只有创建视图层次结构的原始线程才能接触其视图

Question

我有一个错误，只有创建视图层次结构的原始线程才能接触它的视图。但我不知道如何在多线程中处理ui，比如列表视图，我也不知道该放在哪里。

 // Download JSON in Background
        public class DownloadJSONFileAsync extends AsyncTask<String, Void, Void> {

            protected void onPreExecute() {
                super.onPreExecute();
                showDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
            }

            @Override
            protected Void doInBackground(String... params) {


                deviceId = generateDeviceId();

                elementsList.add(new BasicNameValuePair("DeviceID", deviceId));

                JSONObject json = jsonParser.makeHttpRequest(
                        url_get_reports, "POST", elementsList);


                Log.d("Create Response", json.toString());

                // check for success tag
                try {
                    int success = json.getInt(TAG_SUCCESS_REPORT);

                        // successfully created
                        // getting JSON string from URL

                        try {

                            if (success == 1) {

                                reports = json.getJSONArray(TAG_Report);



                                report_data = new Report[reports.length()];





                                // looping through All Products
                                for (int i = reports.length()-1; i >= 0; i--) {
                                    JSONObject c = reports.getJSONObject(i);
                                    reportID = c.getString("reportID");

                                     Drawable drawable = LoadImageFromWeb(url+c.getString(TAG_IMAGE));

                                String state = "";

                                if(c.getString("state").equals("1")){
                                    state = "Pinding";
                                }else if(c.getString("state").equals("2")){
                                    state = "Inprogress";
                                }else{
                                    state = "Completed";
                                }


                                    if(c.getString(TAG_TITLE).equals("")){
                                        report_data[i] = new Report(reportID,"Report "+(i+1),c.getString(TAG_TIME),drawable,url+c.getString(TAG_IMAGE),state,c.getString("coordination")) ;

                                    }else{
                                        report_data[i] = new Report(reportID,c.getString(TAG_TITLE),c.getString(TAG_TIME),drawable,url+c.getString(TAG_IMAGE),state,c.getString("coordination"));

                                    }




                                   if(json.getInt("successReplies")==1){


                                        replies = json.getJSONArray(TAG_REPLIES);



                                        ArrayList<String> arr = new ArrayList<String>();


                                        for(int j=0;j<replies.length();j++){
                                        JSONObject c2 = replies.getJSONObject(j);

                                        if(reportID.equals(c2.getString("ReportID")))
                                        {

                                            arr.add(c2.getString("RepliesContent")+"\n"+c2.getString("RepliesTime"));

                                        }

                                        }


                                   report_data[i].setRepliesArray(arr);


                                   }    


                                }



                                list = (ListView)findViewById(R.id.list);
                                ReportAdapter adapter = new ReportAdapter(Display_Reports.this,report_data);

                                list.setAdapter(adapter);


                            // Click event for single list row
                                list.setOnItemClickListener(new OnItemClickListener() {
                                    @Override
                                    public void onItemClick(
                                            AdapterView<?> arg0, View arg1,
                                            int position, long id) {
                                        Intent intent = new Intent(Display_Reports.this, Display_Report_Details.class);
                                        intent.putExtra("ID", report_data[position].ID);
                                        intent.putExtra("Name", report_data[position].Name);
                                        intent.putExtra("State", report_data[position].State);
                                        intent.putExtra("Time", report_data[position].Time);
                                        intent.putExtra("ImageUrl", report_data[position].ImageUrl);
                                        intent.putExtra("Coordination", report_data[position].Coordination);
                                        intent.putStringArrayListExtra("RepliesContent", report_data[position].getRepliesArray());
                                        startActivity(intent);

                                    }
                                }); 

                            } else {
                                // no Entities found
                                Toast.makeText(Display_Reports.this, "No reports found",
                                        Toast.LENGTH_LONG).show();
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }





                } catch (JSONException e) {
                    e.printStackTrace();
                }

                return null;

            }

            protected void onPostExecute(Void unused) {

                dismissDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
                removeDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);

            }


        }

Answer 1

不能从后台线程修改UI。您是否使用AsyncTask，或处理程序，或runOnUiThread（），或post（），在主应用程序线程上完成工作取决于您。

您可能希望回顾线程上的留档和其中的一些技术。