android - android无法运行后台服务

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109 5

在后台服务中使用LocationListener类接收用户的当前位置,然后将它的与存储在数据库中的一些数据进行比较。但当我尝试的时候,我有错误

 package com.example.alert;
 import android.app.Service;
 import android.content.Context;
 import android.content.Intent;
 import android.location.Location;
 import android.location.LocationListener;
 import android.location.LocationManager;
 import android.media.MediaPlayer;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.widget.Toast;
 public class service extends Service{
LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
@Override
public IBinder onBind(Intent arg0) {
//TODO Auto-generated method stub
 return null;
}
public void onCreate() {
 Toast.makeText(this,"Background Service Created", Toast.LENGTH_LONG).show();
}
public void onDestroy() {
 Toast.makeText(this,"My Service Stopped", Toast.LENGTH_LONG).show();
}
public void onStart(Intent intent, int startid) {
 Toast.makeText(this,"My Service Started", Toast.LENGTH_LONG).show();
 Intent myIntent=new Intent(service.this,CurrentLocation.class);
 startActivity(myIntent);
 }
}

这是我的仪表板

11-10 04:54:54.819: E/AndroidRuntime(768): FATAL EXCEPTION: main
11-10 04:54:54.819: E/AndroidRuntime(768): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.alert/com.example.alert.service}: java.lang.NullPointerException
 11-10 04:54:54.819: E/AndroidRuntime(768): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
 11-10 04:54:54.819: E/AndroidRuntime(768): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
11-10 04:54:54.819: E/AndroidRuntime(768): at android.app.ActivityThread.access$600(ActivityThread.java:130)
11-10 04:54:54.819: E/AndroidRuntime(768): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
11-10 04:54:54.819: E/AndroidRuntime(768): at android.os.Handler.dispatchMessage(Handler.java:99)
11-10 04:54:54.819: E/AndroidRuntime(768): at android.os.Looper.loop(Looper.java:137)
11-10 04:54:54.819: E/AndroidRuntime(768): at android.app.ActivityThread.main(ActivityThread.java:4745)
11-10 04:54:54.819: E/AndroidRuntime(768): at java.lang.reflect.Method.invokeNative(Native Method)
11-10 04:54:54.819: E/AndroidRuntime(768): at java.lang.reflect.Method.invoke(Method.java:511)
11-10 04:54:54.819: E/AndroidRuntime(768): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-10 04:54:54.819: E/AndroidRuntime(768): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-10 04:54:54.819: E/AndroidRuntime(768): at dalvik.system.NativeStart.main(Native Method)
11-10 04:54:54.819: E/AndroidRuntime(768): Caused by: java.lang.NullPointerException
11-10 04:54:54.819: E/AndroidRuntime(768): at android.content.ContextWrapper.getSystemService(ContextWrapper.java:416)
11-10 04:54:54.819: E/AndroidRuntime(768): at com.example.alert.service.<init>(service.java:15)
11-10 04:54:54.819: E/AndroidRuntime(768): at java.lang.Class.newInstanceImpl(Native Method)
11-10 04:54:54.819: E/AndroidRuntime(768): at java.lang.Class.newInstance(Class.java:1319)

