傳回在單獨線程中創建的變量？ Android

Question

我一直在嘗試使用JSON/PHP Web服務層來通過我的Android應用程序訪問MySQL數據庫，它的工作原理（從日誌中我可以看到變量持有正確的信息），但是當我嘗試並通過值返回到主線程，他們沒有被存儲？

public class ViewErrands extends Activity { 
public String result = ""; 
InputStream is; 
String json = "lol"; //set as lol to begin with, to be overwritten with string from DB 
TextView tv; 
public int iss; 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_view); 
    tv = (TextView) findViewById(R.id.tvtv); 
    sendPostRequest(); 
    tv.setText(json + "LOL" + iss); // the "lol" + "LOL" + 0 (should be 6) appear 
} 

public void sendPostRequest() { 
    class runCode extends AsyncTask<String, String, String> { // seperate task 

     @Override 
     protected String doInBackground(String... params) { 
      ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(); 
      nameValuePairs.add(new BasicNameValuePair("idnum", "1")); 

      try { 
       HttpClient httpclient = new DefaultHttpClient(); 
       HttpPost httppost = new HttpPost("http://192.168.1.182/FYP/xshowall.php"); // PHP script to show all where id > POST 
       httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); 
       HttpResponse response = httpclient.execute(httppost); 
       HttpEntity entity = response.getEntity(); 
       is = entity.getContent(); 
      } catch (Exception e) { 
       Log.e("log_tag", "error in http conn " + e.toString()); 
      } 

      try { 
       BufferedReader reader = new BufferedReader(new InputStreamReader(is), 8); 
       StringBuilder sb = new StringBuilder(); 
       String line = null; 
       while ((line = reader.readLine()) != null) { 
        sb.append(line + "\n"); 
       } 
       is.close(); 
       result = sb.toString(); 
      } catch (Exception e) { 
       Log.e("log_tag", "error converting " + e.toString()); 
      } 

      try { 
       JSONArray jArray = new JSONArray(result); 
       for (int i = 0; i < jArray.length(); i++) { 
        JSONObject json_data = jArray.getJSONObject(i); 
        json = "id: " + json_data.getInt("ID") + ", title: " + json_data.getString("TITLE") 
          + ", content: " + json_data.getString("CONTENT"); 

         ); 

       } 
      } catch (JSONException e) { 
       Log.e("log_tag", "Error parsing data " + e.toString()); 
      } 
      return null; 
     } 
    } 
    runCode sendPostReqAsyncTask = new runCode(); 
    sendPostReqAsyncTask.execute(); 
} 

首先，當我嘗試複製一個值時，json變量保持爲'lol'，就好像它從未改變過一樣。 這是與獨立進程有關嗎？我能做些什麼呢？

Answer 1

您已解析數據，但從未再次設置爲textview。

你可以在onPostExecute中這樣做，這個方法將在UI線程中調用，所以它的安全。 （不要試圖在doInBackground中設置任何視圖的屬性，這會導致您的例外）

public void sendPostRequest() { 
    class runCode extends AsyncTask<String, String, String> { // seperate task 

     @Override 
     protected String doInBackground(String... params) { 
      ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(); 
      nameValuePairs.add(new BasicNameValuePair("idnum", "1")); 

      try { 
       HttpClient httpclient = new DefaultHttpClient(); 
       HttpPost httppost = new HttpPost("http://192.168.1.182/FYP/xshowall.php"); // PHP script to show all where id > POST 
       httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); 
       HttpResponse response = httpclient.execute(httppost); 
       HttpEntity entity = response.getEntity(); 
       is = entity.getContent(); 
      } catch (Exception e) { 
       Log.e("log_tag", "error in http conn " + e.toString()); 
      } 

      try { 
       BufferedReader reader = new BufferedReader(new InputStreamReader(is), 8); 
       StringBuilder sb = new StringBuilder(); 
       String line = null; 
       while ((line = reader.readLine()) != null) { 
        sb.append(line + "\n"); 
       } 
       is.close(); 
       result = sb.toString(); 
      } catch (Exception e) { 
       Log.e("log_tag", "error converting " + e.toString()); 
      } 

      try { 
       JSONArray jArray = new JSONArray(result); 
       for (int i = 0; i < jArray.length(); i++) { 
        JSONObject json_data = jArray.getJSONObject(i); 
        json = "id: " + json_data.getInt("ID") + ", title: " + json_data.getString("TITLE") 
          + ", content: " + json_data.getString("CONTENT"); 

         ); 

       } 
      } catch (JSONException e) { 
       Log.e("log_tag", "Error parsing data " + e.toString()); 
      } 
      return null; 
     } 
     @Override 
     protected void onPostExecute(String result) { 
      tv.setText(json); 
     } 
    } 
    runCode sendPostReqAsyncTask = new runCode(); 
    sendPostReqAsyncTask.execute(); 
}