我有一个带有三个片段的应用程序，我需要Asynctask每次刷卡。但似乎Asynctask只在应用程序的开放时运行。但是当它已经创建时，只有第一个和第三个片段在AsyncTask中运行良好，第二个片段在更新数据库时不会改变。
这是我的 MainActivity.java
package com.example.RadarOperationMonitoringSystem;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
/**
* Created by Lemueloodle on 2/12/14.
*/
public class MainActivity extends FragmentActivity{
ViewPager Tab;
TabPagerAdapter TabAdapter;
ActionBar actionBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TabAdapter = new TabPagerAdapter(getSupportFragmentManager());
Tab = (ViewPager)findViewById(R.id.viewPager);
Tab.setOnPageChangeListener(
new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar = getActionBar();
actionBar.setSelectedNavigationItem(position); }
});
Tab.setAdapter(TabAdapter);
actionBar = getActionBar();
//Enable Tabs on Action Bar
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.TabListener tabListener = new ActionBar.TabListener(){
@Override
public void onTabReselected(android.app.ActionBar.Tab tab,
FragmentTransaction ft) {
// TODO Auto-generated method stub
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
Tab.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(android.app.ActionBar.Tab tab,
FragmentTransaction ft) {
// TODO Auto-generated method stub
}};
//Add New Tab
actionBar.addTab(actionBar.newTab().setText("FirstFragment").setTabListener(tabListener));
actionBar.addTab(actionBar.newTab().setText("SecondFragment").setTabListener(tabListener));
actionBar.addTab(actionBar.newTab().setText("ThirdFragment").setTabListener(tabListener));
}
}
这是我的 TabPagerAdapter
package com.example.RadarOperationMonitoringSystem;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
/**
* Created by Lemueloodle on 2/12/14.
*/
public class TabPagerAdapter extends FragmentStatePagerAdapter {
public TabPagerAdapter(FragmentManager fm) {
super(fm);
// TODO Auto-generated constructor stub
}
@Override
public Fragment getItem(int i) {
switch(i) {
case 0:
return new FirstFragment();
case 1:
return new SecondFragment();
case 2:
return new ThirdFragment();
}
return null;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return 3; //No of Tabs
}
}
这是我的 FirstFragment.java
package com.example.RadarOperationMonitoringSystem;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class FirstFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View first = inflater.inflate(R.layout.first_frag, container, false);
// get the listview
((TextView)first.findViewById(R.id.textView)).setText("SecondFragment");
return first;
}
}
SecondFragment.java
package com.example.RadarOperationMonitoringSystem;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class SecondFragment extends ListFragment {
private ProgressDialog pDialog;
// URL to get contacts JSON
private static final String url = "http://10.0.2.2/radaroperations/networkstatus.php";
private static final String TAG_SITENAME1 = "siteName1";
private static final String TAG_NETSTAT1 = "netlink_stats1";
private static final String TAG_FORECAST1 = "forcasting_stats1";
private static final String TAG_MDSI1 = "pagasa_mdsi_stats1";
private static final String TAG_PNOAH1 = "projectnoah_stats1";
....so on
String site1 = "";
String netstat1 = "";
String forecast1 = "";
String mdsi1 = "";
String pnoah1 = "";
.....so on
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View second = inflater.inflate(R.layout.second_frag, container, false);
((TextView)second.findViewById(R.id.textView)).setText("SecondFragment");
return second;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// We set clear listener
new GetContactsb().execute();
}
