Question

我想从我的网站获取数据，然后将这些信息放入微调器中。我已经使用了一些教程，我想出了这段代码

package com.thenewboston.christian;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class hospitalhttp extends Activity{

private ProgressDialog pDialog;
JSONParser jParser = new JSONParser();

private static String url_all_products = "http://www.photosbychristian.com/ems/hospitals.php";

//private static final String TAG_HID = "hid";
private static final String TAG_HOSPITAL = "hospital";

JSONArray hosps = null;
ArrayAdapter <String> adapter =  new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item );

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.spinnertest);

    new LoadAllProducts().execute();

}


class LoadAllProducts extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(hospitalhttp.this);
        pDialog.setMessage("Loading hospitals. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    /**
     * getting All products from url
     * */
    protected String doInBackground(String... args) {
        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        // getting JSON string from URL
        JSONObject json = jParser.makeHttpRequest(url_all_products, "GET",
                params);

        // Check your log cat for JSON reponse
        Log.d("All Products: ", json.toString());


        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        try {
            // products found
            // Getting Array of Products
            hosps = json.getJSONArray("PA");

            // looping through All Products
            for (int i = 0; i < hosps.length(); i++) {
                JSONObject c = hosps.getJSONObject(i);

                // Storing each json item in variable
                //String id = c.getString(TAG_HID);
                String name = c.getString(TAG_HOSPITAL);

                adapter.add(name);

            }

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

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after getting all products
        pDialog.dismiss();
        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {
                /**
                 * Updating parsed JSON data into ListView
                 */

                Spinner state = (Spinner) findViewById(R.id.spinner1);
                state.setAdapter(adapter);

            }
        });

    }

}
}

我尝试运行我的应用程序并收到此错误

02-22 22:29:48.131: E/AndroidRuntime(1200): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.thenewboston.christian/com.thenewboston.christian.hospitalhttp}: java.lang.IllegalStateException: System services not available to Activities before onCreate()

所以我在oncreate bolck之后移动所有这些，我仍然得到相同的错误

private ProgressDialog pDialog;
JSONParser jParser = new JSONParser();

private static String url_all_products = "http://www.photosbychristian.com/ems/hospitals.php";

//private static final String TAG_HID = "hid";
private static final String TAG_HOSPITAL = "hospital";

JSONArray hosps = null;
ArrayAdapter <String> adapter =  new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item );

所以我不知道该怎么做，知道任何帮助将不胜感激

Answer 1

移动代码无济于事。 Java是一种范围内的语言，如果在方法之后或之前放置某些东西并不重要。它仍然在同一范围内。

这条线可能引发了这个问题：

ArrayAdapter <String> adapter =  new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item );

您希望在对象范围初始值设定项中加载布局。这种代码甚至在构造函数之前运行。您必须将值赋值移动到onCreate方法中，如下所示：

ArrayAdapter <String> adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.spinnertest);

   adapter =  new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item);

   new LoadAllProducts().execute();
}

Answer 2

所以我在oncreate bolck之后移动所有这些，我仍然得到相同的错误

当您声明静态值时，该代码不能在方法内部。因此，该代码必须位于任何方法之外，这意味着它将在任何方法之前执行，因此将在onCreate()之前执行。

那里的某些内容 - 可能是您的JSONParser - 正在尝试做一些在{em> super.onCreate()执行完{em> onCreate()之前无法完成的事情。super.onCreate()方法。您的Java堆栈跟踪将具体告诉您哪些行（如果有）是您的难点的来源。然后，您需要在调用 onCreate()之后执行该代码，例如将其放在{{1}}方法的末尾。

Android系统服务不可用

2 个答案: