i < people.length(); i++) {
//System.out.println(courses.getJSONObject(i).toString());
JSONObject p = people.getJSONObject(i);
// Storing each json item in variable
String person_id = p.getString("someString1");
items.add(person_id);
/*Log.v("--", "People: \n" + "\n UPI: " + person_id);*/
}
//jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
protected void onPostExecute(JSONObject json) {
ListView myListView = (ListView)findViewById(R.id.peopleList);
myListView.setAdapter(new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, items));
}
}
答案 4 :(得分：0)
package com.example.json_test;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.util.ArrayList;
import java.util.zip.GZIPInputStream;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends Activity
{
ArrayList<String> items = new ArrayList<String>();
static InputStream is = null;
private static String url = "http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";
JSONArray people = null;
private static final String TAG_COURSES = "codeField";
private static final String TAG_SEMESTER="semesterField";
static JSONObject jObj = null;
static String json = "";
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new MyTasks().execute();
}
private class MyTasks extends AsyncTask<URL, Void, JSONObject>
{
@Override
protected JSONObject doInBackground(URL... urls)
{
try
{
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
catch (UnsupportedEncodingException e)
{
e.printStackTrace();
}
catch (ClientProtocolException e)
{
e.printStackTrace();
} catch (IOException e)
{
e.printStackTrace();
}
try
{
InputStream inputStream = is;
GZIPInputStream input = new GZIPInputStream(inputStream);
InputStreamReader reader = new InputStreamReader(input);
BufferedReader in = new BufferedReader(reader);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = in.readLine()) != null)
{
sb.append(line);
}
is.close();
json = sb.toString();
} catch (Exception e)
{
Log.e("Buffer Error", "Error converting result " + e.toString());
}
try
{
JSONArray people = new JSONArray(json);
for (int i = 0; i < people.length(); i++)
{
JSONObject p = people.getJSONObject(i);
String Courses = p.getString(TAG_COURSES);
String semester=p.getString(TAG_SEMESTER);
items.add(Courses);
items.add(semester);
}
} catch (JSONException e)
{
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
return jObj;
}
@SuppressWarnings({ "unchecked", "rawtypes" })
protected void onPostExecute(JSONObject json)
{
ListView myListView = (ListView)findViewById(R.id.peopleList);
myListView.setAdapter(new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, items));
}
}
}