Android Http Asynctask問題

Question

我開發了一個搜索功能，它接受來自用戶的兩個參數，將參數傳遞給php服務器，並使用參數執行sql查詢。我已經成功地從數據庫中檢索基於參數的數據，但是當我想要顯示結果時，我的應用會發生衝突。我無法弄清楚編碼中的錯誤，任何人都可以幫助我嗎？謝謝。

PHP

<?php 

$response = array(); 

require_once 'include/db_connect.php'; 

$db = new DB_CONNECT(); 

if (isset($_GET["location"]) && isset($_GET["category"])) { 

$location = $_GET['location']; 
$category = $_GET['category']; 

$result = mysql_query("SELECT *FROM image_detail WHERE category = '$category' AND location = '$location'"); 

    if (mysql_num_rows($result) > 0) { 

     $response["products"] = array(); 

     while ($row = mysql_fetch_array($result)) { 

      $product = array(); 
      $product["uid"] = $row["uid"]; 
      $product["itemname"] = $row["itemname"]; 
      $product["price"] = $row["price"]; 
      $product["description"] = $row["description"]; 
      $product["path"] = $row["path"]; 
      $timestamp = $row["posted_at"]; 

      $now = date('m/d/Y h:i:s a', time()); 
      $product["posted_at"] = xTimeAgo($timestamp, $now, "x"); 

      // push single product into final response array 
      array_push($response["products"], $product); 
     } 
     // success 
     $response["success"] = 1; 

     // echoing JSON response 
     echo json_encode($response); 
    } else { 
     // no product found 
     $response["success"] = 0; 
     $response["message"] = "No product table found"; 

     // echo no users JSON 
     echo json_encode($response); 
    } 


} else { 
// required field is missing 
$response["success"] = 0; 
$response["message"] = "Required field(s) is missing"; 

// echoing JSON response 
echo json_encode($response); 
} 

function xTimeAgo ($oldTime, $newTime, $timeType) { 
    $timeCalc = strtotime($newTime) - strtotime($oldTime);   
    if ($timeType == "x") { 
     if ($timeCalc < 60) { 
      $timeType = "s";    
     } 
     if ($timeCalc > 60) { 
      $timeType = "m"; 
     } 
     if ($timeCalc > (60*60)) { 
      $timeType = "h"; 
     } 
     if ($timeCalc > (60*60*24)) { 
      $timeType = "d"; 
     } 
    }   
    if ($timeType == "s") { 
     $timeCalc .= " seconds ago"; 
    } 
    if ($timeType == "m") { 
     $timeCalc = round($timeCalc/60) . " minutes ago"; 
    }   
    if ($timeType == "h") { 
     $timeCalc = round($timeCalc/60/60) . " hours ago"; 
    } 
    if ($timeType == "d") { 
     $timeCalc = round($timeCalc/60/60/24) . " days ago"; 
    }   
    return $timeCalc; 
} 
?> 

Search.java

public class Search extends Activity implements OnItemSelectedListener { 

private Spinner searchCategory, searchLocation; 
private Button search; 
ListView list; 

private SweetAlertDialog pDialog; 

LazyAdapter adapter; 

ArrayList<HashMap<String, String>> productsList; 

JSONArray products = null; 

private String [] Category = {"IT Gadgets","Men Fashion","Women Fashion","Beauty","Sports","Cars and Motors","Furnitures","Music Instrument","Books","Property","Photography","Games and Toys","kids and Baby","Health", "Others"}; 
private String [] Location = {"Kuala Lumpur","Melacca","Johor","Selangor","Kelantan","Kedah","Negeri Sembilan","Pahang","Perak","Perlis","Penang","Sabah","Sarawak","Terengganu"}; 

JSONParser2 jsonParser2 = new JSONParser2(); 

private static final String url_search_items = "http://gemini888.tk/GP_trade_api_v2/image_connect/search_items.php"; 

// JSON Node names 
public static final String TAG_SUCCESS = "success"; 
public static final String TAG_PRODUCTS = "products"; 
public static final String TAG_PID = "uid"; 
public static final String TAG_NAME = "itemname"; 
public static final String TAG_PRICE = "price"; 
public static final String TAG_PATH = "path"; 
public static final String TAG_TIME = "posted_at"; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.search_activity); 

    searchCategory = (Spinner) findViewById(R.id.spin_search_category); 
    searchLocation = (Spinner) findViewById(R.id.spin_search_location); 
    search = (Button) findViewById(R.id.button_search); 
    list = (ListView) findViewById(android.R.id.list); 

    ArrayAdapter<String> adapter_Category = new ArrayAdapter<String> 
    (this, android.R.layout.simple_spinner_item, Category); 

    ArrayAdapter<String> adapter_Location = new ArrayAdapter<String> 
    (this, android.R.layout.simple_spinner_item, Location); 

    adapter_Category.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
    adapter_Location.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 

    searchCategory.setAdapter(adapter_Category); 
    searchLocation.setAdapter(adapter_Location); 

    searchCategory.setOnItemSelectedListener(this); 
    searchLocation.setOnItemSelectedListener(this); 

    search.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View arg0) { 

      new searchItem().execute(); 

     } 

    }); 

} 

class searchItem extends AsyncTask<String, String, String> { 

    JSONObject json = null; 

    @Override 
    protected void onPreExecute() { 

     super.onPreExecute(); 
     pDialog = new SweetAlertDialog(Search.this, SweetAlertDialog.PROGRESS_TYPE); 
     pDialog.getProgressHelper().setBarColor(Color.parseColor("#A5DC86")); 
     pDialog.setTitleText("Loading product details...Please wait..."); 
     pDialog.setCancelable(true); 
     pDialog.show(); 
    } 

    @Override 
    protected String doInBackground(String... args) { 

     String selectedCategory = searchCategory.getSelectedItem().toString(); 
     String selectedLocation = searchLocation.getSelectedItem().toString(); 

     List<NameValuePair> params = new ArrayList<NameValuePair>(); 
     params.add(new BasicNameValuePair("location", selectedLocation)); 
     params.add(new BasicNameValuePair("category", selectedCategory)); 

     json = jsonParser2.makeHttpRequest(url_search_items, "GET", params); 

     Log.d("Search Details", json.toString()); 

     try { 
      // Checking for SUCCESS TAG 
      int success = json.getInt(TAG_SUCCESS); 

      if (success == 1) { 
       // products found 
       // Getting Array of Products 
       products = json.getJSONArray(TAG_PRODUCTS); 

       // looping through All Products 
       for (int i = 0; i < products.length(); i++) { 
        JSONObject c = products.getJSONObject(i); 

        // Storing each json item in variable 
        String id = c.getString(TAG_PID); 
        String iname = c.getString(TAG_NAME); 
        String price = c.getString(TAG_PRICE); 
        String path = c.getString(TAG_PATH); 
        String posted_at = c.getString(TAG_TIME); 

        // creating new HashMap 
        HashMap<String, String> map = new HashMap<String, String>(); 

        // adding each child node to HashMap key => value 
        map.put(TAG_PID, id); 
        map.put(TAG_NAME, iname); 
        map.put(TAG_PRICE, price); 
        map.put(TAG_PATH, path); 
        map.put(TAG_TIME, posted_at); 
        // adding HashList to ArrayList 
        productsList.add(map); 
       } 
      } else { 
       // no products found 
       // Launch Add New product Activity 
       Intent i = new Intent(getApplicationContext(), 
         MainActivity.class); 
       // Closing all previous activities 
       i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
       startActivity(i); 
      } 
     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 
     return null; 
    } 

    protected void onPostExecute(String file_url) { 

     pDialog.dismiss(); 

     runOnUiThread(new Runnable() { 
      public void run() { 

     adapter=new LazyAdapter(Search.this, productsList); 
     list.setAdapter(adapter); 

      } 
     }); 

    } 

} 

@Override 
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, 
     long arg3) { 
    // TODO Auto-generated method stub 

} 


@Override 
public void onNothingSelected(AdapterView<?> arg0) { 
    // TODO Auto-generated method stub 

} 

} 

JSONParser.java

public class JSONParser2 { 

static InputStream is = null; 
static JSONObject jObj = null; 
static String json = ""; 

// constructor 
public JSONParser2() { 

} 

// function get json from url 
// by making HTTP POST or GET mehtod 
public JSONObject makeHttpRequest(String url, String method, 
     List<NameValuePair> params) { 

    // Making HTTP request 
    try { 

     // check for request method 
     if(method == "POST"){ 
      // request method is POST 
      // defaultHttpClient 
      DefaultHttpClient httpClient = new DefaultHttpClient(); 
      HttpPost httpPost = new HttpPost(url); 
      httpPost.setEntity(new UrlEncodedFormEntity(params)); 

      HttpResponse httpResponse = httpClient.execute(httpPost); 
      HttpEntity httpEntity = httpResponse.getEntity(); 
      is = httpEntity.getContent(); 

     }else if(method == "GET"){ 
      // request method is GET 
      DefaultHttpClient httpClient = new DefaultHttpClient(); 
      String paramString = URLEncodedUtils.format(params, "utf-8"); 
      url += "?" + paramString; 
      HttpGet httpGet = new HttpGet(url); 

      HttpResponse httpResponse = httpClient.execute(httpGet); 
      HttpEntity httpEntity = httpResponse.getEntity(); 
      is = httpEntity.getContent(); 
     }   

    } catch (UnsupportedEncodingException e) { 
     e.printStackTrace(); 
    } catch (ClientProtocolException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

    try { 
     BufferedReader reader = new BufferedReader(new InputStreamReader(
       is, "iso-8859-1"), 8); 
     StringBuilder sb = new StringBuilder(); 
     String line = null; 
     while ((line = reader.readLine()) != null) { 

      //if(!line.startsWith("<", 0)){ 
      //if(!line.startsWith("(", 0)){          
      sb.append(line + "\n"); 
     } 
     is.close(); 
     json = sb.toString(); 
     // json = json.replaceAll("db_connect.php", ""); 

    } catch (Exception e) { 
     Log.e("Buffer Error", "Error converting result " + e.toString()); 
    } 

    // try parse the string to a JSON object 
    try { 
     jObj = new JSONObject(json); 
     //jObj = new JSONObject(json.substring(3)); 
    } catch (JSONException e) { 
     Log.e("JSON Parser", "Error parsing data " + e.toString()); 
    } 

    // return JSON String 
    return jObj; 

} 
} 

錯誤日誌

07-21 05:03:51.410: D/Search Details(917): {"success":1,"products":[{"posted_at":"20 days ago","path":"http:\/\/testing88ff8.tk\/GPFileUpload\/uploads\/hffjfi20150701_122718.jpg","uid":"49","price":"","itemname":"???????","description":""},{"posted_at":"17 days ago","path":"http:\/\/testing88ff8.tk\/GPFileUpload\/uploads\/hffjfi.jpg", 
07-21 05:03:51.430: W/dalvikvm(917): threadid=16: thread exiting with uncaught exception (group=0xb2ac7ba8) 
07-21 05:03:51.470: E/AndroidRuntime(917): FATAL EXCEPTION: AsyncTask #1 
07-21 05:03:51.470: E/AndroidRuntime(917): Process: gemini.lobang, PID: 917 
07-21 05:03:51.470: E/AndroidRuntime(917): java.lang.RuntimeException: An error occured while executing doInBackground() 
07-21 05:03:51.470: E/AndroidRuntime(917): at android.os.AsyncTask$3.done(AsyncTask.java:300) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.util.concurrent.FutureTask.setException(FutureTask.java:222) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.util.concurrent.FutureTask.run(FutureTask.java:242) 
07-21 05:03:51.470: E/AndroidRuntime(917): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.lang.Thread.run(Thread.java:841) 
07-21 05:03:51.470: E/AndroidRuntime(917): Caused by: java.lang.NullPointerException 
07-21 05:03:51.470: E/AndroidRuntime(917): at gemini.lobang.Search$searchItem.doInBackground(Search.java:159) 
07-21 05:03:51.470: E/AndroidRuntime(917): at gemini.lobang.Search$searchItem.doInBackground(Search.java:1) 
07-21 05:03:51.470: E/AndroidRuntime(917): at android.os.AsyncTask$2.call(AsyncTask.java:288) 
07-21 05:03:51.470: E/AndroidRuntime(917): at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
07-21 05:03:51.470: E/AndroidRuntime(917): ... 4 more 

Lazyadapter

public class LazyAdapter extends BaseAdapter { 

private Activity activity; 
private ArrayList<HashMap<String, String>> data; 
private static LayoutInflater inflater=null; 
public ImageLoader imageLoader; 

public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) { 
    activity = a; 
    data=d; 
    inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    imageLoader=new ImageLoader(activity.getApplicationContext()); 
} 


@Override 
public int getCount() { 
    return data.size(); 
} 

@Override 
public Object getItem(int position) { 
    return position; 
} 

@Override 
public long getItemId(int position) { 
    return position; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    View vi=convertView; 
    if(convertView==null) 
     vi = inflater.inflate(R.layout.list_item, null); 

    TextView pid = (TextView)vi.findViewById(R.id.pid); 
    TextView itemname = (TextView)vi.findViewById(R.id.name); 
    TextView price = (TextView)vi.findViewById(R.id.price); 
    TextView time = (TextView)vi.findViewById(R.id.time); 
    ImageView thumb_image = (ImageView)vi.findViewById(R.id.imageView1); 

    HashMap<String, String> song = new HashMap<String, String>(); 
    song = data.get(position); 

    pid.setText(song.get(ProductAll.TAG_PID)); 
    itemname.setText(song.get(ProductAll.TAG_NAME)); 
    price.setText(song.get(ProductAll.TAG_PRICE)); 
    time.setText(song.get(ProductAll.TAG_TIME)); 
    imageLoader.DisplayImage(song.get(ProductAll.TAG_PATH), thumb_image); 


