我尝试将信息表单数据库（mysql）检索为列表视图，这样可以正常工作 但如果我点击列表中的项目来显示信息 它在logcat中显示这个问题
09-20 21:40:12.125: E/AndroidRuntime(5003): FATAL EXCEPTION: main
09-20 21:40:12.125: E/AndroidRuntime(5003): android.os.NetworkOnMainThreadException
09-20 21:40:12.125: E/AndroidRuntime(5003): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1084)
09-20 21:40:12.125: E/AndroidRuntime(5003): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:74)
09-20 21:40:12.125: E/AndroidRuntime(5003): at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
09-20 21:40:12.125: E/AndroidRuntime(5003): at libcore.io.IoBridge.connect(IoBridge.java:112)
09-20 21:40:12.125: E/AndroidRuntime(5003): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
09-20 21:40:12.125: E/AndroidRuntime(5003): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
09-20 21:40:12.125: E/AndroidRuntime(5003): at java.net.Socket.connect(Socket.java:842)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
09-20 21:40:12.125: E/AndroidRuntime(5003): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
09-20 21:40:12.125: E/AndroidRuntime(5003): at com.ksu.sms.JSONParser.makeHttpRequest(JSONParser.java:62)
09-20 21:40:12.125: E/AndroidRuntime(5003): at com.ksu.sms.ViewCourseStudent$GetCourseDetails$1.run(ViewCourseStudent.java:91)
09-20 21:40:12.125: E/AndroidRuntime(5003): at android.os.Handler.handleCallback(Handler.java:605)
09-20 21:40:12.125: E/AndroidRuntime(5003): at android.os.Handler.dispatchMessage(Handler.java:92)
09-20 21:40:12.125: E/AndroidRuntime(5003): at android.os.Looper.loop(Looper.java:137)
09-20 21:40:12.125: E/AndroidRuntime(5003): at android.app.ActivityThread.main(ActivityThread.java:4340)
09-20 21:40:12.125: E/AndroidRuntime(5003): at java.lang.reflect.Method.invokeNative(Native Method)
09-20 21:40:12.125: E/AndroidRuntime(5003): at java.lang.reflect.Method.invoke(Method.java:511)
09-20 21:40:12.125: E/AndroidRuntime(5003): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-20 21:40:12.125: E/AndroidRuntime(5003): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-20 21:40:12.125: E/AndroidRuntime(5003): at dalvik.system.NativeStart.main(Native Method)
这是我的代码，用于检索整个信息 并显示为列表
package com.ksu.sms;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
public class ViewALLCourseStudent extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser(); //class
ArrayList<HashMap<String, String>> coursesList;
//url to get all products list
private static String url_all_course = "http://10.0.2.2/SmsPhp/view_all_course.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_course = "course";
private static final String TAG_CourseID = "CourseID";
private static final String TAG_Name = "Name";
// course JSONArray
JSONArray courses = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_all_course_student);
coursesList = new ArrayList<HashMap<String, String>>();
// Loading courses in Background Thread
new LoadAllCourses().execute();
// Get list view
ListView lv = getListView();
// on seleting single course
// launching Edit course Screen
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) //one of the list
{
// getting values from selected ListItem
String CourseID = ((TextView) view.findViewById(R.id.CourseID)).getText()
.toString();
// Starting new intent
Intent ViewCourseStudent = new Intent(getApplicationContext(),
ViewCourseStudent.class);
// sending Course ID to next activity
ViewCourseStudent.putExtra(TAG_CourseID, CourseID);
// starting new activity and expecting some response back
startActivityForResult(ViewCourseStudent, 100);
}
});
}
// Response from view course Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user view course
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all course by making HTTP Request
* */
class LoadAllCourses extends AsyncTask<String, String, String>
{
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(ViewALLCourseStudent.this);
pDialog.setMessage("Loading Courses. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from u r l
* */
@Override
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_course, "GET", params);
// Check your log cat for JSON response
Log.d("All courses: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// course found
// Getting Array of course
courses = json.getJSONArray(TAG_course);
// looping through All courses
for (int i = 0; i < courses.length(); i++)//course JSONArray
{
JSONObject c = courses.getJSONObject(i); // read first
// Storing each json item in variable
String CourseID = c.getString(TAG_CourseID);
String Name = c.getString(TAG_Name);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_CourseID, CourseID);
map.put(TAG_Name, Name);
// adding HashList to ArrayList
coursesList.add(map);
}
} else {
Toast.makeText(getBaseContext(),"there is no course" ,Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
**/
ListAdapter adapter = new SimpleAdapter(
ViewALLCourseStudent.this, coursesList,
R.layout.list_item, new String[] { TAG_CourseID,
TAG_Name},
new int[] { R.id.CourseID, R.id.Name });
// updating listview
setListAdapter(adapter);
}
}
}
最后，如果数据库为空，它也会在logcat中显示此问题
09-20 22:07:20.665: E/AndroidRuntime(5260): FATAL EXCEPTION: AsyncTask #1
09-20 22:07:20.665: E/AndroidRuntime(5260): java.lang.RuntimeException: An error occured while executing doInBackground()
答案 0 :(得分：0)
为什么要在AsyncTask的后台线程中使用runOnUiThread()？使用它的全部要点是使操作在后台线程上运行。
无论哪种方式，你都可以做两件事来解决这个问题。
使用以下网址为低于蜂窝的API构建应用：
<uses-sdk android:minSdkVersion="8" android:targetSdkVersion="9" />
删除AsyncTask的runOnUiThread()部分，并让代码在后台线程中运行。
答案 1 :(得分：0)
这个问题有两个解决方案。
1）不要在主UI线程中编写网络调用，为此使用异步任务。
2）在setContentView（R.layout.activity_main）之后将下面的代码写入MainActivity文件;
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}