Ich weiß, dass diese Frage oft gestellt wurde, aber alle anderen Threads haben mein Problem überhaupt nicht gelöst. Ich kann mit meinem Code nichts Falsches feststellen. Vielleicht habe ich hier etwas verpasst, kann mir jemand helfen?

Code für den Intent Service:

package Services;

import android.app.IntentService;
import android.content.Intent;
import android.widget.Toast;

public class WifiSearchService extends IntentService {

  /** 
   * A constructor is required, and must call the super IntentService(String)
   * constructor with a name for the worker thread.
   */
  public WifiSearchService() {
      super("WifiSearchService");
  }

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
      Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();
      return super.onStartCommand(intent,flags,startId);
  }

  /**
   * The IntentService calls this method from the default worker thread with
   * the intent that started the service. When this method returns, IntentService
   * stops the service, as appropriate.
   */
  @Override
  protected void onHandleIntent(Intent intent) {
      // Normally we would do some work here, like download a file.
  // For our sample, we just sleep for 5 seconds.
      long endTime = System.currentTimeMillis() + 5*1000;
      while (System.currentTimeMillis() < endTime) {
          synchronized (this) {
              try {
                  wait(endTime - System.currentTimeMillis());
              } catch (Exception e) {
              }
          }
      }
  }

}

Starten des Dienstes durch Betätigen eines Schalters:

package com.cdobiz.wifimapper;

import Services.WifiSearchService;
import android.os.Bundle;
import android.app.Activity;
import android.app.ActivityManager;
import android.app.ActivityManager.RunningServiceInfo;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.Switch;

public class MainActivity extends Activity {

    private Context context;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        context = this;

        setContentView(R.layout.activity_main);


        Switch serviceSwitch = (Switch) this.findViewById(R.id.switchService);

        serviceSwitch.setChecked(isMyServiceRunning());

        serviceSwitch.setOnCheckedChangeListener(new OnCheckedChangeListener(){

            @Override
            public void onCheckedChanged(CompoundButton view, boolean state) {

                if(state){
                    startService(new Intent(context, WifiSearchService.class));
                }else{
                    stopService(new Intent(context, WifiSearchService.class));
                }
            }

        });

    }

    private boolean isMyServiceRunning() {
        ActivityManager manager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        for (RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
            Log.v("debug", service.service.getClassName());
            if ("com.cdobiz.wifimapper.services.WifiSearchService".equals(service.service.getClassName())) {
                return true;
            }
        }
        return false;
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

Manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.cdobiz.wifimapper"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="17" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.cdobiz.wifimapper.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:enabled="true" android:name=".services.WifiSearchService"></service>
    </application>

</manifest>