我正在开发一个Tabbed Android项目，其中有2个包含2个AsyncTask类的片段。在片段1中，它要求其中的一个AsyncTask类从URL中获取JSON；在片段2中，它调用驻留在该片段中的另一个AsyncTask类，以从URL中获取另一个JSON，这现在导致应用程序运行时崩溃。因此，如何能够同时运行来自两个不同Fragment的两个AsyncTask类？请帮忙！这是这两个片段的代码片段...
Tab2Fragment.java
public class Tab2Fragment extends Fragment {
SharedPreferences sharedPreferences;
private static boolean jsonExists = false;
ArrayList<HashMap<String, String>> itemList = new ArrayList<HashMap<String, String>>();
private static final String TAG_LIST = "Shelter List";
private static final String TAG_TYPE = "Image";
private static final String TAG_NAME = "Name";
private static final String TAG_COORDINATE = "Coordinate";
private static final String TAG_IMG = "Img";
View view;
ListView list;
JSONArray mapArray = null;
boolean connected = false;
String[] from = new String[]{ TAG_NAME, TAG_TYPE, TAG_COORDINATE, TAG_IMG };
int[] to = new int[]{R.id.name, R.id.type, R.id.coordinate, R.id.lvimage };
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
view = inflater.inflate(R.layout.tab2_fragment, container, false);
if (isOnline()) {
connected = true;
//new JSONParse().execute();
new JSONParse().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
connected = false;
if (jsonExists) {
Toast.makeText(getContext(), "No Internet Connection! " +
"Please, turn on internet connection to get updated data!!", Toast.LENGTH_SHORT).show();
//new JSONParse().execute();
new JSONParse().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
view = inflater.inflate(R.layout.tab2_fragment, container, false);
Toast.makeText(getContext(), "No Internet Connection! " +
"Please, turn on internet connection to get going!!", Toast.LENGTH_SHORT).show();
}
}
return view;
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(getContext());
pDialog.setMessage("Getting Updated Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
JsonParser jParser = new JsonParser();
JSONObject json;
if (connected) {
// Getting JSON from URL
//JSONObject json = jParser.getJSONFromUrl(url);
String url;
// Getting Current District Name from Globals class
String myCurrentLocation = ((Globals) getActivity().getApplication()).getCurrentLocation();
if (myCurrentLocation == null) {
url = "http://192.168.1.126/json_files/parser_ex.json";
Log.i("Current URL Name: ", url);
} else {
String[] parts = myCurrentLocation.split("\\ ");
String url_name = parts[0];
url = "http://192.168.1.126/json_files/"+url_name+".json";
}
Log.i("Current URL Name: ", url);
json = jParser.getJSONFromUrl(url);
} else {
if (jsonExists) {
// Getting JSON from SharedPreferences
String jsnString = getStringProperty("json");
json = jParser.getJSONFromCache(jsnString);
Log.i("JSON File", "String Array: "+jsnString);
} else {
Toast.makeText(getContext(), "No Internet Connection Available! "+
"Please, turn on the internet to get data!!", Toast.LENGTH_LONG);
json = null;
}
}
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
// Getting JSON Array from URL
mapArray = json.getJSONArray(TAG_LIST);
for (int i = 0; i < mapArray.length(); i++) {
JSONObject c = mapArray.getJSONObject(i);
// Storing JSON item in a Variable
String name = c.getString(TAG_NAME);
String type = c.getString(TAG_TYPE);
String cod = c.getString(TAG_COORDINATE);
// Adding value HashMap key => value
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_TYPE, type);
map.put(TAG_NAME, name);
map.put(TAG_COORDINATE, cod);
if(type.startsWith("school")) {
Integer pic = R.drawable.school;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("hospital")) {
Integer pic = R.drawable.hospital;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("fscd")) {
Integer pic = R.drawable.fscd;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("ps")) {
Integer pic = R.drawable.ps;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("cs")) {
Integer pic = R.drawable.cs;
map.put(TAG_IMG, pic.toString());
} else {
Integer pic = R.drawable.school;
map.put(TAG_IMG, pic.toString());
}
itemList.add(map);
setStringProperty("json", String.valueOf(map));
jsonExists = true;
ListAdapter adapter = new SimpleAdapter(getContext(), itemList,
R.layout.map_data_list, from, to);
list = (ListView) view.findViewById(R.id.mapData);
list.setAdapter(adapter);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// Launching new Activity on selecting single List Item
Intent i = new Intent(getContext(), Tab2Activity.class);
// sending data to new activity
i.putExtra("coordinate", itemList.get(+position).get("Coordinate"));
startActivity(i);
}
});
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public String getStringProperty(String key) {
sharedPreferences = this.getActivity().getSharedPreferences("preferences", Context.MODE_PRIVATE);
String res = null;
if (sharedPreferences != null) {
res = sharedPreferences.getString(key, null);
}
}
