Android Http Asynctask問題

Question

我已經開發了一個搜索功能，該功能可以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。 我已經成功地根據參數從數據庫中檢索了數據，但是我的應用程序想要顯示結果時發生沖突。 我無法弄清楚編碼中的錯誤，有人可以幫助我嗎？ 謝謝。

的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;

}
}

錯誤日志

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

惰性適配器

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

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

在這里，您嘗試使用局部變量而不是局部變量，只需將它們重命名為

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

Answer 2

您無法直接從doInBackground（）方法啟動活動，因為該活動在與UI線程不同的線程上運行。

Answer 3

在DoInBackground()內部啟動活動會導致此問題，因為Asynctask尚未完成其工作，因此，如果您想更改某些文本或啟動，而活動則可以在onPostExecute() 。

您可以在OnClickListener內部實現AsyncTask，而無需定義searchItem類。 這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();
        }
    });

我希望這能解決您的問題。

Answer 4

如下更改您的onPostExecute()方法：

protected void onPostExecute(String file_url) {

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

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

    }