Question

我是Android应用程序开发的新手。我正在做这个教程的应用程序。当我在模拟器中运行它时，它说“不幸的是AndroidJSONParsingActivity已停止工作。 “代码中没有错误.API级别为17，仿真器为Nexus S. 请帮帮我。

我从JSON tutorial

获得了教程CODE

AndroidJsonParsing.java

package com.example.androidjsonparsingactivity;

import java.util.ArrayList; 
import java.util.HashMap; 

import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.app.ListActivity; 
import android.content.Intent; 
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; 

public class AndroidJSONParsing extends ListActivity {    
// url to make request 
private static String url = "http://api.androidhive.info/contacts/"; 

// JSON Node names 
private static final String TAG_CONTACTS = "contacts"; 
private static final String TAG_ID = "id"; 
private static final String TAG_NAME = "name"; 
private static final String TAG_EMAIL = "email"; 
private static final String TAG_ADDRESS = "address"; 
private static final String TAG_GENDER = "gender"; 
private static final String TAG_PHONE = "phone"; 
private static final String TAG_PHONE_MOBILE = "mobile"; 
private static final String TAG_PHONE_HOME = "home"; 
private static final String TAG_PHONE_OFFICE = "office"; 

// contacts JSONArray 
JSONArray contacts = null; 

@Override
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 

    // Hashmap for ListView 
    ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>(); 

    // Creating JSON Parser instance 
    JSONParser jParser = new JSONParser(); 

    // getting JSON string from URL 
    JSONObject json = jParser.getJSONFromUrl(url); 

    try { 
        // Getting Array of Contacts 
        contacts = json.getJSONArray(TAG_CONTACTS); 

        // looping through All Contacts 
        for(int i = 0; i < contacts.length(); i++){ 
            JSONObject c = contacts.getJSONObject(i); 

            // Storing each json item in variable 
            String id = c.getString(TAG_ID); 
            String name = c.getString(TAG_NAME); 
            String email = c.getString(TAG_EMAIL); 
            String address = c.getString(TAG_ADDRESS); 
            String gender = c.getString(TAG_GENDER); 

            // Phone number is agin JSON Object 
            JSONObject phone = c.getJSONObject(TAG_PHONE); 
            String mobile = phone.getString(TAG_PHONE_MOBILE); 
            String home = phone.getString(TAG_PHONE_HOME); 
            String office = phone.getString(TAG_PHONE_OFFICE); 

            // creating new HashMap 
            HashMap<String, String> map = new HashMap<String, String>(); 

            // adding each child node to HashMap key => value 
            map.put(TAG_ID, id); 
            map.put(TAG_NAME, name); 
            map.put(TAG_EMAIL, email); 
            map.put(TAG_PHONE_MOBILE, mobile); 

            // adding HashList to ArrayList 
            contactList.add(map); 
        } 
    } catch (JSONException e) { 
        e.printStackTrace(); 
    } 


    /** 
     * Updating parsed JSON data into ListView 
     * */
    ListAdapter adapter = new SimpleAdapter(this, contactList, 
            R.layout.list_item, 
            new String[] { TAG_NAME, TAG_EMAIL, TAG_PHONE_MOBILE }, new int[] { 
                    R.id.name, R.id.email, R.id.mobile }); 

    setListAdapter(adapter); 

    // selecting single ListView item 
    ListView lv = getListView(); 

    // Launching new screen on Selecting Single ListItem 
    lv.setOnItemClickListener(new OnItemClickListener() { 

        @Override
        public void onItemClick(AdapterView<?> parent, View view, 
                int position, long id) { 
            // getting values from selected ListItem 
            String name = ((TextView) view.findViewById(R.id.name)).getText().toString(); 
            String cost = ((TextView) view.findViewById(R.id.email)).getText().toString(); 
            String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString(); 

            // Starting new intent 
            Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class); 
            in.putExtra(TAG_NAME, name); 
            in.putExtra(TAG_EMAIL, cost); 
            in.putExtra(TAG_PHONE_MOBILE, description); 
            startActivity(in); 
        } 
    }); 
} 

}

JSONParser.java

package com.example.androidjsonparsingactivity;

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.io.UnsupportedEncodingException; 

import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.client.ClientProtocolException; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.util.Log; 

public class JSONParser { 

static InputStream is = null; 
static JSONObject jObj = null; 
static String json = ""; 

// constructor 
public JSONParser() { 

} 

public JSONObject getJSONFromUrl(String url) { 

    // Making HTTP request 
    try { 
        // defaultHttpClient 
        DefaultHttpClient httpClient = new DefaultHttpClient(); 
        HttpPost httpPost = new HttpPost(url); 

        HttpResponse httpResponse = httpClient.execute(httpPost); 
        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, "iso-8859-1"), 8); 
        StringBuilder sb = new StringBuilder(); 
        String line = null; 
        while ((line = reader.readLine()) != null) { 
            sb.append(line + "\n"); 
        } 
        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 { 
        jObj = new JSONObject(json); 
    } catch (JSONException e) { 
        Log.e("JSON Parser", "Error parsing data " + e.toString()); 
    } 

    // return JSON String 
    return jObj; 

}
}

SingleMenuItemActivity.java

package com.example.androidjsonparsingactivity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class SingleMenuItemActivity  extends Activity {