public void setStringProperty(String key, String value) {
sharedPreferences = this.getActivity().getSharedPreferences("preferences", Context.MODE_PRIVATE);
if (sharedPreferences != null) {
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, value);
editor.commit();
}
}
public boolean isOnline() {
ConnectivityManager cm = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnectedOrConnecting()) {
return true;
} else {
return false;
}
}
}
Tab3Fragment.java
public class Tab3Fragment extends Fragment {
SharedPreferences sharedPreferences;
private static boolean jsonExists = false;
ArrayList<HashMap<String, String>> agroList = new ArrayList<HashMap<String, String>>();
private static final String TAG_LIST = "Agro List";
private static final String TAG_TYPE = "Type";
private static final String TAG_TITLE = "Title";
private static final String TAG_SHORT_DESCRIPTION = "ShortDesc";
private static final String TAG_DESCRIPTION = "Description";
private static final String TAG_IMG = "Img";
View view;
ListView list;
JSONArray agroArray = null;
boolean connected = false;
String[] from = new String[]{ TAG_TITLE, TAG_TYPE, TAG_SHORT_DESCRIPTION, TAG_IMG };
int[] to = new int[]{R.id.agroTitle, R.id.agroType, R.id.agroShortTitle, R.id.agroImage };
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
view = inflater.inflate(R.layout.tab3_fragment, container, false);
if (isOnline()) {
connected = true;
//new AGROJSONParse().execute();
new AGROJSONParse().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//new AGROJSONParse().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
connected = false;
if (jsonExists) {
Toast.makeText(getContext(), "No Internet Connection! " +
"Please, turn on internet connection to get updated data!!", Toast.LENGTH_SHORT).show();
//new AGROJSONParse().execute();
new AGROJSONParse().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
view = inflater.inflate(R.layout.tab3_fragment, container, false);
Toast.makeText(getContext(), "No Internet Connection! " +
"Please, turn on internet connection to get going!!", Toast.LENGTH_SHORT).show();
}
}
return view;
}
private class AGROJSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(getContext());
pDialog.setMessage("Getting Updated Agricultural Tips Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
JsonParser jParser = new JsonParser();
JSONObject json;
if (connected) {
// Getting JSON from URL
String url;
// Getting Current District Name from Globals class
String myCurrentLocation = ((Globals) getActivity().getApplication()).getCurrentLocation();
if (myCurrentLocation == null) {
url = "http://192.168.1.126/json_files/parser_ex1.json";
Log.i("Current URL Name: ", url);
} else {
String[] parts = myCurrentLocation.split("\\ ");
String url_name = parts[0];
url = "http://192.168.1.126/json_files/"+url_name+"_Agro.json";
}
Log.i("Current URL Name: ", url);
json = jParser.getJSONFromUrl(url);
} else {
if (jsonExists) {
// Getting JSON from SharedPreferences
String jsnString = getStringProperty("json");
json = jParser.getJSONFromCache(jsnString);
Log.i("JSON File", "String Array: "+jsnString);
} else {
Toast.makeText(getContext(), "No Internet Connection Available! "+
"Please, turn on the internet to get data!!", Toast.LENGTH_LONG);
json = null;
}
}
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
// Getting JSON Array from URL
agroArray = json.getJSONArray(TAG_LIST);
for (int i = 0; i < agroArray.length(); i++) {
JSONObject c = agroArray.getJSONObject(i);
// Storing JSON item in a Variable
String name = c.getString(TAG_TITLE);
String type = c.getString(TAG_TYPE);
String shortDesc = c.getString(TAG_SHORT_DESCRIPTION);
// Adding value HashMap key => value
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_TYPE, type);
map.put(TAG_TITLE, name);
map.put(TAG_SHORT_DESCRIPTION, shortDesc);
if(type.startsWith("crops")) {
Integer pic = R.drawable.crops;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("cattle")) {
Integer pic = R.drawable.cattle;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("poultry")) {
Integer pic = R.drawable.poultry;
map.put(TAG_IMG, pic.toString());
} else if(type.startsWith("fisheries")) {
Integer pic = R.drawable.fisheries;
map.put(TAG_IMG, pic.toString());
} else {
Integer pic = R.drawable.crops;
map.put(TAG_IMG, pic.toString());
}
agroList.add(map);
setStringProperty("json", String.valueOf(map));
jsonExists = true;
ListAdapter adapter = new SimpleAdapter(getContext(), agroList,
R.layout.agro_list_view, from, to);
list = (ListView) view.findViewById(R.id.agroData);
list.setAdapter(adapter);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// Launching new Activity on selecting single List Item
Intent i = new Intent(getContext(), Tab2Activity.class);
// sending data to new activity
i.putExtra("descriptionText", agroList.get(+position).get("Description"));
i.putExtra("shortDescriptionText", agroList.get(+position).get("ShortDesc"));
i.putExtra("titleText", agroList.get(+position).get("Title"));
startActivity(i);
}
});
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public String getStringProperty(String key) {
sharedPreferences = this.getActivity().getSharedPreferences("preferences", Context.MODE_PRIVATE);
String res = null;
if (sharedPreferences != null) {
res = sharedPreferences.getString(key, null);
}
return res;
}
public void setStringProperty(String key, String value) {
sharedPreferences = this.getActivity().getSharedPreferences("preferences", Context.MODE_PRIVATE);
if (sharedPreferences != null) {
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, value);
editor.commit();
}
}
public boolean isOnline() {
ConnectivityManager cm = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnectedOrConnecting()) {
return true;
} else {
return false;
}
}
}
我尝试从两个片段中删除AsyncTask.THREAD_POOL_EXECUTOR，也从两个doInBackground方法中删除Toast.show()，并且在我的应用崩溃时在运行时收到了这些错误消息。
Logcat消息
07-25 07:36:19.122 13478-13478/com.example.mehedi.mytab4 V/ActivityThread: updateVisibility : ActivityRecord{92a92cb token=android.os.BinderProxy@d84150f {com.example.mehedi.mytab4/com.example.mehedi.mytab4.MainActivity}} show : true
07-25 07:36:41.202 13478-13637/com.example.mehedi.mytab4 I/System.out: AsyncTask #1 calls detatch()
07-25 07:36:41.202 13478-13637/com.example.mehedi.mytab4 W/System.err: org.apache.http.conn.HttpHostConnectException: Connection to http://192.168.1.126 refused
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:248)
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:172)
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:130)
07-25 07:36:41.212 13478-13637/com.example.mehedi.mytab4 W/System.err: at org.apache.http.impl.client.DefaultRequestDirector.executeOriginal(DefaultRequestDirector.java:1337)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:705)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:578)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:494)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:472)
at com.example.mehedi.mytab4.JsonParser.getJSONFromUrl(JsonParser.java:35)
at com.example.mehedi.mytab4.Tab2Fragment$JSONParse.doInBackground(Tab2Fragment.java:170)
at com.example.mehedi.mytab4.Tab2Fragment$JSONParse.doInBackground(Tab2Fragment.java:121)
at android.os.AsyncTask$2.call(AsyncTask.java:295)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
07-25 07:36:41.222 13478-13637/com.example.mehedi.mytab4 W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
07-25 07:36:41.232 13478-13637/com.example.mehedi.mytab4 W/System.err: Caused by: java.net.ConnectException: failed to connect to /192.168.1.126 (port 80): connect failed: ETIMEDOUT (Connection timed out)
07-25 07:36:41.262 13478-13637/com.example.mehedi.mytab4 W/System.err: at libcore.io.IoBridge.connect(IoBridge.java:124)
07-25 07:36:41.312 13478-13637/com.example.mehedi.mytab4 W/System.err: at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:183)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:452)
at java.net.Socket.connect(Socket.java:884)
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:124)
07-25 07:36:41.322 13478-13637/com.example.mehedi.mytab4 W/System.err: at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:193)
... 16 more
Caused by: android.system.ErrnoException: connect failed: ETIMEDOUT (Connection timed out)
at libcore.io.Posix.connect(Native Method)
at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:111)
at libcore.io.IoBridge.connectErrno(IoBridge.java:137)
at libcore.io.IoBridge.connect(IoBridge.java:122)
... 21 more
07-25 07:36:41.322 13478-13637/com.example.mehedi.mytab4 E/Buffer Error: Error converting result java.lang.NullPointerException: lock == null
07-25 07:36:41.332 13478-13637/com.example.mehedi.mytab4 E/JSON Parser: Error parsing data org.json.JSONException: End of input at character 0 of
07-25 07:36:41.332 13478-13478/com.example.mehedi.mytab4 D/AndroidRuntime: Shutting down VM
07-25 07:36:41.332 13478-13478/com.example.mehedi.mytab4 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.mehedi.mytab4, PID: 13478
java.lang.NullPointerException: Attempt to invoke virtual method 'org.json.JSONArray org.json.JSONObject.getJSONArray(java.lang.String)' on a null object reference
at com.example.mehedi.mytab4.Tab2Fragment$JSONParse.onPostExecute(Tab2Fragment.java:206)
at com.example.mehedi.mytab4.Tab2Fragment$JSONParse.onPostExecute(Tab2Fragment.java:121)
at android.os.AsyncTask.finish(AsyncTask.java:651)
at android.os.AsyncTask.access$500(AsyncTask.java:180)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
答案 0 :(得分：0)
LogCat具有解决方案：“ java.net.ConnectException：无法连接到/192.168.1.126（端口80）：连接失败：ETIMEDOUT（连接超时）”