我有一个从json填充并使用自定义适配器的ListView。
这是我在ZoznamActivity中缩短的代码:
public class Zoznam extends AppCompatActivity{
private ArrayList<Actors> actorsList;
private ActorAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.search_filter);
final ListView lv = findViewById(R.id.listView1);
actorsList = new ArrayList<>();
adapter = new ActorAdapter(this, "Zoznam", actorsList);
lv.setAdapter(adapter);adapter.notifyDataSetChanged();
new GetContacts(Zoznam.this).execute("all","all");
private static class GetContacts extends AsyncTask<String, Void, String> {
ProgressDialog dialog;
private final WeakReference<Zoznam> activityReference;
GetContacts(Zoznam context) {
activityReference = new WeakReference<>(context);
}
@Override
protected void onPreExecute() {
Zoznam activity = activityReference.get();
if (activity == null || activity.isFinishing()) return;
super.onPreExecute();
dialog = new ProgressDialog(activity);
dialog.setMessage(activity.getResources().getString(R.string.Loading));
dialog.setTitle(activity.getResources().getString(R.string.connecting));
dialog.show();
dialog.setCancelable(false);
}
@Override
protected String doInBackground(String... sText1) {final Zoznam activity = activityReference.get();
HttpHandler sh = new HttpHandler();
String url = "URL";
String jsonStr = sh.makeServiceCall(url);
if (jsonStr != null) {
try {JSONObject jsonObj = new JSONObject(jsonStr);
JSONArray actors = jsonObj.getJSONArray("result");
for (int i = 0; i < actors.length(); i++) {
JSONObject c = actors.getJSONObject(i);
Actors actor = new Actors();
actor.setLetter(c.getString("letter"));
actor.setNazov(c.getString("nazov"));
actor.setThumb(c.getString("thumb"));
activityReference.get().actorsList.add(actor);
}
} catch (final JSONException e) {
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(activity,
R.string.Nodata,
Toast.LENGTH_LONG).show();
}
}); }
return jsonStr;
} else {
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(activity,
R.string.Network,
Toast.LENGTH_LONG).show();
}
});
return null;
}
}
protected void onPostExecute(String result) {
Zoznam activity = activityReference.get();
if (activity == null || activity.isFinishing()) return;
dialog.dismiss();
activity.adapter.notifyDataSetChanged();
super.onPostExecute(result);
}
}
protected void onResume() {
super.onResume();
adapter.notifyDataSetChanged();
}
问题是,在崩溃报告中我发现了此错误:
适配器的内容已更改,但ListView尚未收到通知。确保不从后台线程修改适配器的内容,而仅从UI线程修改。确保您的适配器在其内容更改时调用notifyDataSetChanged()。
但是,仅在一台设备上发生了一次,但是我想解决这个问题。
我已经阅读了更多有关此的主题,但是我仍然没有解决方案。正如您在我的代码中看到的那样,我也在onResume和onPostExecute上调用notifyDataSetChanged(),所以不确定将其放在其他位置。
我认为我需要在从json的for循环之后的某个地方使用activity.runOnUiThread(new Runnable()),在该地方我将项目添加到arraylist,但不确定如何执行此操作以及是否可以解决问题。
我最近的代码更新:
for (int i = 0; i < actors.length(); i++) {
JSONObject c = actors.getJSONObject(i);
final Actors actor = new Actors();
actor.setLetter(c.getString("letter"));
actor.setNazov(c.getString("nazov"));
actor.setThumb(c.getString("thumb"));
actor.setPerex(c.getString("perex"));
actor.setTyp(c.getString("typ"));
actor.setPlace(c.getString("place"));
actor.setExterier(c.getString("adresar"));
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
activityReference.get().actorsList.add(actor);
activity.adapter.notifyDataSetChanged();
}
});
}
您可能得到了例外,因为您在后台线程上更新了适配器列表。
activityReference.get().actorsList.add(actor);
doInBackground
方法中的这一行正在更新您传递给适配器的实际列表。 doInBackground
中的所有计算必须非常快地进行,并且notifyDataSetChanged
中的onPostExecute
被调用。我不确定如何操作,但是这一次没有及时调用您的onPostExecute
,因此您的列表已更新,但是您的ListView
没有收到通知。
您可以在AsyncTask
中创建本地列表,并在onPostExecute
中更新活动列表。