將微調值作爲參數傳遞給異步任務

Question

我是android新手。我需要將spinner的值作爲參數傳遞給asynctask，直到現在我成功地在spinner中成功顯示結果。現在我需要將選定的值從微調器傳遞給另一個按鈕點擊的活動（作爲asynctask的參數）。以下是代碼。提前致謝。
BackgroundFetchWorker.java：

public class BackgroundFetchWorker extends AsyncTask<String,Void,String> { 
String json_string; 
ProgressDialog progressDialog; 
Context context; 

BackgroundFetchWorker(Context ctx) 
{ 
    context = ctx; 
} 

@Override 
protected String doInBackground(String... params) { 
    String type2 = params[0]; 
    String student_fetch_url = "http://pseudoattendance.pe.hu/studentFetch.php"; 
    if (type2.equals("fetchSubject")) { 
     try { 
      String semester = params[1]; 
      String stream = params[2]; 

      URL url = new URL(student_fetch_url); 
      HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection(); 
      httpURLConnection.setRequestMethod("POST"); 
      httpURLConnection.setDoOutput(true); 
      httpURLConnection.setDoOutput(true); 

      OutputStream outputStream = httpURLConnection.getOutputStream(); 
      BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8")); 
      String post_data = URLEncoder.encode("semester", "UTF-8") + "=" + URLEncoder.encode(semester, "UTF-8") 
        + URLEncoder.encode("stream","UTF-8")+"="+URLEncoder.encode(stream,"UTF-8"); 
      bufferedWriter.write(post_data); 
      bufferedWriter.flush(); 
      bufferedWriter.close(); 
      outputStream.close(); 

      InputStream inputStream = httpURLConnection.getInputStream(); 
      BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1")); 
      String result = " "; 
      String line = ""; 
      while ((line = bufferedReader.readLine()) != null) { 
       result += line; 
      } 
      bufferedReader.close(); 
      inputStream.close(); 
      httpURLConnection.disconnect(); 

      return result; 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

    } 
    return null; 
} 
@Override 
protected void onPreExecute() { 

    progressDialog = new ProgressDialog(context); 
    progressDialog.setTitle("Fetching Data...."); 
    progressDialog.setMessage("This may take a while.."); 
    progressDialog.show(); 
} 

@Override 
protected void onPostExecute(String result) { 

    progressDialog.dismiss(); 
    String s = result.trim(); 
    if(s.equals("{\"result\":[]}")){ 
     Toast.makeText(context, "ERROR OCCURED", Toast.LENGTH_SHORT).show(); 
    } 
    else { 
     json_string = result; 
     Intent i = new Intent(context, TakeAttendanceActivity.class); 
     i.putExtra("studentdata", json_string); 
     context.startActivity(i); 
     Toast.makeText(context, "Success", Toast.LENGTH_SHORT).show(); 
    } 

} 
@Override 
protected void onProgressUpdate(Void... values) { 
    super.onProgressUpdate(values); 
} 

}

FacultyWelcomeActivity.java：

public class FacultyWelcomeActivity extends AppCompatActivity implements Spinner.OnItemSelectedListener{ 
String JSON_STRING; 
JSONObject jsonObject; 
JSONArray jsonArray; 
ContactAdapter contactAdapter; 
ListView listView; 


//Declaring an Spinner 
private Spinner spinner; 
private Spinner spinner1; 

//An ArrayList for Spinner Items 
private ArrayList<String> students; 
private ArrayList<String> stream; 

//JSON Array 
private JSONArray result; 
private JSONArray result1; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_faculty_welcome); 
    //Initializing the ArrayList 
    students = new ArrayList<String>(); 
    stream = new ArrayList<String>(); 
    //Initializing Spinner 
    spinner = (Spinner) findViewById(R.id.spinner); 

    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() { 
     @Override 
     public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { 
      String semesters= parent.getItemAtPosition(position).toString(); 

      String stream= parent.getItemAtPosition(position).toString(); 

     } 

     @Override 
     public void onNothingSelected(AdapterView<?> parent) { 

     } 
    }); 
    spinner1 = (Spinner) findViewById(R.id.spinner1); 

