Question

伙计我在使用JSON从php服务器获取结果时遇到问题。基本上第一个活动运行良好，并通过PHP Server从Database获得适当的结果。第一项活动的结果是年数。

比用户选择年份并希望根据所选年份获得结果。

但是当选择年份时，从PHP文件和数据库获得的结果是错误的。它在第二个活动中获得了前一个结果年份，而不是图像的月份，路径和字节数组。

显示年度活动类：

public class DisplayYears extends ListActivity {
private ProgressDialog pDialog;
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> magazinesList;
private static final String TAG_SUCCESS = "success";
private static final String TAG_MAGAZINE = "magazines";
private static final String TAG_PID = "ID";
private static final String TAG_YEAR = "year";
JSONArray magazines = null;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.display_years);
    magazinesList = new ArrayList<>();
    new LoadAllYears().execute();
    ListView lv = getListView();
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
            int pyears = Integer.parseInt(((TextView) view.findViewById(R.id.years)).getText()
                    .toString());
            Intent in = new Intent(getApplicationContext(),
                    DisplayMagazine.class);
            in.putExtra("year", pyears);
            startActivity(in);
        }
    });
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == 100) {
        Intent intent = getIntent();
        finish();
        startActivity(intent);
    }
}
class LoadAllYears extends AsyncTask<String, String, String> {
   @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(DisplayYears.this);
        pDialog.setMessage("Loading Years. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }
    protected String doInBackground(String... args) {
        List<NameValuePair> params = new ArrayList<>();
        //String url_all_magazines = "http://172.16.26.190/shifaspeaks/get_all_years.php";
        String url_all_magazines = "http://192.168.1.4/shifaspeaks/get_all_years.php";
        JSONObject json = jParser.makeHttpRequest(url_all_magazines, "GET", params);
        Log.d("All Magazines: ", json.toString());
        try {
            int success = json.getInt(TAG_SUCCESS);
            if (success == 1) {
                magazines = json.getJSONArray(TAG_MAGAZINE);
                for (int i = 0; i < magazines.length(); i++) {
                    JSONObject c = magazines.getJSONObject(i);
                    String year = c.getString(TAG_YEAR);
                    HashMap<String, String> map = new HashMap<>();
                    map.put(TAG_YEAR, year);
                    magazinesList.add(map);
                }
            } else {
                Intent i = new Intent(getApplicationContext(),
                        MainActivity.class);
                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() {
                ListAdapter adapter = new SimpleAdapter(
                        DisplayYears.this, magazinesList,
                        R.layout.list_item, new String[] { TAG_PID,
                        TAG_YEAR},
                        new int[] { R.id.id, R.id.years});
                setListAdapter(adapter);
            }
        });
    }
}

显示年份PHP文件：

<?php
mysql_connect('127.0.0.1:3306','root','');
mysql_select_db("shifaspeaks");
$response = array();
$result = mysql_query("SELECT DISTINCT year FROM magazine") 
die(mysql_error());
if (mysql_num_rows($result) > 0) {
 $response["magazines"] = array();
while ($row = mysql_fetch_array($result)) {
    // temp user array
    $magazine = array();
    //$magazine["id"] = $row["ID"];
    //$magazine["month"] = $row["month"];
    $magazine["year"] = $row["year"];
    //$magazine["path"] = $row["path"];
    array_push($response["magazines"], $magazine);
}
$response["success"] = 1;
echo json_encode($response);
}

 else {
$response["success"] = 0;
$response["message"] = "No magazines found";
echo json_encode($response);
}
?>

