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我想在另一个异步方法中做一个异步调用我不知道如果我正确地这样做，或者如果它甚至可能。首先调用从数据库中获取partID，然后获取零件的lotNumbers。我这样做的理由是能够循环并将关联的partLotNumebrs放入一个Spinner中，并在ListView中显示一个Spinners列表。我究竟做错了什么？这甚至有可能吗？我知道你不能在主内部进行HTTP调用，所以我不知道有任何其他方式来做到这一点。Android在另一个Async任务中调用异步任务？
我得到的错误。
02-13 11:04:16.431: E/AndroidRuntime(1369): FATAL EXCEPTION: main
02-13 11:04:16.431: E/AndroidRuntime(1369): java.lang.NullPointerException
02-13 11:04:16.431: E/AndroidRuntime(1369): at com.cbs.iomamobile.ViewOrderlineAssemblyActivity$getPartLotNumbers.onPostExecute(ViewOrderlineAssemblyActivity.java:258)
02-13 11:04:16.431: E/AndroidRuntime(1369): at com.cbs.iomamobile.ViewOrderlineAssemblyActivity$getPartLotNumbers.onPostExecute(ViewOrderlineAssemblyActivity.java:1)
02-13 11:04:16.431: E/AndroidRuntime(1369): at android.os.AsyncTask.finish(AsyncTask.java:602)
02-13 11:04:16.431: E/AndroidRuntime(1369): at android.os.AsyncTask.access$600(AsyncTask.java:156)
02-13 11:04:16.431: E/AndroidRuntime(1369): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
02-13 11:04:16.431: E/AndroidRuntime(1369): at android.os.Handler.dispatchMessage(Handler.java:99)
02-13 11:04:16.431: E/AndroidRuntime(1369): at android.os.Looper.loop(Looper.java:137)
02-13 11:04:16.431: E/AndroidRuntime(1369): at android.app.ActivityThread.main(ActivityThread.java:4340)
02-13 11:04:16.431: E/AndroidRuntime(1369): at java.lang.reflect.Method.invokeNative(Native Method)
02-13 11:04:16.431: E/AndroidRuntime(1369): at java.lang.reflect.Method.invoke(Method.java:511)
02-13 11:04:16.431: E/AndroidRuntime(1369): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
02-13 11:04:16.431: E/AndroidRuntime(1369): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
02-13 11:04:16.431: E/AndroidRuntime(1369): at dalvik.system.NativeStart.main(Native Method)
它指向此行
textView.setText(temp.getString("name"));
似乎没有我的微调或TextView的是有效的，不知道为什么。
assembly.class
public class ViewOrderlineAssemblyActivity extends ListActivity{
// Progress Dialog
private ProgressDialog pDialog;
String productName;
String olid;
String assemblyName;
// Creating JSON Parser object
JSONParser jsonParser = new JSONParser();
// url to get all orders list
private static String url_get_assembly_parts = "http://10.0.2.2/android_connect/get_assembly_parts.php";
// url to get all orders list
private static String url_get_part_partlotnumbers = "http://10.0.2.2/android_connect/get_part_partLotNumbers.php";
// orders JSONArray
JSONArray assembly = null;
JSONArray parts = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_assemblies);
// getting product details from intent
Intent i = getIntent();
// getting product id (pid) from intent
assemblyName = i.getStringExtra("assemblyName");
olid = i.getStringExtra(TAG_OLID);
Log.d("assemblyName", "" + assemblyName);
// Loading orders in Background Thread
new LoadAllAssemblyParts().execute();
}
// Response from Edit Order Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all assemblyparts by making HTTP Request
* */
class LoadAllAssemblyParts extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
}
/**
* getting All orders from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("assemblyName", assemblyName));
// getting JSON string from URL
JSONObject json = jsonParser.makeHttpRequest(url_get_assembly_parts, "GET", params);
// Check log cat for JSON reponse
Log.d("All partID's: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// orders found
// Getting Array of Parts
assembly = json.getJSONArray("assembly");
// looping through All Parts
for (int i = 0; i < assembly.length(); i++) {
JSONObject c = assembly.getJSONObject(i);
// Storing each json item in variable
String id = c.getString("partID");
String name = c.getString("assemblyName");
new getPartLotNumbers().execute(id);
}
} else {
// no part ID's found
}
} 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 orders
}
}
class getPartLotNumbers extends AsyncTask<String, String, JSONArray>{
Spinner spinner;
TextView textView;
@Override
protected JSONArray doInBackground(String... args) {
JSONArray parts = null;
int success;
String partID = args[0];
try{
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("partID", partID));
// getting part Lot Numbers by making HTTP request
// Note that part Lot Numbers will use GET request
JSONObject json = jsonParser.makeHttpRequest(url_get_part_partlotnumbers, "GET", params);
// check log for json response
Log.d("List of PartID's", json.toString());
// json success tag
success = json.getInt(TAG_SUCCESS);
if(success == 1){
// successfully received part Lot Numbers
parts = json.getJSONArray("parts"); // JSON Array
}else{
// part Lot Numbers not not found
}
}catch(JSONException e){
e.printStackTrace();
}
//return array of part Lot Numbers
return parts;
}
protected void onPostExecute(JSONArray products){
//spinner and textview
spinner = (Spinner) findViewById(R.id.LotNumbers);
textView = (TextView) findViewById(R.id.partName);
//list of partLotNumbers
List<String> partLotNumberList = new ArrayList<String>();
//move list from JSON to List
try{
for(int i=0;i<products.length();i++){
JSONObject temp = products.getJSONObject(i);
partLotNumberList.add(temp.getString("partLotNumber"));
}
//get Part Name
JSONObject temp = products.getJSONObject(0);
textView.setText(temp.getString("name"));
} catch(JSONException e){
e.printStackTrace();
}
//adapter for Spinner
ArrayAdapter<String> adp1=new ArrayAdapter<String>(getBaseContext(), android.R.layout.simple_list_item_1, partLotNumberList);
adp1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
//set the adapter to the spinnner
spinner.setAdapter(adp1);
}
}
}
all_assembly_parts.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
view_assembly_parts.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/partName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<Spinner
android:id="@+id/LotNumbers"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
你最好保持简单并使用一个AsyncTask。您可以在同一个doInBackground方法中执行多个网络请求。 – elevine