如何解决Android AsyncTask和setAdapter帮助
| 我正在尝试获取解析XML并创建对象和arraylist的AsyncTask，以将对象的arraylist传递给setAdapter，以便向用户显示图库。 但是，我得到这个：06-24 15:24:07.972: ERROR/AndroidRuntime(4402): FATAL EXCEPTION: main
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): java.lang.IllegalStateException: System services not available to Activities before onCreate()
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.app.Activity.getSystemService(Activity.java:3886)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.gallery.ImageAdapter.<init>(ImageAdapter.java:41)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.gallery.GalleryActivity$ParseXML.onPostExecute(GalleryActivity.java:150)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.gallery.GalleryActivity$ParseXML.onPostExecute(GalleryActivity.java:1)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.os.AsyncTask.finish(AsyncTask.java:590)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.os.AsyncTask.access$600(AsyncTask.java:149)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:603)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.os.Handler.dispatchMessage(Handler.java:99)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.os.Looper.loop(Looper.java:132)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at android.app.ActivityThread.main(ActivityThread.java:4025)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at java.lang.reflect.Method.invokeNative(Native Method)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at java.lang.reflect.Method.invoke(Method.java:491)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
06-24 15:24:07.972: ERROR/AndroidRuntime(4402): at dalvik.system.NativeStart.main(Native Method)
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
galleryView.setAdapter(new ImageAdapter(new GalleryActivity(),listOfDish));
public class GalleryActivity extends Activity
{
private Gallery galleryView;
private ArrayList<Dish >listOfDish;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ParseXML p = new ParseXML();
p.execute();
galleryView = (Gallery)findViewById(R.id.galleryid);
galleryView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView parent,View v,int position,long id) {
Toast.makeText(GalleryActivity.this,\"\" + position,Toast.LENGTH_SHORT).show();
}
});
}
private class ParseXML extends AsyncTask<String,Void,ArrayList<Dish>>
{
protected ArrayList<Dish> doInBackground(String... arg0)
{
listOfDish = new ArrayList<Dish>();
...parse xml (this works)
listOfDish.add(dish);
}
return listOfDish;
}
@Override
protected void onPostExecute(ArrayList<Dish> result)
{
galleryView.setAdapter(new ImageAdapter(new GalleryActivity(),listOfDish));
}
}
public static String getElement(Element a,String name)
{
NodeList elementList = a.getElementsByTagName(name);
Element b = (Element)elementList.item(0);
if (b != null)
{
NodeList list = b.getChildNodes();
System.out.println(name + \": \" + ((Node)list.item(0)).getNodeValue().trim() );
return ((Node)list.item(0)).getNodeValue().trim();
}
return null;
}
public static String getXML(int num){
String line = null;
try
{
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(\"http://reddit.com/.xml\");
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
line = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
line = \"<results status=\\\"error\\\"><msg>Can\'t connect to server1</msg></results>\";
} catch (MalformedURLException e) {
line = \"<results status=\\\"error\\\"><msg>Can\'t connect to server2</msg></results>\";
} catch (IOException e) {
line = \"<results status=\\\"error\\\"><msg>Can\'t connect to server3</msg></results>\";
}
return line;
}
public final static Document XMLfromString(String xml){
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(xml));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
System.out.println(\"XML parse error: \" + e.getMessage());
return null;
} catch (SAXException e) {
System.out.println(\"Wrong XML file structure: \" + e.getMessage());
return null;
} catch (IOException e) {
System.out.println(\"I/O exeption: \" + e.getMessage());
return null;
}
return doc;
}
}
public class ImageAdapter extends BaseAdapter {
private Activity activity;
private static LayoutInflater inflater = null;
private ArrayList<Dish> listOfDish;
private int[] data;
private String[] name;
public ImageAdapter(Activity a,ArrayList<Dish> listOfDish) {
activity = a;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
this.listOfDish = listOfDish;
data = new int[listOfDish.size()];
name = new String[listOfDish.size()];
for (int i = 0; i < data.length; i++)
{
data[i] = R.drawable.sample_0;
name[i] = \"test\";
}
}
public int getCount() {
return data.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public static class ViewHolder{
public TextView text,dssnum;
public ImageView image;
}
public View getView(int position,View convertView,ViewGroup parent)
{
View vi = convertView;
ViewHolder holder;
if (convertView == null)
{
vi = inflater.inflate(R.layout.caption,null);
holder = new ViewHolder();
holder.text = (TextView) vi.findViewById(R.id.textView1);
holder.dssnum = (TextView) vi.findViewById(R.id.dss_num);
holder.image = (ImageView) vi.findViewById(R.id.image);
vi.setTag(holder);
}
else
holder = (ViewHolder) vi.getTag();
holder.text.setText(name[position]);
holder.dssnum.setText(\"DSS \" + listOfDish.get(position).getSubsystems().get(0).getDSSNum());
final int stub_id = data[position];
holder.image.setImageResource(stub_id);
return vi;
}
}
解决方法
不要使用ѭ5来传递GalleryActivity的上下文...
在
onPostExecute(...)
@Override
protected void onPostExecute(ArrayList<Dish> result)
{
galleryView.setAdapter(new ImageAdapter(GalleryActivity.this,listOfDish));
}
public ImageAdapter(Context context,ArrayList<Dish> listOfDish) {
inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
ParseXML p = new ParseXML();
p.execute();
new Handler().post(new Runnable() {
public void run() {
ParseXML p = new ParseXML();
p.execute();
}
});
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