我的意图服务没有启动。它给出了一个错误。我是安卓新手。我正在使用restful web api。我在 android 设备上使用服务。我创建了一个同步模块，如果没有覆盖区域，应用程序会将数据存储在数据库中，并每 60 秒检查一次网络。
当它上线时，它将在服务器上上传数据。我希望这个过程在后台运行。为此，我使用了 Intent Service，它在后台运行并在执行后通知用户。但是服务没有开始我在网上查看了许多教程，它们都是相同的方法。但我的不工作。
<p><b>Below is my error code</b><p>
<code>
10-11 11:45:30.734: W/dalvikvm(396): threadid=1: thread exiting with uncaught exception (group=0x40015560)
10-11 11:45:30.774: E/AndroidRuntime(396): FATAL EXCEPTION: main
10-11 11:45:30.774: E/AndroidRuntime(396): java.lang.RuntimeException: Unable to instantiate service com.remote.synchronizer.haris.OfflineDataService: java.lang.NullPointerException
10-11 11:45:30.774: E/AndroidRuntime(396): at android.app.ActivityThread.handleCreateService(ActivityThread.java:1929)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.app.ActivityThread.access$2500(ActivityThread.java:117)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:985)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.os.Handler.dispatchMessage(Handler.java:99)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.os.Looper.loop(Looper.java:123)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.app.ActivityThread.main(ActivityThread.java:3683)
10-11 11:45:30.774: E/AndroidRuntime(396): at java.lang.reflect.Method.invokeNative(Native Method)
10-11 11:45:30.774: E/AndroidRuntime(396): at java.lang.reflect.Method.invoke(Method.java:507)
10-11 11:45:30.774: E/AndroidRuntime(396): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-11 11:45:30.774: E/AndroidRuntime(396): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-11 11:45:30.774: E/AndroidRuntime(396): at dalvik.system.NativeStart.main(Native Method)
10-11 11:45:30.774: E/AndroidRuntime(396): Caused by: java.lang.NullPointerException
10-11 11:45:30.774: E/AndroidRuntime(396): at android.content.ContextWrapper.getSystemService(ContextWrapper.java:363)
10-11 11:45:30.774: E/AndroidRuntime(396): at com.android.internal.app.AlertController$AlertParams.<init>(AlertController.java:742)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.app.AlertDialog$Builder.<init>(AlertDialog.java:273)
10-11 11:45:30.774: E/AndroidRuntime(396): at com.remote.synchronizer.haris.OfflineDataService.<init>(OfflineDataService.java:23)
10-11 11:45:30.774: E/AndroidRuntime(396): at java.lang.Class.newInstanceImpl(Native Method)
10-11 11:45:30.774: E/AndroidRuntime(396): at java.lang.Class.newInstance(Class.java:1409)
10-11 11:45:30.774: E/AndroidRuntime(396): at android.app.ActivityThread.handleCreateService(ActivityThread.java:1926)
10-11 11:45:30.774: E/AndroidRuntime(396): ... 10 more
</code>
<p><b>Intent Service</b></p>
<code><pre>
package com.remote.synchronizer.haris;
import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
import org.apache.http.NameValuePair;
import android.app.AlertDialog;
import android.app.IntentService;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;
public class OfflineDataService extends IntentService {
boolean wifi,edge;
private Timer timer= new Timer();
SQLiteDatabase db;
String un,shop,city,date,order,InsertQuery;
AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this);
public OfflineDataService() {
super("OfflineDataService");
}
/*@Override
public void onCreate() {
super.onCreate();
Log.e("Service Example", "Service Started.. ");
db= openOrCreateDatabase("Product", MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS Order (UserName VARCHAR(10), Shop VARCHAR(15), City VARCHAR(15), Date VARCHAR(10), Order VARCHAR(50));");
} */
@Override
protected void onHandleIntent(Intent intent) {
Bundle bundle=intent.getExtras();
un=bundle.getString("un");
shop=bundle.getString("shop");
city=bundle.getString("city");
date=bundle.getString("date");
order=bundle.getString("order");
/*InsertQuery="INSERT INTO Order VALUES ('"+ un + "','"+ shop + "','" + city + "','" + date + "','" + order + "');";
db.execSQL(InsertQuery);*/
/*timer.scheduleAtFixedRate(new TimerTask(){
@Override
public void run() {
//Checking network connectivity
wifi=NetworkInfo.Wifi(OfflineDataService.this);
edge=NetworkInfo.EDGE(OfflineDataService.this);
if(wifi==true||edge==true)
{
DataSender();
}
else
{
dlgAlert.setMessage("Testing");
dlgAlert.show();
// Toast toast=Toast.makeText(getApplicationContext(), "Testing", toast.LENGTH_LONG).show();
}
}
}, 1000, 5000);*/
}
/*@Override
public void onDestroy() {
super.onDestroy();
Log.e("Service Example", "Service Destroyed.. ");
//notifications
}
private void DataSender()
{
timer.cancel();
}*/
}
</code></pre>
<p><b>Calling Method</b></p>
<code><pre>
Intent serviceIntent= new Intent(this, OfflineDataService.class);
Bundle bundle= new Bundle();
bundle.putString("un", msg);
bundle.putString("shop", shop.getText().toString());
bundle.putString("city", city.getText().toString());
bundle.putString("date", reportDate);
bundle.putString("order", order.getText().toString());
serviceIntent.putExtras(bundle);
startService(serviceIntent);
</code></pre>
<p><b>AndroidManifest Declaration</b></p>
<code><pre>
android:enabled="true"
android:name=".OfflineDataService"
</code></pre>
<p>what is wrong in my code?</p>
<h3><b>Thanks in advance</b></h3>