我是android新手。我需要将值从微调器传递给asynctask作为参数，直到现在我成功地在微调器中成功显示结果。现在我需要将微调器中的选定值传递给按钮单击时的另一个活动（作为asynctask的参数）。下面是代码。提前谢谢。
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) {}}
答案 0 :(得分：1)
您正以这种方式将参数传递给doInBackground()：
background.execute("your string");
现在字符串"your string"将成为doInBackground()回调中的参数：
@Override
protected String doInBackground(String... params) {
String type2 = params[0]; // type2 == "your string"
...
}
有关详细信息，请参阅docs。