下面是位置监听器的其他代码

 package com.example.alert;
 import android.app.Activity;
 import android.content.Context;
 import android.location.Location;
 import android.location.LocationListener;
 import android.location.LocationManager;
 import android.os.Bundle;
 import android.widget.Toast;
 public class CurrentLocation extends Activity {
LocationManager lm ;
@Override
protected void onCreate(Bundle savedInstanceState) {
//TODO Auto-generated method stub
 super.onCreate(savedInstanceState);
/* Use the LocationManager class to obtain GPS locations */
 LocationListener ll = new MyLocationListener();
//lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 5*60*10000, 0, ll);
 lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, ll);
}
/* Class My Location Listener */
public class MyLocationListener implements LocationListener
{
 public void onLocationChanged(Location loc)
 {
 if(loc!=null)
 {
 double x;
 String Text ="My current location is:" +"Latitud =" + loc.getLatitude() +"Longitud =" + loc.getLongitude();
 Toast.makeText( getApplicationContext(),Text,Toast.LENGTH_SHORT).show(); 
//for loop, alerters retrieving one by one
//x= calcDistance(loc.getLatitude(),loc.getLongitude(),,);
//if(x<1)
//distance <1, retrieve data from DB and trigger 
 }
 }
 public void onProviderDisabled(String provider)
 {
 Toast.makeText( getApplicationContext(),"Gps Disabled - @From :Alert Me",Toast.LENGTH_SHORT ).show();
 }
 public void onProviderEnabled(String provider)
 {
 Toast.makeText( getApplicationContext(),"Gps Enabled - @From :Alert Me",Toast.LENGTH_SHORT).show();
 }
 public void onStatusChanged(String provider, int status, Bundle extras)
 {
 }
}/* End of Class MyLocationListener */
public double calcDistance(double latA, double longA, double latB, double longB) {
 double theDistance = (Math.sin(Math.toRadians(latA)) * Math.sin(Math.toRadians(latB)) + Math.cos(Math.toRadians(latA)) * Math.cos(Math.toRadians(latB)) * Math.cos(Math.toRadians(longA - longB)));
 return new Double((Math.toDegrees(Math.acos(theDistance))) * 69.09*1.6093);
}
}

清单文件

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.alert"
android:versionCode="1"
android:versionName="1.0"> 
<uses-sdk
 android:minSdkVersion="8"
 android:targetSdkVersion="15"/>
<application
 android:icon="@drawable/ic_launcher"
 android:label="@string/app_name"
 android:theme="@style/AppTheme"> 
 <activity
 android:name=".MainActivity"
 android:label="@string/title_activity_main"> 
 <intent-filter>
 <action android:name="android.intent.action.MAIN"/>
 <category android:name="android.intent.category.LAUNCHER"/>
 </intent-filter>
 </activity>
 <activity android:name=".Instructions" android:label="Instructions"></activity>
 <activity android:name=".AboutApp" android:label="About ALERT ME!"></activity>
 <activity android:name=".ViewAlerters" android:label="Alerters Active"></activity> 
 <activity android:name=".AddAlerter" android:label="Add an Alerter"></activity>
 <activity android:name=".EditAlerter" android:label="Edit an alerter"></activity> 
 <activity android:name=".AddLocation" android:label="Add Location to Alerter"></activity>
 <activity android:name=".AddTrigger" android:label="Add trigger to Alerter"></activity>
 <activity android:name=".SilVib" android:label="Silent/Vibrate Trigger"></activity>
 <activity android:name=".CallMode" android:label="Call Mode Trigger"></activity>
 <activity android:name=".service"></activity>
 <activity android:name=".Status_Notify"></activity>
 <activity android:name=".Notifier"></activity> 
 <activity android:name=".Message"></activity>
 <activity android:name=".Message_sent"></activity>
 <activity android:name=".StoringEntire"></activity>
 <activity android:name=".CurrentLocation"></activity>
 <uses-library android:name="com.google.android.maps"/>
<service
 android:enabled="true"
 android:name=".service"/>
 </application>
 <uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.SEND_SMS"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_BACKGROUND_SERVICE"/>
</manifest>
时间:原作者:0个回答

112 2

aecq状态:

Caused by: java.lang.NullPointerException
 at android.content.ContextWrapper.getSystemService(ContextWrapper.java:416)
 at com.example.alert.service.<init>(service.java:15)

只要将这里代码移动到 onCreate() 中,就可以等待上下文初始化:

public class service extends Service {
 LocationManager lm;
 @Override
 public void onCreate() {
//This line needs an existing context
 lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
 Toast.makeText(this,"Background Service Created", Toast.LENGTH_LONG).show();
 }
//etc
原作者:
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