我正在尝试在另一个Async方法中进行异步调用我不确定我是否正确地执行此操作，或者甚至是否可能。第一次调用从数据库中获取partID，然后第二次获取该部分的lotNumbers。我这样做的理由是能够遍历并将关联的partLotNumebrs放在Spinner中并在Listview中显示Spinners列表。我究竟做错了什么？这甚至可能吗？我知道你不能在主要内部进行HTTP调用，所以我不确定是否有其他方法可以做到这一点。
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)
它指向这一行
textView.setText(temp.getString("name"));
似乎我的Spinner或textView都不是有效的，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>
答案 0 :(得分：1)
好的，我会先解决崩溃问题。
您有一个仅包含列表的ListActivity。我猜你发布的两个布局文件是用于显示信息的自定义单元格。在AsyncTask中，当您调用findViewById（）时，它会查看活动的布局（仅包含列表视图）而不是每个单元格的布局。这就是为什么你将它们都变为null的原因，因为活动中没有这样的项目。如果要更新单元格中的信息，则不是这样做的。
您需要查看自定义单元格，列表视图。谷歌举一个简单的例子。
希望这有助于理解崩溃。