    //Adding an Item Selected Listener to our Spinner 
    //As we have implemented the class Spinner.OnItemSelectedListener to this class iteself we are passing this to setOnItemSelectedListener 

    getData(); 
    getData1(); 


    listView = (ListView) findViewById(R.id.lectureList); 

    contactAdapter = new ContactAdapter(this, R.layout.rowlayout); 
    listView.setAdapter(contactAdapter); 
    JSON_STRING = getIntent().getExtras().getString("JSON Data"); 

    try { 
     jsonObject = new JSONObject(JSON_STRING); 
     jsonArray = jsonObject.getJSONArray("result"); 
     int count = 0; 
     String sub1, sub2, sub3, sub4; 
     while (count < jsonArray.length()) { 
      JSONObject JO = jsonArray.getJSONObject(count); 

      sub1 = JO.getString("fname"); 
      sub2 = JO.getString("lname"); 
      sub3 = JO.getString("id"); 
      sub4 = JO.getString("email"); 

      Contacts contacts = new Contacts(sub1, sub2, sub3, sub4); 
      contactAdapter.add(contacts); 
      count++; 
     } 
    } catch (JSONException e) { 
     e.printStackTrace(); 
    } 
} 
    public void fetchSubject(View view) { 
     String type2 = "fetchSubject"; 
     String spinnerdata = spinner.getSelectedItem().toString(); 
     String spinner1data = spinner1.getSelectedItem().toString(); 
     BackgroundFetchWorker background = new BackgroundFetchWorker(this); 
     background.execute(type2,spinnerdata,spinner1data); 
    } 

private void getData1(){ 

    StringRequest stringRequest = new StringRequest(Config2.DATA_URL, 
      new Response.Listener<String>() { 
       @Override 
       public void onResponse(String response) { 
        JSONObject j = null; 
        try { 
         //Parsing the fetched Json String to JSON Object 
         j = new JSONObject(response); 

         //Storing the Array of JSON String to our JSON Array 
         result1 = j.getJSONArray(Config2.JSON_ARRAY); 
         getStudents1(result1); 
        } catch (JSONException e) { 
         e.printStackTrace(); 
        } 
       } 
      }, 
      new Response.ErrorListener() { 
       @Override 
       public void onErrorResponse(VolleyError error) { 

       } 
      }); 

    RequestQueue requestQueue = Volley.newRequestQueue(this); 

    requestQueue.add(stringRequest); 
} 

private void getData(){ 

    StringRequest stringRequest = new StringRequest(Config.DATA_URL, 
      new Response.Listener<String>() { 
       @Override 
       public void onResponse(String response) { 
        JSONObject j = null; 
        try { 
         //Parsing the fetched Json String to JSON Object 
         j = new JSONObject(response); 
         result = j.getJSONArray(Config.JSON_ARRAY); 
         getStudents(result); 
        } catch (JSONException e) { 
         e.printStackTrace(); 
        } 
       } 
      }, 
      new Response.ErrorListener() { 
       @Override 
       public void onErrorResponse(VolleyError error) { 

       } 
      }); 

    RequestQueue requestQueue = Volley.newRequestQueue(this); 

    requestQueue.add(stringRequest); 
} 

private void getStudents(JSONArray j){ 

    for(int i=0;i<j.length();i++){ 
     try { 
      //Getting json object 
      JSONObject json = j.getJSONObject(i); 


      students.add(json.getString(Config.TAG_SEMESTER)); 
     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 
    } 


    spinner.setAdapter(new ArrayAdapter<String>(FacultyWelcomeActivity.this, android.R.layout.simple_spinner_dropdown_item, students)); 
} 

private void getStudents1(JSONArray j){ 
    //Traversing through all the items in the json array 
    for(int i=0;i<j.length();i++){ 
     try { 
      //Getting json object 
      JSONObject json = j.getJSONObject(i); 

      //Adding the name of the student to array list 
      stream.add(json.getString(Config2.TAG_STREAM)); 
     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 
    } 


    spinner1.setAdapter(new ArrayAdapter<String>(FacultyWelcomeActivity.this, android.R.layout.simple_spinner_dropdown_item, stream)); 
} 


@Override 
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { 
    //check which spinner triggered the listener 
} 
@Override 
public void onNothingSelected(AdapterView<?> parent) {}} 

Answer 1

您將參數傳遞給doInBackground()這樣：

background.execute("your string"); 

現在字符串"your string"將doInBackground()回調中的參數：

@Override 
protected String doInBackground(String... params) { 
    String type2 = params[0]; // type2 == "your string" 
    ... 
} 

更多信息，請參見docs。