在 Java 类中，我有三个 List 作为类中的字段。所以我相信我让全班都可以使用它们？和所有内部类？
但是，这不起作用：（例如，我将在这里只显示一个列表，而不是全部三个）
class Items extends ListActivity {
List<String> items = null; // field
Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// stuff
items = new ArrayList<String>();
new Task().execute();
Log.d("Size", String.valueOf(items.size()));
}
class Task extends AsyncTask<String, String, Void> {
// in this subclass, I parse items from JSON and add to List "items".
items = add(item);
}
退出任务后，我似乎丢失了列表中的项目。它记录“大小 0”；如果我在任务中执行此操作，它会显示适当数量的项目。我在这里错过了关于 List 变量范围的一个非常基本的观点吗？
编辑：下面是完整的任务类（稍微清理一下以供发布）
class Task extends AsyncTask<String, String, Void> {
private InputStream is = null;
private String result = "";
@Override
protected Void doInBackground(String... params) {
String url_select = "items.php";
param = new ArrayList<NameValuePair>();
param.add(new BasicNameValuePair("category", Category));
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url_select);
try {
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// read content
is = httpEntity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
try {
BufferedReader br = new BufferedReader(
new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
// TODO: handle exception
Log.e("log_tag", "Error converting result " + e.toString());
}
return null;
}
protected void onPostExecute(Void v) {
try {
JSONArray jArray = new JSONArray(result);
JSONObject json_data = null;
for (int i = 0; i < jArray.length(); i++) {
json_data = jArray.getJSONObject(i);
item = json_data.getString("item");
items.add(item);
Log.d("Items", item);
}
} catch (JSONException e1) {
Toast.makeText(getBaseContext(), "No items!",
Toast.LENGTH_SHORT).show();
} catch (ParseException e1) {
e1.printStackTrace();
}
}
}