public class GetContactsb extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Please wait...");
pDialog.setCancelable(true);
pDialog.show();
}
@Override
public Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler2 sh = new ServiceHandler2();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler2.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject c = new JSONObject(jsonStr);
// Getting JSON Array node
site1 = c.getString(TAG_SITENAME1);
netstat1 = c.getString(TAG_NETSTAT1);
forecast1 = c.getString(TAG_FORECAST1);
mdsi1 = c.getString(TAG_MDSI1);
pnoah1 = c.getString(TAG_PNOAH1);
..so on
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_SITENAME1, site1);
contact.put(TAG_NETSTAT1, netstat1);
contact.put(TAG_FORECAST1, forecast1);
contact.put(TAG_MDSI1, mdsi1);
contact.put(TAG_PNOAH1, pnoah1);
...so on
// adding contact to contact list
contactList.clear();
contactList.add(contact);
} catch (JSONException e) {
e.printStackTrace();
}
}else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
@Override
public void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
*
*/
ListAdapter adapter = new SimpleAdapter(
getActivity(), contactList,
R.layout.list_item2, new String[] { TAG_SITENAME1,TAG_SITENAME2,TAG_SITENAME3,TAG_SITENAME4,
TAG_SITENAME5,TAG_SITENAME6,TAG_SITENAME7},
new int[] { R.id.sitename1, R.id.sitename2, R.id.sitename3, R.id.sitename4,R.id.sitename5,
R.id.sitename6, R.id.sitename7}){
//This will change the color of the value depending on the limit given
public View getView(int position, View convertView, ViewGroup parent) {
View view = super.getView(position, convertView, parent);
TextView netstata = (TextView) view.findViewById(R.id.netstat1);
TextView forecasta = (TextView) view.findViewById(R.id.forecast1);
TextView mdsia = (TextView) view.findViewById(R.id.pmdsi1);
TextView pnoaha = (TextView) view.findViewById(R.id.pnoah1);
....so on
//1 - Red = No link
//2 - Yellow = Delay
//3 - Green = Good
//Radar 1
//Network Link Status
if (netstat1.equals("1")){
netstata.setText("No-Link");
netstata.setTextColor(getResources().getColor(R.color.red));
}
else if(netstat1.equals("2")){
netstata.setText("Delay");
netstata.setTextColor(getResources().getColor(R.color.yellow));
}
else if(netstat1.equals("3")){
netstata.setText("Good");
netstata.setTextColor(getResources().getColor(R.color.green));
}
...so on to Radar 7
return view;
};
};
// updating listviews
setListAdapter(adapter);
}
}
}
ThirdFragment.java
package com.example.RadarOperationMonitoringSystem;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class ThirdFragment extends ListFragment {
private ProgressDialog pDialog;
// URL to get contacts JSON
private static final String url = "http://10.0.2.2/radaroperations/energyreadings.php";
private static final String TAG_SITENAME1 = "siteName1";
private static final String TAG_FREQUENCY1 = "Frequency1";
private static final String TAG_ACCURRENT1 = "AC_Voltage1";
private static final String TAG_ACVOLTAGE1 = "AC_Current1";
private static final String TAG_FSTAT1 = "Flimitstat1";
private static final String TAG_VSTAT1 = "Vlimitstat1";
private static final String TAG_CSTAT1 = "Climitstat1";
...so on
// contacts JSONArray
JSONObject c = null;
String site1 = "";
String freq1 = "";
String curr1 = "";
String volts1 = "";
String fstat1 = "";
String vstat1 = "";
String cstat1 = "";
.. so on
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View third = inflater.inflate(R.layout.third_frag, container, false);
((TextView)third.findViewById(R.id.textView)).setText("ThirdFragment");
return third;
}
public void StartProgress() {