    Animation animation; 
    animation = AnimationUtils.loadAnimation(activity, R.anim.slide); 
    //animation = AnimationUtils.loadAnimation(activity, (position > lastPosition) ? 
     // R.anim.up_from_bottom : R.anim.down_from_top); 
    vi.startAnimation(animation); 

    return vi; 
} 

public void clear() { 
    data.clear(); 
} 

} 

Answer 1

在DoInBackground()中開始活動會導致問題，因爲Asynctask尚未完成其工作，所以如果您想更改一些文本或開始活動，請在onPostExecute()中完成。

您可以在OnClickListener內部實現AsyncTask，而無需定義searchItem類。以下是您可以使用的代碼：

search.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View arg0) { 
      final JSONObject json = null; 

      String selectedCategory = searchCategory.getSelectedItem().toString(); 
      String selectedLocation = searchLocation.getSelectedItem().toString(); 

      //define params outside AsyncTask 
      List<NameValuePair> params = new ArrayList<NameValuePair>(); 
      params.add(new BasicNameValuePair("location", selectedLocation)); 
      params.add(new BasicNameValuePair("category", selectedCategory)); 
      // you can either use as AsyncTask<String,String,String> or AsyncTask() 
      new AsyncTask(){ 
       @Override 
       protected void onPreExecute() { 

        pDialog = new SweetAlertDialog(Search.this, SweetAlertDialog.PROGRESS_TYPE); 
        pDialog.getProgressHelper().setBarColor(Color.parseColor("#A5DC86")); 
        pDialog.setTitleText("Loading product details...Please wait..."); 
        pDialog.setCancelable(true); 
        pDialog.show(); 
       } 

       @Override 
       protected Object doInBackground(Object[] params) { 
        // now you can put params as parameter in json 
        json = jsonParser2.makeHttpRequest(url_search_items, "GET", params); 

        Log.d("Search Details", json.toString()); 
        return json; 
        // returned object will be directly send to onPostExecute() 
       } 

       @Override 
       protected void onPostExecute(Object o) { 
        // cast returned object from doInBackground() to JSONObject 
        json = (JSONObject)o; 
        try { 
         // Checking for SUCCESS TAG 
         int success = json.getInt(TAG_SUCCESS); 

         if (success == 1) { 
          // products found 
          // Getting Array of Products 
          products = json.getJSONArray(TAG_PRODUCTS); 

          // looping through All Products 
          for (int i = 0; i < products.length(); i++) { 
           JSONObject c = products.getJSONObject(i); 

           // Storing each json item in variable 
           String id = c.getString(TAG_PID); 
           String iname = c.getString(TAG_NAME); 
           String price = c.getString(TAG_PRICE); 
           String path = c.getString(TAG_PATH); 
           String posted_at = c.getString(TAG_TIME); 

           // creating new HashMap 
           HashMap<String, String> map = new HashMap<String, String>(); 

           // adding each child node to HashMap key => value 
           map.put(TAG_PID, id); 
           map.put(TAG_NAME, iname); 
           map.put(TAG_PRICE, price); 
           map.put(TAG_PATH, path); 
           map.put(TAG_TIME, posted_at); 
           // adding HashList to ArrayList 
           productsList.add(map); 
          } 
         } else { 
          // no products found 
          // Launch Add New product Activity 
          // you can put SEARCH.this instead of getApplicationContext() 
          Intent i = new Intent(SEARCH.this, 
            MainActivity.class); 
          // Closing all previous activities 
          i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
          startActivity(i); 
         } 
        } catch (JSONException e) { 
         e.printStackTrace(); 
        } 

        pDialog.dismiss(); 

        runOnUiThread(new Runnable() { 
         public void run() { 

          adapter=new LazyAdapter(Search.this, productsList); 
          list.setAdapter(adapter); 

         } 
        }); 
       } 
      }.execute(); 
     } 
    }); 

我希望這可以解決您的問題。

Answer 2

String selectedCategory = searchCategory.getSelectedItem().toString(); 
String selectedLocation = searchLocation.getSelectedItem().toString(); 

在這裏你要使用局部變量，而不是當地的一個只是其中重命名爲

String selCategory = searchCategory.getSelectedItem().toString(); 
String selLocation = searchLocation.getSelectedItem().toString(); 

Answer 3

你可以」直接從doInBackground（）我開始活動因爲它在與UI線程不同的線程上運行。

Answer 4

更改onPostExecute()方法象下面這樣：

protected void onPostExecute(String file_url) { 

     if(pDialog.isShowing){ 
      pDialog.dismiss(); 
     } 

     adapter=new LazyAdapter(Search.this, productsList); 
     list.setAdapter(adapter); 

    }