// JSON node keys
private static final String TAG_NAME = "name";
private static final String TAG_EMAIL = "email";
private static final String TAG_PHONE_MOBILE = "mobile";
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.single_list_item);

    // getting intent data
    Intent in = getIntent();

    // Get JSON values from previous intent
    String name = in.getStringExtra(TAG_NAME);
    String cost = in.getStringExtra(TAG_EMAIL);
    String description = in.getStringExtra(TAG_PHONE_MOBILE);

    // Displaying all values on the screen
    TextView lblName = (TextView) findViewById(R.id.name_label);
    TextView lblCost = (TextView) findViewById(R.id.email_label);
    TextView lblDesc = (TextView) findViewById(R.id.mobile_label);

    lblName.setText(name);
    lblCost.setText(cost);
    lblDesc.setText(description);
}
}

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.androidjsonparsingactivity"
android:versionCode="1"
android:versionName="1.0" >
<uses-permission android:name="android.permission.INTERNET" />

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.androidjsonparsingactivity.AndroidJSONParsing"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".SingleListItem"
                android:label="Single Item Selected"></activity> 

</application>


</manifest>

logcat的

08-01 07:32:35.531: D/dalvikvm(1121): GC_FOR_ALLOC freed 42K, 7% free 2609K/2792K, paused 37ms, total 41ms
08-01 07:32:35.541: I/dalvikvm-heap(1121): Grow heap (frag case) to 3.288MB for 635812-byte allocation
08-01 07:32:35.591: D/dalvikvm(1121): GC_FOR_ALLOC freed 2K, 6% free 3227K/3416K, paused 47ms, total 47ms
08-01 07:32:35.672: D/dalvikvm(1121): GC_CONCURRENT freed <1K, 6% free 3237K/3416K, paused 9ms+16ms, total 82ms
08-01 07:32:35.740: D/AndroidRuntime(1121): Shutting down VM
08-01 07:32:35.740: W/dalvikvm(1121): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
08-01 07:32:35.761: E/AndroidRuntime(1121): FATAL EXCEPTION: main
08-01 07:32:35.761: E/AndroidRuntime(1121): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.androidjsonparsingactivity/com.example.androidjsonparsingactivity.AndroidJSONParsing}: android.os.NetworkOnMainThreadException
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.os.Looper.loop(Looper.java:137)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.ActivityThread.main(ActivityThread.java:5041)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at java.lang.reflect.Method.invokeNative(Native Method)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at java.lang.reflect.Method.invoke(Method.java:511)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at dalvik.system.NativeStart.main(Native Method)
08-01 07:32:35.761: E/AndroidRuntime(1121): Caused by: android.os.NetworkOnMainThreadException
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at java.net.InetAddress.getAllByName(InetAddress.java:214)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at com.example.androidjsonparsingactivity.JSONParser.getJSONFromUrl(JSONParser.java:38)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at com.example.androidjsonparsingactivity.AndroidJSONParsing.onCreate(AndroidJSONParsing.java:54)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.Activity.performCreate(Activity.java:5104)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
08-01 07:32:35.761: E/AndroidRuntime(1121):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
08-01 07:32:35.761: E/AndroidRuntime(1121):     ... 11 more

Answer 1

对于Android 4.0及更高版本，您无法在UI线程上执行网络操作，并且需要使用后台线程。

您正在从主线程调用以下代码而不是后台线程因此抛出此异常。

  // getting JSON string from URL 
    JSONObject json = jParser.getJSONFromUrl(url);

而是创建async task并在异步任务的doInBackground（）中执行此操作

异步任务在后台执行opertaion而不是在主/ UI线程上执行

class FetchJsonTask extends AsyncTask<Void, Void, void> {


    protected Void doInBackground(Void... params) {
        try {
             // getting JSON string from URL 
        JSONObject json = jParser.getJSONFromUrl(url); 
        } catch (Exception e) {

        }
    }

    protected void onPostExecute(Void result) {
         super.onPostExecute(result);
       //code to be executed after background task is finished
    }


     protected void onPreExecute() {
         super.onPreExecute();
      //code to be executed before background task is started
     }
  return null;
}

在onCreate（）中，调用以下列方式执行异步任务：

new FetchJsonTask().execute();

相关链接：

How to fix android.os.NetworkOnMainThreadException?

Answer 2

您已从主线程调用Web。那就是为什么你有

Caused by: android.os.NetworkOnMainThreadException

在android 4.0之后，你无法在其UIThread上进行网络操作。你需要使用后台线程。我更愿意使用AsyncTask进行网络呼叫。

希望它能帮助!!

Answer 3

阅读评论过的部分并根据它更改您的代码。

class MyAsync extends AsyncTask<String, Void, Void> {

         @Override
         protected void onPreExecute() {
             super.onPreExecute();
         }

         @Override
         protected Void doInBackground(String... params) {
             // do your JSON parse here
             return null;
         }

         @Override
         protected void onPostExecute(Void result) {
             // after gettin json data do whatever you want here
             super.onPostExecute(result);
         }
    }

在你的oncreate中调用你的异步类：

new MyAsync().execute();

不幸的是app已经停止工作

3 个答案: