Question

我有关于asynctask和spinner的问题。我有一个微调器，一个列表视图和2个按钮。

我是通过点击第一个按钮（带有json
来数据绑定微调器） asynctask服务）Spinner正确显示数据，没问题
之后我点击另一个按钮进行数据绑定列表视图
（使用asynctask的json服务）。列表视图显示数据
没错，
但是现在当我点击微调器时，微调器没有数据，它会丢失数据。它只显示我填写之前选择的最后一项列表视图。

我正在使用asynctask类，就像这个BackgroundTast.java

public class BackGroundTask extends AsyncTask<String, String, JSONObject> {

    List<NameValuePair> postparams = new ArrayList<NameValuePair>();
    String URL = null;
    String method = null;
    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    public BackGroundTask(String url, String method, List<NameValuePair> params) {
        this.URL = url;
        this.postparams = params;
        this.method = method;
    }

    @Override
    protected JSONObject doInBackground(String... params) {
        // TODO Auto-generated method stub
        // Making HTTP request
        try {
            // Making HTTP request
            // check for request method

            if (method.equals("POST")) {
                // request method is POST
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(URL);
                httpPost.setEntity(new UrlEncodedFormEntity(postparams));

                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(postparams,
                 * "utf-8"); URL += "?" + paramString;
                 */
                String paramString = "";
                int i = 0;
                for (i = 0; i < postparams.size(); i++) { // foreach loop
                    NameValuePair nm = postparams.get(i);
                    if (i == 0)
                        paramString += nm.getValue();
                    else
                        paramString += "/" + nm.getValue();

                }
                if (i > 0)
                    URL += "/" + paramString;
                Log.w("myApp", URL);
                HttpGet httpGet = new HttpGet(URL);

                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }

            // read input stream returned by request into a string using
            // StringBuilder
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "utf-8"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();

            // create a JSONObject from the json string
            jObj = new JSONObject(json);

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // return JSONObject (this is a class variable and null is returned if
        // something went bad)
        return jObj;

    }
}

我正在使用此函数来数据绑定微调器

private BackGroundTask bgt;
Spinner dropdown1;
Button button_UseSelectedItem;
ArrayList<sobject2> arrayListem = new ArrayList<sobject2>();
public void buildCountryDropDown() {
    // EditText textbx = (EditText)findViewById(R.id.editText1);
    // Building post parameters, key and value pair
    List<NameValuePair> apiParams = new ArrayList<NameValuePair>();
    apiParams.add(new BasicNameValuePair("idx", "BL"));
    arrayListem.clear();
    bgt = new BackGroundTask(
            "http://10.200.1.167/json/Service1.svc/GetAllCustomers3",
            "GET", apiParams);
    try {
        JSONObject countryJSON = bgt.execute().get();
        // Getting Array of countries
        JSONArray countries = countryJSON
                .getJSONArray("GetAllCustomers3Result");
        // looping through All countries

        arrayListem.add(new sobject2("seçim yapınız", "-1"));

        for (int i = 0; i < countries.length(); i++) {

            JSONObject c = countries.getJSONObject(i);

            sobject2 yeniDeger = new sobject2(c.optString("ad"),
                    c.optString("id"));

            arrayListem.add(yeniDeger);
        }

        dropdown1 = (Spinner) findViewById(R.id.dropdown1);
        ArrayAdapter<sobject2> myAdapter = new ArrayAdapter<sobject2>(this,
                android.R.layout.simple_spinner_item, arrayListem);
        dropdown1.setAdapter(myAdapter);


    } catch (JSONException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (ExecutionException e) {
        e.printStackTrace();
    }

}

我正在填写我的列表视图

    private BackGroundTask bgt_listview;
ListView listview1;
AlertsAdapter arrayAdapter2;
ArrayList<alertx> arrayListem2 = new ArrayList<alertx>();

public void buildListView(String paramx) {
    // EditText textbx = (EditText)findViewById(R.id.editText1);
    // Building post parameters, key and value pair
    List<NameValuePair> apiParams = new ArrayList<NameValuePair>();
    apiParams.add(new BasicNameValuePair("idx", paramx));
    arrayListem.clear();
    bgt_listview = new BackGroundTask(
            "http://10.200.1.167/json/Service2.svc/getOrders", "GET",
            apiParams);

    try {
        JSONObject countryJSON = bgt_listview.execute().get();
        // Getting Array of countries
        JSONArray countries = countryJSON
                .getJSONArray("getOrdersParamResult");
        // looping through All countries

        for (int i = 0; i < countries.length(); i++) {

            JSONObject c = countries.getJSONObject(i);

            alertx yeniDeger = new alertx(c.optString("CustomerID"),
                    c.optString("OrderID"));

            arrayListem2.add(yeniDeger);
        }

        listview1 = (ListView) findViewById(R.id.listem1);
        arrayAdapter2 = new AlertsAdapter(this, R.layout.listitems,
                arrayListem2);
        listview1.setAdapter(arrayAdapter2);

        /*----------------------------------------------------------------*/

        /**********************************************************************************/

    } catch (JSONException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (ExecutionException e) {
        e.printStackTrace();
    }

}

这些是buttonevents

    public void butonEventt(View view) {
    buildCountryDropDown();
}

public void butonEventtListe(View view) {
    buildListView("BLO");
}

首先我点击butonEventt for spinner，然后点击butonEventtListe for listview.But spinner在点击第二个按钮后丢失了它的内容。感谢任何帮助。谢谢。

Answer 1

我认为这与您使用异步任务周围的事件错误有关。

单击“开”按钮，清除列表，并告知从Web资源加载异步任务。

但是你马上继续并使用结果重新填充列表。但是，由于它是异步任务，主线程不会等待它完成。因此无法保证已访问Web资源，并且及时返回列表。

所以你基本上是清理列表，然后不再添加任何内容。

要添加到列表中的代码应位于异步任务的onPostExecute()方法内。这是doinBackground()中实现的任何事情应该传递到UI线程的地方。

阅读android Docs以获取此基本示例。

Spinner在多次asynctask后丢失内容

1 个答案: