由多个 Java 片段使用的异步任务

Question

我目前正在做一个项目，在那里我从Android上的JSON转储中获取数据。到目前为止，我是否在每个片段中设置了一个自定义的异步任务，我需要从 JSON 转储中获取数据。我好奇的是我是否可以拥有一个公共 Java 类，这些片段可以在需要获取数据时"使用"它。

这是我如何尝试这样做的一个例子。首先是从公共 java 类调用 Asynctask 的片段：

public class DataTabelFragment extends Fragment {
private TextView sensor1;
private Button jsonButton;
jsonAsynctask jsonasynctask = new jsonAsynctask();

public DataTabelFragment() {
// Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate( R.layout.fragment_data_tabel, container, false );
sensor1 = (TextView) view.findViewById( R.id.sensor1Box );
//jsonButton = (Button) view.findViewById( R.id.buttonjson );
new jsonAsynctask().execute();
for (int i = 0; i < jsonasynctask.allId.size(); i++) {
sensor1.append( jsonasynctask.allId.get( i ) + " | " + jsonasynctask.allDevice.get( i ) + " | " + jsonasynctask.allTemp.get( i ) + " | " + jsonasynctask.allHum.get( i ) + " | " + jsonasynctask.allBat.get( i ) + " | " + jsonasynctask.allMode.get( i ) + " | " + jsonasynctask.allLux.get( i ) + " | " + jsonasynctask.allDate_time.get( i ) + "nn" );
}
//new jsonConnection().execute();
/*
jsonButton.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View v) {
new jsonConnection().execute();
}
} );*/

return view;
}

}

这是带有Asynctask的java类：

public class jsonAsynctask extends MainActivity {
private TextView sensor1;
private Button jsonButton;
JSONObject deviceArray;
JSONObject tempArray;
JSONObject humArray;
JSONObject batArray;
JSONObject modeArray;
JSONObject date_timeArray;
JSONObject luxArray;
JSONArray json2;
List<String> allId = new ArrayList<String>();
List<String> allDevice = new ArrayList<String>();
List<String> allTemp = new ArrayList<String>();
List<String> allHum = new ArrayList<String>();
List<String> allBat = new ArrayList<String>();
List<String> allMode = new ArrayList<String>();
List<String> allDate_time = new ArrayList<String>();
List<String> allLux = new ArrayList<String>();
String basicAuth;
String line;
String json_string;
String json;
String cxwebURL;
String credentials;
String password;
String username;
Gson gson;
ProgressDialog pd;
String data = "";
HttpURLConnection connection;
BufferedReader bufferedReader;
String id = "";
JSONObject idArray;
URL url;
private static String encodeBase64URLSafeString(byte[] binaryData) {
return android.util.Base64.encodeToString( binaryData, android.util.Base64.URL_SAFE );
}
public class jsonConnection extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... voids) {
username = "xxx";
password = "xxx";
credentials = username + ":" + password;
cxwebURL = "https://" + credentials + "@xxx.com/fetch.php?device=xxx";
try {
url = new URL( cxwebURL );
connection = (HttpsURLConnection) url.openConnection();
basicAuth = "Basic " + new String( encodeBase64URLSafeString( credentials.getBytes() ) );
connection.setRequestProperty( "Authorization", basicAuth );
connection.setRequestMethod( "GET" );
connection.setRequestProperty( "Content-Type", "application/x-www-form-urlencoded" );
connection.setRequestProperty( "Content-Language", "en-US" );
connection.setUseCaches( false );
connection.setDoInput( true );
connection.setDoOutput( true );
connection.connect();
InputStream stream = connection.getInputStream();
bufferedReader = new BufferedReader( new InputStreamReader( stream ) );
line = "";
while (line != null) {
line = bufferedReader.readLine();
data = data + line;
}
json2 = new JSONArray( data );
for (int i = 0; i < json2.length(); i++) {
idArray = json2.getJSONObject( i );
deviceArray = json2.getJSONObject( i );
tempArray = json2.getJSONObject( i );
humArray = json2.getJSONObject( i );
batArray = json2.getJSONObject( i );
modeArray = json2.getJSONObject( i );
date_timeArray = json2.getJSONObject( i );
luxArray = json2.getJSONObject( i );
id = idArray.getString( "id" );
String temp = tempArray.getString( "temp" );
String device = deviceArray.getString( "device" );
String hum = humArray.getString( "hum" );
String bat = batArray.getString( "bat" );
String mode = modeArray.getString( "mode" );
String date_time = date_timeArray.getString( "time" );
String lux = luxArray.getString( "light" );
allId.add( id );
allDevice.add( device );
allTemp.add( temp );
allHum.add( hum );
allBat.add( bat );
allMode.add( mode );
allDate_time.add( date_time );
allLux.add( lux );