new GetContactsc().execute();
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// We set clear listener
new GetContactsc().execute();
}
public class GetContactsc extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Please wait...");
pDialog.setCancelable(true);
pDialog.show();
}
@Override
public Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler3 sh = new ServiceHandler3();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler3.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject c = new JSONObject(jsonStr);
// Getting JSON Array node
site1 = c.getString(TAG_SITENAME1);
freq1 = c.getString(TAG_FREQUENCY1);
curr1 = c.getString(TAG_ACCURRENT1);
volts1 = c.getString(TAG_ACVOLTAGE1);
fstat1 = c.getString(TAG_FSTAT1);
vstat1 = c.getString(TAG_VSTAT1);
cstat1 = c.getString(TAG_CSTAT1);
...so on
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_SITENAME1, site1);
contact.put(TAG_FREQUENCY1, freq1);
contact.put(TAG_ACCURRENT1, curr1);
contact.put(TAG_ACVOLTAGE1, volts1);
contact.put(TAG_FSTAT1, fstat1);
contact.put(TAG_VSTAT1, vstat1);
contact.put(TAG_CSTAT1, cstat1);
...so on
// adding contact to contact list
contactList.clear();
contactList.add(contact);
} catch (JSONException e) {
e.printStackTrace();
}
}else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
@Override
public void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
*
*/
ListAdapter adapter = new SimpleAdapter(
getActivity(), contactList,
R.layout.list_item, new String[] { TAG_SITENAME1, TAG_FREQUENCY1, TAG_ACCURRENT1,
TAG_ACVOLTAGE1,TAG_SITENAME2, TAG_FREQUENCY2, TAG_ACCURRENT2,
TAG_ACVOLTAGE2,TAG_SITENAME3, TAG_FREQUENCY3, TAG_ACCURRENT3,
TAG_ACVOLTAGE3, TAG_SITENAME4, TAG_FREQUENCY4, TAG_ACCURRENT4,
TAG_ACVOLTAGE4, TAG_SITENAME5, TAG_FREQUENCY5, TAG_ACCURRENT5,
TAG_ACVOLTAGE5, TAG_SITENAME6, TAG_FREQUENCY6, TAG_ACCURRENT6,
TAG_ACVOLTAGE6, TAG_SITENAME7, TAG_FREQUENCY7, TAG_ACCURRENT7,
TAG_ACVOLTAGE7},
new int[] { R.id.sitename1, R.id.frequency1,
R.id.accurrent1, R.id.acvoltage1, R.id.sitename2, R.id.frequency2,
R.id.accurrent2, R.id.acvoltage2, R.id.sitename3, R.id.frequency3,
R.id.accurrent3, R.id.acvoltage3, R.id.sitename4, R.id.frequency4,
R.id.accurrent4, R.id.acvoltage4, R.id.sitename5, R.id.frequency5,
R.id.accurrent5, R.id.acvoltage5, R.id.sitename6, R.id.frequency6,
R.id.accurrent6, R.id.acvoltage6, R.id.sitename7, R.id.frequency7,
R.id.accurrent7, R.id.acvoltage7}){
//This will change the color of the value depending on the limit given
public View getView(int position, View convertView, ViewGroup parent) {
View view = super.getView(position, convertView, parent);
TextView freqa = (TextView) view.findViewById(R.id.frequency1);
TextView voltsa = (TextView) view.findViewById(R.id.acvoltage1);
TextView curra = (TextView) view.findViewById(R.id.accurrent1);
... so on
//Radar 1
if (fstat1.equals("1")){
freqa.setTextColor(getResources().getColor(R.color.green));
}
else if(fstat1.equals("2")){
freqa.setTextColor(getResources().getColor(R.color.red));
}
if(vstat1.equals("1")){
voltsa.setTextColor(getResources().getColor(R.color.green));
}
else if(vstat1.equals("2")){
voltsa.setTextColor(getResources().getColor(R.color.red));
}
if(cstat1.equals("1")){
curra.setTextColor(getResources().getColor(R.color.green));
}
else if(cstat1.equals("2")){
curra.setTextColor(getResources().getColor(R.color.red));
}
... so on to Radar 7
return view;
};
};
// updating listviews
setListAdapter(adapter);
}
}
}
答案 0 :(得分：0)
我遇到了和你一样的问题。我认为这个问题是因为ViewPager保存了上一个和下一个寻呼机的状态，并在它们到来之前构建它们。尝试设置tab.setOffscreenPageLimit（0）。通过这样做，你可能会遇到一个问题，即当你刷页面时，页面将被重建。