java - 致命异常 : AsyncTask, 接收 json

Question

我正在我的应用程序中进行一些数据库工作，我想从我的网络数据库中提取所有位置并将其显示在应用程序的 ListView 中。我创建了“API”，其中响应是 Json。

json所在链接:http://000100023.host56.com/db_all.php

使用本教程:http://www.androidhive.info/2012/05/how-to-connect-android-with-php-mysql/

Logcat:

11-14 16:50:21.508: E/AndroidRuntime(22809): FATAL EXCEPTION: AsyncTask #1
11-14 16:50:21.508: E/AndroidRuntime(22809): Process: com.spxc.nightclubratings, PID: 22809
11-14 16:50:21.508: E/AndroidRuntime(22809): java.lang.RuntimeException: An error occured while executing doInBackground()
11-14 16:50:21.508: E/AndroidRuntime(22809):    at android.os.AsyncTask$3.done(AsyncTask.java:300)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.lang.Thread.run(Thread.java:841)
11-14 16:50:21.508: E/AndroidRuntime(22809): Caused by: java.lang.NullPointerException
11-14 16:50:21.508: E/AndroidRuntime(22809):    at com.spxc.nightclubratings.SearchLocationActivity$LoadAllProducts.doInBackground(SearchLocationActivity.java:132)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at com.spxc.nightclubratings.SearchLocationActivity$LoadAllProducts.doInBackground(SearchLocationActivity.java:1)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at android.os.AsyncTask$2.call(AsyncTask.java:288)
11-14 16:50:21.508: E/AndroidRuntime(22809):    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
11-14 16:50:21.508: E/AndroidRuntime(22809):    ... 4 more
11-14 16:50:22.199: E/WindowManager(22809): android.view.WindowLeaked: Activity com.spxc.nightclubratings.SearchLocationActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{42313208 V.E..... R......D 0,0-729,192} that was originally added here
11-14 16:50:22.199: E/WindowManager(22809):     at android.view.ViewRootImpl.<init>(ViewRootImpl.java:346)
11-14 16:50:22.199: E/WindowManager(22809):     at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:248)
11-14 16:50:22.199: E/WindowManager(22809):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.Dialog.show(Dialog.java:286)
11-14 16:50:22.199: E/WindowManager(22809):     at com.spxc.nightclubratings.SearchLocationActivity$LoadAllProducts.onPreExecute(SearchLocationActivity.java:119)
11-14 16:50:22.199: E/WindowManager(22809):     at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
11-14 16:50:22.199: E/WindowManager(22809):     at android.os.AsyncTask.execute(AsyncTask.java:535)
11-14 16:50:22.199: E/WindowManager(22809):     at com.spxc.nightclubratings.SearchLocationActivity.onCreate(SearchLocationActivity.java:59)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.Activity.performCreate(Activity.java:5243)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.ActivityThread.access$700(ActivityThread.java:135)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
11-14 16:50:22.199: E/WindowManager(22809):     at android.os.Handler.dispatchMessage(Handler.java:102)
**11-14 16:50:22.199: E/WindowManager(22809):   at android.os.Looper.loop(Looper.java:137)
11-14 16:50:22.199: E/WindowManager(22809):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-14 16:50:22.199: E/WindowManager(22809):     at java.lang.reflect.Method.invokeNative(Native Method)
11-14 16:50:22.199: E/WindowManager(22809):     at java.lang.reflect.Method.invoke(Method.java:515)
11-14 16:50:22.199: E/WindowManager(22809):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-14 16:50:22.199: E/WindowManager(22809):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-14 16:50:22.199: E/WindowManager(22809):     at dalvik.system.NativeStart.main(Native Method)

Json解析器: 公共(public)类 JSONParser {

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

    // constructor
    public JSONParser() {

    }

    // 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) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } 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);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

搜索位置 Activity :

public class SearchLocationActivity extends ListActivity {

    // Progress Dialog
    private ProgressDialog pDialog;

    // Creating JSON Parser object
    JSONParser jParser = new JSONParser();

    ArrayList<HashMap<String, String>> productsList;

    // url to get all products list
    private static String url_all_products = "http://http://000100023.host56.com/db_all.php";

    // JSON Node names
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_PRODUCTS = "locations";
    private static final String TAG_PID = "id";
    private static final String TAG_NAME = "name";

    // products JSONArray
    JSONArray products = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_search_location);

        // Hashmap for ListView
        productsList = new ArrayList<HashMap<String, String>>();

        // Loading products in Background Thread
        new LoadAllProducts().execute();

        // Get listview
        ListView lv = getListView();

        // on seleting single product
        // launching Edit Product Screen
        lv.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                // getting values from selected ListItem
                String pid = ((TextView) view.findViewById(R.id.pid)).getText()
                        .toString();

                // Starting new intent
                //Intent in = new Intent(getApplicationContext(),
                  //      EditProductActivity.class);
                // sending pid to next activity
                //in.putExtra(TAG_PID, pid);

                // starting new activity and expecting some response back
                //startActivityForResult(in, 100);
            }
        });

    }

    // Response from Edit Product Activity
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        // if result code 100
        if (resultCode == 100) {
            // if result code 100 is received
            // means user edited/deleted product
            // reload this screen again
            Intent intent = getIntent();
            finish();
            startActivity(intent);
        }

    }

    /**
     * Background Async Task to Load all product by making HTTP Request
     * */
    class LoadAllProducts extends AsyncTask<String, String, String> {

        /**
         * Before starting background thread Show Progress Dialog
         * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(SearchLocationActivity.this);
            pDialog.setMessage("Loading locations. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        /**
         * getting All products from url
         * */
        protected String doInBackground(String... args) {
            // Building Parameters
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            // getting JSON string from URL
            JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);

            // Check your log cat for JSON reponse
            Log.d("All Products: ", 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 name = c.getString(TAG_NAME);

                        // 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, name);

                        // adding HashList to ArrayList
                        productsList.add(map);
                    }
                } else {
                    // no products found
                    // Launch Add New product Activity
                    //Intent i = new Intent(getApplicationContext(),
                      //      NewProductActivity.class);
                    // Closing all previous activities
                    //i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    //startActivity(i);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        /**
         * After completing background task Dismiss the progress dialog
         * **/
        protected void onPostExecute(String file_url) {
            // dismiss the dialog after getting all products
            pDialog.dismiss();
            // updating UI from Background Thread
            runOnUiThread(new Runnable() {
                public void run() {
                    /**
                     * Updating parsed JSON data into ListView
                     * */
                    ListAdapter adapter = new SimpleAdapter(
                            SearchLocationActivity.this, productsList,
                            R.layout.list_item, new String[] { TAG_PID,
                                    TAG_NAME},
                            new int[] { R.id.pid, R.id.name });
                    // updating listview
                    setListAdapter(adapter);
                }
            });

        }

    }
}

非常感谢任何帮助!

Answer 1

你的URL字符串是错误的，你这样写:

Private static String url_all_products = "http://http://000100023.host56.com/db_all.php";

应该是:

Private static String url_all_products = "http://000100023.host56.com/db_all.php";

一个http://就足够了;)