}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog( new MainActivity() );
pd.setMessage( "Være sød at vente" );
//pd.setCancelable( false );
pd.show();
}
@Override
public void onPostExecute(Void result) {
super.onPostExecute( result );
if (pd.isShowing()) {
pd.dismiss();
}
System.out.println( data );
gson = new Gson();
json = gson.toJson( data );
System.out.println( "String json: " + json );
json_string = data;
System.out.println( "json_string: " + json_string );
//            System.out.println( "DET HER ER ID!!: " + allId.get( 1 ) );
//textView2.setMovementMethod( new ScrollingMovementMethod() );

System.out.println("Size of Array: " + allId.size());

}
}

}

我是否可以像这样编程，或者我应该继续在每个片段中都有一个异步任务？顺便说一句，片段中的"new jsonAsynctask((.execute((;"不起作用，我收到此错误：

错误：找不到符号类执行

*更新*

这是 Java 类中的更新，其中 Asynctask 位于其中。

public class jsonAsynctask extends AsyncTask<Void, Void, Void> {
private TextView sensor1;
private Button jsonButton;
JSONObject deviceArray;
JSONObject tempArray;
JSONObject humArray;
JSONObject batArray;
JSONObject modeArray;
JSONObject date_timeArray;
JSONObject luxArray;
JSONArray json2;
List<String> allId = new ArrayList<String>();
List<String> allDevice = new ArrayList<String>();
List<String> allTemp = new ArrayList<String>();
List<String> allHum = new ArrayList<String>();
List<String> allBat = new ArrayList<String>();
List<String> allMode = new ArrayList<String>();
List<String> allDate_time = new ArrayList<String>();
List<String> allLux = new ArrayList<String>();
String basicAuth;
String line;
String json_string;
String json;
String cxwebURL;
String credentials;
String password;
String username;
Gson gson;
ProgressDialog pd;
String data = "";
HttpURLConnection connection;
BufferedReader bufferedReader;
String id = "";
JSONObject idArray;
URL url;
private static String encodeBase64URLSafeString(byte[] binaryData) {
return android.util.Base64.encodeToString( binaryData, android.util.Base64.URL_SAFE );
}
@Override
protected Void doInBackground(Void... voids) {
username = "xxx";
password = "xxx";
credentials = username + ":" + password;
cxwebURL = "https://" + credentials + "@xxx.com/fetch.php?device=xxx";

try {
url = new URL( cxwebURL );
connection = (HttpsURLConnection) url.openConnection();
basicAuth = "Basic " + new String( encodeBase64URLSafeString( credentials.getBytes() ) );
connection.setRequestProperty( "Authorization", basicAuth );
connection.setRequestMethod( "GET" );
connection.setRequestProperty( "Content-Type", "application/x-www-form-urlencoded" );
connection.setRequestProperty( "Content-Language", "en-US" );
connection.setUseCaches( false );
connection.setDoInput( true );
connection.setDoOutput( true );
connection.connect();
InputStream stream = connection.getInputStream();
bufferedReader = new BufferedReader( new InputStreamReader( stream ) );
line = "";
while (line != null) {
line = bufferedReader.readLine();
data = data + line;
}
json2 = new JSONArray( data );

for (int i = 0; i < json2.length(); i++) {
idArray = json2.getJSONObject( i );
deviceArray = json2.getJSONObject( i );
tempArray = json2.getJSONObject( i );
humArray = json2.getJSONObject( i );
batArray = json2.getJSONObject( i );
modeArray = json2.getJSONObject( i );
date_timeArray = json2.getJSONObject( i );
luxArray = json2.getJSONObject( i );
id = idArray.getString( "id" );
String temp = tempArray.getString( "temp" );
String device = deviceArray.getString( "device" );

String hum = humArray.getString( "hum" );
String bat = batArray.getString( "bat" );
String mode = modeArray.getString( "mode" );
String date_time = date_timeArray.getString( "time" );
String lux = luxArray.getString( "light" );
allId.add( id );
allDevice.add( device );
allTemp.add( temp );
allHum.add( hum );
allBat.add( bat );
allMode.add( mode );
allDate_time.add( date_time );
allLux.add( lux );

}

} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog( new MainActivity() );
pd.setMessage( "Være sød at vente" );
pd.show();
}
@Override
public void onPostExecute(Void result) {
super.onPostExecute( result );
if (pd.isShowing()) {
pd.dismiss();
}
gson = new Gson();
json = gson.toJson( data );
json_string = data;

}
}
}

我收到的错误：

错误：需要类、接口或枚举

我感谢您的帮助！提前谢谢。

Answer 1

为 AsynctTask 创建单独的类比在每个片段中创建 AsyncTask 更好。 您收到错误，因为在 new jsonAsynctask((.execute((//jsonAsyncTask 从 MainActivity 扩展而来，所以它不是 AsyncTask

将上面的行替换为新的 jsonConnection .execute((