显示杂志活动类：

public class DisplayMagazine extends ListActivity {
private ProgressDialog pDialog;
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> magazinesList;
int year;
private static final String TAG_SUCCESS = "success";
private static final String TAG_MAGAZINE = "magazines";
private static final String TAG_MAGAZINE_IMAGE="magazineImage";
private static final String TAG_MONTH = "month";
private static final String TAG_PATH = "path";
JSONArray magazines = null;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.display_magazine);
    Intent i=getIntent();
    year=i.getIntExtra("year",0);
    magazinesList = new ArrayList<>();
    new LoadAllMagazines().execute();
    ListView lv = getListView();
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
        }
    });
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == 100) {
        Intent intent = getIntent();
        finish();
        startActivity(intent);
    }
}
class LoadAllMagazines extends AsyncTask<String, String, String> {
   @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(DisplayMagazine.this);
        pDialog.setMessage("Loading Magazines. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }
    protected String doInBackground(String... args) {
        List<NameValuePair> params = new ArrayList<>();
        params.add(new BasicNameValuePair("year", String.valueOf(year)));
        //String url_all_magazines = "http://172.16.26.190/shifaspeaks/get_all_magazines.php";
        String url_all_magazines = "http://192.168.1.4/shifaspeaks/get_all_magazines.php";
        JSONObject json = jParser.makeHttpRequest(url_all_magazines, "GET", params);
        Log.d("All Magazines: ", json.toString());
        try {
            int success = json.getInt(TAG_SUCCESS);
            if (success == 1) {
                magazines = json.getJSONArray(TAG_MAGAZINE);
                    for (int i = 0; i < magazines.length(); i++) {
                    JSONObject c = magazines.getJSONObject(i);
                    String month = c.getString(TAG_MONTH);
                    String path = c.getString(TAG_PATH);
                    String imageString=c.getString(TAG_MAGAZINE_IMAGE);
                    byte[] image= Base64.decode(imageString.getBytes(), Base64.DEFAULT);
                    Bitmap decodedByte= BitmapFactory.decodeByteArray(image,0,image.length);
                    HashMap<String, String> map = new HashMap<>();
                    map.put(TAG_MONTH, month);
                    map.put(TAG_PATH, path);
                    map.put(TAG_MAGAZINE_IMAGE,decodedByte.toString());
                    magazinesList.add(map);
                }
            } else {
                Intent i = new Intent(getApplicationContext(),
                        MainActivity.class);
                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() {
                ListAdapter adapter = new SimpleAdapter(
                        DisplayMagazine.this, magazinesList,
                        R.layout.list_item2, new String[] {TAG_MAGAZINE_IMAGE, TAG_MONTH,
                        TAG_PATH},
                        new int[] {R.id.magazineImage, R.id.month, R.id.path});
                setListAdapter(adapter);
            }
        });
    }
}

显示杂志PHP文件：

<?php
mysql_connect('127.0.0.1:3306','root','');
mysql_select_db("shifaspeaks");
$response = array(); 
if(isset($_GET["year"])){
$year = $_GET["year"];
$result = mysql_query("SELECT month, path, magazineImage FROM magazine where year='$year'") or die(mysql_error());
if (mysql_num_rows($result) > 0) {
    $response["magazines"] = array();
    while ($row = mysql_fetch_array($result)) {
        $magazine = array();
        $magazine["month"] = $row["month"];
        $magazine["magazineImage"]=$row["magazineImage"];
        $magazine["path"] = $row["path"];
        array_push($response["magazines"], $magazine);
    }
    $response["success"] = 1;
    echo json_encode($response);
} else {
    $response["success"] = 0;
    $response["message"] = "No magazines found";
    echo json_encode($response);    
}
}
?>

请提前帮助我，谢谢你。

Answer 1

您应该将listview和数组适配器作为类属性。我们必须通过适配器将数据从源（ArrayList）显示到列表视图。

在活动DisplayYears中：

public class DisplayYears extends ListActivity 
{
   ...
   private ArrayList<HashMap<String, String>> magazinesList;

   private ArrayAdapter arrayAdapter; // Here you have to define the Adapter (ArrayAdapter, CursorAdapter, or a custom Adapter, etc ...)

   private ListView lv;
   ...

在onCreate方法中，您必须告诉listview谁是将提供数据的适配器。

protected void onCreate(Bundle savedInstanceState)
{
   super.onCreate(savedInstanceState);
   setContentView(R.layout.display_years);

   // Init ArrayList
   magazinesList = new ArrayList<>();

   //Set Array Adapter with Array List
   arrayAdapter = new ArrayAdapter(this, magazinesList);

   // Get a reference to the ListView, and attach this adapter to it.
   lv = (ListView) findViewById(R.id.listviewXmlLayout);

   lv.setAdapter(arrayAdapter);

   // Here lv.setOnItemClickListener implementation

   // Start Request to Server 
   new LoadAllYears().execute();
}

这里的关键部分是来自LoadAllMagazines类的onPostExecute。在onPostExecute中，AsynTask线程与UI线程进行通信。

你应该从doInBackground方法返回一个Json，如下所示：

JSONObject doInBackground(String... args)

我们需要使用onPostExecute上从服务器接收的数据更新ArrayList（magazinesList）。（不要再将内存分配给magazinesList，因为适配器（arrayAdapter）具有对magazinesList的内存引用，并且新的内存分配将破坏此关系）。

class LoadAllMagazines extends AsyncTask<String, String, JSONObject> 
{
   ...

   JSONObject doInBackground(String... args)
   {
      // Return Json received from server.
   }

   protected void onPostExecute(JSONObject file_url) 
   {
      pDialog.dismiss();

      // Parse the Json file

      // Clear the ArrayList
      magazinesList.clear();

      // Load magazinesList with data received from server

      // And the magic happens here! You only have to notify the adapter about the new changes in the ArrayList       
      arrayAdapter.notifyDataSetChanged();

      // It is using observer pattern. Any changes in the ArrayList, we notify the Adapter and then it will tell the listView about the new changes.
   };
}

请检查它是否适合你！

PHP Server中的Android应用程序出错

1 个答案: