您好,我有此代码,它在 android 3 和 4 设备上给了我错误。我知道我可以用 async 解决这个问题,但我之前没有使用过同步任务,也不知道它是如何工作的。有人可以用我的代码给我一个小例子或建议如何实现它吗?
我的代码:
package com.wemait.obd.emmen;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.wemait.obd.emmen.JSONParser;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
public class Nieuws extends Activity {
// url om request te maken
private static String URL = "http://www.iappministrator.com/OBDE/webservice/android_news_items.php";
// JSON Node namen
static final String TAG_ITEMS = "items";
static final String TAG_TITLE = "title";
static final String TAG_MESSAGE = "message";
static final String TAG_DATE = "date";
static final String TAG_IMAGES = "images";
// Nieuws JSONArray
JSONArray newsArray = null;
ListView list;
LazyAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.nieuws);
// Hashmap voor listView
final ArrayList<HashMap<String, String>> newsList = new ArrayList<HashMap<String, String>>();
// Maak een JSON Parser instance
JSONParser jParser = new JSONParser();
// Pakt JSON string uit URL
JSONObject json = jParser.getJSONFromUrl(URL);
try{
// Pakt de Array van Nieuwsartikelen
newsArray = json.getJSONArray(TAG_ITEMS);
// Loop door alle Nieuwsartikels
for(int i=0; i < newsArray.length(); i++){
JSONObject c = newsArray.getJSONObject(i);
// Het plaatsen van elk json item in variabele
String title = c.getString(TAG_TITLE);
String message = c.getString(TAG_MESSAGE);
//String date = c.getString(TAG_DATE);
String images = c.getString(TAG_IMAGES);
// maak een nieuwe HashMap
HashMap<String, String> map = new HashMap<String, String>();
// voeg elk item child node in de Hashmap -> value
map.put(TAG_TITLE, title);
map.put(TAG_MESSAGE, message);
//map.put(TAG_DATE, date);
map.put(TAG_IMAGES, images);
// voeg de HashList toe aan ArrayList
newsList.add(map);
}
} catch(JSONException e){
e.printStackTrace();
}
list=(ListView)findViewById(R.id.list);
adapter=new LazyAdapter(this, newsList, R.layout.list_row,
new String[]{TAG_TITLE, TAG_MESSAGE, TAG_DATE, TAG_IMAGES}, new int[] {
R.id.title, R.id.artist, R.id.duration, R.id.list_image});
list.setAdapter(adapter);
// Click event for single list row
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
HashMap<String, String> map = newsList.get(position);
Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
//Intent in = new Intent(SingleMenuItemActivity.this, org.scout.android.library.LibraryDetail.class);
in.putExtra(TAG_TITLE, map.get(TAG_TITLE));
in.putExtra(TAG_MESSAGE, map.get(TAG_MESSAGE));
in.putExtra(TAG_DATE, map.get(TAG_DATE));
in.putExtra(TAG_IMAGES, map.get(TAG_IMAGES));
startActivity(in);
/* old code public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String title = ((TextView) view.findViewById(R.id.title)).getText().toString();
String date = ((TextView) view.findViewById(R.id.duration)).getText().toString();
String message = ((TextView) view.findViewById(R.id.artist)).getText().toString();
//String images = ((TextView) view.findViewById(R.id.list_image)).getText().toString();
//ImageView thumb_image = (ImageView) view.findViewById(R.id.thumbnail); // thumb image
String images = ((ImageView)view.findViewById(R.id.list_image)).getImageMatrix().toString();
//String images = ((ImageView)view.findViewById(R.id.list_image)).toString();
//String images = ((ImageView)view.findViewById(R.id.list_image)).getContext().toString();
// Start de nieuwe intent
Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
//Bitmap bitmap = (Bitmap) in.getParcelableExtra(TAG_IMAGES);
in.putExtra(TAG_TITLE, title);
in.putExtra(TAG_DATE, date);
in.putExtra(TAG_MESSAGE, message);
in.putExtra(TAG_IMAGES, images);
startActivity(in);*/
}
});
}
}
我收到的错误:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.wemait.obd.emmen/com.wemait.obd.emmen.Nieuws}: android.os.NetworkOnMainThreadException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
at android.app.ActivityThread.access$600(ActivityThread.java:127)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4511)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099)
at java.net.InetAddress.lookupHostByName(InetAddress.java:391)
at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)
at java.net.InetAddress.getAllByName(InetAddress.java:220)
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
at com.wemait.obd.emmen.JSONParser.getJSONFromUrl(JSONParser.java:38)
at com.wemait.obd.emmen.Nieuws.onCreate(Nieuws.java:53)
at android.app.Activity.performCreate(Activity.java:4470)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
我的适配器类:
package com.wemait.obd.emmen;
import java.util.ArrayList;
import java.util.HashMap;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d, int listRow, String[] strings, int[] is) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.list_row, null);
TextView title = (TextView)vi.findViewById(R.id.title); // title
TextView artist = (TextView)vi.findViewById(R.id.artist); // artist name
TextView duration = (TextView)vi.findViewById(R.id.duration); // duration
ImageView thumb_image=(ImageView)vi.findViewById(R.id.list_image); // thumb image
HashMap<String, String> song = new HashMap<String, String>();
song = data.get(position);
// Setting all values in listview
title.setText(song.get(CustomizedListView.TAG_TITLE));
artist.setText(song.get(CustomizedListView.TAG_MESSAGE));
duration.setText(song.get(CustomizedListView.TAG_DATE));
imageLoader.DisplayImage(song.get(CustomizedListView.TAG_IMAGES), thumb_image);
return vi;
}
}